As São Paulo faces a climate-induced water crisis, campaigners are fighting to reverse the impact of pollution and illegal deforestation on its largest reservoir
By Sam Cowie and Avener Prado in São Paulo
Thu 4 Jun 2026 14.15 BSTShare
In a small motorboat laden with water-monitoring equipment, biologist Marta Marcondes and community activist Wesley Silvestre Rosa cross Billings reservoir on the far southern edge of São Paulo. Bright white herons glide over the water, which is flanked by thick dark green clusters of Brazil’s Atlantic forest, as the boat heads towards one of the more polluted parts of the reservoir.
“We see where sewage is entering, we see what has been deforested and how that has affected the water quality of the reservoir,” Marcondes says.
Marcondes and Rosa are dedicated to the upkeep of Billings, which at 127 sq km (49 sq miles) is Brazil’s largest urban reservoir by surface area and volume and a vital water source for the almost 22 million people who live in São Paulo’s metropolitan area. It also generates energy via a hydroelectric dam and plays a crucial role in flood control and irrigation; it provides a cooling effect during periods of extreme heat and people use its cleaner parts for recreation and fishing.
Biologist Marta Marcondes collects water samples from the reservoir to monitor contamination levels. Photograph: Avener Prado/The Guardian
Despite its importance, large areas of Billings are polluted: contaminated with household and industrial waste, pharmaceutical residues, microplastics and fecal matter. Urban planners blame neglect by local authorities, flawed water management policies and uncontrolled urban expansion.
This problem has been dragging on for decades. If we don’t do something now, we risk having a collapsed system
Marta Marcondes
As the boat reaches a heavily polluted part of Billings called Grota Funda, Marcondes observes bubbles rising from the water, which she identifies as fermenting bacteria. Donning rubber gloves, she lowers a metallic collection device into the water, empties its dark contents into a bucket before taking a sample in a plastic tube.
“Good lord, what a smell,” she says. “You could die if you drank this.”
Marcondes, who analyses water samples at the lab she runs at the nearby Municipal University of São Caetano do Sul, is also the project coordinator for the local NGO Water Pollutant Index. She notes that water quality and the reservoir’s storage capacity have deteriorated over the past 10 years.
A green algal bloom – typically associated with excess nutrients from sewage and urban runoff – spreads across the surface of the reservoir. Photograph: Avener Prado/The Guardian
“This problem has been dragging on for decades, and if we don’t do something about it now, we risk having a collapsed system,” she says.
In January, residents blamed São Paulo’s water utility, Sabesp, for dumping waste into the reservoir and the company was later fined by environmental authorities. Sabesp says: “The recorded incident was caused by the irregular entry of rainwater into the sewage network and the carrying of garbage, a situation intensified by the rains, which caused a hydraulic overload of the system.”
As the boat heads toward the Pedreira pumping station, which connects Billings to the Pinheiros River, the water thickens and turns green. Billings, which marked its 100th anniversary last year, was built to power the growing industrial base of São Paulo, South America’s richest city, via the Henry Borden hydroelectric plant that captures energy from water cascading over the Serra do Mar mountain range. Nabil Bonduki,a city council member with the Workers’ party and veteran urban planner, says the redirection of polluted water from the Pinheiros and Tietê rivers to supply the plant has turned Billings into an environmental sacrifice zone.
Environmental activist Wesley Silvestre Rosa documents construction debris left inside Parque dos Búfalos, near the Billings reservoir. Photograph: Avener Prado/The Guardian
Roughly 1.5 million people live around Billings, many in favelas or other irregular housing, up from 110,000 in 1970, after which rural migrants increasingly flocked to Brazil’s capitals in search of industrial jobs. But the pollution contributes to health problems.
“According to the São Paulo city climate plan, our region is one of the most susceptible places to climate change in the city,” says Rosa, who lives in Jardim Apurá, a densely populated, lower-income neighbourhood on the edge of the reservoir.
In 2018, authorities completed construction of Residencial Espanha, a development of nearly 4,000 public housing units for lower-income families in Jardim Apurá, but access to housing remains a critical issue in the region.
Wanderley da Silva, 46, lives in the Favela da Fumaça on the edge of Billings. His makeshift wooden home, which has a corrugated plastic roof, floods up to his knees during heavy rains. “All of a sudden it’s really hot, and then it pours down,” he says. “Everyone knows why, after humankind destroys nature, then comes the payback.”
Wanderley da Silva with his son in their home in Favela da Fumaça. During heavy rains the house on the edge of the Billings reservoir floods. Photograph: Avener Prado/The Guardian
Bonduki says Billings serves as a stark warning of what São Paulo’s other reservoirs could become, especially Guarapiranga, in the southern zone.
“Billings is deeply compromised, but it is not a lost battle,” he says.
Bonduki blames insufficient inspections from local authorities for the reservoir’s continued degradation. “It’s a political issue. It’s about having a public authority that wants to do something. These days, we have satellites that can detect deforestation in real time.”
Illegal deforestation along the reservoir’s banks, mostly to clear land for clandestine construction, increases sediment levels in the reservoir and reduces its water storage and flood-control capacity, Marcondes says.
Livestock farming persists in parts of the environmentally protected watershed, raising concerns about erosion, runoff and water contamination. Photograph: Avener Prado/The Guardian
Almost all of Billings’ 700km (435 miles) of shoreline is technically protected under local environmental laws. Yet with a booming demand for real estate in São Paulo, powerful local actors seek to circumvent these rules for profit. Advertisements offering plots of land and properties for sale proliferate in the region and across online social media groups.
In a statement, São Paulo’s public prosecutor’s office for housing and urban planning blamed “the emergence and growth of illegal land subdivisions in the water catchment area of the southern region of the municipality of São Paulo”, and mentioned a civil inquiry “aimed at investigating the structure, planning, and possible deficiencies of state and municipal bodies”.
A stream runs through Favela da Fumaça before flowing into the Billings reservoir. The community lies within the protected watershed area. Photograph: Avener Prado/The Guardian
State legislation specifically prohibits heavy construction and dense urbanisation around the Billings reservoir. Yet using a drone from one of its polluted shorelines, it is possible to observe pockets of construction in cleared patches of Atlantic forest.
The structures are solid and professionally built, unlike the precarious dwellings of the Favela da Fumaça. Bonduki refers to them as “clandestine allotments”, speculative constructions often illegally built for future profits.
The Guardian spoke to sources, who asked not to be named, who cited collusion between local land barons, dominant political networks in the region and organised crime groups, enabled by corrupt lawyers and inspectors.
An abandoned car near Favela da Fumaça. The neighbourhood experiences flooding and has limited access to infrastructure. Photograph: Avener Prado/The Guardian
In a statement, São Paulo city hall acknowledged environmental crimes had happened around the reservoir, such as “deforestation of native vegetation”, “the disposal of solid waste, mainly construction waste and human waste” and “the clandestine sale of land plots, non-compliance with embargos and the illegal subdivision of land”.
It says that “in partnership with the state government, [it] operates an integrated water defence operation (OIDA) focused on protecting water sources such as Billings and Guarapiranga”. These operations “focus on inspection, fines, and seizures of materials and machinery, as well as the dismantling of unfinished or uninhabited constructions, based on court orders”. In 2026, the note concludes, about 20 operations have already been carried out.
A sign advertises land for sale on Estrada do Alvarenga, Pedreira, near Billings reservoir. Photograph: Avener Prado/The Guardian
The challenges facing Billings reservoir are becoming more urgent as São Paulo experiences mounting water shortages due to the climate crisis. In 2015, the Billings reservoir became part of São Paulo’s drought response, as authorities used it to help supply the city during the worst water crisis in its history. As a new crisis approaches, with climate-induced drought already depleting the city’s reservoirs ahead of the dry season, the NGO Institute of Water and Sanitation has warned that without planning, resilience is impossible.
Now, Billings is set to play a larger role during times of scarcity, with a new infrastructure project by Sabesp. In periods of crisis, clean water will be drawn from it to help supply the city.
To protect remaining green space around the reservoir, local people campaigned to create Buffalo Park, a home to 101 species of wildlife where local people can plant seeds. Matthew Richmond, a lecturer in political geographyat Newcastle University and Alameda Institute affiliate says: “Environmental activists on São Paulo’s peripheries are fighting to salvage the green spaces that survived, in the face of continued state neglect and unmet housing demand, which drives new land occupations.”
Rosa says local people have been blamed unfairly. “We suffer from environmental racism,” he says. “They blame us for the pollution, but we, the poor, black and peripheral people, keep our green spaces clean and alive.”
People walk through Parque dos Búfalos in Jardim Apurá, which lies within a protected watershed zone of the reservoir. Photograph: Avener Prado/The Guardian
A single day of extreme heat in India is associated with an estimated 3,400 excess deaths, while a heatwave lasting five consecutive days could lead to around 30,000 additional deaths, according to a study covered by the Hindustan Times. The newspaper explains that University of California, Berkeley researchers adapted findings from a multi-city study of heat-related deaths in 10 Indian cities and applied them to entire districts. India Today notes that these numbers are significant because official government counts are so low – “sometimes just a few hundred in a bad season, because many heat-related deaths are not labelled as such”. The researchers tell the Wire that their estimates are likely still “conservative”. The news outlet says “such evidence‑based estimates for heat can help us argue for investment in heat‑resilient infrastructure, systems and processes”.
BBC News reports from Banda, Uttar Pradesh, a region that was the hottest place in India in May, reaching 47-48C. The outlet notes that, according to the new study, Uttar Pradesh alone could account for more than 8,000 excess deaths during a severe five-day heatwave.
MORE ON EXTREME HEAT
A Guardian article explores how “cool roofs” with reflective paint could “help millions avoid deadly heat” in Africa.
The Hong Kong Free Press reports on NGO calls for Hong Kong to strengthen its climate adaptation policies, “as the city is expected to endure an extremely hot summer this year”.
The Independent reports that invasive Asian hornet populations are “expected to soar as the UK experiences unusually hot weather”.
One day of extreme heat tied to 3,400 excess deaths in India, nearly 30,000 over five days: Study (Hindustan Times)
Temperatures have remained above 45 degrees Celsius in parts of Madhya Pradesh, Rajasthan, Uttar Pradesh and Haryana in recent days.
A day of extreme heat is associated with an estimated 3,400 excess deaths across India, while a heatwave lasting five consecutive days could lead to nearly 30,000 additional deaths, according to a new study.
Women cover themselves with scarf to beat the heat, in New Delhi on Thursday. (Jitender Gupta)
The research, conducted by Piyush Narang and Ashok Gadgil of the India Energy and Climate Center at the University of California Berkeley, sought to address the lack of accessible district-level data on heatwave-related mortality in India, according to news agency PTI.
To estimate the impact nationwide, the researchers adapted findings from a multi-city study of heat-related deaths across 10 Indian cities and applied them to districts across the country.
Excess deaths refer to the number of deaths occurring above what would normally be expected based on historical trends.
Published in the journal Frontiers in Environmental Health, the study combined district-level mortality data from the Civil Registration System with 2024 population projections to estimate deaths linked to one-day and five-day heatwave events.
“We estimate that a single day of extreme heat causes approximately 3,400 excess deaths nationally; a five-day heatwave causes nearly 30,000,” the authors wrote.
The findings come as heatwave to severe heatwave conditions continue across northern, central and eastern India.
Temperatures have remained above 45 degrees Celsius in parts of Madhya Pradesh, Rajasthan, Uttar Pradesh and Haryana in recent days.
What areas were impacted most?
The analysis found that Uttar Pradesh alone could account for around 8,100 excess deaths during a five-day heatwave. Districts including Ahmedabad, Jaipur and Surat were projected to record more than 250 excess deaths each during a single heatwave event.
Researchers also identified a significant mismatch between mortality burden and economic capacity. Uttar Pradesh, Bihar, Madhya Pradesh, Rajasthan and Gujarat together accounted for 66 per cent of the country’s projected excess deaths during a five-day heatwave, despite contributing only 29 per cent of India’s GDP.
The researchers said the findings have important implications for India’s heat adaptation and resilience planning.
“The 2.3× GDP disproportion documented here provides a quantitative basis for arguing that federal adaptation investment, including funding under the National Disaster Management Authority and the National Action Plan on Climate Change, should be weighted toward high-burden, low-GDP states rather than allocated in proportion to population or administrative capacity,” they wrote.
100 most vulnerable districts
The study also found that the 100 most vulnerable districts, home to nearly one-third of India’s population, accounted for 44 per cent of projected excess deaths during a five-day heatwave.
Further, “heatwave mortality risk is not merely proportional to population size but is structurally concentrated in states with lower economic output (which are) precisely those with the least fiscal capacity to invest in adaptation,” the authors said.
They added that the district-level estimates are consistent with a growing body of epidemiological and modelling evidence indicating that South Asia, particularly India, faces heightened vulnerability to heat-related deaths.
Hundreds of scientists gathered in London this week to discuss the role of migration as a way for communities to adapt to climate change.
The impacts of a warming world, such as sea level rise and worsening extremes, are pushing many people around the world to leave their homes.
As a form of climate adaptation, a decision to migrate involves an array of different factors, such as politics, conflict and economic opportunity.
The conference unpacked these topics, as well as the impacts of climate change on livelihoods, relocation and gender norms across Africa and Asia.
The event had a strong focus on urban areas, with one co-convenor stating that “half of the world’s population now lives in the cities…A lot of the battles of climate adaptation will be won and lost in cities.”
Another co-convenor told Carbon Brief that the conference’s “focus really is on the climate change adaptation community, showing that migration is not a failure of adaptation – it is part of adaptation”.
Carbon Brief attended the conference to report on the sessions and speak to world-leading experts on climate-driven migration.
Migration as adaptation
The two-day conference on “mobility in adaptation to climate change” was held at Wellcome’s headquarters in London. It gathered more than 100 leading experts in migration, adaptation and climate change from countries across Europe, Africa and Asia.
“Our focus really is on the climate change adaptation community, showing that migration is not a failure of adaptation – it is part of adaptation.”
In his opening address, Adger highlighted that there were still many unknowns on climate migration – such as how and when it is an appropriate way to adapt to climate change, and who benefits and loses in these situations.
Prof Neil Adger from the University of Exeter, opening the conference. Credit: Hemant Kumar from the IIHS Media Lab.
“We are all migrants. We are all part of the same history.”
She urged the scientific community to “learn the language and the political perspective” needed to support and engage with policymakers about climate-driven migration.
Conference co-convenor Dr Chandni Singh from the Indian Institute for Human Settlements (IIHS) then delivered the first in-depth talk of the conference, outlining the current state of knowledge on climate change and migration.
She explained that cross-border migration is “emotionally and economically arduous” adding “under a changing climate, people choose to move within national borders first”. (Estimates suggest that around three-quarters of total global migration is internal.)
Singh emphasised that “mobility choices are extremely complex and nuanced, based on one’s aspirations and capabilities, social norms and asset bases”. She continued:
“Some [people] are forced to move or are displaced, others are relocated preemptively to move people out of harm’s way and others choose to stay despite escalating risk – or because resilience-building measures allow people to stay.”
She stressed that people need resources to migrate, so the poorest people are often unable to move – leaving them in a state of “immobility”. However, she also noted that most people do not want to leave their homes, stressing the “visceral reality of place attachment”.
Singh explained that many families “live dual lives”, in which family members work in the city to save money for a life back in their village. This dynamic of living across two locations is often referred to as “translocality”.
For example, Singh shared the story of residents from the Indian village of Kolar, who travel more than 100km to and from Bangalore for work every day, or else live there in informal settlements.
These workers send the money they earn back home, where it is often used to dig bore wells to access water. However, Singh warned that climate change and poor water management mean these wells often fail year after year, trapping people in this cycle of travelling to Bangalore to earn more money.
Singh also stressed the prevalence of rural-to-urban migration. She cited UN estimates (that do not explicitly include climate-driven migration), which find that around 2.5 billion people are expected to migrate from rural to urban areas by 2050. It adds that 90% of the change occurring in Africa and Asia.
Singh added:
“Half of the world’s population now lives in the cities…A lot of the battles of climate adaptation will be won and lost in cities.”
She noted that although migration “helps to manage risks”, it also has “significant financial, personal and social costs”.
Singh went on to discuss the global goal on adaptation – a set of 59 indicators to measure global progress on adaptation. Singh said that “migration and mobility are completely invisible…and therefore completely overlooked” in the goals.
She concluded by discussing the importance of new narratives on climate change and migration, saying:
“It’s the narratives and stories we tell of this moment that can help us first acknowledge what is happening, help subvert misinformation and untruths, and really demand accountability.”
Cities and livelihoods
Migration from villages to cities was a central theme of the conference.
On day two of the conference, Dr Aromar Revi, founding director of the IIHS, told delegates that the “root cause of the climate emergency is maldevelopment” and emphasised the importance of pursuing adaptation, mitigation and development goals together.
Dr Aromar Revi, founding director of the IIHS, addressing conference attendees. Credit: Hemant Kumar from the IIHS Media Lab.
“Cities concentrate opportunities, but they also concentrate poverty, inequality and risk. And that’s something that we really don’t know how to understand, especially in a changing climate.”
Throughout the conference, many of the delegates presented nuanced stories of rural-to-urban migration from individual communities. These case studies highlighted the complex, interlinking factors that drive a person’s decision to move and the wide range of outcomes.
Dr Aysha Jennath from the IIHS presented the results from her research, which unpacks the experiences of migrants who have moved from rural to urban areas, for a range of reasons including the changing climate and for better livelihoods.
Jennath and her colleagues interviewed thousands of migrants living in informal settlements, or working in informal jobs, in large cities in Bangladesh, Bhutan, India and Nepal. The researchers’ questions aimed to understand the migrants’ “wellbeing, adaptive capacity and precarity”.
Overall, Jennath found that migrants in large cities are vulnerable to poor housing, unsafe working conditions and a lack of basic social services.
They conducted hundreds of surveys to identify how households are adapting to the changing climate and grouped responses into a series of “pathways” describing the impacts of rural-to-urban migration on their livelihoods.
Dr Binaya Pasakhala and Dr Sabarnee Tuladhar from the International Centre for Integrated Mountain Development and Halvard Buhaug Peace Research Institute Oslo answering questions in a panel discussion. Credit: Hemant Kumar from the IIHS Media Lab.
For example, Tuladhar noted that in Bhutan, there is a huge emphasis on education, which has “changed the aspirations of the community – especially the youth”. This drives “huge depopulation” from rural areas as young, educated people migrate to urban areas or internationally, she said.
This mass movement into the cities provides opportunities for young people. It also provides money for the families back home – a type of finance known as remittances.
However, it also “weakened resilience” in the villages through “gungtong” – a phrase which translates literally to “empty houses”.
However, they also described the case of Nepal’s Baragon mountain community, where remittances from people who moved to urban centres has allowed communities in the villages to shift livelihoods away from subsidence farming towards commercialised farming and tourism. In this case, “migration has actually strengthened the resilience of the community”, Tuladhar said.
She told the conference that when men are forced to leave for work, due to a lack of other options, a lot of their earnings go towards “survival” and less is saved. On the other hand, “mixed migration” – such as the movement of a father and son – is often “aspirational”. It typically yields higher remittances and improves adaptive capacity back home, according to Rao.
Speaking to Carbon Brief, Rao argued that in order to “make migration a case of adaptation and not just survival in the short term”, destination cities need to do more to welcome migrants.
Prof Nitya Rao addressing conference attendees. Credit: Hemant Kumar from the IIHS Media Lab.
They suggested that as a drought intensifies, there may be a threshold at which households decide to leave. The authors compared drought indices to immigration patterns across communities in Ghana, Mali, Kenya and Ethiopia, but did not find evidence of a social tipping point.
This could be because households anticipate severe droughts and leave before they hit, the speakers suggested. They also noted that there are many government-led policy responses to drought that could affect a household’s decision to stay or leave.
For example, Kenya has a livestock-insurance policy to help families who lose animals during drought. Similarly the African Union uses satellite data to assess the severity of droughts and provide compensation to affected households.
In the final session of the conference, Dr Kasia Paprocki, an associate professor of environment at the London School of Economics and Political Science, provided a counterpoint to the idea that the vast majority of villagers want to abandon farming and move to the city.
She argued that people are often displaced from rural communities and unable to live farming lifestyles, even if they want to, adding:
“I have found that agrarian dispossession is being intensified through development interventions that are today being referred to as climate change adaptation.”
She argued for the need to “reorganise economies” to enable people to stay “if they would like to”, adding:
“Climate change adaptation and climate migration without meaningful agrarian reform will not produce climate justice.”
Immobility and relocation
Movement from rural to urban areas was not the only migration pattern discussed in the conference. Experts also discussed movement patterns including planned relocation and immobility.
The graphic below – adapted from the 2021 Groundswell report and originally published in Carbon Brief’s 2024 explainer on climate-driven migration – shows different categories of mobility and immobility due to climate change.
Different categories of human mobility and immobility due to climate change. Source: Adapted from the Groundswell report (2021).
He told Carbon Brief that immobility is “basically the absence of movement”, adding:
“The are different types of immobility. We have voluntary and involuntary immobility – and sometimes these different forms are not so clearly distinguishable, but there’s more sort of a continuum. Basically, the question is whether people are able to realise their aspirations to move or to stay.”
In his talk, Hoffman noted that media narratives around migration often focus on large movements of people, while the topic of immobility “falls between the cracks”.
Immobility is often seen as a problem experienced by the poorest and most vulnerable members of society – for example, because people cannot find or afford the resources they need, such as food or transportation, because they are not healthy enough to move or because they do not have the social network they require to make such a big change.
However, Dr Joyce Soo from the Lund University Centre for Sustainability Studies, explained that there are also instances when “wealth enables immobility”.
Soo explained that in coastal regions of Sweden that are exposed to extreme events, many residents there choose to stay, as there is “strong trust in government protection”, such as coastal defences. She explained that in this instance “immobility is linked to identity and status”.
A separate session at the conference focused on planned relocation – the organised movement of a group of people away from a site that is highly vulnerable to climate extremes.
Dr Ricardo Safra de Campos, a senior lecturer in human geography at the University of Exeter, told the delegates that planned relocation is “arguably the most controversial aspect of mobility as a response to climate change” and is usually implemented when “all other forms of in-situ adaptation have failed”.
Safra de Campos and Nihal Ranjit, a senior research associate at IIHS, worked with a team of researchers to interview people who underwent planned relocation programmes in India and Bangladesh.
They told delegates that planned relocation is often implemented when people feel unsafe – for example due to climate extremes – resulting in an “erosion of habitability”.
However, Ranjit explained “safety alone doesn’t make relocation successful”. He argued that the most important aspect of planned relocation is to ensure that migrants do not lose their livelihoods.
He presented the example of Ramayapatnam – a fishing village in India where houses were slowly being lost to coastal erosion. Ranjit explained that a planned relocation programme was set up to move people away from the coast, but that many people refused to move, as doing so would mean losing their only means of earning money.
He also noted the many Indian citizens hold a deep mistrust of the government and question the authorities’ intentions.
Relocation must be “rights-based, participatory, livelihood-centred and attentive to culture, community and long-term wellbeing”, Ranjit said.
When devastating flash floods hit Queensland in January 2011, a relocation programme led by the local government was set up to move people. The first houses were built within a year, and people were moved in “extremely fast”, Pigott-McKellar said. She explained that the goal was to keep the town together and “keep some level of social continuity”.
Conference attendees asking questions to the panel. Credit: Hemant Kumar from the IIHS Media Lab.
Conversely, when northern New South Wales faced severe flooding in 2022, the response was slow, according to Pigott-McKellar. She explained that different members of the community were offered varying levels of assistance by the state. For example, some households offered buybacks for their lost properties, while others were not.
The result was a “fragmented and dispersed mobility pathway” that saw the community split up and mistrust in the government grow.
Pigott-McKellar emphasised the importance of follow-through and continuity in relocation, stating:
“Relocation isn’t a moment in time. It is a process that unfolds over months or years”.
Legal pathways
Most human migration happens within borders. However, conference delegates also discussed cases in which people move to other countries, with a focus on the possible legal pathways.
Prof Jon Barnett, professor in the school of geography, Earth and atmospheric sciences at the University of Melbourne, explained migration patterns in the south Pacific islands.
He told delegates that climate change is causing “significant social impacts” across the islands, adding:
“While we can’t say that climate change is a major factor in migration decisions…there is a “fingerprint of climate change in [all] migration decisions.”
Barnett outlined legal migration routes for Pacific islanders, such as Fiji’s climate relocation trust fund, which has already had more than 2,000 requests, or seasonal worker schemes to New Zealand, which have already issued 137,000 visas.
However, he noted that there is a “massive burden” for the women who stay on the Pacific islands when their husbands leave. He explained that not only do women substitute for the labour of the men, but climate change can also amplify their workload by making farming more difficult and illnesses more widespread.
He concluded:
“Migration cannot be the only adaptation strategy we offer to the Pacific Islands. It’s got to be one strategy in the portfolio.”
Speaking separately to Carbon Brief, he said:
“As climate change amplifies pressures on people’s livelihoods, we may end up with a whole series of transnational populations that are kind of constantly in churn – where they’re not just living on the island, but also in Australia, New Zealand, the US.
“That’s not necessarily a bad thing, I think, so long as people still have a right to return to their islands and can do so – and are making informed choices…to manage their climate risk.”
Demographer Prof Raya Muttarak, from the University of Bologna, told delegates that Italy is the only EU country with explicit legislation for climate-related protection.
This six-month residence permit was introduced in 2018, for people who are found to have faced a “contingent and exceptional calamity”. However, she noted that there are flaws in the evidence base for making these claims, which can make it difficult for people to obtain the permits.
Changing narratives
Many speakers discussed the framing of climate change and migration in their talks. There was also a workshop on how to develop and promote “new narratives” around migration as an adaptation response to a changing climate on the first day of the conference.
Workshop on “new narratives”. Credit: Hemant Kumar from the IIHS Media Lab.
Dr Reetika Subramanian, a senior research associate at UEA who helped to organise the conference, told Carbon Brief that many media narratives around migration are “alarmist” and “crisis-based”, with a focus on people from poorer countries illegally entering wealthier countries.
However, explained that the conference convenors wanted to begin work on developing a new framing for migration – both in response to climate change and more generally – focusing on its “adaptive aspects”.
However, he said that he sees migration as a “solution”, describing it as the “fastest way for intergenerational upward social mobility for people from socially and economically disadvantaged populations”.
Prof Kerilyn Schewel, assistant professor of sociology at the University of North Carolina at Chapel Hill, told Carbon Brief that the migration community has “moved beyond a ‘push factor’ narrative – that climate change is coming and uprooting communities – to a more nuanced perspective that recognises that people are already moving for all kinds of reasons”.
She said the new “research frontier” is “seeing how environmental factors intersect with these other social or developmental outcomes”, such as education.
Liby Johnson, the executive director of development organisation Gram Vikas, told the conference his reason for hope:
Attendees of the “mobility in adaptation to climate change” conference. Credit: Hemant Kumar from the IIHS Media Lab.
“Communities are figuring this out. They are not rejecting mobility – they are asking for mobility that is safer, fairer and more dignified. Communities affected by climate uncertainty are not simply enduring crises – they are actively using mobility to diversify risk, protect dignity and build better futures.”
Revi, from the IIHS, told Carbon Brief:
“The future of mobility is much more certain than the climate futures are. People have been mobile for a very long time. That’s been an important part of the transformation of societies and economies for centuries…Mobility is part of the solution. It is not the full solution, but it’s part of the solution. People are voting with their feet and with their aspirations to make a change.”
Khaleej Times reports that more than 100 people have died “following the intense heatwave” in the southern Indian states of Andhra Pradesh and Telangana. It adds that “[m]ore than a dozen districts saw temperatures above 45C” in Andhra Pradesh, with temperatures “soar[ing]” over 48C in its East and West Godavari regions. According to ETV Bharat, Telangana’s Warangal registered 23 heat deaths, the highest in the region. While national crime record data says Telangana recorded 116 heat deaths in 2024, the state’s 2026 heatwave action plan “places the deaths at just 10 for the same period”, according to the New Indian Express, sparking concern that “the true human cost of extreme heat may remain invisible in official records”. In the neighbouring eastern state of Odisha, the state government confirmed that three people died of sunstroke, reports the New Indian Express.
Meanwhile, doctors tell the Independent that health impacts are “getting worse” because of record night-time temperatures, with Delhi recording “its warmest May night in almost 14 years” this week. As temperatures approach 46C in the capital today, authorities warn that heatwave conditions will continue over large parts of central and north-western India, says the Indian Express. According to Down to Earth, the current heatwave is pushing India’s power grid into “uncharted territory”, with “residential cooling demand now overtaking industrial demand growth in several regions”. An opinion piece in the Hindustan Times by health researchers argues that heat mortality is not caused by “temperature alone”, but “infrastructure design failure” and “severely limited access to cooling”.
The UK and Europe have experienced “mind-boggling” new temperature records for May amid a deadly heatwave, reports the Financial Times. The extreme heat has been linked to “about a dozen” deaths across the region, the newspaper says, adding: “Temperatures hit 35.1C in London on Tuesday, breaching the record of 34.8C set the previous day, according to provisional readings from the UK’s Met Office. This was 2C higher than the previous May record set in 1944. A new record was also set in Ireland on Tuesday, and agencies said France could reach new highs under a so-called heat dome where warm air from northern Africa is trapped by a high-pressure system over western Europe.” The FT quotes Prof Peter Thorne, director ICARUS Climate Research Centre at Maynooth University, who calls the temperatures “mind-boggling crazy”.
The Associated Press reports that the UK “smashed a century-old temperature record for the second time in 24 hours on Tuesday”. It adds that London experienced a “rare ‘tropical night’, defined as one in which the temperature does not fall below 20C”. It adds: “Records also fell in France, where temperatures reached 36C on Monday in the country’s southwest and widely remained above 20C at night.” France’s national weather service, Météo-France, said that its “heat dome” was “producing temperatures more than 10C above what is usual for this time of year”, according to the newswire. ABC News says the heatwave has been linked to 11 deaths in the UK and France. This includes seven people in France, five of whom died by drowning and two who suffered heat-related deaths while competing in sporting events, says the Guardian. The Independent reports that four teenagers also drowned in the UK amid the record heat. France24 reports that “restrictions on outdoor work were imposed in parts of Italy”. CNN adds that, in the UK, “a wildfire broke out near Arthur’s Seat, a hill in Edinburgh, Scotland, and hundreds of properties in south-east England were left without water as demand spiked”.
Several publications look into why Europe is experiencing a record heatwave and the links to climate change. BBC News says: “The immediate cause of the heatwave is a ‘heat dome’ – where an area of high pressure gets ‘stuck’ over Europe, trapping warm air underneath. But scientists have little doubt that human-caused climate change – largely the result of the burning of coal, oil and gas – has supercharged the heat.” Richard Betts, head of climate impacts research at the Met Office and a professor at the University of Exeter, tells BBC News: “When we have a heatwave it’s happening more severely, because it’s on top of a warming climate. I’ve been a climate scientist for 33 years and we’re seeing exactly the kinds of things that we were warning back then… [although] these records are perhaps more extreme and coming sooner than we had expected.” The Independent reports that the heatwave “has the fingerprints of climate change all over it”. The Guardian examines why heat can be a “silent killer”. Sky News has a video on whether the UK can expect more record-smashing heat. Inside Climate News and Scientific American also cover the climate links.
The U.S. was among eight countries that voted against endorsing the nonbinding ruling that said all nations must take steps to limit temperature rise to 1.5 degrees Celsius.
Vanuatu’s Climate Change Minister Ralph Regenvanu attends an International Court of Justice session on July 23, 2025, in The Hague, Netherlands. Credit: John Thys/AFP via Getty Images
The United Nations General Assembly on Wednesday voted overwhelmingly in favor of a climate justice resolution championed by the small Pacific Island nation of Vanuatu. The resolution welcomes the historic advisory opinion on climate change issued by the International Court of Justice in July 2025 and calls upon U.N. member states to act upon the court’s unanimous guidance, which clarified that addressing the climate crisis is not optional but rather is a legal duty under multiple sources of international law.
“Last year, the International Court of Justice ruled that countries have a legal duty to protect the climate, and today the world has not only reaffirmed that ruling, but committed to making it a reality. This must be a turning point in accountability for damaging the climate,” Vishal Prasad, director of Pacific Island Students Fighting Climate Change—the group that initiated the campaign to request a climate change advisory opinion from the ICJ—said in a statement.
While nonbinding, the court’s opinion is widely viewed as an authoritative interpretation of existing law. Legal experts say it could be used as persuasive authority in domestic climate litigation and in diplomatic arenas like the annual U.N. climate summits.
In its opinion, the ICJ—the principal judicial body of the United Nations—affirmed that limiting long-term global temperature rise to 1.5 degrees Celsius remains the primary goal for global climate action. It clarified that customary legal obligations apply to all countries regardless of whether they are parties to the U.N. climate treaties, and that protection of the environment is a precondition for the enjoyment of human rights.
The court also said the countries have a duty to reduce their greenhouse gas emissions, including by regulating private actors, and it suggested that continued boosting of fossil fuels could be considered an internationally wrongful act.
The resolution adopted by the General Assembly on Wednesday seeks to operationalize the court’s opinion. It calls upon countries to comply with their international obligations as clarified by the court. It also urges countries to implement measures to achieve the 1.5-degree objective, including by transitioning away from fossil fuels. And it requests that the U.N. Secretary-General issue a report exploring ways to advance compliance.
When the vote finally came, following some procedural wrangling over proposed amendments, it passed by a resounding majority with 141 member states voting in support, and 28 abstaining.
Only eight countries, Belarus, Iran, Israel, Liberia, Russia, Saudi Arabia, the United States and Yemen, voted against the resolution.
Prior to the vote, the U.S. delivered an oral statement strongly opposing the proposal and urging all countries to vote against it. “The United States continues to have serious legal and policy concerns about this resolution,” Tammy Bruce, deputy representative of the United States to the United Nations, said on the assembly floor. She called it “highly problematic” in directing states to comply with “so-called obligations,” including the duty to prevent transboundary harm to the global climate, which she said was “legally wrong.”
“The resolution includes inappropriate political demands relating to fossil fuels and on other climate topics,” Bruce added. She further argued that it makes “alarmist political statements such as the idea that climate change is an unprecedented challenge of civilizational proportions.”
In a speech before the General Assembly in September 2025, President Donald Trump called climate change the “greatest con job” in history and described renewable energy and other measures to reduce carbon emissions as a “green scam,” urging member nations to reject climate measures and consume American oil and gas.
The court itself stated in its opinion, aligning with warnings from top climate and Earth system scientists, that climate change is an “existential problem of planetary proportions that imperils all forms of life and the very health of our planet.”
In the months leading up to the vote on the resolution, the U.S. had reportedly tried pressuring other countries to oppose it and demand that Vanuatu withdraw it altogether. Vanuatu did not drop the resolution, but it did make some compromises on the text, such as eliminating a call to establish a global registry to track climate-related loss and damage.
In the end, though, the resolution endorsing the court’s opinion passed by a considerable margin, without any last-minute amendments that climate justice advocates say would have weakened the text even further. Advocates celebrated the milestone.
“Today’s vote marks an important step in advancing climate justice,” said Camile Cortez, senior campaigner on climate justice at Amnesty International. “This resolution brings renewed momentum towards ensuring accountability for climate-driven human rights harms and protecting present and future generations.”
Joie Chowdhury, senior attorney and climate justice and accountability manager at the Center for International Environmental Law, said the resolution’s power comes from the “strong majority” of countries voting yes. “It sends a clear signal in very troubled times that governments remain committed to the rule of law, and to collective action to protect the climate,” Chowdhury told Inside Climate News. “And it’s a victory for constructive multilateralism and cooperation.”
“It demonstrates the collective refusal by the global majority to let a handful of holdouts block the path to climate justice,” Chowdhury added. “And crucially, it helps ensure that the ICJ’s advisory opinion is not a one-off breakthrough, but is a lasting compass for advancing ambition and equity.”
Among a flurry of posts on social media last weekend, US president Donald Trump declared “good riddance” to a specific emissions scenario used in global climate projections.
The “RCP8.5” scenario, which envisages a future of very high carbon emissions, was “wrong, wrong, wrong”, the president wrote in block capitals.
The post was quickly picked up by right-leaning media, amplifying Trump’s misrepresentation of emissions scenarios and the role of the IPCC.
His claim follows the publication of a new set of emissions scenarios that will feed into the next IPCC reports.
While the new scenarios no longer include such high emissions as in RCP8.5, they also show it is “not possible” to limit global warming to 1.5C above pre-industrial levels without significant “overshoot”, one of the authors tells Carbon Brief.
Moreover, projections suggest that the world is still on course for between 2.5C and 3C of warming, another author says.
This level of warming was previously described as “catastrophic” by the UN.
In this factcheck, Carbon Brief looks at Trump’s comments, the debate around RCP8.5 and the “good” and “bad” news within the latest scenarios.
In the late evening of Saturday 16 May, Trump posted the following message on his Truth Social social-media platform:
“Dumocrats” is a derogatory nickname for Democrat politicians, debuted by the president in a televised Fox News interview on Thursday 14 May, according to the Independent.
By “top climate committee”, the president was presumably referring to the IPCC, the UN body responsible for assessing science about human-caused climate change.
However, the IPCC does not develop, control or own climate scenarios. Moreover, it has not published anything stating that any climate scenario is “wrong”. (For more, see: How is the IPCC involved?)
Nevertheless, right-leaning media outlets have reported on Trump’s comments, in many instances repeating his false assertion that the RCP8.5 climate scenario had been developed by the IPCC.
The New York Post misleadingly claimed that the IPCC “had quietly adjusted” its framework of emission scenarios. The Daily Caller, a pro-Trump conspiratorial US outlet, adds its own falsehoods stating that “IPCC researchers revised their modelling approach last month, swapping the extreme pathway for seven alternative scenarios”. The climate-sceptic Australian claimed that scientists had “quietly scrapped the apocalyptic forecasts that have terrified policymakers and the public”.
With Fox News also covering Trump’s comments, along with an earlier article by the Times, much of the reporting around RCP8.5 in recent days has been driven by media controlled by the climate-sceptic mogul Rupert Murdoch.
It is not the first time the Trump administration has attacked RCP8.5. In an executive order issued in May 2025 – entitled, “Restoring gold-standard science” – the White House included the climate scenario in a list of examples of how the previous government had “used or promoted scientific information in a highly misleading manner”.
Excerpt from White House executive order, issued in May 2025.
Federal agencies, it claimed, had been using RCP8.5 to “assess the potential effects of climate change in a higher warming scenario”, despite scientists warning that “presenting RCP8.5 as a likely outcome is misleading”.
The executive order came after Project 2025 – a policy wishlist for Trump’s second term published in 2023 by the Heritage Foundation, an influential rightwing, climate-sceptic thinktank in the US – criticised the climate scenario.
The manifesto said a “day-one” priority for the new government should be to “eliminate” the US Environmental Protection Agency’s “use of unauthorised regulatory inputs”, such as “unrealistic climate scenarios, including those based on RCP8.5”.
What is RCP8.5?
Scientists use emissions scenarios to explore potential future climates, based on how global energy and land use could change in the decades to come.
These scenarios are not predictions or forecasts of what will happen in the future. Therefore, Trump’s declaration that projections under RCP8.5 were “wrong, wrong, wrong” misrepresents the purpose of emissions scenarios.
Different modelling groups have produced thousands of different scenarios over the years. RCP8.5 was developed by scientists back in the early 2010s as one of a set of four consistent “representative concentration pathways”, or RCPs, for climate modellers to use.
As their name suggests, the RCPs were representative of the vast array of scenarios in the scientific literature.
Their corresponding numbers – 2.6, 4.5, 6.0 and 8.5 – do not describe temperature rise (as some mistakenly assume), but the level of “radiative forcing” that each pathway reaches by 2100. This forcing level is a measure of the change in the Earth’s “energy balance” (in watts per square metre) caused by human-caused greenhouse gas emissions.
As the highest forcing of the set, RCP8.5 was a scenario of very high emissions and extensive global warming.
When it was originally published in 2011, RCP8.5 was intended to reflect the high end – roughly the 90th percentile – of the baseline scenarios available in the scientific literature at the time.
“RCP8.5 was developed as a no-climate-policy scenario, often called ‘reference’ or ‘baseline’ scenarios. These are used to benchmark the actions of climate policy.”
Under RCP8.5, the IPCC’s fifth assessment report (AR5) in 2013 projected a best estimate of 4.3C of temperature rise by 2081-2100, compared to the pre-industrial period, with a “likely” range of 3.2C to 5.4C.
The RCPs were succeeded in 2017 by the “shared socioeconomic pathways”, or SSPs. The SSPs included a set of five socioeconomic “narratives”, which described factors such as population change, economic growth and the rate of technological development.
The SSPs were then used in the IPCC’s sixth assessment (AR6) cycle, which ran over 2015-23. The upper end of the AR6 temperature projections was provided by the successor to RCP8.5, known as SSP5-8.5, which indicated warming of 4.4C by 2081-2100, with a “very likely” range of 3.3C to 5.7C.
Why is RCP8.5 so hotly debated?
Prof Detlef van Vuuren from Utrecht University, a leading figure in the development of emissions scenarios for many years, tells Carbon Brief that RCP8.5 is a “low-probability, high-risk scenario and it was always meant like that”.
The scenario assumed a world without climate policy and was designed to explore the consequences of high levels of greenhouse gases and global warming. It was not, van Vueren says, a “best-guess scenario” of what the future held in store.
However, in some research papers, RCP8.5 was characterised as “business as usual”, suggesting that it was the likely outcome if society did not pursue climate action.
This was “incorrect”, says van Vuuren, noting that RCP8.5 “is not a likely outcome”. He adds: “It’s never been a likely outcome.”
Over time, RCP8.5 became hotly debated in academic circles, with some scientists arguing that such high emissions were becoming increasingly unlikely and others claiming that RCP8.5 was still consistent with historical cumulative carbon dioxide (CO2) emissions.
Carbon Brief unpacked the arguments in this debate in a detailed explainer in 2019.
The charts below, originally included in a 2012 Nature commentary and then updated each year by the authors, shows how projected CO2 emissions under RCP8.5 (red line) compares with the other RCPs (bold coloured lines) and observations (black line).
The left-hand chart shows total CO2 emissions, including land-use change, while the right-hand chart shows CO2 emissions from burning fossil fuels and producing cement – the dominant drivers of 21st century emissions.
Global total CO2 emissions from fossil fuels and land use (left) and global fossil CO2 emissions (left) for historical observations (black lines) and the four RCP (coloured bold lines) for 1980-2050. Originally produced as part of Peters et al. (2012) and since updated by Glen Peters and Robbie Andrew.
While emission trends up to the early 2010s approximately tracked RCP8.5, a flattening of emissions growth in the years since has meant they have not kept pace with the sustained rises that were assumed in the scenario.
Over the past decade, global emissions have more closely tracked RCP4.5, one of the two “medium stabilisation scenarios” of the original four RCPs.
The debate around RCP8.5 has not just focused on current emissions, but also on the scenario’s underlying assumptions for the future.
When it was published in 2011, the world had just seen unprecedented growth in global CO2 emissions, which had increased by 30% over the previous decade. Global coal use had increased by nearly 50% over the same period. Cleaner alternatives remained expensive in most countries and the idea of continued rapid growth in coal use seemed realistic.
Critics of RCP8.5 point to its assumptions for a dramatic expansion of coal use in the future, as well as high growth in global population.
For example, in a 2017 paper, two scientists argued that the “return to coal” envisaged in RCP8.5 would require an unprecedented five-fold increase in global coal use by the end of the century. Such an outcome was “exceptionally unlikely”, the authors wrote.
However, others have argued that while high-emissions scenarios are becoming increasingly unlikely, they still have an important role to play. For example, they highlight risks that only emerge under higher levels of warming.
In addition, research has shown that feedbacks in the climate system – where warming triggers the release of more CO2 and methane, which warms the planet further – could mean that human-caused emissions lead to a higher radiative forcing and have a greater climate impact than initially assumed.
How has RCP8.5 been replaced?
As the IPCC heads into its seventh assessment cycle (AR7), scientists have been developing the emissions scenarios and climate model projections that will – eventually – feed into its reports.
For the emissions scenarios, that process – known as ScenarioMIP – started back in 2023 at a meeting in Reading, UK. This involved scientists representing “different climate research communities”, explains van Vuuren.
This “brainstorming” session devised the outlines for the new scenarios, he says. After more meetings, these were subsequently developed into a proposal that was – after review – translated into a journal paper. After review from scientists and the public, the final paper was published in April.
The paper sets out seven all-new emissions scenarios, replacing the SSPs (and its predecessors, the RCPs). For simplicity, the new scenarios are named according to their levels of greenhouse gas emissions.
The figures below show the emissions (left) and the estimated global temperature changes (right) under the proposed scenarios, from the “low-to-negative” emissions scenario (turquoise) up to a “high-emissions” scenario (brown).
The greenhouse gas emissions for each of the CMIP7 climate scenarios (left) and the associated estimated average temperature change over 2000-2150 from a 1850-1900 baseline (right) using the FaIR emulator. Source: Adapted from Van Vuuren et al. (2026)
(It should be noted that, while the ScenarioMIP paper has been published, there remains an embargo on using the scenario data produced by integrated assessment models – often referred to as IAMs – to publish academic papers, analysis or even social media posts until 1 September this year. Carbon Brief will publish a detailed explainer on the new scenarios once the embargo lifts.)
When compared to the SSPs that came before, the range in future emissions in the new scenarios “will be smaller”, the authors say in the paper:
“On the high-end of the range, the…high emission levels (quantified by SSP5-8.5) have become implausible, based on trends in the costs of renewables, the emergence of climate policy and recent emission trends…At the low end, many…emission trajectories have become inconsistent with observed trends during the 2020-30 period.”
In other words, the combination of technological progress and action on climate change that, to date, remains insufficient, means that scenarios of very high or very low emissions are now not considered plausible.
Another way of looking at it is that the “range of potential futures has narrowed”, explains Smith, one of the authors on the paper.
If you “draw a fan or plume of potential future emissions that start in 2025”, it lies entirely within the spread of scenarios from a decade ago, he says:
“So you’ve ruled out futures at the high end. You’ve also ruled out futures at the low end – so it’s now not possible to limit warming to 1.5C, at least in the short term or the medium term.”
This is a mix of “good” and “bad” news, Smith adds.
“In the latest set of scenarios, the lowest [scenario sees] peaking at about 1.7C, so we’ve also lost that low end, but the good news is we’ve lost the high end…Back in 2010, RCP8.5 wasn’t an implausible future, we’ve now made it an implausible future, because we’ve actually bent the curve [on emissions] enough to eliminate that possibility.”
The new “high” scenario projects warming in 2100 of closer to 3.2C (with a range of 2.5C to 4.3C).
To be clear, this “high” scenario would still come with catastrophic climate impacts, even if the level of warming would remain slightly below what was set out in RCP8.5.
Van Vuuren adds that the world is “now on a trajectory to 2.5-3C of warming”. As a result, “we don’t have any scenario anymore that can reach 1.5C with limited overshoot – we will have a significant overshoot”.
How is the IPCC involved?
Contrary to Trump’s claims, the common set of future emissions scenarios used by climate scientists are not developed by the IPCC, the UN climate-science body that produces landmark reports about climate change.
Instead, the development process described above is driven by a group of Earth system modelling experts convened by the Coupled Model Intercomparison Project (CMIP).
CMIP – an initiative of another UN body, the World Climate Research Programme – coordinates the work of dozens of climate modelling centres around the world.
Working in six-to-eight year cycles, CMIP asks modelling centres around the world to run a common set of climate-model experiments – simulations that use the same inputs and conditions – that allows for results to be collected together and more easily compared.
For experiments that explore how the climate might change in the future, modelling centres are instructed to run simulations against a fixed set of future climate scenarios, each with different levels of concentrations of greenhouse gases, aerosols and other drivers of climate change.
These future emissions scenarios are revisited each time CMIP embarks on a new “phase” of climate-modelling coordination, to reflect advances in scientific understanding and the pace of real-world climate action.
The group tasked with producing the design of future scenarios, as well as the “input files” for climate models, is the “scenario model intercomparison project”, or ScenarioMIP.
CMIP aligns its work with the schedule of the IPCC, coordinating a new set of model runs for each IPCC assessment cycle.
For example, the IPCC’s AR5 in 2013 featured climate models from the fifth phase of CMIP (CMIP5), whereas AR6 in 2021 used climate models from CMIP’s sixth phase (CMIP6).
AR7 will feature models from CMIP’s ongoing seventh phase (CMIP7). The first results from CMIP7 model runs are expected later this year.
The IPCC is consulted during the CMIP process, van Vuuren tells Carbon Brief, but its input is “no different from any other review comment” that the ScenarioMIP team received.
Thus, while the IPCC relies on model runs coordinated by CMIP in its landmark reports, it does not play a role in designing future emissions scenarios, nor in deciding when they should be retired.
Dr Robert Vautard, co-chair of IPCC AR7 Working Group I, tells Carbon Brief that the IPCC does not “do or coordinate research”. Its role, he says, is to “synthesise existing knowledge” and produce “regular” reviews of climate-science literature.
He adds that ScenarioMIP is just one set of scenarios the climate-science body assesses in its reports:
“IPCC assesses all scenarios, or sets of scenarios, that the scientific community produces. IPCC does not produce scenarios. CMIP7 will be [one] set of scenarios assessed by IPCC [for AR7] – but there will be many others.”
Chennai was not on the list this time, but is no stranger to high temperatures. In the south-eastern coastal capital of Tamil Nadu, extreme humidity and heat are inescapable facts of life.
“The heat is by no means manageable, but we have no choice but to deal with it,” said Mohammed S, a 29-year-old grocery platform delivery worker, speaking to Carbon Brief.
Last year, Chennai became India’s first ever city to roll out air-conditioned lounges for millions of gig workers, like Mohammed, navigating India’s increasingly hotter cities.
Gig workers leave their slippers outside the lounge. Credit: Ishan Tankha / Scorched
Through the building’s tinted windows, workers wearing synthetic jerseys emblazoned with food delivery app logos are stretched out on wooden benches meant to seat 25 people.
The lounge has charging points for phones, a water cooler and a unisex toilet. It might not seem like much, but workers tell Carbon Brief that it has made a “huge difference” to their lives – even on a day when the air conditioner stopped working.
“Before this, life was very difficult,” said Mohammed. He continued:
“We would park our [electric] bikes and try to find a tree to sleep under, stop for tea and tea shop owners would tell us we couldn’t sit there for more than 10 minutes, try to rest in a building’s stairwell and be chased away, then try to find shade under a flyover. Now we can sit in the AC and avoid the worst of the heat.”
Dinesh, 27, said his day starts at dawn before the sun is up, picking up packages from companies in north Chennai – another critical heat hotspot.
For the next seven hours, there is no “off point” or breaks for Dinesh as apps rush deliveries.
Some of Chennai’s gig workers told Carbon Brief they try to avoid the worst of afternoon temperatures from noon to 3pm, but for many – especially migrant workers – sitting back in the lounge is not a choice they can afford. One of them explained:
“If you don’t have cash to cover your bills or have to send money back home, you head out into the heat for a 12-hour shift and hope for the best.”
Dinesh checks his orders in the gig worker’s lounge. Credit: Ishan Tankha / Scorched
Feeling ‘gear’
In Chennai, heat might be normalised, but it has its own vocabulary. Speaking to Carbon Brief, the city’s gig workers, auto rickshaw drivers and fish sellers used an all-encompassing term – “gear” – to describe their symptoms, including dizziness, exhaustion and nausea.
Last summer, researchers offered Delhi’s gig workers a Rs 200 (roughly £2) cash transfer on the first day of a heatwave, to provide them with a means to achieve “real-time” adaptation to heat risk. Workers who received a cash transfer reported fewer heat-related symptoms, according to the study.
Asked if they would accept similar incentives to stay home on 40C days, workers in the T Nagar lounge expressed disbelief. Dinesh – who also trains technicians on how to repair air conditioners to support his income – told Carbon Brief:
“They [the apps] offer us incentives to go out in the heat when there are fewer riders.”
Barring a few, none of the dozens of outdoor workers Carbon Brief spoke to had an air conditioner at home or in their hostels, making the lounge the only place they could cool down.
Anna Bawden Health and social affairs correspondent
Sat 16 May 2026 05.00 BST
The climate crisis should be declared a global public health emergency by the World Health Organization, or millions more people will die unnecessarily, leading international experts have said.
The international spread of vector-borne disease, such as dengue and chikungunya, as well as the health impacts of extreme weather events, global heating, food insecurity and air pollution make a Pheic necessary, said the commission’s report, which will be presented to European ministers on Sunday before the WHO’s world health assembly starts on Monday.
Pheics are the highest level of health alert. Previous declarations include infectious diseases such as Covid and Mpox. While declaring one would not on its own reverse climate change, it would trigger the kind of coordinated international response that the scale of the health crisis demands but has not yet materialised.
The 11-strong independent commission, which includes former health and climate ministers, said: “Far from being a fading priority or fake news, climate change poses an immediate and long-term threat to health, economic, food, water, environmental, personal, community and national security.”
Andrew Haines and Katrin Jakobsdóttir, the commission’s chief scientific adviser and chair respectively. Photograph: WHO/Hedinn Halldorsson
In an interview with the Guardian, Katrín Jakobsdóttir, a former prime minister of Iceland who chaired the commission, said: “The climate crisis may not be a pandemic, but it’s still a public health emergency that threatens humanity’s very health and survival. And if we don’t act more quickly and comprehensively, many millions more people could die or face life-changing illness.”
Sir Andrew Haines, a professor of environmental change and public health at the London School of Hygiene & Tropical Medicine, and the commission’s chief scientific adviser, said: “WHO has already recognised that climate change is a major threat to global health. What we’re asking for is a step further.”
He added: “If we carry on emitting at current rates, that will accelerate the risks to health for both current and future generations including: more people suffering and dying from excess heat, floods and infectious diseases, air pollution from wildfires, more preterm births and more food insecurity.”
The commission also urged governments to stop subsidising fossil fuels, which are directly responsible for 600,000 premature deaths a year in Europe alone. The region spends about €444bn (£387bn) a year on subsidies for oil and gas production, the report said. In 12 European countries, fossil fuel subsidies exceeded 10% of national health expenditure in 2023 and in four exceeded the entire health budget, the report observed.
“This is not a sustainable energy policy. It’s really more of a public health failure,” Jakobsdóttir said. “And it’s one that could get a lot worse. New subsidies for fossil fuels as well as countries considering redrilling in the wake of the Iran crisis would be catastrophic for health.
“European governments are subsidising the very industries responsible for their own citizens’ premature deaths. We need health leaders to really step into the climate debate and not just be on the receiving end of it.”
The commission urged governments to stop subsidising fossil fuels, which are responsible for 600,000 premature deaths a year in Europe. Photograph: Christopher Furlong/Getty Images
The report also called for measures to tackle disinformation, greater use of national climate health impact assessments, as well as recognition that climate change was also a mental health crisis.
Jakobsdóttir said: “The way to challenge climate scepticism and misinformation is simple: make it personal. Climate change is not happening somewhere else, to someone else, in the future. It is shortening lives in European cities right now. It is filling hospitals. It is driving anxiety and stress and other mental health issues. And the policies that would fix it – clean air, active travel, insulated homes, sustainable food – are exactly the policies that make people healthier and happier today.
“When the health argument and the climate argument are the same argument, it becomes very hard to oppose.”
The report also recommended that countries’ healthcare systems needed to become more resilient to the rapidly changing environment in order to try to adapt as much as possible.
“Every country needs to be aware of where its health facilities are situated, how likely it is to be flooded and how they would deal with an extreme and prolonged heatwave,” Haines said, pointing out that hospitals were often built on floodplains and frequently were not energy efficient.
“Even in the UK, which is a temperate country, we know that many hospitals struggle when it comes to extreme heat,” he added. “Many of the buildings were designed before climate change.”
The healthcare sector accounts for 5% of global emissions worldwide, so needs to prioritise adaptation to become more resilient, the report concluded.
Members of the emergency military unit try to extinguish a wildfire in Ourense province, Spain, in August 2025. Photograph: Pablo Blázquez Domínguez/Getty Images
Responding to the recommendations, Dr Hans Kluge, the WHO’s regional director for Europe, said: “The conflicts in Ukraine and the Middle East have clearly shown what fossil fuel dependency really means – not just higher bills, but strained or broken health systems, disrupted food and fuel supplies and societies under pressure.
“The case for acting on climate now is not just environmental. It is a security argument, a health argument and an economic argument, all at once. And it is a moral imperative.”
Kluge added: “The decisions taken by governments today will determine the disease burden carried by people who are currently in primary school. It now falls to the rest of us to act on their recommendations and protect future generations. I commit to ensuring that climate change is treated as the health emergency it is across the 53 member states of the WHO European region.”
Johan Rockström, the director of the Potsdam Institute for Climate Impact Research, welcomed the report. He said: “The current state of the planet, where we are breaching multiple planetary boundaries, and which manifests itself as public health threats impacting millions of people across the world, provides ample scientific evidence that climate change should be declared a public health emergency of international concern.”
AI forecast models offer some clear benefits over traditional physical models, but they are ill-equipped to handle the increasing volatility of a warming climate.
On November 12, 1970, the Bhola cyclone slammed into the coast of what was then East Pakistan. The storm brought maximum sustained wind speeds of 130 miles per hour (205 kilometers per hour) and a 35-foot (10.5-meter) storm surge, killing an estimated 300,000 to 500,000 people.
Today, the Bhola cyclone remains the deadliest tropical storm on record. But if it had struck a decade later, it might not have been so devastating. Weather forecasting changed dramatically in the 1970s as meteorologists adopted physics-based computer models that improved storm prediction. With the rise of AI, forecasting is evolving again—but this time, experts worry the new models may be less reliable when it comes to predicting unprecedented weather events.
Researchers are calling this the “gray swan” problem. Gray swan weather extremes are physically plausible but so rare that they are poorly represented in training datasets. The trouble is, climate change is leading to more first-of-their-kind weather extremes. Think: the 2021 Pacific Northwest heatwave. This event was so severe that it would have been virtually impossible without climate change.
Physical forecast models can simulate gray swan events like the Pacific Northwest heatwave, though they are labeled extremely rare. They can do that because they are built on the laws of physics. AI models are trained on past weather data, wherein gray swans are practically nonexistent.
“They fail on gray swans,” Pedram Hassanzadeh, an associate professor of geophysical sciences at the University of Chicago, told Gizmodo. He and his colleagues published a study last April that removed all Category 3 through 5 hurricanes from an AI model’s training dataset, then tested it on Category 5 storms. The results showed that AI models cannot accurately forecast previously unseen events, as this would require extrapolation.
“The concern isn’t occasional misses. It’s that AI models can miss silently, producing confident forecasts of unremarkable weather while a record-breaking event is unfolding,” Rose Yu, an associate professor of computer science and engineering at the University of California San Diego, told Gizmodo in an email.
“Other risks matter too,” she said. “AI models can violate conservation laws in subtle ways that don’t show up in standard metrics. When they bust a forecast, diagnosing why is harder. They depend on stable observing systems, which is a real concern given current pressure on satellite programs. And institutionally, if we consolidate around AI too quickly and let physics-based infrastructure atrophy, we lose the redundancy that currently catches AI’s failures.”
The case for AI forecasting
Despite these pitfalls, meteorologists are rapidly adopting AI forecast models, and it’s actually easy to understand why. They’re faster, cheaper, and require far less computational infrastructure than physical models. When it comes to predicting typical weather patterns and events (not gray swans), their accuracy is comparable and improving rapidly.
“The typical rate of progress for most state-of-the-art physical models has been something like a day more accurate per decade, which doesn’t sound like a lot, but that’s consequential,” Andrew Charlton-Perez, a professor of meteorology and head of the School of Mathematical, Physical, and Computational Sciences at the University of Reading, told Gizmodo.
“The rate of accuracy growth for machine learning models has vastly exceeded that,” he said. “They are now competitive, and two-three years ago, they were not even in the same ballpark.”
During the 2025 Atlantic hurricane season, for example, Google DeepMind’s model outperformed nearly every physical model on storm track and intensity. In fact, since 2023, leading AI models such as GraphCast, Pangu-Weather, and the ECMWF’s AIFS have matched or outperformed the best physical models on medium-range forecasting metrics, according to Yu.
AI models are proving especially valuable in parts of the world that lack traditional forecasting resources—regions that are often on the frontlines of climate change. Hassanzadeh co-directed an initiative that provided 38 million farmers across India with AI-based monsoon forecasts, giving them up to four weeks’ advance notice of the rainy season’s onset.
“A lot of countries were left behind in that first revolution of weather forecasting, because [traditional] weather forecasting requires a supercomputer, hundreds of millions of dollars, various fields, workforce, and experts,” Hassanzadeh explained. AI models, by comparison, are far more accessible to lower-income countries.
Filling the knowledge gaps
Still, rapidly adopting these models without addressing the risks would be dangerous, especially in parts of the world highly vulnerable to the impacts of climate change. Shruti Nath, a postdoctoral research associate at the University of Oxford, recently co-authored an editorial calling for more rigorous testing of AI forecast models before public agencies widely adopt them.
“There is still a lot of work to be done in understanding the limits of these models, alongside where they could supplement physical models and why,” she told Gizmodo in an email.
Nath’s editorial outlines a framework for testing AI forecast models that would deliberately withhold a designated set of “iconic” extreme events (like the Pacific Northwest heat wave, for example) from the training dataset. These events would be reserved solely for testing in order to assess the models’ ability to extrapolate unprecedented weather extremes, or gray swans.
Actually implementing this AI Retraining Without Iconic Events (AIRWIE) protocol “would require the meteorological community to agree on which high-impact events constitute a rigorous benchmark,” the editorial states. This would be a great undertaking, but Nath believes most researchers agree that there is an urgent need for this kind of testing.
“We need to be a bit more organized, however, in ensuring that proper protocols can be followed and that robust safeguards are put in place and maintained by the community,” Nath said. “This is difficult when things are in such a hype phase and no one wants to miss out on the bandwagon.”
Other researchers, like Hassanzadeh, are developing ways to teach AI forecast models to predict gray swans. He and his colleagues are investigating whether combining AI systems with “relevant sampling” methods—which allow them to generate samples of gray swan events—can improve the models’ ability to extrapolate unprecedented extremes.
Efforts to understand and address the limitations of AI forecasting will be critical, because there’s no turning back now. AI is already reshaping the way we predict the weather, and as the climate becomes increasingly volatile, meteorologists will need every tool in their arsenal to be sharp and reliable. Despite their current limitations, there is much to gain from continuing to push these systems forward and figuring out how to best integrate them with physical forecasting.
“The research agenda is about making AI models physically consistent, well-calibrated, and robust to distribution shift,” Yu said. “Abandoning this approach because of the gray swan problem means giving up the biggest improvement in forecasting in a generation.”
A panel of global experts has been launched to provide scientific input for countries that want to reduce their dependence on fossil fuels and manage the growing risks of high oil prices, geopolitical conflict and extreme weather damage.
The initiative was announced on the opening day of a groundbreaking climate action meeting in Santa Marta, where the Colombian hosts set out a draft roadmap for their own national energy transition.
It marked a high-ambition start to the first global conference on transitioning away from fossil fuels. The event, from 24-29 April, has brought together more than 50 nations, dozens of subnational governments and an estimated 2,800 civil society representatives in a “coalition of the willing” aimed at reinvigorating international efforts to reduce planet-heating emissions from oil, gas and coal.
The new science panel for global energy transition is intended to add intellectual weight to those efforts. Experts in climate, economics and technology will offer advice to policymakers looking to create roadmaps out of the fossil fuel era.
Based partly on the model of the UK’s climate change committee, it includes national and sector-level milestones for eliminating fossil fuels in line with scenarios that return global heating to 1.5C by the end of the century.
The panel will be chaired by Vera Songwe, the Cameroonian co-chair of the High Level Expert Panel on Climate Finance; Ottmar Edenhofer, the German director and chief economist of the Potsdam Institute for Climate Impact Research; and Gilberto M Jannuzzi, a Brazilian professor of energy systems at Universidade Estadual de Campinas.
Jannuzzi said there was still time to bring about an energy transition. “Technically, there is no problem. The problem is how to disseminate the information and secure the financing,” he said.
The panel’s formation follows calls by the president of Cop30 in Belém to establish roadmaps for accelerating the transition away from fossil fuels and deforestation.
“We encourage governments and institutions to draw on the panel’s analyses, policy briefs and country-level engagement to strengthen nationally determined contributions, inform sectoral strategies and accelerate implementation of just and orderly energy transitions across different national contexts,” André Aranha Corrêa do Lago said.
The Colombian and Dutch hosts of the Santa Marta meeting have also expressed support for the initiative, which has been convened by Johan Rockström of the Potsdam Institute for Climate Impact Research and Carlos Nobre of the University of São Paulo.
Rockström said the presence of a third of the world’s countries at Santa Marta would help keep the transition from fossil fuels on the global agenda and demonstrate how it can be achieved. “These are solvable problems that can create better futures for local communities,” he said. “The science panel can play a unique role in providing updates on what needs to happen year by year.”
The 54 countries that are attending the fast track transition conference include major fossil fuel producers such as Nigeria, Mexico, Brazil and Angola, for whom giving up a major source of income will be challenging.
Those challenges, and their possible solutions, were outlined in the new draft roadmap for Colombia, which gets about half of its export revenues from fossil fuels. Drawn up by global experts with Colombian officials, the plan says that a rapid switch to cheaper and more efficient renewables would bring long-term benefits to energy security, health, the climate and the economy.
Reducing fossil fuel use by 90% by 2050 would allow energy demand to continue growing while generating direct economic benefits estimated at $280bn over the next 24 years, the roadmap calculates. “Considerable upfront investment is needed to achieve this transition, but by the early 2040s, this delivers annual net savings to the Colombian economy,” the plan states.
The authors stressed this outline needs to be debated and refined, but they hoped it could help to inform the national debate.
“We are really excited about the roadmap,” said Prof Piers Forster, director of the Priestley Centre for Climate Futures at the University of Leeds. “It shows that it is cost effective to phase out petrol and diesel. And also very cost effective to build renewables. And now we all appreciate the importance of energy security.”
He said he hoped other countries would follow suit and develop their own roadmaps and climate councils. “We want to work with countries to build internal capacity to do it themselves because they understand the opportunities, roadblocks and political sensibilities within their countries.”
Na última noite do Grupo Especial, nessa terça (17/02), foram 800 atendimentos médicos nos seis postos da Secretaria Municipal de Saúde (SMS) instalados no Sambódromo. Desses, mais de 300 foram causados pelo calor. E olha que os termômetros marcavam “apenas” 28°C na região da Apoteose – mas imaginem usando uma fantasia de 20 kg, plumas, paetês, luz de refletores e muito calor humano misturado ao álcool?
Entre as principais ocorrências, além da turma derretida, estão a descompensação de doenças crônicas, picos de pressão, mal-estar e fadiga por esforço, dor de cabeça, cortes, entorses, lesões ortopédicas, contusões e intoxicação por consumo exagerado de bebidas alcoólicas.
No balanço geral de todos os dias de desfile, foram 2.843 atendimentos. Destes, 167 precisaram ser encaminhados para hospitais da rede. Durante a passagem de algumas escolas, foi possível ver o resgate de integrantes na pista e de foliões nas frisas e arquibancadas.
Fevereiro no Rio é mistura de loteria climática com teste de sobrevivência, a cidade já viveu carnaval debaixo d’água e sob calor escaldante. Segundo pesquisas sobre aquecimento global, não há Fundação Cacique Cobra Coral que resolva contrato com o clima em definitivo. Num futuro não muito distante, o carnaval vai precisar mudar o calendário?
O biólogo Mario Moscatelli diz: “A conta climática é imprevisível, e estamos longe de entender perfeitamente como o sistema funciona. O Rio não consegue resolver nem os velhos problemas estruturais, quanto mais se preparar para os novos. Ondas de calor estão cada vez mais frequentes, enchentes seguem devastadoras, e a perda de biodiversidade — apontada por especialistas como a sexta extinção em massa — já é uma realidade”.
Ele lembra ainda que ano de eleição também é ano de escolha: “A forma de mudar esse ecocídio global passa pelos votos de pessoas mais antenadas com a questão ambiental e menos com as páginas policiais relacionadas a superfaturamentos, desvios de verbas, criação de mais facilidades para as castas públicas e por aí vai. Quem não for 300% competente na gestão dessa nova realidade vai pagar um preço muito alto, tanto do ponto de vista de perdas materiais, como humanas e ambientais. Acabou a fase da improvisação”.
Skardu, Pakistan – As Pakistan grapples with the effects of rising temperatures that are melting its glaciers, residents in the country’s high-altitude Himalayan region have adopted a traditional technique, known as glacier grafting, to counter water scarcity.
Pakistan, home to an estimated 13,000 glaciers, ranks among the top 10 most climate-vulnerable nations, even though it contributes less than one percent of global emissions.
As global warming worsens, the effect of more glaciers melting is “likely to be significant”, Pakistan’s National Disaster Management Authority (NDMA) said last year.
What is glacier grafting?
Glacier grafting, locally known as glacier marriage, is a technique that involves “planting” ice at carefully chosen high-altitude locations to create new artificial glaciers – a process that experts say dates back centuries.
The technique involves storing ice fetched from glaciers closer to human settlements amid periods of water scarcity.
According to Zakir Hussain Zakir, professor and researcher at the University of Baltistan in Skardu, the earliest recorded instance of glacier grafting goes back to the 14th century, when the Sufi saint Mir Syed Ali Hamadani grafted a glacier in the village of Giyari.
“That glacier blocked the route through which invaders from Yarkand came to loot the people,” Zakir, who has researched the practice in the Himalayan region, told Al Jazeera.
Over time, what began as a defensive act evolved into a method for managing water scarcity in one of the world’s most fragile mountain ecosystems.
People in the Ladakh region across the border on the Indian side also use traditional knowledge to preserve ice amid climate change and receding natural glaciers. A relatively newer technique has been developed in Ladakh to create an “ice stupa”, which is formed after spraying water in freezing temperatures. The conical shape ice structure remains frozen for a longer period as its surface is not fully exposed to the sun.
How is glacier grafting carried out?
So-called “male” and “female” ice is sourced from different locations and brought together to create an artificial glacier. Villagers where this technique has been implemented as well as experts told Al Jazeera that volunteers go out to collect around 200kg (441 pounds) of “male” ice from one valley and “female” ice from another. Male ice is typically black in colour, while female ice is usually lighter, providing more fertile water that enhances agricultural productivity, according to locals.
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In ancient times, due to the absence of available transportation as well as steep, narrow and slippery routes through the mountains, volunteers would travel on foot for several days, carrying the ice in traditional wooden cages on their backs.
The process requires specific materials: coal, grass, salt and water collected from seven different streams. Before setting out to the grafting site, the group would recite Quranic verses, perform spiritual rituals and pray for success.
The material, including both sets of ice blocks, would be carried to the site while “strictly following environmentally respectful and culturally sacred practices”, the locals said.
They would avoid the use of plastics, refrain from immoral actions and only consume locally produced foods such as wheat, barley, apricots and homemade bread during the process.
Humour, music, or harm to living creatures is strictly prohibited, as the procedure was viewed as both a spiritual and ecological responsibility.
At the grafting site, a small trench would be dug in a safe area, away from avalanche or flood-risk zones. The male and female ice pieces would be carefully layered together, mixed with salt, coal and grass.
“The male pieces are put on the right, while on the left, female ice pieces,” Zakir said.
Pakistan is home to an estimated 13,000 glaciers [Faras Ghani/Al Jazeera]
Water collected from the seven streams would slowly be dripped over the ice to help bind the layers.
Over several months, the pieces fused into a single ice mass. If the site received seasonal snowfall, the mass would gradually develop into a glacier. After surviving for at least three years and enduring seasonal snow cycles, the artificially grafted glacier would expand. Over the next few years, it would become a reliable water source.
Zakir added that site selection is critical in the process: north-facing slopes, strong winds, less sun exposure and protection from direct flowing water are essential.
Rituals, discipline and collective labour
Locals and experts told Al Jazeera that the deep spiritual and cultural aspects surrounding this technique are what distinguish glacier grafting from purely technical interventions.
Ice pieces are never allowed to touch the ground and must remain in continuous motion from collection to planting.
“Often, vehicles that carry these ice pieces are never switched off,” Zakir recalled, adding that those helping out are forbidden from speaking, using plastic or relieving themselves near the site.
“If one volunteer feels tired, without lying down, he will pass the basket [carrying the ice] to another volunteer.”
Historically, glacier grafting has also concluded with local music known as Gang Lho that is sung directly to the ice. One such song, the professor recalled, addresses the glacier as a living being, calling it “my dear baby glacier” having “pastures to grow… mountains to climb”.
Often, volunteers and villagers would have tears in their eyes, praying for the glacier’s establishment and survival in order to aid their survival and livelihood.
How long does glacier grafting take? Is it guaranteed to survive?
A successfully grafted glacier can start supplying water within two decades, making it a long-term investment in water security.
However, experts warn that the process is vulnerable – not only to a failure of the natural process, a lack of snowfall, drops in temperatures, and climate change, but also to conflict.
“In abnormal climatic conditions, such as during war, the process may fail,” Zakir warned.
“Both India and Pakistan have deployed military forces in the glaciers, and the bullets they use, as well as the movement of soldiers and equipment, are very harmful to glaciers.”
The South Asian neighbours have fought three wars over the disputed Kashmir region, which they both govern parts of.
Can glacier grafting solve water scarcity problems?
The mean temperature in Pakistan since the 1950s has risen by 1.3 degrees Celsius (2.34 degrees Fahrenheit), which is twice as fast as the global mean change, according to the World Bank.
With temperatures rising globally, glacier grafting may not be able to offer a wholesome solution to Pakistan’s melting glaciers problem. But it remains a powerful example of how Indigenous knowledge, culture and collective care have long shaped survival in the mountains.
Locals told Al Jazeera that glacier grafting is now more critical than ever to counter water scarcity and erratic snowfall that cause problems for irrigation, domestic consumption and livestock.
They also worry that the practice of glacier grafting is rapidly disappearing. Younger generations, drawn to urban centres and alternative livelihoods such as tourism, education and business, no longer engage in traditional irrigation.
This shift has disrupted the intergenerational transfer of Indigenous knowledge, they lamented.
This story was produced in partnership with the Pulitzer Center.
O cientista sueco Johan Rockström, diretor do Instituto Potsdam para Pesquisa de Impacto Climático (PIK), é reconhecido mundialmente por ter desenvolvido a estrutura dos limites planetários
Por Naiara Bertão
Um Só Planeta — São Paulo
28/08/2025
cientista sueco Johan Rockström, diretor do Instituto Potsdam para Pesquisa de Impacto Climático (PIK), — Foto: Naiara Bertão / Um Só Planeta
O cientista sueco Johan Rockström, diretor do Instituto Potsdam para Pesquisa de Impacto Climático (PIK), voltou a chamar atenção para os riscos que a humanidade corre ao avançar sobre os limites ambientais que garantem a estabilidade da Terra. Reconhecido mundialmente por ter desenvolvido a estrutura dos limites planetários em 2009, Rockström afirmou que já estamos numa situação perigosa, em que a própria sobrevivência de sociedades humanas complexas está em jogo.
O cientista participou nesta terça-feira (26) do encontro Futuro Vivo, evento organizado pela empresa de telecomunicações Vivo com o objetivo de ser um espaço de debate sobre os limites da tecnologia e de como desenvolver soluções sustentáveis para o meio ambiente.
Os limites planetários mostram exatamente os espaços seguros para um planeta estável — Foto: Divulgação/Netflix
Na palestra, ele retomou o conceito dos nove limites planetários que regulam o funcionamento da Terra para alertar a todos sobre os riscos que a humanidade corre ao ultrapassar os limites ambientais que garantem a estabilidade do planeta.
“Estamos começando a atingir o teto dos processos biofísicos que regulam a resiliência, a estabilidade e a habitabilidade da Terra”, disse em sua palestra.
“Seja em São Paulo, em Estocolmo ou em Pequim, o que acontece em diferentes partes do planeta interage e influencia a estabilidade de todo o sistema climático, da hidrologia e do suporte à vida na Terra. É por isso que precisamos definir um espaço operacional seguro para o desenvolvimento humano no planeta.”
A teoria dos limites planetários definiu estes princípios: clima, biodiversidade, uso da terra, ciclos de nitrogênio e fósforo, recursos hídricos, oceanos, poluição do ar, camada de ozônio e poluentes químicos. “O grande avanço científico não foi apenas identificá-los, mas quantificá-los”, explicou.
Segundo o cientista, a noção de que era possível explorar recursos sem limites ficou no passado. “Há 50 anos, não precisávamos disso. Hoje, ocupamos o planeta inteiro e não há mais espaço para sermos insustentáveis.”
Logo no início de sua palestra, Rockström lembrou que o planeta atravessou, nos últimos 10 mil anos, o período mais estável de sua história recente: o Holoceno. Foi nessa era que surgiram a agricultura e as civilizações humanas, sustentadas por condições climáticas e ecológicas favoráveis. “O Holoceno é o único estado do planeta que sabemos com certeza ser capaz de sustentar nossa vida. É o que eu chamo de Jardim do Éden”, afirmou.
Seca histórica ameaça valiosas colheitas na Califórnia, maior produtora de amêndoas no mundo — Foto: Justin Sullivan / Getty Images
Contudo, essa estabilidade está sendo rompida com a ascensão do Antropoceno, a era em que o ser humano é a principal força de mudança no planeta. “O sistema econômico global está no banco do motorista, superando os impactos de erupções vulcânicas, variações solares e terremotos. Essas forças naturais ainda existem, mas nós as dominamos e até as sobrepujamos.”
Para Rockström, a pressão sobre os sistemas naturais pode levar a mudanças abruptas e irreversíveis.
“O planeta é um sistema complexo e auto-adaptativo, que tem pontos de inflexão. Se empurrarmos demais, a Amazônia, a Groenlândia ou os recifes de coral podem colapsar e passar para estados que deixarão de nos sustentar. Esses pontos de virada não apenas reduzem a resiliência dos ecossistemas, mas também ameaçam diretamente economias e sociedades.”
Para o cientista, os dados não deixam dúvidas. “Estamos em uma situação perigosa. Estamos ameaçando a saúde de todo o planeta.” Ele explica que foram definidas zonas seguras, zonas de incerteza e zonas de alto risco na metodologia dos limites planetários.
“O problema é que, em 2023, já mostramos que seis desses nove limites estão sendo ultrapassados — clima, biodiversidade, mudanças no uso da terra, consumo de água doce, excesso de nitrogênio e fósforo, e a enorme carga de substâncias químicas no sistema terrestre.”
Sobrevoo do Greenpeace mostra a expansão do garimpo na terra Yanomami em 2021 — Foto: Christian Braga/Greenpeace
Essa constatação tem relação direta com o debate sobre políticas públicas no Brasil e no mundo. A Amazônia, por exemplo, é um dos sistemas mais próximos de um ponto de inflexão — quando mudanças irreversíveis podem ser desencadeadas. “O planeta é um sistema complexo e auto-adaptativo, que tem pontos de inflexão. Se empurrarmos demais, a Amazônia, a Groenlândia ou os recifes de coral podem colapsar e passar para estados que deixarão de nos sustentar”, alertou.
Apesar do alerta, o cientista vê na pesquisa uma ferramenta de esperança. Desde 2009, a metodologia dos limites planetários foi refinada e hoje já permite oferecer parâmetros para políticas públicas e decisões empresariais. “Hoje conseguimos oferecer à humanidade um mapa de navegação do Antropoceno. Definimos as fronteiras seguras para o futuro da vida na Terra. Isso nos dá a possibilidade de sermos responsáveis em escala planetária”, disse.
Para Rockström, reconhecer esses limites não é apenas uma questão científica, mas de sobrevivência. “Estamos ameaçando a saúde de todo o planeta. Esse é o diagnóstico da ciência, e ele deve servir como base para qualquer estratégia de desenvolvimento daqui para frente.”
A boa notícia, diz, é que já temos as soluções e já sabemos o que deve ser feito. Seguir o Acordo de Paris e buscar frear o aquecimento do planeta em 1,5ºC é primordial e, segundo ele, é possível. Mas o ritmo de mudanças precisa acelerar urgentemente.
Papel da política internacional e da COP30
A fala de Rockström chega em um momento estratégico: o Brasil se prepara para sediar a COP30, em Belém (PA) em novembro. A conferência deve ser marcada pelo foco em florestas tropicais e na transição justa para países em desenvolvimento. O conceito dos limites planetários, cada vez mais adotado por governos e empresas, oferece um “mapa de navegação” para esse processo.
“Hoje conseguimos oferecer à humanidade um mapa de navegação do Antropoceno. Definimos as fronteiras seguras para o futuro da vida na Terra. Isso nos dá a possibilidade de sermos responsáveis em escala planetária”, disse.
Para especialistas, integrar esse tipo de ciência ao processo político será crucial para que a COP30 avance em compromissos concretos — especialmente em temas como desmatamento zero, proteção da biodiversidade e financiamento climático.
“Estamos ameaçando a saúde de todo o planeta. Esse é o diagnóstico da ciência, e ele deve servir como base para qualquer estratégia de desenvolvimento daqui para frente”, concluiu Rockström.
Dados dos Centros de Controle e Prevenção de Doenças mostram que o calor extremo é o fenômeno climático mais mortal dos EUA. — Foto: NASA
No dia 28 de junho de 2021, a americana Julie Leon, de 65 anos, foi encontrada inconsciente em seu carro, no caminho para casa. Paramédicos tentaram reanimá-la, mas sem sucesso. Mais tarde, o legista determinou que a causa da morte foi hipertermia, condição na qual a temperatura corporal aumenta de forma excessiva e perigosa, geralmente acima de 40°C.
Agora, passados quase quatro anos, a filha da vítima, Misti, entrou com um processo inédito em Washington contra ExxonMobil, BP, Chevron, Shell, ConocoPhillips e Phillips 66.
A ação por homicídio culposo é a primeira movida em nome de uma vítima individual das mudanças climáticas nos Estados Unidos, e busca responsabilizar essas empresas pelo papel que desempenharam na causa da morte.
Na época em que Leon faleceu, áreas do noroeste do Pacífico dos Estados Unidos e Canadá experimentaram temperaturas nunca antes observadas, com recordes quebrados em muitos lugares em vários graus Celsius. Em Seatle, onde ela vivia, no dia da sua morte, a temperatura subiu acima de 38°C pelo terceiro dia consecutivo.
Cientistas da World Weather Attribution (WWA) avaliaram, com base em observações e modelagem, que a onda de calor do Pacífico Noroeste de 2021, como foi chamado o fenômeno, seria virtualmente impossível sem as mudanças climáticas causadas pelo homem.
A WWA é uma iniciativa científica internacional que busca avaliar a influência das mudanças climáticas, causadas por atividades humanas, principalmente queima de combustíveis fósseis, em eventos extremos de clima, como ondas de calor, secas, inundações e tempestades.
“As grandes petrolíferas sabem há décadas que seus produtos causariam desastres climáticos catastróficos que se tornariam mais mortais e destrutivos se não mudassem seu modelo de negócios. Mas, em vez de alertar o público e tomar medidas para salvar vidas, mentiram e deliberadamente aceleraram o problema. Agora, pessoas estão morrendo, e esses arquitetos da negação e da mentira climática terão que responder por sua conduta em um tribunal”, disse Richard Wiles, presidente do grupo de defesa Centro para Integridade Climática (CCI), em comunicado.
Ele acrescentou que as vítimas das grandes petrolíferas merecem responsabilização: “Esta é uma indústria que está causando e acelerando condições climáticas que matam pessoas. Elas sabem disso há 50 anos e, em algum momento, precisarão ser responsabilizadas”
Misti quer que as empresas de petróleo, gás e carvão paguem indenizações em valores que serão determinados em julgamento, e, também, está tentando forçar essas companhias a realizar uma campanha de educação pública para corrigir “décadas de desinformação”.
Theodore Boutrous, advogado da Chevron, criticou a ação. “Explorar uma tragédia pessoal para promover litígios políticos sobre danos climáticos é contrário à lei, à ciência e ao bom senso”, afirmou à NPR. “O tribunal deveria adicionar essa alegação absurda à crescente lista de processos climáticos sem mérito que tribunais estaduais e federais já rejeitaram.”
Representantes da Shell, ConocoPhillips, BP e Phillips 66 não quiseram comentar. E um porta-voz da ExxonMobil disse que um comentário da empresa não estava disponível no momento.
Processos por todo os EUA
Petrolíferas enfrentam vários outros processos climáticos movidos por estados e municípios americanos por supostamente enganarem o público durante décadas sobre os perigos da queima de petróleo, gás e carvão, a principal causa das mudanças climáticas.
Segundo o CCI, 10 estados (Califórnia, Connecticut, Delaware, Havaí, Maine, Massachusetts, Minnesota, Nova Jersey, Rhode Island e Vermont), o Distrito de Columbia e dezenas de governos municipais, distritais e tribais de Califórnia, Colorado, Havaí, Illinois, Maryland, Nova Jersey, Nova York, Oregon, Pensilvânia, Carolina do Sul, Washington e Porto Rico, entraram com ações judiciais contra elas.
Esses casos, em conjunto, representam mais de 1 em cada 4 pessoas que vivem nos Estados Unidos. E, conforme destaca o NPR, buscam recursos para ajudar comunidades a lidar com os riscos e danos do aquecimento global, incluindo tempestades, inundações e ondas de calor mais extremas.
Até agora, os resultados foram mistos. Por exemplo, na Pensilvânia, um juiz rejeitou recentemente uma ação climática movida pelo Condado de Bucks contra diversas petrolíferas. Segundo ele, como se tratava principalmente de emissões de gases de efeito estufa, essa era uma questão que caberia ao governo federal, de acordo com a Lei do Ar Limpo.
Por outro lado, em janeiro, a Suprema Corte rejeitou uma tentativa de empresas de petróleo e gás de bloquear uma ação climática movida por Honolulu, e em março os juízes rejeitaram um pedido de procuradores-gerais republicanos para tentar impedir ações climáticas movidas por estados como Califórnia, Connecticut, Minnesota e Rhode Island.
Em declaração enviada à agência NPR na época, o Instituto Americano de Petróleo (ANP) disse que estava decepcionado com as decisões da Suprema Corte, pois as ações são uma “distração” e um “desperdício de recursos do contribuinte”.
Bertopolis, Brazil – The hottest region in Brazil is blanketed with guinea grass: thick, invasive and highly flammable. Black swaths of burned earth checkerboard the rolling hills — evidence of the fires that have increased along with the temperature.
Yet enter the village of Pradinho, and a verdant patchwork emerges. Here, lush banana palms, cassava plants and guava trees sprout from the dry plains.
These flourishing lots are the product of Hāmhi Terra Viva, an Indigenous-led agroforestry project in the eastern state of Minas Gerais where ancestral songs and traditions are woven into the planting process.
Each oasis of trees, cultivated in backyard plots or large reforestation areas, signals a kind of rebirth for the local Maxakali people, also known as the Tikmũ’ũn.
The Atlantic Forest, a complex ecosystem of rainforests, coastal broadleaf trees and mangroves, used to cover the Maxakali territory. Its dense canopy trapped in moisture and fostered one of the most biodiverse regions in the world.
But the destruction of the Atlantic Forest has exacerbated the local effects of climate change — and with it, heightened the risks of wildfires.
In Brazil, the Jequitinhonha Valley, where the four Maxakali territories are located, has suffered a dramatic rise in temperatures in recent years.
Twenty Brazilian cities registered temperatures five degrees Celsius (nine degrees Fahrenheit) higher than the average daily maximum, according to 2023 government data analysed by the newspaper O Globo. Of those cities, 18 were in the Jequitinhonha Valley.
The city of Araçuaí even shattered the record for the hottest temperature in Brazil’s history in November of that year, with thermometers rising to 44.8 degrees Celsius — or 112.6 degrees Fahrenheit. It lies a mere 130km (81 miles) from Maxakali territory.
“We are in the epicentre of the climate crisis in Brazil,” said Rosângela Pereira de Tugny, coordinator of the Hāmhi project.
A fire in the Minas Gerais grassland smoulders, sending smoke drifting across the landscape [Sara Van Horn/Al Jazeera]
More than 85 percent of the Atlantic Forest has been destroyed, as agriculture, development and practices like logging encroach upon its land. In Minas Gerais, experts estimate, less than eight percent of the forest remains.
“When I was a kid, there was lots of forest,” said Lúcio Flávio Maxakali, a schoolteacher and a master’s degree student at the Federal University of Minas Gerais. “There were lots of animals and we planted food — corn, beans, sugarcane — in the middle of the woods.”
But over the centuries, colonial settlers used fire to clear vast tracts of the Atlantic Forest. Farmers often seeded the burned areas with guinea grass, brought from Africa, to feed their cattle.
Lúcio Flávio Maxakali remembers the landscape being radically different when he was a child [Sara Van Horn/Al Jazeera]
“The farmers changed the landscape,” said Manuel Damásio Maxakali, the 52-year-old leader of Pradinho village.
His wrinkled hands drawing makeshift maps in the dusty earth, Damásio was eager to communicate the destruction that the farmers wrought. “They burned everything. They added fences. They added cattle. They cut down everything. Each time, the farmers took more land.”
Brazil’s dictatorship, from 1964 to 1985, set the stage for even greater destruction of the region’s tropical forests.
Governed by the motto “integrate to not surrender”, the military leadership cut roadways through dense forest and pushed for development projects in remote regions to stimulate economic growth.
Deforestation ultimately hit a peak in the period between 1995 and 2004, when as much as 27,772 square kilometres (10,723 square miles) of forest in Brazil were destroyed per year.
Manuel Damásio Maxakali draws maps in the dirt to illustrate how the landscape has changed [Sara Van Horn/Al Jazeera]
That, in turn, increased temperatures across the country. In the region of the Atlantic Forest in particular, one study found that the surface temperature of a hectare increased by one degree Celsius (1.8 degrees Fahrenheit) whenever a quarter of its tree cover was razed.
If the entire hectare of forest was demolished, the study said, temperatures could spike by four degrees Celsius (7.2 degrees Fahrenheit).
Without the moist tree cover, experts say the Maxakali territory has grown hotter and drier. That increases the likelihood of wildfires sparking.
Last year even broke a record for the number of wildfires in Minas Gerais. In less than nine months, 24,475 wildfires were tallied — far exceeding the previous record high in the whole of 2021.
Scarce rainfall also heightens the risk of fires, as does the seemingly endless guinea grass, which creates a thick carpet of flammable material across the landscape.
Grass fires can spread four times as quickly as forest fires, leading the Maxakali to nickname the invasive plant “kerosene”.
Men attempt to beat back flames spreading across the dry grassland [Sara Van Horn/Al Jazeera]
Some blazes are started accidentally within the Maxakali communities themselves.
Fire, after all, is a frequent part of Maxakali death rites, which often involve the burning of the deceased’s clothing, tools and house, and it is also used for cooking and to clear areas of snakes.
But wildfires are not the only consequence of the changing climate. The river in the village of Pradinho has shrunk so much that villagers are unable to bathe.
“There’s no water. The water has dried up,” Damásio explained. “We normally use water from the river, but there’s nothing now.”
The Atlantic Forest has been destroyed throughout much of the Maxakali territory [Sara Van Horn/Al Jazeera]
Maxakali territory once spanned at least three large valleys in the Atlantic Forest. Elders in the village remember how the forest supplied food, medicine and construction materials — in addition to serving as habitat for the yãmĩyxop, spiritual beings central to Maxakali beliefs.
“There were medicines in the forest for us,” explained Damásio. “When we had stomachaches, we would use the bark from the trees to feel better. But now, it’s just grass. The farmers burned everything.”
But the four remaining Maxakali reservations — reduced to 6,434 hectares (15,900 acres) of pasture — contain less than 17 percent of their original vegetation. Some experts consider the Atlantic Forest to be regionally extinct.
That absence has many Maxakali leaders turning to reforestation — and finding in their musical traditions an ecological blueprint of the past.
Manuel Damásio Maxakali tends to banana trees in Minas Gerais, Brazil [Sara Van Horn/Al Jazeera]
Singing organises life in Maxakali villages: Music, for instance, is used to cure illness, teach history or transmit practical instructions, like how to make bags or weave fishing nets.
“Songs tie together the whole Tikmũ’ũn social structure,” said de Tugny, the Hāmhi project coordinator, who is also a musicologist at the Federal University of Minas Gerais. “People don’t compose songs. They have songs.”
To have a song, she added, means being capable of taking care of the spirit considered to be the song’s creator.
Ancestral songs also provide an extremely detailed register of local ecology. Twelve musical canons, distinct in grammar and lexicon, total about 360 hours of song. Contained in the lyrics are hundreds of species of flora and fauna now extinct in the territory.
“We sing about everything: the saplings, the bananas, ourselves,” explained Manuel Kelé, leader of the village of Água Boa. “Even dogs have a song within our religion.”
Caretakers at the Hāmhi nursery tend to the growing trees and plants [Sara Van Horn/Al Jazeera]
One song, for example, lists 33 species of bees, some of which don’t have names in Brazil’s national language, Portuguese, and only two of which are currently present in the territory. The lyrics supply information about bee behaviour that many Maxakali have never witnessed first-hand.
“The songs are snapshots,” said de Tugny. “They are like photographs of every detail that exists in the Atlantic Forest: the names of insects, birds, plants, moments of relationship between an animal and a leaf. All these are registered.”
For the Maxakali, ritual songs also play a crucial role in helping the forest regenerate. Singing is a daily part of their work in Hāmhi’s tree nurseries.
Nursery caretakers not only sing to seeds as they are buried, but they also make music as part of the regular rhythms of harvesting and cultivation. Caretakers divide into groups, position themselves around the nursery, and sing in concert with each other. The song lyrics help participants remember the ecological knowledge of their ancestors.
And while some of the work at Hāmhi is dedicated to planting fruit trees and other crops, the project’s leaders see reforestation as key to reducing the region’s fire risks.
Song is an important part of the growing cycle in Maxakali culture [Sara Van Horn/Al Jazeera]
Since its inception in 2023, the Hāmhi project has planted over 60 hectares (148 acres) of fruit trees and 155 hectares (383 acres) of Atlantic Forest vegetation. The goal is a reforested area nearly twice that size.
Programme participants have also organised themselves into a provisional fire brigade and even created natural fire barriers, using traditional methods like planting species of fire-resistant vegetation.
“Songs help the forest grow,” said Damásio, the village leader. “We ask those who have died to help us. They walk here and assist us. We are calling on the forest to grow back.”
For the past few years, scientists have watched, aghast, as global temperatures have surged — with both 2023 and 2024 reachingaround 1.5 degrees Celsius above the preindustrial average. In some ways, that record heat was expected: Scientists predicted that El Niño, combined with decreasing air pollution that cools the earth, would cause temperatures to skyrocket.
But even those factors, scientists say, are not sufficient to explain the world’s recent record heat.
Earth’s overall energy imbalance — the amount of heat the planet is taking in minus the amount of heat it is releasing — also continues to rise, worrying scientists. The energy imbalance drives global warming. If it rises, scientists expect global temperatures to follow.
Two new studies offer a potential explanation: fewer clouds. And the decline in cloud cover, researchers say, could signal the start of a feedback loop that leads to more warming.
“We have added a new piece to the puzzle of where we are headed,” Helge Goessling, a climate physicist at the Alfred Wegener Institute in Germany and the author of one of the studies,saidin a video interview.
For years, scientists have struggled to incorporate clouds’ influence into the large-scale climate models that help them predict the planet’s future. Clouds can affect the climate system in two ways: First, their white surfaces reflect the sun’s light, cooling the planet. But clouds also act as a kind of blanket, reflecting infrared radiation back to the surface of the planet, just like greenhouse gases.
Which factor wins out depends on the type of cloud and its altitude. High, thin cirrus clouds tend to have more of a warming effect on the planet. Low, fluffy cumulus clouds have more of a cooling effect.
“Clouds are a huge lever on the climate system,” said Andrew Gettelman, an affiliate scientist at the University of Colorado at Boulder. “A small change in clouds could be a large change in how we warm the planet.”
Researchers are beginning to pinpoint how clouds are changing as the world warms. In Goessling’s study, published in December in the journal Science, researchers analyzed how clouds have changed over the past decade. They found that low-altitude cloud cover has fallen dramatically — which has also reduced the reflectivity of the planet. The year 2023 — which was 1.48 degrees Celsius above the preindustrial average — had the lowest albedo since 1940.
In short, the Earth is getting darker.
That low albedo, Goessling and his co-authors calculated, contributed 0.2 degrees Celsius of warming to 2023’s record-high temperatures — an amount roughly equivalent to the warming that has so far been unexplained. “This number of about 0.2 degrees fairly well fits this ‘missing warming,’” Goessling said.
Researchers are still unsure exactly what accounts for this decrease. Some believe that it could be due to less air pollution: When particulates are in the air, it can make it easier for water droplets to stick to them and form clouds.
Another possibility, Goessling said, is a feedback loop from warming temperatures. Clouds require moisture to form, and moist stratocumulus clouds sit just underneath a dry layer of air about one mile high. If temperatures warm, hot air from below can disturb that dry layer, mixing with it and making it harder for wet clouds to form.
But those changes are difficult to predict — and not all climate models show the same changes. “It’s really tricky,” Goessling said.
Other scientists have also found decliningcloud cover. In a preprint study presented at a science conference in December, a group of researchers at NASA found that some of the Earth’s cloudiest zones have been shrinking over the past two decades. Three areas of clouds — one that stretches around the Earth’s equator, and two around the stormy midlatitude zones in the Northern and Southern Hemispheres — have narrowed since 2000, decreasing the reflectivity of the Earth and warming the planet.
George Tselioudis, a climate scientist at NASA’s Goddard Institute for Space Studies and the lead author of the preprint, said this decrease in cloud cover can help explain why the Earth’s energy imbalance has been growing over the past two decades. Overall, the cloud cover in these regions is shrinking by about 1.5 percent per decade, he said, warming the Earth.
Tselioudis said that warming could be constraining these cloud-heavy regions — thus heatingthe planet.“We’ve always understood that the cloud feedback is positive — and it very well could be strong,” he said. “This seems to explain a big part of why clouds are changing the way they are.”
If the cloud changes are part of a feedback loop, scientists warn, that could indicate more warming coming, with extreme heat for billions of people around the globe. Every hot year buttresses the idea that some researchers have now embraced, that global temperature rise will reach the high end of what models had predicted. If so, the planet could pass 1.5 degrees Celsius later this decade.
Researchers now say that they are rushing to understand these effects as the planet continues to warm. “We are kind of in crunch time,” Goessling said. “We have a really strong climate signal — and from year to year it’s getting stronger.”
Sineia Bezerra do Vale, indígena do povo Wapichana, atua há ao menos três décadas com discussões sobre a emergência do clima e defende que cientistas incluam as experiências dos povos tradicionais nos estudos sobre o assunto.
Sineia Bezerra do Vale, lidernaça indígena do povo Wapichana, ao receber o prêmio “Cientista indígena do Brasil”, em São Paulo — Foto: Patricia Zuppi/Rede RCA/Cristiane Júlião/Divulvação
Referência em Roraima por estudos sobre a crise climática em comunidades indígenas, a gestora ambiental Sineia Bezerra do Vale agora também é “cientista indígena do Brasil” reconhecida pelo Planetary Guardians, iniciativa que discute a emergência do clima em todo o mundo e tem como foco restaurar a estabilidade da Terra.
Indígena do povo Wapichana, Sineia do Vale recebeu o título no último dia 25 em São Paulo, no mesmo evento em que o cientista brasileiro Carlos Nobre, referência global nos efeitos das mudanças climáticas na Amazônia, foi anunciado com novo membro dos Planetary Guardians – guardiões planetários, em português.
Sineia do Vale tem como principal atuação o foco sobre a crise do clima, que impacta em consequências devastadoras em todo o mundo. Foi dela o primeiro estudo ambiental sobre as transformações do clima ao longo dos anos na vida dos povos tradicionais em Roraima.
Ao receber o prêmio de “cientista indígena do Brasil” das mãos de Carlos Nobre, a defensora ambiental destacou que quando se trata da crise climática, a ciência também precisa levar em conta a experiência de vida que os indígenas vivenciam no dia a dia – discurso que ela sempre defende nos debates sobre o assunto.
“Esse é um momento muito importante para os povos indígenas. Neste momento em que a gente se coloca junto com a ciência que chamamos de ciência universal, a ciência indígena tem uma importância tanto quanto a que os cientistas traduzem para nós, principalmente na questão do clima”, disse Sineia do Vale.
Sineia do Vale (terceira mulher da direira para a esquerda) atua há anos com foco na crise climática e os povos indígenas — Foto: Patricia Zuppi/Rede RCA/Cristiane Júlião/Divulvação
No evento em São Paulo, ela exemplificou como a crise climática é percebida nas comunidades. “Os indígenas já colocaram em seus planos de enfrentamento às mudanças climáticas que as águas já aqueceram, que os peixes já sumiram e que não estamos mais vivendo o período de adaptação, mas o de crise climática.”
“Precisamos de resposta rápidas. Não podemos mais deixar que os países não cumpram seus acordos porque à medida que o globo terrestre vai aquecendo, os povos indígenas sofrem nas suas terras com grandes catástrofes ambientais”, destacou a gestora.
A indicação para que Sineia recebesse o título ocorreu após indicação da ativista ambiental e geógrafa Hindou Oumarou, que é co-presidente do Fórum Internacional de Povos Indígenas sobre Mudanças do Clima e presidente do Fórum Permanente da ONU sobre questões indígenas chadiana.
Além da roraimense, também receberam a honraria de “cientista indígena do Brasil”: as antropólogas indígenas Braulina Baniwa e Cristiane Julião, do povo Pankararu, confundadoras da Articulação Nacional das Mulheres Guerreiras da Ancestralidade (Anmiga), e o antropólogo e escritor Francisco Apurinã, que pesquisa mudanças ecológicas na perspectiva indígena pela Universidade de Helsinki, na Finlândia.
Mais sobre Sineia do Vale
Sineia do Vale participa desde 2011 da Conferência das Nações Unidas sobre as Mudanças Climáticas – COP, em inglês, e promove junto às lideranças indígenas a avaliação climática a partir do conhecimento ancestral.
Ela também participa ativamente das discussões internacionais sobre mudanças climáticas há mais de 20 anos, entre elas, a Conferência de Bonn sobre Mudanças Climáticas – chamada de SB60, que ocorre todos os anos em Bonn, na Alemanha. Este ano, a COP29 ocorrerá de 11 a 24 de novembro em Baku, capital do Azerbaijão.
No ano passado, ela foi recebeu o “Troféu Romy – Mulheres do Ano“, honraria concedida a mulheres que se destacaram em suas áreas de atuação em 2023.
Gestora ambiental de formação, Sineia cursa mestrado em Sustentabilidade junto a Povos e Territórios Tradicionais na Universidade de Brasília (UnB), coordena o Departamento de Gestão Territorial e Ambiental do Conselho Indígena de Roraima (CIR), e integra a Convenção-Quadro das Nações Unidas sobre a Mudança do Clima (UNFCCC), focada na agenda indígena e a implementação de ações em nível local.
Flooding from Hurricane Helene in Asheville, North Carolina, on Saturday. Photograph: Melissa Sue Gerrits/Getty Images
Nestled in the bucolic Blue Ridge mountains of western North Carolina and far from any coast, Asheville was touted as a climate “haven” from extreme weather. Now the historic city has been devastated and cut off by Hurricane Helene’s catastrophic floodwaters, in a stunning display of the climate crisis’s unlimited reach in the United States.
Helene, which crunched into the western Florida coast as a category 4 hurricane on Thursday, brought darkly familiar carnage to a stretch of that state that has experienced three such storms in the past 13 months, flattening coastal homes and tossing boats inland.
But as the storm, with winds peaking at 140mph (225 km/h), carved a path northwards, it mangled places in multiple states that have never seen such impacts, obliterating small towns, hurling trees on to homes, unmooring houses that then floated in the floodwater, plunging millions of people into power blackouts and turning major roads into rivers.
In all, about 100 people have died across five states, with nearly a third of these deaths occurring in the county containing Asheville, a city of historic architecture where new residents have flocked amid boasts by real estate agents of a place that offers a reprieve from “crazy” extreme weather.
Now, major highways into Asheville have been severed by flooding from surging rainfall, its mud-caked and debris-strewn center turned into a place where access to cellphone reception, gasoline and food is scarce. The water supply, as well as the roads, is expected to be affected for weeks. It is, according to Roy Cooper, North Carolina’s governor, an “unprecedented tragedy”.
“Everyone thought this was a safe place, somewhere you could move with your kids for the long term, so this is just unimaginable, it’s catastrophic,” said Anna Jane Joyner, a climate campaigner who grew up in the area and whose family still lives in Black Mountain, near Asheville. Several of her friends narrowly avoided being swept away by the floodwater.
“I never, ever considered the idea that Asheville would be wiped out,” she said. “It was our backup plan to move there, so the irony is stark and scary and it’s hard for me to emotionally process. I’ve been working in the climate movement for 20 years and feel like I’m now living in a movie I imagined in my head when I started. Nowhere is safe now.”
The damage wrought by Helene is “a staggering and horrific reminder of the ways that the climate crisis can turbocharge extreme weather”, according to Al Gore, the former US vice-president. Hurricanes gain strength from heat in the ocean and atmosphere and Helene, one of the largest ever documented, sped across a record-hot Gulf, quickly turning from a category 1 to a category 4 storm within a day.
Extra heat not only helps storms spin faster, it also holds more atmospheric moisture that is then unleashed in torrents upon places such as western North Carolina, which got a month’s rain in just a couple of days. Helene was the eighth category 4 or 5 hurricane to strike the US since 2017 – the same number of such extreme storms to hit the country in the previous 57 years.
“This storm has the fingerprints of climate change all over it,” said Kathie Dello, North Carolina’s state climatologist. “The ocean was warm and it grew and grew and there was a lot of water in the atmosphere. Unfortunately, our worst fears came true. Helene was supercharged by climate change and we should expect more storms like this going forward.”
Dello said that it would take months or even years for communities, particularly in the poorer, more rural areas of the state that have been cut off completely by the storm, to recover, compounding the impacts of previous storms such as Florence, in 2018, and Fred, in 2021, that pose major questions over how, if at all, to rebuild.
“I don’t know where you run to escape climate change. Everywhere has some sort of risk,” she said. “It’s really been quite rattling to see these places which you love be devastated, knowing they have been changed forever. We can’t just rebuild like before.”
Heavy rains from Hurricane Helene caused record flooding and damage in Asheville, North Carolina. Photograph: Melissa Sue Gerrits/Getty Images
In Asheville, the historic area of Biltmore Village has been submerged underwater while, in a gloomy irony, the US’s premier climate data center has been knocked offline.
The storm has been “devastating for our folks in Asheville”, said a spokesperson for the National Oceanic and Atmospheric Administration, who said the National Centers for Environmental Information facility had lost its water supply and had shut down.
“Even those who are physically safe are generally without power, water or connectivity,” the spokesperson said of the effort to contact the center’s marooned staff.
The destruction may cast a shadow over the climate-haven reputation of Asheville, much like how Vermont’s apparent distance from the climate crisis has been rethought in the wake of recentfloods, but it probably won’t defy a broader trend where Americans are flocking to some of the places most at risk from heatwaves, storms and other climate impacts due to the ready availability of housing and jobs.
“This flood will likely accelerate development,” said Jesse Keenan, an expert in climate adaptation at Tulane University, who noted that for every one person who moves away from Asheville, three people move to the city, one of the highest such ratios in the US.
“Some people will not be inclined or unable to rebuild and their properties will be bought up by wealthy people who can afford to build private infrastructure and buildings that have the engineering resilience to withstand floods.”
“There is no truly safe place,” Keenan, who previously listed Asheville as one of the better places to move amid the climate crisis, acknowledged. But the city will “see a post-disaster boom”, he said. “This is a cycle that has happened over and over again in America.”
Cooling the earth by blocking out the sun, although potentially disastrous, is now a real answer to climate change. As a Harvard research paper published late last year proved, solar geo-engineering is both technically feasible and relatively cheap. With governments and international bodies considering the technology, a South African university has just announced a study. But how convenient is this answer for our politicians and heavy emitters?
I.Global Hollywood
In his book The Planet Remade: How Geo-engineering Could Change the World, Oliver Morton laid down a potential scenario from the not-too-distant future. As briefings editor at The Economist and former chief news and features editor at the scientific journal Nature, it was a given that this scenario—a thought experiment on the deployment into the stratosphere of “climate engineering” aerosols—would be based more in science fact than science fiction. Which is exactly what made it, like the best work of Robert Heinlein or Charlie Brooker, truly terrifying.
According to a Harvard study published in November 2018, three years after the release of Morton’s book, it would work in practice like this: a fleet of purpose-built aircraft, with disproportionately large wings relative to their fuselages, so as to allow “level flight at an altitude of 20 kilometres while carrying a 25-ton payload,” would inject 0.2 million tons of sulphur dioxide into the lower stratosphere per year—thereby reflecting enough solar radiation back out into space to cut the rate of global warming progressively in half. Pre-launch costs in 2018 values would come in at $3.5 billion, with yearly operating costs at $2.25 billion. Given that in 2017 around 50 nations had military budgets of $3 billion or more, noted the Harvard scientists, the barriers to entry would be remarkably low.
“It is not a large nation that does it—indeed, it is not a single nation’s action at all,” speculated Morton back in 2015. “Sometime in the 2020s, there is a small group of them, two of which are in a position to host the runways. They call themselves the Concert; once they go public, others call them the Affront. None of them is a rich nation, but nor are they among the least developed. All of them already have low carbon-dioxide emissions, and all of them are on pathways to no emissions at all. In climate terms, they look like the good guys. But their low emissions and the esteem of the environmentally conscious part of the international community are doing nothing to reduce the climate-related risks their citizens face.”
So why “truly terrifying”?
Because, as Morton went on to explain, solar geo-engineering—otherwise known as solar radiation management, or SRM—was not (or at least was no longer) a conceptual absurdity. When he wrote his book, its probability of deployment was already based on two of the most urgent existential questions in the history of humanity: 1) Are the risks of climate change great enough to warrant serious action aimed at mitigating them? 2) Will the world’s largest industrial economies be able to lower their carbon emissions to net zero by the middle of the century?
But terrifying more specifically because, by 2018, the answer to the first question was a scientifically unqualified “yes” and to the second a statistically implausible “no”—and yet the effect of SRM on the biosphere was still unknown. With the results from the Harvard study leading to the scheduling of tests as early as the first half of 2019, the Berlin-based climate science and policy institute Climate Analytics wasted no time in recommending a global ban on the technology.
“Solar radiation management aims at limiting temperature increase by deflecting sunlight, mostly through injection of particles into the atmosphere,” the institute noted. “At best, SRM would mask warming temporarily, but more fundamentally is itself a potentially dangerous interference with the climate system.”
SRM, argued the scientists at Climate Analytics, would “alter the global hydrological cycle as well as fundamentally affect global circulation patterns such as monsoons.” It would not “halt, reverse or address in any other way the profound and dangerous problem of ocean acidification which threatens coral reefs and marine life as it does not reduce CO2 emissions and hence influence atmospheric C02 concentration.” Also, the scientists pointed out, the approach was “unlikely to attenuate the effects of global warming on global agricultural production” as its “potentially positive effect due to cooling” was projected to be counterbalanced by “negative effects on crop production of reducing solar radiation at the earth’s surface.”
In other words, according to Climate Analytics, while cooler temperatures would be helpful to the world’s farmers, the crops would still need sunlight to grow. And none of the above even counted as the number one reason that the institute was raising the alarm—SRM’s gravest danger, these scientists and policy experts insisted, was that it would divert attention from the core problem, which remained the unprecedented amount of carbon being spewed daily into the atmosphere by the extraction of coal, crude oil and natural gas.
For Morton, this was the predicament known as the “superfreak pivot”—the turning of large masses of humanity from the position that “global warming requires no emissions reduction because it isn’t a real problem” to the position that “the Concert has it all covered”. It was a predicament highlighted too by Harvard scientist David Keith, who told the Guardian in 2017:
“One of the main concerns I and everyone involved in this have is that Trump might tweet ‘geoengineering solves everything—we don’t have to bother about emissions.’ That would break the slow-moving agreement among many environmental groups that sound research in this field makes sense.”
As for South Africa, less than two months after publication of the seminal Harvard paper of late 2018, a press release was issued by the African Climate and Development Initiative of the University of Cape Town.
“UCT researchers to embark on pioneering study on potential impacts of solar geoengineering in southern Africa,” it stated.
II. Local Hollywood
As the recipient of a grant from the international DECIMALS Fund (Developing Country Impacts Modelling Analysis for SRM), the UCT team cited two reasons for going ahead with the study—and both of them had to do with the social and economic havoc that anthropogenic climate change had so far wrought in our corner of the world. First, the 2015/16 summer rainfall failure over southern Africa, which led to 30 million people becoming food insecure in South Africa, Mozambique, Botswana and Zimbabwe. Second, Cape Town almost running out of water in 2018. If SRM could be done in a safe and reliable manner, so the rationale went, it was “the only known way” to quickly offset the temperature increases that were behind the droughts.
“We want to understand the impact of solar radiation management on drought conditions,” Dr Romaric Odoulami, the project’s leader, told Daily Maverick, “that’s our motivation. What will the implications be for regional agriculture? But I want to make one thing clear: SRM has never been implemented in the real world… and we are not going to do it either.”
What the African Climate and Development Initiative was going to do, said Odoulami, was climate modelling. The project, he added, would run for the next “one or two years”—as soon as he got “something interesting,” he promised, he would let Daily Maverick know. For the moment, he wanted to leave us with this:
“Solar radiation management doesn’t stop climate change. It doesn’t stop global emissions of greenhouse gases. The only thing it does is help to reduce the global temperature by reducing the amount of solar radiation reaching the earth’s surface.”
This caution in the face of the sheer unprecedented scale of the thing was also detectable in the words of Andy Parker, project director of the Solar Radiation Management Governance Initiative, the UK-based organisation—founded in 2010 by, among others, The World Academy of Sciences and the Royal Society—that set up the DECIMALS Fund in 2018. Speaking to Daily Maverick from a conference in Bangladesh, Parker was vague yet morbidly fascinating on the legislative context that could eventually give the green light to SRM.
“That’s really tricky to predict,” he said. “We can imagine various different deployment scenarios. There’s the desperation scenario, where a country or perhaps a coalition of countries that are really suffering from climate change decide that they are going to use solar geo-engineering to stop the temperature from rising. That could be seen as unilateral and illegitimate deployment. At the other end of things, it’s possible that through the United Nations—the UN General Assembly or one of the UN conventions—there’s a much broader coalition that comes together with much more legitimacy to develop a decision-making infrastructure for if we were to ever use this, or indeed, for how we would reject it.
“Really, at this stage, we don’t know what’s going to happen. We don’t know what’s going to happen with the research, we don’t know how governments are going to deal with this, and we don’t know how quickly and how deeply the impacts of climate change are going to bite.”
In South Africa, unfortunately, all indications are that the bite is going to be serious. As Daily Maverick learned from the country’s leading land-based climate scientist in October last year, we are warming at twice the global average. At 3°C of global warming, which is 6°C regionally—and which at current emission rates we are steaming towards, as per the most conservative estimates, before the end of the century—there will be a total collapse of the maize crop and livestock industry. This is something that the Department of Environmental Affairs seems to understand well, as evidenced by their “Third National Communication” under the United Nations Framework Convention on Climate Change, submitted in March 2018.
But the other unknown factor in this general SRM universe of “unknown unknowns” is the person that currently sits atop the DEA. Has Nomvula Mokonyane, who was named at the State Capture inquiry on Monday for allegedly accepting bribes in the form of monthly cash payments, even read the Third National Communication? Does President Cyril Ramaphosa plan on replacing her with someone who will? Aside from Tito Mboweni at treasury, does anyone in the upper echelons of the ANC get the urgency of the situation?
These are the questions that highlight the possibility of South Africa one day performing the superfreak pivot. Because it might not only suit the government to defer to technology when the food and water shortages get real, it might also suit Sasol, the coal mining companies and the country’s heavy emitters at large. DM
Solar Radiation Modification refers to deliberate, large-scale interventions in the global climate system to increase the amount of sunlight reflected away from the planet to reduce global temperatures. Illustrative image: (Generated with Flux AI)
In a webinar on Tuesday, scientists and other experts agreed on the need for solar geoengineering research to enhance the portfolio of climate change responses.
Solar geoengineering, whether through space mirrors or stratospheric particles, is a complex, controversial and contentious field. In a webinar on Tuesday, atmospheric scientists and other experts from across Africa agreed that it is completely rational to explore its role in a portfolio of climate change responses.
Geoengineering refers to deliberate, large-scale interventions in the Earth’s natural systems with the aim of counteracting climate change. The primary goal of geoengineering is to mitigate the adverse effects of global warming and manage the Earth’s climate system. There are two main categories of geoengineering: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR).
The webinar focused on the former, which The Alliance for Just Deliberation on Solar Geoengineering says refers to “deliberate, large-scale interventions in the global climate system to increase the amount of sunlight reflected away from the planet to reduce global temperatures”.
The Intergovernmental Panel on Climate Change (IPCC) in its Sixth Assessment Report defines SRM as “a range of radiation modification measures not related to greenhouse gas mitigation that seek to limit global warming. Most methods involve reducing the amount of incoming solar radiation reaching the surface, but others also act on the longwave radiation budget by reducing optical thickness and cloud lifetime.”
(Source: The Alliance for Just Deliberation on Solar Geoengineering)
Hassaan Sipra, director of global engagement at The Alliance and a climate researcher, explained that SRM – in line with conclusions by the IPCC – is not meant to stop climate change but only to buy time for the deep reductions in greenhouse gas emissions needed to limit global warming. He also set out the context wherein SRM was an increasingly attractive area of research.
During the UN climate conference in Paris, the world agreed to accelerate efforts to limit the global average temperature increase over pre-industrial levels to below 1.5°C. At present, we are on a trajectory to exceed even 2°C. This is important because every fraction of a degree drastically increases the risks associated with anthropogenic climate change.
“And typically, now, within this context,” said Sipra, “what is being talked about is the use of carbon dioxide removal technologies. So we know that we’re not going to get to net zero emissions until about 2100 if we’re looking for 1.5°C. If it’s 2°C, we’re not going to get there until after 2100. So in the meantime, we also need to start scaling up our carbon dioxide removal technologies so that whatever carbon is in the atmosphere, we are immediately able to capture it and bring that back.”
Put differently, carbon removal will still be necessary in the future because even with significant reductions in greenhouse gas emissions, existing atmospheric carbon levels must be reduced to meet net zero targets and stabilise global temperatures, as outlined in the Paris Agreement. This ensures long-term climate goals are achievable by offsetting any remaining emissions.
Sipra explained that the problem with carbon dioxide removal was the interrelated problems of cost and scale.
It’s “an expensive technology or a set of technologies that would take a long time to scale up and would require a tremendous amount of resources, and at present, those resources are not yet scalable… they’re not yet available, the technologies are not yet fully tested, and so we need a lot of time before we’re going to get to carbon dioxide removal technologies.
“We need time to cut emissions and we need time to get to carbon dioxide removal technologies. Yet climate impacts are continuing to rise in the meantime. And this is the point where for scientists, policymakers, civil society, the deliberation has begun as to what might be the possibility of buying some additional time; putting in a potential stopgap measure.”
Napkin diagram roughly showing SRM’s role in managing climate risks.(This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.)
SRM is a “stopgap measure”, Sipra explained, in contrast to emissions reductions or carbon dioxide removal because “it does not actually offer a solution to our climate problems, it merely masks it. And so, without addressing the root cause of climate change, you are kind of just giving yourself this, in essence, a drug which may delay – potentially – some of the impacts of climate change”.
But just how is SRM meant to achieve this?
Prof Babatunde Abiodun, an expert in climate model developments and applications, shared some details on the state of SRM research and the various approaches being explored and experiments undertaken. Three of the projects he noted are highlighted here:
Stratospheric Aerosol Processes, Budget and Radiative Effects (SABRE): SABRE investigates how tiny particles in the stratosphere may reflect sunlight to cool the Earth. The project is “an extended airborne science measurement programme” and aims to understand the effectiveness and potential impacts of these aerosols so as to strengthen the “scientific foundation to inform policy decisions related to regulating global emissions that impact the stratosphere (eg ozone depleting substances, rocket exhaust) and the potential injection of material into the stratosphere to combat global warming (climate intervention)”.
Stratospheric Controlled Perturbation Experiment (SCoPex): SCoPex, a Harvard University-led project, explores the feasibility of dispersing reflective particles in the stratosphere to mimic volcanic cooling effects using a high-altitude balloon to release small amounts of aerosols over a small area. However, the project has recently moved away from its focus on science related to solar geoengineering.
Geoengineering Assessment Across Uncertainties, Scenarios and Strategies (GAUSS): GAUSS evaluates the potential risks and benefits of various geoengineering methods by using complex computer simulations. Early findings suggest that while geoengineering can reduce global temperatures, it may also lead to regional climate changes, emphasising the need for careful, scenario-based planning. They explain that “one challenge today is a degree of arbitrariness in the scenarios used in current SRM simulations”.
SRM and other geoengineering approaches, however, are not without controversy. The main concerns are the potential for unintended environmental side effects, ethical issues regarding the manipulation of natural systems and the risk of unequal impacts on different regions potentially exacerbating global inequalities.
The IPCC says in the Summary for Policymakers of its Sixth Assessment Report that, with high confidence, “solar radiation modification approaches, if they were to be implemented, introduce a widespread range of new risks to people and ecosystems, which are not well understood. Solar radiation modification approaches have the potential to offset warming and ameliorate some climate hazards, but substantial residual climate change or overcompensating change would occur at regional scales and seasonal timescales.
“Large uncertainties and knowledge gaps are associated with the potential of solar radiation modification approaches to reduce climate change risks. Solar radiation modification would not stop atmospheric CO₂ concentrations from increasing or reducing resulting ocean acidification under continued anthropogenic emissions.”
To this, the gathered scientists and experts said that while they recognised the potential risks, these should be weighed against the risk of the status quo or inaction.
“It makes sense to think about SRM as a very risky proposition, but it’s a risky proposition that has to be compared to an alternative risky proposition, which is worsening climate change. So, climate change increases risks to peoples and ecosystems. With each ton of carbon dioxide we’re adding into the atmosphere, with each incremental bit of warming, those risks rise exponentially.
“So, just like climate change has its risks, SRM has risks. It also has potential benefits, and it has a large amount of uncertainties, and none of them are well understood. So, in order to make a comparison against climate change with SRM, we need to really have an informed decision-making process around SRM so that we can have a better sense of its benefits and its drawbacks,” said Sipra.
“We need to explore SRM in the context of worsening climate change,” he said, adding that geoengineering would “not be a discussion if the climate situation had been resolved after the Rio summit when they formulated the UN Framework Convention on Climate Change.
The fact that the climate is getting worse; the fact that we are not mitigating, is the reason people are beginning to have a conversation about SRM. So, it can only ever be contextualised in comparison to climate change.” DM
Polêmica, a liberação de aerossóis diminuiria a quantidade de luz solar que chega à Terra, mas seus efeitos colaterais negativos poderiam ser maiores que os positivos
Aumentar a quantidade de aerossóis na atmosfera poderia barrar a chegada à Terra de uma pequena fração da luz solar e resfriar provisoriamente o planeta. Cadan Cummings / Jacobs / JETS / NASA-JSC
Depois de ter permanecido em silêncio por 600 anos, o monte Pinatubo, nas Filipinas, acordou em 1991. Uma série de pequenas explosões ao longo de dois meses culminou em uma grande erupção em meados de junho daquele ano, considerada a segunda maior do século passado. Cerca de 200 mil pessoas tiveram de deixar suas casas e mais de 700 morreram no arquipélago filipino como consequência da eclosão. A explosão produziu uma coluna de fumaça e cinzas vulcânicas que se elevou até 40 quilômetros (km) acima da superfície e invadiu a estratosfera, a segunda das cinco camadas da atmosfera que envolve a Terra. Esse manto de partículas em suspensão, geralmente com tamanhos micrométricos, atrapalhou o tráfego aéreo, queimou plantas e cultivos e produziu outros danos locais.
Apesar de ter causado grandes prejuízos materiais e a perda de vidas humanas nas Filipinas, a erupção do Pinatubo é lembrada hoje no meio científico por ter tido uma consequência surpreendente no clima global: a temperatura média da Terra reduziu-se cerca de 0,5 grau Celsius (°C) nos dois anos seguintes à sua atividade vulcânica. A enorme quantidade de partículas em suspensão, os chamados aerossóis, lançada pelo vulcão entrou no sistema de circulação de ar da estratosfera, espalhou-se pelo planeta e atuou por meses como uma espécie de filtro solar: parte dos raios do Sol que chegariam normalmente à superfície terrestre foi refletida ao incidir sobre essa quantidade extra de partículas de aerossóis injetados no sistema. Essa ação produziu um resfriamento temporário do planeta.
Os aerossóis também resfriam a Terra quando estão na troposfera, a camada mais baixa da atmosfera, mas sua ação é mais intensa na estratosfera. O efeito Pinatubo serve de inspiração para uma linha de pesquisa polêmica, cercada de incertezas científicas e riscos ambientais e geopolíticos: a geoengenharia solar ou modificação da radiação solar (SRM, na sigla derivada do inglês). Ela começou a tomar corpo lentamente nos últimos 20 anos em algumas universidades dos Estados Unidos e da Europa à medida que o aquecimento global se tornou mais pronunciado. A ideia central dessa abordagem é aumentar deliberadamente o albedo da Terra, sobretudo na estratosfera, para que ela passe a refletir mais radiação de volta ao espaço e, assim, torne-se um pouco menos quente.
Glauco Lara
O albedo é a fração da luz refletida em relação à absorvida por um corpo ou superfície. Quanto maior o albedo, como em superfícies claras ou brancas, menor a quantidade de calor absorvida. Injetar aerossóis na atmosfera é uma das formas de tentar aumentar o albedo terrestre. Alguns cálculos indicam que uma redução de 1% a 2% da quantidade de radiação solar que normalmente chega à Terra seria suficiente para diminuir sua temperatura média em um 1 °C.
A possibilidade de reduzir a quantidade de radiação solar sobre a Terra começou a ser aventada ainda na década de 1960. Mas sempre foi vista como uma excentricidade perigosa, quase um devaneio. A ideia só ganhou alguma relevância científica depois da erupção do Pinatubo e, mais recentemente, com a emergência da crise climática, causada pelo aumento significativo da temperatua global decorrente da emissão de gases de efeito estufa. Ainda assim, a pesquisa experimental – que envolveria a soltura de alguns quilos de aerossóis na estratosfera para observar seus eventuais efeitos em âmbito local (não global, como ocorreu na gigantesca erupção do vulcão nas Filipinas) – pouco progrediu até hoje em razão da oposição de parte da comunidade científica e de grupos ambientalistas.
“Até agora, existem poucos trabalhos de modelagem climática envolvendo as técnicas de geoengenharia solar”, comenta o físico Paulo Artaxo, do Instituto de Física da Universidade de São Paulo (IF-USP), especialista no estudo de aerossóis atmosféricos. “Nenhum experimento mais significativo foi feito em campo.” Duas abordagens que visam à modificação da radiação solar dominam as discussões. A principal delas é a injeção de aerossóis na estratosfera, a 15 ou 20 km de altitude, conhecida pela sigla SAI, que tenta reproduzir de forma artificial o que as grandes erupções fazem de maneira natural.
Glauco Lara
A outra, vista como de impacto mais localizado, é o clareamento de nuvens marítimas (marine cloud brightening ou MCB). Ela também envolve a liberação de aerossóis (nesse caso, partículas de sal marinho), que funcionam como núcleos de condensação das nuvens. Mas a soltura dessas partículas ocorre em altitudes bem mais baixas, de no máximo 2 km, ainda na troposfera. Com mais aerossóis, as gotas de nuvens ficam menores, refletem mais radiação solar de volta ao espaço e resfriam a superfície. Há outras técnicas cogitadas, como aumentar o albedo em grandes superfícies brancas do planeta, como o Ártico, mas as duas primeiras propostas dominam o debate.
Artaxo colabora com um grupo da Universidade Harvard, dos Estados Unidos, em estudos de modelagem computacional para tentar entender se o comportamento dos aerossóis na estratosfera é realmente similar à sua ação na troposfera. “Precisamos de mais pesquisas sobre esse tema antes de sequer pensarmos em implementar alguma intervenção desse tipo”, comenta o físico da USP, um dos coordenadores do Programa FAPESP de Pesquisa sobre Mudanças Climáticas Globais. “Não temos condições de garantir que a injeção de mais aerossóis não vá, por exemplo, diminuir as chuvas de monções no Sudeste Asiático e colocar em risco uma população de bilhões de pessoas. Se isso ocorrer, quem decide se essa injeção de aerossóis para ou continua? Esse tipo de decisão não pode ficar na mão de um pequeno grupo de países ou de um bilionário que financie um experimento desse tipo.”
Também há indícios de que uma dose extra de aerossóis na estratosfera poderia afetar a camada de ozônio, que protege a vida terrestre da ação nociva da radiação ultravioleta vinda do Sol. Isso sem falar que essas partículas em suspensão são uma forma de poluição do ar. Elas naturalmente se depositam, descem da estratosfera para a troposfera, onde podem causar ou agravar problemas de saúde, sobretudo os respiratórios. Por ora, essas e outras questões não têm respostas satisfatórias.
A posição do físico da USP é partilhada por muitos colegas. “A modificação da radiação solar é um tema sensível e o IPCC [Painel Intergovernamental sobre Mudanças Climáticas, da ONU]reconhece que ainda há muitas incertezas sobre seus potenciais efeitos”, comenta a matemática Thelma Krug, que foi vice-presidente do painel entre 2015 e 2023 e representou o Brasil em negociações internacionais sobre o clima por uma década. “Pessoalmente, sou a favor da pesquisa na área. Mas é preciso ir passo a passo com os experimentos, ter transparência e estabelecer uma governança para esse processo.”
Erupção do vulcão Pinatubo, em 1991, é considerada a segunda maior do século passadoArlan Naeg / AFP via Getty Images
O tema é tão controverso que alguns pesquisadores são contra até que se faça pesquisa sobre as técnicas de geoengenharia solar. Isso porque elas não têm impacto na redução das emissões de gases de efeito estufa, que causam o aumento da temperatura da Terra. Ainda que se mostrem relativamente seguras e eficientes em esfriar temporariamente a Terra, objetivo que hoje é apenas uma hipótese, técnicas como a SAI seriam, no máximo, paliativas. No fundo, dizem os críticos dessa abordagem, os trabalhos nessa área desviariam recursos e tomariam um tempo que poderia ser mais bem empregado na busca por ações que reduzissem a emissão de gases como dióxido de carbono (CO2) e metano (CH4). “Os estudos sobre geoengenharia solar também poderiam ser usados como a desculpa perfeita para que os grandes produtores de gases de efeito estufa não reduzissem suas emissões”, pondera o climatologista Carlos Nobre, do Instituto de Estudos Avançados (IEA) da USP.
Além de ser encarada como um diversionismo em relação à meta central de zerar as emissões de gases de efeito estufa nas próximas décadas, a adoção das técnicas de SRM poderia tornar o planeta refém desse tipo de intervenção climática por um prazo muito longo e indefinido, de décadas ou séculos. Isso criaria um problema extra: o risco de promover o chamado termination shock. Quando o planeta abandonasse o emprego das técnicas de SRM, a temperatura subiria novamente – só que dessa vez de forma muito mais rápida do que no cenário atual de aquecimento global. Isso tornaria quase impossível a adaptação a essa brusca elevação de temperatura. Qualquer oscilação significativa da temperatura, para cima ou para baixo, em um curto período, representa um desafio adaptativo.
Alguns estudos de modelagem climática têm sugerido cenários preocupantes em simulações de possíveis impactos do emprego de técnicas de geoengenharia solar. Esses trabalhos costumam averiguar que outros efeitos (colaterais) essas técnicas de intervenção no clima poderiam induzir, além da redução temporária da temperatura terrestre. Um dos problemas é que a maioria desses estudos se concentra em possíveis consequências no hemisfério Norte, onde ficam os países mais ricos e vive e trabalha a maior parte dos pesquisadores do clima.
Começam, no entanto, a surgir pesquisas com foco em outras partes do planeta. Trabalho publicado em junho deste ano na revista Environmental Research Climate sugere que a adoção da SAI ao longo deste século alteraria os prováveis impactos do aquecimento global sobre a formação de ciclones extratropicais no hemisfério Sul, como aqueles que se formam com certa regularidade na região Sul do Brasil. A previsão é de que, até o fim deste século, o aumento da temperatura global reduza o número de ciclones gerados nessa parte do globo terrestre, mas aumente a intensidade dos fenômenos produzidos. Ou seja, menos ciclones, mas mais fortes.
Glauco Lara
Quando diferentes regimes de injeção de aerossóis na estratosfera são simulados em três modelos climáticos internacionais até 2100, os resultados sinalizam um aumento na frequência de ciclones, mas uma redução em sua força em relação aos prognósticos obtidos em cenários de aquecimento global sem a adoção de qualquer protocolo da SAI. “Não somos contra nem a favor da geoengenharia solar”, diz a pesquisadora Michelle Reboita, da Universidade Federal de Itajubá (Unifei), de Minas Gerais, coordenadora do estudo. “Precisamos é estudá-la. Ela pode produzir resultados positivos em uma parte do mundo e negativos em outra.”
Há também estudos de simulação que tentam prever os possíveis impactos da SAI sobre a biodiversidade. “Nosso objetivo é entender como a SAI pode afetar as espécies de vertebrados terrestres no cenário das mudanças climáticas”, conta o biólogo brasileiro Andreas Schwarz Meyer, que faz estágio de pós-doutorado na Universidade da Cidade do Cabo, na África do Sul, e coordena um projeto de pesquisa sobre o tema. “Em outras palavras, queremos saber quais seriam as espécies ‘vencedoras’ e ‘perdedoras’ no globo caso o emprego dessas técnicas para diminuir a temperatura do planeta venha a se tornar uma realidade.”
No projeto, que ainda está em andamento, Meyer adota uma abordagem chamada perfis horizontais de biodiversidade, que usa dados climáticos históricos para estimar o intervalo térmico (a temperatura máxima e a mínima) e o grau de umidade em que as espécies ocorrem. A técnica é normalmente usada para estimar o impacto sobre as espécies de diferentes cenários de aquecimento global previstos pelo IPCC ao longo deste século.
“Assim, temos uma ideia de quantas espécies serão expostas a essas mudanças, quando e o quão rapidamente isso poderá ocorrer”, comenta o biólogo. Em 2022, o brasileiro publicou um artigo no periódico científico Philosophical Transactions of the Royal Society B em que simulou os efeitos sobre mais de 30 mil espécies de vertebrados marinhos e terrestres de um cenário particular ao longo deste século: primeiro haveria um aquecimento global superior a 2 °C e, em seguida, ocorreria uma redução de temperatura da Terra de forma artificial, por meio da remoção direta de dióxido de carbono da atmosfera. A retirada do principal gás de efeito estufa é hoje ensaiada por um conjunto de técnicas que, por ora, são muito caras e ineficientes em perseguir esse objetivo.
Trilhas de nuvens criadas no mar pela emissão de partículas de poeira por navios
A conclusão geral do estudo é que a subida e a posterior queda artificial da temperatura terrestre poderiam inviabilizar a sobrevivência de muitas espécies e produziriam danos a essas comunidades décadas após se ter atingido uma hipotética estabilização da temperatura do planeta. Meyer está fazendo um estudo semelhante agora, mas com o emprego da SAI no lugar da remoção direta de carbono.
Os trabalhos de Reboita e Meyer se dão no âmbito de uma iniciativa internacional, a Developing country governance research and evaluation for SRM, ou simplesmente Degrees. Seu objetivo é estimular estudos e formar recursos humanos especializados nas técnicas de modificação da radiação solar em países da África, América Latina e sul da Ásia. A Degrees nasceu na década passada dentro da Academia Mundial de Ciências (TWAS) e posteriormente foi assumida por uma organização não governamental britânica, a homônima Degrees. Ela financia quase 40 projetos. No Brasil, além das pesquisas da meteorologista da Unifei, duas linhas de estudo de professores da Universidade Federal de Santa Catarina (UFSC) passaram a ser apoiadas em julho passado.
Com parceiros no exterior, a equipe do engenheiro Mauricio Uriona, do Departamento de Engenharia de Produção e Sistemas da UFSC, pretende estudar como é a percepção do setor produtivo, do governo e da comunidade científica de três países (Brasil, Índia e África do Sul) sobre os potenciais riscos das técnicas de SRM. “Trabalhamos no passado com o tema da transição energética com uma abordagem de cunho socioeconômico e vimos agora uma boa oportunidade de fazer um estudo semelhante sobre geoengenharia solar”, afirma Uriona.
A socióloga ambiental Julia S. Guivant, do Instituto de Pesquisa em Riscos e Sustentabilidade (Iris), da UFSC, vai estudar como diversos atores-chave do país, como a comunidade científica, reguladores políticos, agricultores e representantes de organizações não governamentais, posicionam-se diante dos desafios de governança da geoengenharia solar. “Não temos uma posição sobre se a SRM deve ser usada ou como seu eventual emprego deve ser governado. Somos a favor das pesquisas e do debate democrático sobre o tema, diante dos problemas para atingir as metas de mitigação e adaptação às mudanças climáticas”, diz a socióloga. Colegas da USP e da Universidade Federal de São Paulo (Unifesp) vão colaborar na pesquisa coordenada por Guivant.
Há preocupação de que a geoengenharia solar possa afetar o regime das chuvas de monções na ÍndiaAmarjeet Kumar Singh / Anadolu Agency via Getty Images
As técnicas de SRM são tão polêmicas e sem qualquer tipo de regulação em acordos internacionais que mesmo grupos de pesquisas de instituições renomadas enfrentam dificuldades extremas de realizar pequenos experimentos de campo. Esses trabalhos não têm o potencial de influenciar o clima global, no máximo produzir ciência para se entender os processos envolvidos, com alguma alteração localmente. Ainda assim, os obstáculos práticos à sua realização são quase intransponíveis.
Em março deste ano, foi abandonado o Stratospheric Controlled Perturbation Experiment (SCoPEx), experimento concebido na década passada pelo grupo do físico-químico Frank Keutsch, da Universidade Harvard. A ideia da iniciativa era usar um balão de alta altitude para injetar 2 quilos de aerossóis (no caso, carbonato de cálcio) cerca de 20 km acima da superfície. “Essa quantidade de partículas é ínfima. Equivale à poluição expelida por um jato comercial durante apenas 1 minuto de voo”, disse Keutsch em entrevista dada em 2021 (ver Pesquisa FAPESP nº 303). O balão do SCoPEx era para ter ganho inicialmente os ares dos Estados Unidos em 2018. Mas isso não ocorreu. Em seguida, sua soltura foi prevista para a Suécia, também sem sucesso. Devido a protestos de ambientalistas e de grupos indígenas, o projeto nunca decolou de fato.
Alguns testes de campo com a técnica de clareamento de nuvens marinhas, uma abordagem menos ambiciosa do que a SAI, têm sido feitos, quase sempre a duras penas e diante de críticas de vários setores da sociedade. Em abril deste ano, um grupo da Universidade de Washington, dos Estados Unidos, usou um tipo de ventilador para espalhar partículas de sal marinho na pista de um navio porta-aviões aposentado que estava estacionado no litoral da cidade de Alameda, na Califórnia. A ideia da iniciativa era apenas ver se as partículas poderiam causar algum mal à saúde. Dois meses mais tarde, o município californiano proibiu esse tipo de experimento em seu território.
Na Austrália, pesquisadores da Southern Cross University e organizações locais tocam desde 2020 um projeto-piloto em que tentam aferir se a técnica de MCB pode ser útil para diminuir o branqueamento de corais na região de Townsville. O objetivo do experimento é averiguar se o método diminuiria localmente a temperatura do oceano no centro da Grande Barreira de Corais. O aquecimento das águas marinhas é a principal causa do branqueamento.
Alterar a capacidade de o Ártico refletir a luz do Sol poderia, em tese, minorar o aquecimento globalsodar99 via Getty Images
A desconfiança dos experimentos de campo deriva, em parte, do surgimento periódico de iniciativas pouco transparentes, geridas às vezes por empresas privadas obscuras. Em 2022, a Make Sunsets, uma startup norte-americana, soltou sem autorização no norte do México dois balões com aerossóis destinados à estratosfera. Pouco depois, o governo mexicano proibiu esse tipo de iniciativa em seu território. Agora, a empresa anunciou que está fazendo esse tipo de experimento nos Estados Unidos, mas os resultados dessas iniciativas são desconhecidos.
Para o físico norte-americano David Keith, da Universidade de Chicago, nos Estados Unidos, o interesse em estimular as pesquisas sobre geoengenharia solar tem aumentado, a despeito das incertezas científicas que cercam o emprego dessas técnicas. “Isso é visível nos principais relatórios internacionais, como os do Programa das Nações Unidas para o Meio Ambiente, do Programa Mundial de Pesquisa do Clima, também da ONU, e de grandes grupos ambientalistas, como Environmental Defense”, comenta Keith, em entrevista por e-mail a Pesquisa FAPESP. “Não há dúvida de que a oposição à investigação enfraqueceu, mas é difícil dizer por quê. Talvez seja por causa do aumento das temperaturas ou porque [acredito que] o mundo esteja fazendo agora esforços substanciais para reduzir as emissões de gases de efeito estufa.”
Keith foi membro do programa de geoengenharia solar de Harvard por 12 anos. Hoje ele é a favor da adoção de uma moratória internacional em experimentos de campo até que a ciência sobre o tema esteja mais bem estabelecida e haja alguma forma de governança internacional. Se esse cenário se materializar algum dia, ele diz que a humanidade deveria considerar a realização de um teste no qual se injetaria por uma década na estratosfera cerca de 10% da quantidade necessária de aerossóis para baixar em 1 °C a temperatura global. Dessa forma, seria possível conferir claramente os efeitos dessa abordagem sem correr muitos riscos.
A operação envolveria transportar cerca de 100 mil toneladas de enxofre por ano para a estratosfera – equivalente a 0,3% da quantidade de poluição por enxofre que chega anualmente à atmosfera – por uma frota de 15 jatinhos capazes de voar em altas altitudes. A operação custaria aproximadamente US$ 500 milhões ao ano. É mais uma ideia polêmica. Para alguns, é possível que a única parte boa da sugestão seja a adoção de uma moratória para esse tipo de experimento.
A reportagem acima foi publicada com o título “Controlando o sol” na edição impressa nº 343, de setembro de 2024.
The climate emulator invites you to explore the controversial climate intervention. I gave it a whirl.
August 23, 2024
James Temple
AI pioneer Andrew Ng has released a simple online tool that allows anyone to tinker with the dials of a solar geoengineering model, exploring what might happen if nations attempt to counteract climate change by spraying reflective particles into the atmosphere.
The concept of solar geoengineering was born from the realization that the planet has cooled in the months following massive volcanic eruptions, including one that occurred in 1991, when Mt. Pinatubo blasted some 20 million tons of sulfur dioxide into the stratosphere. But critics fear that deliberately releasing such materials could harm certain regions of the world, discourage efforts to cut greenhouse-gas emissions, or spark conflicts between nations, among other counterproductive consequences.
The goal of Ng’s emulator, called Planet Parasol, is to invite more people to think about solar geoengineering, explore the potential trade-offs involved in such interventions, and use the results to discuss and debate our options for climate action. The tool, developed in partnership with researchers at Cornell, the University of California, San Diego, and other institutions, also highlights how AI could help advance our understanding of solar geoengineering.
The current version is bare-bones. It allows users to select different emissions scenarios and various quantities of particles that would be released each year, from 25% of a Pinatubo eruption to 125%.
Planet Parasol then displays a pair of diverging lines that represent warming levels globally through 2100. One shows the steady rise in temperatures that would occur without solar geoengineering, and the other indicates how much warming could be reduced under your selected scenario. The model can also highlight regional temperature differences on heat maps.
You can also scribble your own rising, falling, or squiggling line representing different levels of intervention across the decades to see what might happen as reflective aerosols are released.
I tried to simulate what’s known as the “termination shock” scenario, exploring how much temperatures would rise if, for some reason, the world had to suddenly halt or cut back on solar geoengineering after using it at high levels. The sudden surge of warming that could occur afterward is often cited as a risk of geoengineering. The model projects that global temperatures would quickly rise over the following years, though they might take several decades to fully rebound to the curve they would have been on if the nations in this simulation hadn’t conducted such an intervention in the first place.
To be clear, this is an exaggerated scenario, in which I maxed out the warming and the geoengineering. No one is proposing anything like this. I was playing around to see what would happen because, well, that’s what an emulator lets you do.
Emulators are effectively stripped-down climate models. They’re not as precise, since they don’t simulate as many of the planet’s complex, interconnected processes. But they don’t require nearly as much time and computing power to run.
International negotiators and policymakers often use climate emulators, like En-ROADS, to get a quick, rough sense of the impact that potential rules or commitments on greenhouse-gas emissions could have.
The Parasol team wanted to develop a similar tool specifically to allow people to evaluate the potential effects of various solar geoengineering scenarios, says Daniele Visioni, a climate scientist focused on solar geoengineering at Cornell, who contributed to Planet Parasol (as well as an earlier emulator).
Climate models are steadily becoming more powerful, simulating more Earth system processes at higher resolutions, and spitting out more and more information as they do. AI is well suited to help draw meaning and understanding from that data. It’s getting ever better at spotting patterns within huge data sets and predicting outcomes based on them.
But he says he’s been spending more and more of his time exploring the potential of solar geoengineering (sometimes referred to as solar radiation management, or SRM), given the threat of climate change and the role that AI can play in advancing the research field.
There are “many things one can do—and that society broadly should work on—to help address climate change, first and foremost decarbonization,” he wrote in an email. “And SRM is where I’m focusing most of my climate-related efforts right now, given that this is one of the places where engineers and researchers can make a big difference (in addition to decarbonization).”
In a 2022 piece, Ng noted that AI could play several important roles in geoengineering research, including “autonomously piloting high-altitude drones” that would disperse reflective particles, modeling effects of geoengineering across specific regions, and optimizing techniques.
Planet Parasol itself is built on top of another climate emulator, developed by researchers at the University of Leeds and the University of Oxford, that relies on the rules of physics to project global average temperatures under various scenarios. Ng’s team then harnessed machine learning to estimate the local cooling effects that could result from varying levels of solar geoengineering, says Jeremy Irvin, a grad student in his research group at Stanford.
One of the clearest limits of the current version of the tool, however, is that the results look dazzling. In the scenarios I tested, solar geoengineering cleanly cuts off the predicted rise in temperatures over the coming decades, which it may well do.
That might lead the casual user of such a tool to conclude: Cool, let’s do it!
But even if solar geoengineering does help the world on average, it could still have negative effects, such as harming the protective ozone layer, disturbing regional rainfall patterns, undermining agriculture productivity, and changing the distribution of infectious diseases.
None of that is incorporated in the results as yet. Plus, a climate emulator isn’t equipped to address deeply complex societal concerns. For instance, does researching such possibilities ease pressure to address the root causes of climate change? Can a tool that works at the scale of the planet ever be managed in a globally equitable way? Planet Parasol won’t be able to answer either of those questions.
Holly Buck, an environmental social scientist at the University at Buffalo and author of After Geoengineering, questioned the broader value of such a tool along similar lines.
In focus groups that she has conducted on the topic of solar geoengineering, she’s found that people easily grok the concept that it can curb warming, even without seeing the results plotted out in a model.
“They want to hear about what can go wrong, the impact on precipitation and extreme weather, who will control it, what it means existentially to fail to deal with the root of the problem, and so on,” she said in an email. “So it is hard to imagine who would actually use this and how.”
Visioni explained that the group did make a point of highlighting major challenges and concerns at the top of the page. He added that they intend to improve the tool over time in ways that will provide a fuller sense of the uncertainties, trade-offs, and regional impacts.
“This is hard, and I struggled a lot with your same observation,” Visioni wrote in an email. “But at the same time … I came to the conclusion it’s worth putting something down and work[ing] to improve it with user feedback, rather than wait until we have the perfect, nuanced version.”
As to the value of the tool, Irvin added that seeing the temperature reduction laid out clearly can make a “stronger, lasting impression.”
“We are calling for more research to push the science forward about other areas of concern prior to potential implementation, and we hope the tool helps people understand the capabilities of SAI and support future research on it,” he said.
Right now, every moment of every day, we humans are reconfiguring Earth’s climate bit by bit. Hotter summers and wetter storms. Higher seas and fiercer wildfires. The steady, upward turn of the dial on a host of threats to our homes, our societies and the environment around us.
We might also be changing the climate in an even bigger way.
For the past two decades, scientists have been raising alarms about great systems in the natural world that warming, caused by carbon emissions, might be pushing toward collapse. These systems are so vast that they can stay somewhat in balance even as temperatures rise. But only to a point.
Once we warm the planet beyond certain levels, this balance might be lost, scientists say. The effects would be sweeping and hard to reverse. Not like the turning of a dial, but the flipping of a switch. One that wouldn’t be easily flipped back.
Mass Death of Coral Reefs
When corals go ghostly white, they aren’t necessarily dead, and their reefs aren’t necessarily gone forever. Too much heat in the water causes the corals to expel the symbiotic algae living inside their tissues. If conditions improve, they can survive this bleaching. In time, the reefs can bounce back. As the world gets warmer, though, occasional bleaching is becoming regular bleaching. Mild bleaching is becoming severe bleaching.
Scientists’ latest predictions are grim. Even if humanity moves swiftly to rein in global warming, 70 percent to 90 percent of today’s reef-building corals could die in the coming decades. If we don’t, the toll could be 99 percent or more. A reef can look healthy right up until its corals start bleaching and dying. Eventually, it is a graveyard.
This doesn’t necessarily mean reef-building corals will go extinct. Hardier ones might endure in pockets. But the vibrant ecosystems these creatures support will be unrecognizable. There is no bouncing back anytime soon, not in the places corals live today, not at any scale.
When it might happen: It could already be underway.
Abrupt Thawing of Permafrost
In the ground beneath the world’s cold places, the accumulated remains of long-dead plants and animals contain a lot of carbon, roughly twice the amount that’s currently in the atmosphere. As heat, wildfires and rains thaw and destabilize the frozen ground, microbes get to work, converting this carbon into carbon dioxide and methane. These greenhouse gasses worsen the heat and the fire and the rain, which intensifies the thawing.
Like many of these vast, self-propelling shifts in our climate, permafrost thaw is complicated to predict. Large areas have already come unfrozen, in Western Canada, in Alaska, in Siberia. But how quickly the rest of it might defrost, how much that would add to global warming, how much of the carbon might stay trapped down there because the thawing causes new vegetation to sprout up on top of it — all of that is tricky to pin down.
“Because these things are very uncertain, there’s a bias toward not talking about it or dismissing the possibility, even,” said Tapio Schneider, a climate scientist at the California Institute of Technology. “That, I think, is a mistake,” he said. “It’s still important to explore the risks, even if the probability of occurrence in the near future is relatively small.”
When it might happen: The timing will vary place to place. The effects on global warming could accumulate over a century or more.
Collapse of Greenland Ice
The colossal ice sheets that blanket Earth’s poles aren’t melting the way an ice cube melts. Because of their sheer bigness and geometric complexity, a host of factors shapes how quickly the ice sheds its bulk and adds to the rising oceans. Among these factors, scientists are particularly concerned about ones that could start feeding on themselves, causing the melting to accelerate in a way that would be very hard to stop.
In Greenland, the issue is elevation. As the surface of the ice loses height, more of it sits at a balmier altitude, exposed to warmer air. That makes it melt even faster.
Scientists know, from geological evidence, that large parts of Greenland have been ice-free before. They also know that the consequences of another great melt could reverberate worldwide, affecting ocean currents and rainfall down into the tropics and beyond.
When it might happen: Irreversible melting could begin this century and unfold over hundreds, even thousands, of years.
Breakup of West Antarctic Ice
At the other end of the world from Greenland, the ice of western Antarctica is threatened less by warm air than by warm water.
Many West Antarctic glaciers flow out to sea, which means their undersides are exposed to constant bathing by ocean currents. As the water warms, these floating ice shelves melt and weaken from below, particularly where they sit on the seafloor. Like a dancer holding a difficult pose, the shelf starts to lose its footing. With less floating ice to hold it back, more ice from the continent’s interior would slide into the ocean. Eventually, the ice at the water’s edge might fail to support its own weight and crack into pieces.
The West Antarctic ice sheet has probably collapsed before, in Earth’s deep past. How close today’s ice is to suffering the same fate is something scientists are still trying to figure out.
“If you think about the future of the world’s coastlines, 50 percent of the story is going to be the melt of Antarctica,” said David Holland, a New York University scientist who studies polar regions. And yet, he said, when it comes to understanding how the continent’s ice might break apart, “we are at Day Zero.”
When it might happen: As in Greenland, the ice sheet could begin to recede irreversibly in this century.
Sudden Shift in the West African Monsoon
Around 15,000 years ago, the Sahara started turning green. It began when small shifts in Earth’s orbit caused North Africa to be sunnier each summer. This warmed the land, causing the winds to shift and draw in more moist air from over the Atlantic. The moisture fell as monsoon rain, which fed grasses and filled lakes, some as large as the Caspian Sea. Animals flourished: elephants, giraffes, ancestral cattle. So did humans, as engravings and rock paintings from the era attest. Only about 5,000 years ago did the region transform back into the harsh desert we know today.
Scientists now understand that the Sahara has flipped several times over the ages between arid and humid, between barren and temperate. They are less sure about how, and whether, the West African monsoon might shift or intensify in response to today’s warming. (Despite its name, the region’s monsoon unleashes rain over parts of East Africa as well.)
Whatever happens will matter hugely to an area of the world where many people’s nutrition and livelihoods depend on the skies.
When it might happen: Hard to predict.
Loss of Amazon Rainforest
Besides being home to hundreds of Indigenous communities, millions of animal and plant species and 400 billion trees; besides containing untold numbers of other living things that have yet to be discovered, named and described; and besides storing an abundance of carbon that might otherwise be warming the planet, the Amazon rainforest plays another big role. It is a living, churning, breathing engine of weather.
The combined exhalations of all those trees give rise to clouds fat with moisture. When this moisture falls, it helps keep the region lush and forested.
Now, though, ranchers and farmers are clearing the trees, and global warming is worsening wildfires and droughts. Scientists worry that once too much more of the forest is gone, this rain machine could break down, causing the rest of the forest to wither and degrade into grassy savanna.
By 2050, as much of half of today’s Amazon forest could be at risk of undergoing this kind of degradation, researchers recently estimated.
When it might happen: Will depend on how rapidly people clear, or protect, the remaining forest.
Shutdown of Atlantic Currents
Sweeping across the Atlantic Ocean, from the western coasts of Africa, round through the Caribbean and up toward Europe before heading down again, a colossal loop of seawater sets temperatures and rainfall for a big part of the globe. Saltier, denser water sinks to the ocean depths while fresher, lighter water rises, keeping this conveyor belt turning.
Now, though, Greenland’s melting ice is upsetting this balance by infusing the North Atlantic with immense new flows of freshwater. Scientists fear that if the motor slows too much, it could stall, upending weather patterns for billions of people in Europe and the tropics.
Scientists have already seen signs of a slowdown in these currents, which go by an unwieldy name: the Atlantic Meridional Overturning Circulation, or AMOC. The hard part is predicting when a slowdown might become a shutdown. At the moment, our data and records are just too limited, said Niklas Boers, a climate scientist at the Technical University of Munich and the Potsdam Institute for Climate Impact Research.
Already, though, we know enough to be sure about one thing, Dr. Boers said. “With every gram of additional CO2 in the atmosphere, we are increasing the likelihood of tipping events,” he said. “The longer we wait” to slash emissions, he said, “the farther we go into dangerous territory.”
The shaded areas on the maps [see here] show the present-day extent of relevant areas for each natural system. They don’t necessarily indicate precisely where large-scale changes could occur if a tipping point is reached.
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Uma (in)certa antropologia 
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