NEWS
07 May 2025
The Advanced Research and Invention Agency is investing £57 million to study climate-manipulating technologies, but says it is taking a cautious approach.
The United Kingdom’s high-risk research agency will fund £56.8 million (US$75 million) worth of projects in the controversial area of geoengineering — manipulating Earth’s environment to avert negative effects of climate change. The 21 projects include small-scale outdoor experiments that will attempt to thicken Arctic sea ice and to brighten clouds so that they reflect more sunlight. The hope is that successful technologies could one day contribute to efforts to prevent the planet from passing dangerous climate tipping points.The UK’s $1-billion bet to create technologies that change the world
Supported by the Advanced Research and Invention Agency (ARIA) as part of its five-year Exploring Climate Cooling programme, the projects are among the most significant geoengineering experiments funded by a government.
The research has the potential to be beneficial, but must be undertaken cautiously, says Peter Frumhoff, a science-policy adviser at the Woodwell Climate Research Center in Falmouth, Massachusetts. “I am strongly supportive of responsible research on solar geoengineering and other climate interventions,” he says.
The funding package is the latest from ARIA, which was established in 2023 by the UK government and is modelled on the US Defense Advanced Research Projects Agency. With an £800-million budget, it funds high-risk, high-reward research into technologies that could have major consequences for humanity, including artificial intelligence and neurotechnology.
Divisive research
Another such area identified by ARIA was geoengineering, says Mark Symes, an electrochemist at the University of Glasgow, UK, who leads the Exploring Climate Cooling programme.
Symes says the programme’s goal is not to find ways to replace more accepted approaches to tackling climate change, such as reducing carbon emissions. Instead, he says, geoengineering could be useful to prevent the world reaching certain tipping points that might occur before emissions reductions can have an effect. That could include “the collapse of circulations in the North Atlantic driven by the runaway melting of the Greenland ice sheet”, he says.
But even as climate change continues unabated, the concept is controversial: last year, researchers at Harvard University in Cambridge, Massachusetts, cancelled a project that would have introduced particles into the atmosphere in an effort to ‘dim’ the Sun after an outcry in Sweden, where the experiment was to take place.
Wary of such concerns, ARIA is taking a cautious approach. “We want to keep this research in the public domain,” says Piers Forster, a climate-change scientist at the University of Leeds, UK, who chairs a committee that will monitor ARIA’s climate-cooling projects. “We want it to be transparent for everyone.”
The 21 projects were selected through a competitive application process, which received about 120 proposals.
These fall into five research categories: studying ways to thicken ice sheets; assessing whether marine clouds could be brightened to offset damage to coral reefs; understanding how cirrus clouds warm the climate; looking at whether materials could be released into the stratosphere to reflect sunlight; and theoretical work on whether a sunshade deployed in space could cool portions of Earth’s surface.
Solar experiment
Five projects involve the most controversial area of geoengineering — outdoor experiments that interact with the environment. Frumhoff says that “building trust will be essential” in conducting such research. “I would be opposed to outdoor experiments being funded by any nation that isn’t aggressively and seriously reducing its own emissions,” he says.
The stratospheric experiment — which is among the first outdoor solar-geoengineering experiment to receive government funding — will involve using balloons to carry materials such as limestone and dolomite dust into the stratosphere, to a height of about 15–50 kilometres, to see how they respond to the conditions. No particles will be released into the stratosphere, says ARIA.
Shaun Fitzgerald at the Centre for Climate Repair in Cambridge, UK, leads one of the ice projects. His team will conduct small-scale experiments in the Norwegian Arctic archipelago of Svalbard and in Canada to pump water from beneath ice sheets and spread it on top, covering up to one square kilometre in area, to see whether such a method could thicken Earth’s diminishing ice sheets.
“We’re going to see whether we’ve actually been able to grow more sea ice in the Arctic winter,” says Fitzgerald. Early results from work that Fitzgerald’s team did last year, before receiving ARIA funding, showed ice growth of “about half a metre”, he says.
Julienne Stroeve, a sea-ice researcher at University College London, isn’t sure how effective this method would be in preventing widespread sea-ice loss. “I do not think this is feasible at any real scale needed,” she says, noting that the impact on local ecosystems is also unclear. ARIA says that Fitzgerald’s experiment will be scaled up only if it is deemed to be “ecologically sound”.
“Any small-scale outdoor experiments will be designed with safety and reversibility at their core, and will undergo environmental-impact assessment with public engagement,” says Ilan Gur, ARIA’s chief executive.
Brighter clouds
One of the cloud-brightening projects will take place off the coast of Australia, led by the Southern Cross University in New South Wales. It will use a large fan to spray seawater particles over the Great Barrier Reef, to make the clouds above it whiter and more reflective. The hope is that this could prevent global warming from damaging coral reefs. “Those particles drift upwards to the cloud base, where the tiny salt particles cause water droplets in the cloud to split into smaller droplets,” says Symes. “The smaller the droplets, the more white [the cloud] is.” The experiment will take place over 10 square kilometres.
The sole space-sunshade project, led by the Planetary Sunshade Foundation in Golden, Colorado, will model whether a physical reflector or a cloud of dust could be placed in space, between Earth and the Sun, to limit the amount of sunlight reaching Earth. “If you did wish to cool parts of Earth, space shades could be the most effective way,” says Symes. Nothing will be launched into space, however — the work is purely theoretical.
Responsible regulation
ARIA’s leaders hope that, by 2030, the outcomes of the programme could inform international regulations for geoengineering. One of the 21 projects will investigate how these approaches could be responsibly governed.
“The issue we are most concerned with is how to make sure activities, should they be pursued in the future, don’t lead to conflict between countries,” says project leader Matthias Honegger, a researcher at the Centre for Future Generations (CFG) in Brussels. For example, one worry is that interventions could cause side effects in neighbouring nations.
“Right now, there is no natural home for this issue within the United Nations,” says Cynthia Scharf, a senior fellow at the CFG in New York who is part of Honegger’s project. “We need to look at the substance of governance and the process of decision-making.”
Nature 641, 567-568 (2025)
doi: https://doi.org/10.1038/d41586-025-01389-1
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