Arquivo da tag: Camada de ozônio

How the world already prevented far worse warming this century (MIT Technology Review)

Uncategorized, , ,

technologyreview.com

The Montreal Protocol was designed to heal the ozone layer. It may have also fended off several degrees of warming—and a collapse of forests and croplands.

James Temple – August 18, 2021

The world has already banded together to enact an international treaty that prevented significant global warming this century—even though that wasn’t the driving goal.

In 1987, dozens of nations adopted the Montreal Protocol, agreeing to phase out the use of chlorofluorocarbons and other chemicals used in refrigerants, solvents, and other industrial products that were breaking down Earth’s protective ozone layer.

It was a landmark achievement, the most successful example of nations pulling together in the face of a complex, collective threat to the environment. Three decades later, the atmospheric ozone layer is slowly recovering, preventing additional levels of ultraviolet radiation that cause cancer, eye damage, and other health problems.

But the virtues of the agreement, ultimately ratified by every country, are more widespread than its impact on the ozone hole. Many of those chemicals are also powerful greenhouse gases. So as a major side benefit, their reduction over the last three decades has already eased warming and could cut as much as 1 ˚C off worldwide average temperatures by 2050.

Now, a new study in Nature highlights yet another crucial, if inadvertent, bonus: reducing the strain that ultraviolet radiation from the sun puts on plants, inhibiting photosynthesis and slowing growth. The Montreal Protocol avoided “a catastrophic collapse of forests and croplands” that would have added hundreds of billions of tons of carbon to the atmosphere, Anna Harper, a senior lecturer in climate science at the University of Exeter and a coauthor of the paper, said in an email.

The Nature paper, published August 18, found that if production of ozone-depleting substances had continued ticking up 3% each year, the additional UV radiation would have curtailed the growth of trees, grasses, ferns, flowers, and crops across the globe.

The world’s plants would absorb less carbon dioxide, releasing as much as 645 billion tons of carbon from the land to the atmosphere this century. That could drive global warming up to 1 ˚C higher over the same period. It would also have devastating effects on agricultural yields and food supplies around the globe.

The impact of rising CFCs levels on plants, plus their direct warming effect in the atmosphere, could have pushed temperatures around 2.5 ˚C higher this century, the researchers found. That would all come on top of the already dire warming projections for 2100.

“While it was originally intended as an ozone protection treaty, the Montreal Protocol has been a very successful climate treaty,” says Paul Young, a climate scientist at Lancaster University and another author of the paper.

All of which poses a question: Why can’t the world enact a similarly aggressive and effective international treaty designed explicitly to address climate change? At least some scholars think there are crucial but largely overlooked lessons in the success of the Montreal Protocol, which are becoming newly relevant as global warming accelerates and the next UN climate conference approaches.

A fresh look

At this point, the planet will continue warming for the next several decades no matter what, as the dire UN climate report warned last week. But how much worse it gets still depends heavily on how aggressively the world cuts climate pollution in the coming decades.

To date, nations have failed, both through the Kyoto Treaty and the Paris climate accord, to pull together an agreement with sufficiently ambitious and binding commitments to phase out greenhouse-gas emissions. Countries will assemble at the next UN conference in Glasgow in early November, with the explicit goal of stepping up those targets under the Paris agreement.

Scholars have written lengthy papers and entire books examining lessons from the Montreal Protocol, and the commonalities and differences between the respective efforts on CFCs and greenhouse gases.

A common view is that the relevance is limited. CFCs were a far simpler problem to solve because they were produced by a single sector—mostly by a few major companies like DuPont—and used in a limited set of applications.

On the other hand, nearly every component of every sector of every nation pumps out greenhouse gases. Fossil fuels are the energy source that drives the global economy, and most of our machines and physical infrastructure are designed around them.

But Edward Parson, a professor of environmental law at the University of California, Los Angeles, says it’s time to take a fresh look at the lessons from the Montreal Protocol.

That’s because as the dangers of climate change become more evident and dire, more and more countries are pushing for stricter rules, and companies are increasingly approaching the stage that those like DuPont did: switching from steadfastly disputing the scientific findings to grudgingly accepting that new rules were inevitable, so they had better figure out how to operate and profit under them.

In other words, we’re reaching a point where enacting more proscriptive rules may be feasible, so it’s crucial to use the opportunity to create effective ones.

Strict rules, consistently enforced

Parson is the author of Protecting the Ozone Layer: Science and Strategy, an in-depth history of the Montreal Protocol published in 2003. He stresses that phasing out ozone-depleting compounds was a more complex problem than is often appreciated, because a sizable fraction of the worldwide economy relied on them in one way or another.

He adds that one of the most persistent misunderstandings about the deal is the notion that the industry had already developed commercially comparable alternative products and therefore was more willing to go along with the agreement in the end.

On the contrary, the development of alternatives happened after the regulations were in place. Rapid innovation continued as the rules tightened, and industry, experts, and technical bodies hashed out how much progress could be achieved and how quickly. That produced ever more and better alternatives “in a repeated positive feedback,” Parson says.

To be sure, the prospect of lucrative new markets also helped.

“DuPoint’s decision to support a CFC ban was based on a belief that it could obtain a significant competitive advantage through the sale of new chemical substitutes because of its proven research and development capabilities to develop chemicals, its (limited) progress already made in developing substitutes and the potential for higher profits in selling new speciality chemicals,” a pair of MIT researchers wrote in an analysis in the late 1990s.

All of this suggests the world shouldn’t wait around for innovations that will make it cheaper and easier to address climate change. Countries need to implement rules that increasingly ratchet down emissions, forcing industries to figure out cleaner ways of generating energy, growing food, producing products, and moving things and people around the world.

Another lesson is to adopt sector-wide rules that force all companies in all countries to abide by the same regulations, avoiding the so-called free-rider problem. This could be especially key for high-emitting companies with stiff international competition. For steel, cement, and other industrial sectors, developing and switching to new products will almost inevitably increase costs at first.

Still, Parson says, there are limits to the comparisons here. The oil and gas sector isn’t in the same position as DuPont, able to reengineer substitutable products and largely keep its businesses and markets intact.

The fossil-fuel sector is certainly making the case that it can carry on in climate-friendly ways, talking up means of capturing emissions from power plants, balancing out pollution through reforestation projects and other sorts of offsets, or sucking carbon out of the atmosphere.

But as studies and articles continually show, it’s difficult to ensure that companies are doing these things in reliable, verifiable, long-lasting, and credible ways. Those tensions are likely to continue complicating international efforts to enact the firm rules required and ensure we’re making the progress that we must.

Still, the Montreal Protocol offers a reminder that international rules binding the global behavior of companies and regulating their products do work, if strictly and consistently enforced. Companies will adapt to survive—even to thrive.

Scientists reveal how landmark CFC ban gave planet fighting chance against global warming (Science Daily)

Uncategorized, , ,

Date: August 18, 2021

Source: Lancaster University

Summary: New modelling by the international team of scientists paints a dramatic vision of a scorched planet Earth without the Montreal Protocol, what they call the ‘World Avoided’. This study draws a new stark link between two major environmental concerns — the hole in the ozone layer and global warming. The research team reveals that if ozone-destroying chemicals, which most notoriously include CFCs, had been left unchecked then their continued and increased use would have contributed to global air temperatures rising by an additional 2.5°C by the end of this century.

Without the global CFC ban we would already be facing the reality of a ‘scorched earth’, according to researchers measuring the impact of the Montreal Protocol.

Their new evidence reveals the planet’s critical ability to absorb carbon from the atmosphere could have been massively degraded sending global temperatures soaring if we still used ozone-destroying chemicals such as CFCs.

New modelling by the international team of scientists from the UK, USA and New Zealand, published today in Nature, paints a dramatic vision of a scorched planet Earth without the Montreal Protocol, what they call the “World Avoided.” This study draws a new stark link between two major environmental concerns — the hole in the ozone layer and global warming.

The research team, led by a Lancaster University scientist, reveals that if ozone-destroying chemicals, which most notoriously include CFCs, had been left unchecked then their continued and increased use would have contributed to global air temperatures rising by an additional 2.5°C by the end of this century.

Their findings, outlined in the paper ‘The Montreal Protocol protects the terrestrial carbon sink’, show that banning CFCs has protected the climate in two ways — curbing their greenhouse effect and, by protecting the ozone layer, shielding plants from damaging increases in ultraviolet radiation (UV). Critically, this has protected plant’s ability to soak up and lock in carbon dioxide from the atmosphere and so prevented a further acceleration of climate change.

The research team developed a new modelling framework, bringing together data on ozone depletion, plant damage by increased UV, the carbon cycle and climate change. Their novel modelling shows an alternative future of a planet where the use of CFCs continued to grow by around three per cent a year.

Their modelling reveals:

  • Continued growth in CFCs would have led to a worldwide collapse in the ozone layer by the 2040s.
  • By 2100 there would have been 60 per cent less ozone above the tropics. This depletion above the tropics would have been worse than was ever observed in the hole that formed above the Antarctic.
  • By 2050 the strength of the UV from the sun in the mid-latitudes, which includes most of Europe including the UK, the United States and central Asia, would be stronger than the present day tropics.

The depleted ozone layer would have seen the planet, and its vegetation, exposed to far more of the sun’s UV.

Plants absorb carbon dioxide (CO2) through photosynthesis and studies have shown that large increases in UV can restrict plant growth, damaging their tissues, and impairing their ability to undertake photosynthesis. This means the plants absorb less carbon.

Less carbon in vegetation also results in less carbon becoming locked into soils, which is what happens to a lot of plant matter after it dies. All of this would have happened on a global scale.

The researchers’ models show that in a world without the Montreal Protocol the amount of carbon absorbed by plants, trees and soils dramatically plummets over this century. With less carbon in plants and soils, more of it remains in the atmosphere as CO2.

Overall, by the end of this century without the Montreal Protocol CFC ban:

  • There would have been 580 billion tonnes less carbon stored in forests, other vegetation and soils.
  • There would be an additional 165-215 parts per million of CO2 in the atmosphere, depending on the future scenario of fossil fuel emissions. Compared to today’s 420 parts per million CO2, this is an additional 40-50%.
  • The huge amount of additional CO2 would have contributed to an additional 0.8°C of warming through its greenhouse effect.

Ozone depleting substances, such as CFCs, are also potent greenhouse gases and previous research has shown that their ban prevented their contribution to global warming through their greenhouse effect. By the end of this century, their greenhouse effect alone would have contributed an additional 1.7°C global warming. This is in addition to the newly quantified 0.8°C warming, coming from the extra CO2 that would have resulted from damaged vegetation, meaning that temperatures would have risen 2.5°C overall.

Dr Paul Young, lead author from Lancaster University, said: “Our new modelling tools have allowed us to investigate the scorched Earth that could have resulted without the Montreal Protocol’s ban on ozone depleting substances.

“A world where these chemicals increased and continued to strip away at our protective ozone layer would have been catastrophic for human health, but also for vegetation. The increased UV would have massively stunted the ability of plants to soak up carbon from the atmosphere, meaning higher CO2 levels and more global warming.

“With our research, we can see that the Montreal Protocol’s successes extend beyond protecting humanity from increased UV to protecting the ability of plants and trees to absorb CO2. Although we can hope that we never would have reached the catastrophic world as we simulated, it does remind us of the importance of continuing to protect the ozone layer. Entirely conceivable threats to it still exist, such as from unregulated use of CFCs.”

The planet has already seen 1°C warming from pre-industrial temperatures. Even if we had somehow managed to get to net zero CO2 emissions, the additional 2.5°C rise would take us to a rise of 3.5°C. This is far in excess of the 1.5°C rise above pre-industrial levels that many scientists see as the most global temperatures can rise in order to avoid some of the most damaging effects of climate change.

Dr Chris Huntingford of the UK Centre for Ecology & Hydrology said: “This analysis reveals a remarkable linkage, via the carbon cycle, between the two global environmental concerns of damage to the ozone layer and global warming.”

Background information

The ozone layer is an essential barrier that protects us by filtering the sun’s harmful UV — when a hole in the layer was discovered above Antarctica in the 1980s, it caused great alarm because of the damage UV can cause to human health through conditions such as skin cancers.

The Montreal Protocol, which was signed in 1987, is championed as an exemplar in environmental diplomacy. By agreeing to a worldwide ban on ozone depleting substances, including CFCs, international leaders were able to save the planet’s ozone layer. Thanks to the Montreal Protocol the ozone layer is undergoing a long process of repair.

Funders: The research was supported by the Engineering and Physical Science Research Council, Natural Environment Research Council, Lancaster University, the UK and New Zealand governments, NASA and the United States’ National Science Foundation.

The study brings together experts across atmospheric chemistry, physicists, plant scientists, and land surface modellers from Lancaster and Exeter Universities, the UK Centre for Ecology & Hydrology, NASA, the National Center for Atmospheric Research, and the National Institute for Water and Atmospheric Research.

Story Source:

Materials provided by Lancaster University. Note: Content may be edited for style and length.

Journal Reference:

  1. Paul J. Young, Anna B. Harper, Chris Huntingford, Nigel D. Paul, Olaf Morgenstern, Paul A. Newman, Luke D. Oman, Sasha Madronich, Rolando R. Garcia. The Montreal Protocol protects the terrestrial carbon sink. Nature, 2021; 596 (7872): 384 DOI: 10.1038/s41586-021-03737-3

Four new human-made ozone depleting gases found in the atmosphere (Science Daily)

Uncategorized,

Date: March 9, 2014

Source: University of East Anglia

Summary: Scientists at the University of East Anglia have identified four new human-made gases in the atmosphere — all of which are contributing to the destruction of the ozone layer. New research reveals that more than 74,000 tonnes of three new chlorofluorocarbons (CFCs) and one new hydrochlorofluorocarbon (HCFC) have been released into the atmosphere.

The largest ozone hole over Antarctica (in purple) was recorded in September 2006. Credit: NASA

Scientists at the University of East Anglia have identified four new human-made gases in the atmosphere — all of which are contributing to the destruction of the ozone layer.

New research published today in the journal Nature Geoscience reveals that more than 74,000 tonnes of three new chlorofluorocarbons (CFCs) and one new hydrochlorofluorocarbon (HCFC) have been released into the atmosphere.

Scientists made the discovery by comparing today’s air samples with air trapped in polar firn snow — which provides a century-old natural archive of the atmosphere. They also looked at air collected between 1978 and 2012 in unpolluted Tasmania.

Measurements show that all four new gases have been released into the atmosphere recently — and that two are significantly accumulating. Emission increases of this scale have not been seen for any other CFCs since controls were introduced during the 1990s. But they are nowhere near peak CFC emissions of the 1980s which reached around a million tonnes a year.

Lead researcher Dr Johannes Laube from UEA’s School of Environmental Sciences said: “Our research has shown four gases that were not around in the atmosphere at all until the 1960s which suggests they are human-made.”

“CFCs are the main cause of the hole in the ozone layer over Antarctica. Laws to reduce and phase out CFCs came into force in 1989, followed by a total ban in 2010. This has resulted in successfully reducing the production of many of these compounds on a global scale. However, legislation loopholes still allow some usage for exempted purposes.

“The identification of these four new gases is very worrying as they will contribute to the destruction of the ozone layer. We don’t know where the new gases are being emitted from and this should be investigated. Possible sources include feedstock chemicals for insecticide production and solvents for cleaning electronic components.

“What’s more, the three CFCs are being destroyed very slowly in the atmosphere — so even if emissions were to stop immediately, they will still be around for many decades to come,” he added.

This research has been funded by the Natural Environment Research Council (NERC), the National Centre for Atmospheric Science (NCAS), the European Union, and the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Journal Reference:

  1. Johannes C. Laube, Mike J. Newland, Christopher Hogan, Carl A. M. Brenninkmeijer, Paul J. Fraser, Patricia Martinerie, David E. Oram, Claire E. Reeves, Thomas Röckmann, Jakob Schwander, Emmanuel Witrant, William T. Sturges. Newly detected ozone-depleting substances in the atmosphere.Nature Geoscience, 2014; DOI: 10.1038/ngeo2109

Profits on Carbon Credits Drive Output of a Harmful Gas (N.Y.Times)

Uncategorized, , , , , ,

Qilai Shen for The New York Times. A view of a coolant-producing factory in Jiangsu Province, China. Some manufacturers of gases used in air-conditioning and refrigeration have earned millions by accumulating emissions credits from the destruction of an obscure waste gas normally released as a byproduct. The credits are then resold on international markets.

By  and 

Published: August 8, 2012

RANJIT NAGAR, India — When the United Nations wanted to help slow climate change, it established what seemed a sensible system.

Greenhouse gases were rated based on their power to warm the atmosphere. The more dangerous the gas, the more that manufacturers in developing nations would be compensated as they reduced their emissions.

But where the United Nations envisioned environmental reform, some manufacturers of gases used in air-conditioning and refrigeration saw a lucrative business opportunity.

They quickly figured out that they could earn one carbon credit by eliminating one ton of carbon dioxide, but could earn more than 11,000 credits by simply destroying a ton of an obscure waste gas normally released in the manufacturing of a widely used coolant gas. That is because that byproduct has a huge global warming effect. The credits could be sold on international markets, earning tens of millions of dollars a year.

That incentive has driven plants in the developing world not only to increase production of the coolant gas but also to keep it high — a huge problem because the coolant itself contributes to global warming and depletes the ozone layer. That coolant gas is being phased out under a global treaty, but the effort has been a struggle.

So since 2005 the 19 plants receiving the waste gas payments have profited handsomely from an unlikely business: churning out more harmful coolant gas so they can be paid to destroy its waste byproduct. The high output keeps the prices of the coolant gas irresistibly low, discouraging air-conditioning companies from switching to less-damaging alternative gases. That means, critics say, that United Nations subsidies intended to improve the environment are instead creating their own damage.

The United Nations and the European Union, through new rules and an outright ban, are trying to undo this unintended bonanza. But the lucrative incentive has become so entrenched that efforts to roll it back are proving tricky, even risky.

China and India, where most of the 19 factories are, have been resisting mightily. The manufacturers have grown accustomed to an income stream that in some years accounted for half their profits. The windfall has enhanced their power and influence. As a result, many environmental experts fear that if manufacturers are not paid to destroy the waste gas, they will simply resume releasing it into the atmosphere.

A battle is brewing.

Disgusted with the payments, the European Union has announced that as of next year it will no longer accept the so-called waste gas credits from companies in its carbon trading system — by far the largest in the world — essentially declaring them counterfeit currency. That is expected to erode their value, but no one is sure by how much.

“Consumers in Europe want to know that if they’re paying for carbon credits, they will have good environmental effects — and these don’t,” Connie Hedegaard, the European commissioner for climate action, said in an interview.

Likewise, the United Nations is reducing the number of credits the coolant companies can collect in future contracts. But critics say the revised payment schedule is still excessive and will have little immediate effect, since the subsidy is governed by long-term contracts, many of which do not expire for years.

Even raising the possibility of trimming future payments “was politically hard,” said Martin Hession, the immediate past chairman of the United Nations Clean Development Mechanism’s executive board, which awards the credits. China and India both have representatives on the panel, and the new chairman, Maosheng Duan, is Chinese.

Carbon trading has become so essential to companies like Gujarat Fluorochemicals Limited, which owns a coolant plant in this remote corner of Gujarat State in northwest India, that carbon credits are listed as a business on the company Web site. Each plant has probably earned, on average, $20 million to $40 million a year from simply destroying waste gas, says David Hanrahan, the technical director of IDEAcarbon, a leading carbon market consulting firm. He says the income is “largely pure profit.”

And each plant expects to be paid. Some Chinese producers have said that if the payments were to end, they would vent gas skyward. Such releases are illegal in most developed countries, but still permissible in China and India.

As the United Nations became involved in efforts to curb climate change in the last 20 years, it relied on a scientific formula: Carbon dioxide, the most prevalent warming gas, released by smokestacks and vehicles, is given a value of 1. Other industrial gases are assigned values relative to that, based on their warming effect and how long they linger. Methane is valued at 21, nitrous oxide at 310. HFC-23, the waste gas produced making the world’s most common coolant — which is known as HFC-22 — is near the top of the list, at 11,700.

The United Nations used the values to calibrate exchange rates when it began issuing carbon credits in 2005 under the Clean Development Mechanism. That system grants companies that reduce emissions in the developing world carbon credits, which they are then free to sell on global trading markets. Buyers of the credits include power plants that need to offset emissions that exceed European limits, countries buying offsets to comply with the Kyoto Protocol — an international environmental treaty — and some environmentally conscious companies that voluntarily offset their carbon footprint.

Since the United Nations program began, 46 percent of all credits have been awarded to the 19 coolant factories, in Argentina, China, India, Mexico and South Korea. Two Russian plants receive carbon credits for destroying HFC-23 under a related United Nations program.

“I was a climate negotiator, and no one had this in mind,” said David Doniger of the Natural Resources Defense Council. “It turns out you get nearly 100 times more from credits than it costs to do it. It turned the economics of the business on its head.”

Destroying the waste gas is cheap and simple, but it is hard to know exactly how much any one company has earned from doing so, since the market price for carbon credits has varied considerably with demand — from about $9 to nearly $40 per credit — and they can be sold at a discount through futures contracts.

The production of coolants was so driven by the lure of carbon credits for waste gas that in the first few years more than half of the plants operated only until they had produced the maximum amount of gas eligible for the carbon credit subsidy, then shut down until the next year, United Nations reports said. The plants also used inefficient manufacturing processes to generate as much waste gas as possible, said Samuel LaBudde of the Environmental Investigation Agency, an organization based in Washington that has long spearheaded a campaign against what he called “an incredibly perverse subsidy.”

Michael Wara, a law professor at Stanford University, has calculated that in years when carbon credits were trading at high prices and coolant was dirt-cheap because of the oversupply, companies were earning nearly twice as much from the credits as from producing the coolant itself.

The United Nations, recognizing the temptation for companies to jump into the lucrative business, has refused since 2007 to award carbon credits to any new factories destroying the waste gas. And last November, it announced that in contract renewals, factories could claim credits for waste gas equivalent only to 1 percent of their coolant production, down from 3 percent. The United Nations believes that eliminates the incentive to overproduce, said Mr. Hession, the former Clean Development Mechanism board chairman.

Even with these adjustments, credits for destroying waste gas this year remain the most common type in the United Nations system, which rewards companies for reducing all types of warming emissions. Eighteen percent of credits in 2012 will go to the 19 coolant plants, compared with 12 percent to 2,372 wind power plants and 0.2 percent for 312 solar projects for the carbon dioxide emissions avoided by the clean energy they produce.

In India, coolant plants received about half of the United Nations carbon credits awarded to companies in that country, for destroying their waste gas, during the system’s first five years. They accrued the power and money to fight efforts to roll back the subsidy.

Compared with Indian representatives, Chinese diplomats have shown greater willingness at international meetings to consider altering the subsidy for waste gas credits, said Stephen O. Andersen, a former United States Environmental Protection Agency official who is now with the Institute for Governance and Sustainable Development in Washington. That is because China has a more centrally controlled economy and because it is developing an industry based on newer coolants. “It’s easier for them to put the national interest before the interest of one manufacturing sector,” he said.

A bigger question is just how much the European Union’s decision to disallow, as of next year, the waste gas credits in its immense carbon trading system will decrease their value.

Banks and companies holding such credits have been rushing to cash them in or sell them. And the potential devaluation of the carbon credits has an impact in other industrialized nations, since the carbon credit projects involve foreign sponsors and investors, who sometimes received carbon credits in exchange for services or financing.

The Gujarat project was financed by Rabobank of the Netherlands and the Sumitomo Corporation of Japan.

A coolant factory in Monterrey, Mexico, that receives carbon credits is 49 percent owned by Honeywell. Goldman Sachs bought many of its carbon credits.

Such credits are likely to have some continued value, because they can be used in other environmental programs that allow their use, like voluntary ones through which companies offset the emissions generated by having a conference or travelers opt to pay a fee to offset the emissions from an airplane flight.

Mr. LaBudde, of the Environmental Investigation Agency, who has long campaigned against the subsidy, said he hoped that no one would buy these “toxic” credits that “have no place in carbon markets” and that they would quickly disappear. In its latest annual report, Gujarat Fluorochemicals acknowledged that its carbon credits “may not have a significant market” starting next year because European companies have previously been their primary buyers.

Mr. Hanrahan, of IDEAcarbon, said that the credits could, at the very least, be sold at a low price to traders who see the possibility for marginal profit in a way similar to the market for junk bonds. Even if all the proposals to make the carbon trade far less valuable succeeded, the 19 factories certified to generate carbon credits by destroying the waste gas could earn $1 billion from that business over the next eight years, according to projections by IDEAcarbon.

And even as the economics shift, one big environmental question remains: Without some form of inducement, will companies like Gujarat Fluorochemicals continue to destroy the waste gas HFC-23? Already, a small number of coolant factories in China that did not qualify for the United Nations carbon credits freely vent this dangerous chemical. And atmospheric levels are rapidly rising.

Elisabeth Rosenthal reported from Gujarat State, India, and Andrew W. Lehren from New York.