Although small, that decline will come sooner than expected, scientists say — and it represents a significant milestone in an international effort to protect the layer of Earth’s stratosphere that blocks dangerous ultraviolet sunlight.
As humanity struggles to curb greenhouse gas pollution, which has already raised global temperatures to record highs, scientists say the progress of HCFCs is a hopeful sign.
“This is a remarkable success story that shows how global policies protect the planet,” said climate scientist Veerabhadran Ramanathan of the University of California, San Diego and Cornell University, who was not involved in the new study.
50 years ago, researchers realized that a hole in the ozone layer over Antarctica was allowing cancer-causing radiation to reach the Earth’s surface. were the main culprits Chlorofluorocarbons (CFCs), which destroy thousands of ozone molecules with one chlorine atom and remain in the atmosphere for hundreds of years.
The discovery prompted countries to sign the 1987 Montreal Protocol, agreeing to phase out the production of CFCs. Under the terms of the agreement, rich countries will first stop production and provide financial and technical assistance to low-income countries that will move away from polluting chemicals. The production of CFCs has been banned worldwide since 2010.
But the most common substitutes are HCFCs—compounds that have one-tenth the ozone-depleting potential of CFCs, but can still cause significant damage. The most commonly used HCFC has a heat-trapping capacity of about 2,000 times that of carbon dioxide over a 100-year period. So in 1992 countries agreed to phase out these chemicals as well.
“This transition has been very successful,” said University of Bristol researcher Luke Western, lead author of the Nature Climate Change study.
The United Nations estimated that the world controlled 98 percent of ozone-depleting substances produced in 1990. Those production curbs will take decades to translate into fewer products and fewer HCFCs in the atmosphere. But Western research, based on data from two global air monitoring programs, shows that the turning point has finally arrived.
The contribution of HCFCs to climate change has risen to about 0.05 degrees Celsius (almost one-tenth of a degree Fahrenheit), and their abundance in the atmosphere is expected to return to 1980 levels by 2080.
“This milestone is a testament to the power of international cooperation,” said Avisa Mahabhadra, director of the Environmental Intelligence Agency’s climate campaign. “For me, it means the ability to do a lot more, and it gives me hope for the climate.”
Mahapatra said the Montreal Protocol’s success would spur efforts to curb planet-warming pollution — another milestone reached last year. By recognizing each country’s needs and setting clear, actionable goals, the agreement spurred people to take action on what was left, he said. The only treaty signed by every country on earth. It is believed to have helped to avoid the world Millions of cases of skin cancer And a size whole degrees Celsius (1.8 degrees Fahrenheit) warming.
But Mahabharata said that the work was not done. Since HCFCs were a flawed substitute for CFCs, they have now been replaced by a new class of refrigerants – hydrofluorocarbons (HFCs) – which are considered climate “super pollutants”. Although the Montreal Protocol was revised in 2016, it called for a reduction in the use of HFCs, which are often used in refrigerants, refrigerators and insulation.
Ultimately, Western said, transitioning away from fossil fuels will be more complicated than limiting the production of ozone-depleting substances. The Montreal Protocol affected relatively little industry, and required companies to change only their products — not their entire businesses.
With climate change, “you’re up against a big beast in some ways,” Western said.
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