Saving the Ozone Layer in 1987 Slowed Global Warming – Here’s How

This is a NASA image showing the ozone hole at its maximum extent for 2015.
Credit: NASA Goddard Space Flight Center

The Montreal Protocol, an international agreement signed in 1987 to stop chlorofluorocarbons (CFCs) destroying the ozone layer, now appears to be the first international treaty to successfully slow the rate of global warming.

New research published today (December 6, 2019) in Environmental Research Letters has revealed that thanks to the Protocol, today’s global temperatures are considerably lower. And by mid-century, the Earth will be – on average – at least 1°C cooler than it would have been without the agreement. Mitigation is even greater in regions such as the Arctic, where the avoided warming will be as much as 3°C – 4°C.

“By mass CFCs are thousands of times more potent a greenhouse gas compared to CO2, so the Montreal Protocol not only saved the ozone layer but it also mitigated a substantial fraction of global warming,” said lead author of the paper Rishav Goyal.

“Remarkably, the Protocol has had a far greater impact on global warming than the Kyoto Agreement, which was specifically designed to reduce greenhouse gases. Action taken as part of the Kyoto Agreement will only reduce temperatures by 0.12°C by the middle of the century – compared to a full 1°C of mitigation from the Montreal Protocol.”

How the Montreal Protocol not only saved the ozone layer but has also slowed the rate of global warming by as much as 25%.
Credit: The Australian Academy of Science.

The findings were made inadvertently when the team set out to quantify how the Montreal Protocol had affected atmospheric circulation around Antarctica. To get their results, the researchers modeled global climate under two scenarios of atmospheric chemistry; one with, and one without the Montreal Protocol being enacted. They then extended these simulations into the future using conservative estimates for unmitigated CFC emissions – set to 3% growth per annum, much less than the observed CFC growth rates at the time of the establishment of the Montreal Protocol. Their results therefore likely underestimate the actual impact of the international treaty to reduce CFCs.

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