Humans Already Slowed The Climate Crisis Once, New Research Shows

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

New research published today in Environmental Research Letters has revealed that today's global heats are considerably lower. The Earth will be least 1 degree Celsius (°C) cooler than it would have been without the Paris agreement by mid-century.

Mitigation is even greater in Arctic and other regions where the avoided warming will be as much as 3°C-4°C. According to the lead author of the paper Rishav Goyal, Montreal Protocol not only saved the ozone layer but it also mitigated a substantial fraction of global warming since mass CFCs are thousands of times more potent a greenhouse gas compared to carbon dioxide (CO2).

"[The] Protocol [has remarkably made a] far greater impact on global warming than the Kyoto Agreement, which was specifically designed to reduce greenhouse gases," said Goyal. The lead author added the steps taken as part of the Kyoto Agreement "would 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."

The results were made inadvertently when the researchers quantified how Montreal Protocol affected atmospheric flow around Antarctica.

The researchers modelled global climate under two atmospheric chemistry conditions to get their results - one with, and one without the Montreal Protocol being enacted.

The team further stimulated into the future through conservative estimates for unmitigated CFC emissions-set to three percent growth per annum, much less than the observed CFC growth rates at the time of establishment of the Montreal Protocol. The results underestimated the actual impact of the international treaty to reduce CFCs.

Montreal Protocol's success in mitigating climate change is even more shocking when focusing on regional domains. Warming of between 0.5°C-1°C, for example, has already been avoided over North America, Africa and Eurasia.

The menti oned regions have already avoided warming for as much as 1.5°C-2°C by midcentury and over the Arctic avoided warming will be as much as 3°C-4°C.

An amount of avoided ice melt were found by the researchers due to the Protocol, with amount of 25 percent of sea ice increase in Arctic than it would have been without any reduction in CFC emissions.

The observed accelerating ice sheet melt over Greenland and the associated sea level rise has also been reduced by the Protocol.

Co-author Dr. Martin Jucker said Montreal Protocol continuously mitigates global warming impacts for more than three decades and surpasses some treaties that were specifically aimed to ameliorate climate change impacts.

The success of the Montreal Protocol, according to co-autjor Matthew England, superbly demonstrates that international treaties to limit greenhouse gas emissions really do work.

England added the Protocol could affect the climate in favourable ways, and they could help avoid dangerous levels of climate change.

The researchers said the next big target of the Protocol would be zeroing out carbon dioxide emissions since Montreal Protocol was able to sort out CFCs.