By 2050 global temperatures will be, on average, 1°C (1.8°F) lower than they would have been without the ozone-protection agreement.
New research carried out by scientists from the University of New South Wales (UNSW), Australia, has shown that the Montreal Protocol, designed to protect the ozone layer by phasing out CFCs, has reduced the global rise in temperatures even more than the Kyoto climate change agreement.
“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,” Rishav Goyal, lead author of the paper, told the UNSW Newsroom website.
The researchers found that, by mid-century, the measures in the Montreal Protocol will have avoided 1°C (1.8°F) of temperature change on a global average. In the Arctic, the effect is even greater, and the avoided temperature there will be as much as 3-4°C (5.4-7.2°F) come 2050. This corresponds to 25% mitigation of global warming, according to the authors.
“Remarkably, the [Montreal] Protocol has had a far greater impact on global warming than the Kyoto Agreement, which was specifically designed to reduce greenhouse gases,” Goyal added. “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.”
The scientists behind the study, published in Environmental Research Letters in December 2019, were modeling global climate scenarios under two different sets of atmospheric chemistry conditions, with and without the Montreal Protocol measures to curb f-gas emissions.
They extended these simulations into the future, using an estimated CFC emissions growth of 3% per year for the scenario without the Montreal Protocol. This is a conservative estimate, and lower than the actual growth seen in the years before the adoption of the protocol.
With these models, the researchers found regional differences. In some areas of North America, Eurasia and Africa a temperature rise of 0.5-1°C (0.9-1.8°F) has already been avoided, and in these areas the estimated reduction in temperature will be 1.5-2°C (2.7-3.6°F) by mid century.
With their models, the researchers also found that the Montreal Protocol measures have helped reduce polar ice melt, with the Arctic sea ice being 25% higher today than it would have been without the protocol.
“The success of the Montreal Protocol demonstrates superbly that international treaties to limit greenhouse gas emissions really do work,” co-author of the study, Professor Matthew England, said. “They can impact our climate in very favorable ways, and they can help us avoid dangerous levels of climate change.”