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Montreal Protocol delays first ice-free Arctic summer

Montreal Protocol delays first ice-free Arctic summer

by Holly Evarts
|May 25, 2023

This story was originally published on Columbia Engineering.

When scientists discovered a hole over Antarctica in 1985, nations across the globe came together to draft a treaty aimed at protecting the ozone layer, protecting the planet and us from harmful levels of ultraviolet radiation. The resulting Montreal Protocol, the only UN treaty ratified by all countries in the world, was signed in 1987 and entered into force in 1989, when little was known about its impact on the global climate.Its purpose is to reduce the atmospheric ozone depleting substancessuch as materials commonly used in products such as refrigerator, air conditioning, fire extinguishers and aerosols. It has been an important mitigation treaty for more than 50 years, affecting many aspects of the global climate.

Arctic iceberg with bottom visible

An iceberg in the Arctic Ocean. Credit: AWeith via Creative Commons

Benefits of Mitigation Treaties

A new study led by climate researchers Columbia Engineering The University of Exeter demonstrates that the treaty’s impact extends all the way to the Arctic: its implementation has delayed the appearance of the first ice-free Arctic by up to 15 years, depending on the details of future emissions. The study was published today in Member of the National Academy of Sciences.

“The first ice-free Arctic summer — with virtually no sea ice in the Arctic Ocean — would be a major milestone in the climate change process, and what we found surprised us,” said the study’s co-authors Lorenzo PolvaniMaurice Ewing and J. Lamar Worzel Professor, Department of Geophysics Applied Physics and Applied Mathematics and professor Earth and Environmental Sciences“Our results show that the climate benefits of the Montreal Protocol are not in the distant future: the protocol is delaying the melting of Arctic sea ice. That’s what a successful climate treaty does: it Produced measurable results during the year.”

Effects of ozone-depleting substances

Polwani pointed to the rapid melting of Arctic sea ice as the largest and clearest signal of man-made climate change. Current projections suggest that the first ice-free Arctic summer could occur by 2050, largely due to increasing concentrations of carbon dioxide in the atmosphere. However, other powerful greenhouse gases have also contributed to the loss of Arctic sea ice, notably ozone-depleting substances. While these substances came under strict control under the Montreal Protocol in the late 1980s, their atmospheric concentrations began to decline in the mid-1990s.

Polvani and his co-authors mark englanda senior fellow at the Royal Commission for the 1851 Exhibition at the University of Exeter and a former doctoral student of Polvani, was particularly interested in exploring the effects of ozone-depleting substances because their molecules, although not commonly found in the atmosphere, have the ability to warm the planet tens of thousands of times that of carbon dioxide.

New climate model simulates

Researchers analyzed new climate model simulations and found that the Montreal Protocol delayed the first ice-free summer in the Arctic by 15 years, depending on future carbon dioxide emissions. They compared the estimated warming of ozone-depleting substances with and without the Montreal Protocol for two scenarios of future CO2 emissions from 1985 to 2050. Their results show that without the enactment of the Montreal Protocol, the estimated global average surface temperature would have risen by about 0.5°C by 2050, and the Arctic polar ice cap would have risen by nearly 1°C.

“This important climate mitigation stems entirely from greenhouse gas warming from regulated ozone-depleting substances reduction, with no effect from avoided stratospheric ozone loss,” England said. “While ozone-depleting substances are not as abundant as other greenhouse gases such as carbon dioxide, they have a real impact on global warming. The impact of ozone-depleting substances on the Arctic is particularly strong, and they were an important driver of Arctic climate change in the second half of the 20th century power. While stopping these effects is not the main objective of the Montreal Protocol, it is a wonderful by-product.”

The Montreal Protocol has successfully reduced atmospheric concentrations of ozone-depleting substances since the mid-1990s, and there are signs that the ozone layer has begun to heal. But with recent research showing that concentrations of ozone-depleting substances rose slightly from 2010 to 2020, England and Polvani stress the importance of vigilance.

Learn more about Lorenzo Polvani and his research:

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