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Banned Ozone Destroying Substances Caused Half of Arctic Warming Between 1955 and 2005: 'Climate Mitigation is in Action'

Ozone destroying substances that were banned in the 1980s may have been responsible for half of all Arctic warming between 1955 and 2005, scientists have said. This could mean the speed of warming in the Arctic in the future is reduced, as the impact of the ban continues.

Ozone-depleting substances (ODS) are synthetic chemicals developed in the 1920s and 30s. They became popular in the 1950s when they were used as refrigerants, solvents and propellants, the researchers note. The substances are best known for their damaging effect on the ozone, causing a hole to form above Antarctica. But they are also highly potent greenhouse gases.

"While the dominant role of carbon dioxide is undisputed, another important set of anthropogenic [greenhouse gasses] was also being emitted over the second half of the twentieth century: ozone-depleting substances," researchers wrote in Nature Climate Change.

The team, led by Lorenzo Polvani from Columbia University, New York, say this is, to their knowledge, the first time the warming effects of ODS have been quantified.

They used a climate model to look at two different climate scenarios. In one, the team input all natural and human emissions as measured between 1955 and 2005. In the other, they removed ODS and the impact they had on ozone.

This allowed them to see how ODS impacted the climate. Findings suggest the chemicals were responsible for approximately half of Arctic surface warming and half of Arctic sea ice loss between 1955 and 2005. ODS also appear to account for around a third of total warming worldwide.

Researchers say OCDs have high warming efficacy, which means they cause more warming per unit that a number of other common greenhouse gasses, including carbon dioxide and methane.

"This paper points out a large role for the ODS in Arctic warming, but we also have to remember the cooling effect of aerosol increases," Professor Martyn Chipperfield, an atmospheric scientist at the University of Leeds, U.K., who was not involved in the study, told Newsweek. "The cooling effect of aerosols is included in the models and offsets some of the greenhouse gas warming."

"For the ODSs, the exact mechanism which leads to a magnified impact in the Arctic remains to be determined. It is a complex problem because there are many different major and minor ODS but only a few are treated in the models. Further modeling studies are needed to investigate this."

Atmospheric concentrations of ODS have declined since the Montreal Protocol came into effect in 1989. The agreement was drawn up and signed by 197 countries after scientists discovered ODS had caused a hole to form in the ozone layer above Antarctica, allowing harmful UV rays from the sun to reach the Earth unfiltered.

As a result of the phase-out, the hole now appears to be closing. Last year, scientists at the EU's Copernicus Atmosphere Monitoring Service said it could be at its smallest in 30 years.

"It is a further reason to ensure that countries adhere fully to the Montreal Protocol," said Chipperfield. "It also shows the potential large impact of so-called minor gases with small abundances, whether they deplete ozone or not, for example some compounds currently being used to replace chlorofluorocarbons. These gases need to be considered in the same way."

The researchers of the latest study say the phase-out could help mitigate warming and ice melt in the Arctic in the future.

"Climate mitigation is in action as we speak because these substances are decreasing in the atmosphere, thanks to the Montreal Protocol," Polvani, a professor in Columbia's Department of Applied Physics and Applied Mathematics, said in a statement. "In the coming decades, they will contribute less and less to global warming. It's a good-news story."

Concluding, they team wrote: "ODS have been important players in the global climate system. Our findings also have implications for the future because the phase-out of ODS, which is well under way, will substantially mitigate Arctic warming and sea-ice melting in the coming decades."

The article has been updated to include comments from Professor Martyn Chipperfield.

Icebergs from Twin Glaciers
Calved icebergs from the nearby Twin Glaciers are seen floating on the water on July 30, 2013 in Qaqortoq, Greenland. The Arctic has seen warming twice as fast as the rest of the Earth. A new study quantifies the effect of ozone-depleting substances. Joe Raedle/Getty
Banned Ozone Destroying Substances Caused Half of Arctic Warming Between 1955 and 2005: 'Climate Mitigation is in Action' | Tech & Science