A new study proposes that the Montreal Protocol or the Ozone Treaty has helped slow down global warming.
The research was published on Sunday, November 10, in the journal Nature Geoscience.
"The two world wars, the Great Depression and a 1987 international treaty on ozone-depleting chemicals put a surprising dent in the rate at which the planet warmed, says research published today in Nature Geoscience," per Nature.
Annual temperature data collected between 1850 and 2010, was analyzed by Francisco Estrada and his colleagues. Estrada, who is an ecological economist at the Free University in Amsterdam, also studied patterns in emission of greenhouse gases like carbon dioxide, methane and CFC between 1880 and 2010, which not only deplete the ozone layer but also trap the heat in the atmosphere.
The researchers also reveal that the introduction of the Montreal Protocol, which was signed in 1987 by 46 countries, impacted global temperatures.
"Our analysis suggests that the reduction in the emissions of ozone-depleting substances under the Montreal Protocol, as well as a reduction in methane emissions, contributed to the lower rate of warming since the 1990s," per the authors.
The researchers used a statistical approach rather than depending on climate model simulations, which helped them delve better into how different components of the climatic system contribute to it becoming cool or warm by trapping heat. This effect is called radiative forcing.
Estrada and his colleagues found that the alterations in warming corresponded with "human-initiated adjustments in greenhouse-gas emissions."
"When the wars end and you have large economic growth, the emissions of CO2 rise fast and you have the onset of modern climate change," says Estrada.
However, according to Ross Salawitch, an atmospheric scientist at the University of Maryland in College Park, Estrada's study would be less debatable and hold more ground if he had taken into account changes in ocean heat uptake, as well as aerosol cooling.
"Without the Montreal Protocol, we'd be warmer than we are now," agrees Ross. "But I question whether the recent pause in global warming is due to that."
James Butler who is the director of global monitoring at the Earth System Research Laboratory of the US National Oceanic and Atmospheric Administration is of the opinion that while the study is a "careful examination" it does not prove the correlation.
"It's a careful examination and offers some strength to the argument that the change in accumulation rates of radiative forces in the atmosphere do influence temperature, but it is a correlation, not a proof of causation," says Butler.
