The headline is straight from the research press release. Of course that suggests alarmists can only hope to blame human-caused ‘carbon emissions’ for the other half of any recent warming, by invoking their own version of a planetary ‘greenhouse effect’.
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Ozone-depleting substances (ODSs) may be responsible for nearly half of Arctic warming from 1955 – 2005, according to a study published in Nature Climate Change.
These findings highlight an unrecognized source of twentieth-century Arctic climate change.
ODSs – halogen compounds that destroy the protective layer of ozone in the upper atmosphere – were used as propellants, refrigerants and solvents during the twentieth century.
Since the 1987 Montreal Protocol, ODS emissions have been curbed, and the ozone layer is now in slow recovery.
However, ODSs are potent greenhouse gases and have long atmospheric lifetimes, so they can add substantially to the anthropogenic greenhouse effect.
Lorenzo Polvani and colleagues use a climate model to estimate what amount of climate warming can be attributed to these substances. The authors simulated two worlds: one with natural and human emissions as measured during 1955 – 2005, and another with ODSs and their ozone impacts removed.
The difference reveals the net impact of ODSs on the climate system. The authors estimate that ODSs may have caused about half of Arctic warming and sea ice loss, as well as nearly one third of globally averaged warming, during that time period.
These results offer a new perspective on the climate impacts of ODSs, and suggest that their continued phase-out via the Montreal Protocol will help mitigate Arctic warming and sea ice melt in the future.