China’s reductions in aerosol emissions have slowed sea ice loss but may have accelerated global warming.
China’s significant reduction in air pollution may have had unexpected benefits in the Arctic. A new study, recently in NPJ, shows that decreased aerosol-fueled thunderstorms and, in turn, reduced sea ice loss.
However, experts point out that at the same time, this huge drop in aerosols may have accelerated global warming.
“This pollution has slowed temporarily global warming and gave the rest of us a little more time to adapt to a warmer climate. What is happening now is that we are seeing the full effects of greenhouse gas-driven warming, which sooner or later we would have had to face anyway,” he explained. Bjorn Samsetsenior researcher at the CICERO Center for International Climate Research in Norway, told .
As the same magazine writes, in late January 2019, wind patterns over the North Pacific changed, and a series of five powerful cyclones swept across the Bering Sea in quick succession. Each drove warm southerly winds over the ice, fragmenting it and pushing it north. Air temperatures across the northern Bering Sea were 12 to 16 degrees Celsius above normal.
By early March, ice coverage had decreased by 82%. This meant a retreat of around 400,000 square kilometers — which represents the biggest decline ever recorded by satellites at this time of year.
Scientists have long known that cyclones can devastate Arctic sea ice. What they are least sure of is what sends these storms there in the first place.
The new study gave an unexpected answer: from 2000 to 2014, smog from chinese industrial chimneys may have been directing winter storms northward across the North Pacific, channeling more of them into the Arctic and destroying ice in the Bering Sea.
Scientists combined four decades of observational data with climate model simulations to examine how aerosol levels over East Asia influenced the trajectories of winter cyclones across the North Pacific.
Comparing 14 years of high aerosol loads between 2000 and 2014 with 15 years of lower aerosol loads from previous decades, the researchers found that cyclone trajectories moved north by as much as 1.23 degrees by the time the storms dissipated — enough to almost double the number of cyclones crossing into the Arctic.
When these storms reach the Bering Sea, their effects can be dramatic. The counterclockwise winds of a cyclone push the ice back into the Chukchi Sea between Alaska and Russia. The waves fragment the ice sheets. Strong winds from the south bring warmer air that can, even in the depths of winter, raise temperatures above freezing, as happened so markedly in 2019.
