Cleaner air from pandemic has added heat to global warming


Earth got a bit of a fever in 2020, in part because of cleaner air from the pandemic lockdown, according to a new study.

For a short time, temperatures in parts of the eastern United States, Russia, and China were up to one-half to two-thirds of a degree (0.3 to 0.37 degree Celsius) plus hot. This is due to less soot and sulfate particles from car exhaust and burning coal, which normally cool the atmosphere temporarily by reflecting heat from the sun, Tuesday’s study reported in the journal Geophysical. Research Letters.

Overall, the planet was about 0.05 degrees (0.03 degrees Celsius) warmer for the year because the air contained less cooling aerosols, which, unlike carbon dioxide, is pollution you can see, according to the study.

“Cleaning the air can actually make the planet warmer because this pollution (by soot and sulphates) causes cooling,” which climatologists have long known, said lead author of the study Andrew Gettelman. , an atmospheric scientist at the National Center for Atmospheric Research. His calculations come from comparing the weather conditions of 2020 with computer models that simulated a 2020 without the pollution reductions due to pandemic lockdowns.

This temporary warming effect due to fewer particles was stronger in 2020 than the effect of reducing heat-trapping carbon dioxide emissions, Gettelman said. This is because carbon stays in the atmosphere for over a century with long-term effects, while aerosols stay in the air for about a week.

Even without the reduction in cooling aerosols, global temperatures in 2020 were already flirting with the annual record heat due to the burning of coal, oil and natural gas – and the aerosol effect might have been enough to make this year the hottest year on NASA measurements. system, said NASA climate scientist Gavin Schmidt, who was not part of that study, but said it confirmed other research.

“Clean air warms the planet a little bit, but it kills a lot less people with air pollution,” Gettelman said.


Follow Seth Borenstein on Twitter: @borenbears


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