Cleaner air during COVID-19 pandemic caused brief temperature spike: Study

The temporary warming from fewer particles was stronger in 2020 than the impact of heat-trapping carbon dioxide emissions, experts said.

The Associated Press February 04, 2021 13:39:43 IST
Cleaner air during COVID-19 pandemic caused brief temperature spike: Study

Greenhouse gases trap heat in the atmosphere, raising temperatures, causing sea levels to rise and driving more extreme weather.

Earth spiked a bit of a fever in 2020, partly because of cleaner air from the pandemic lockdown, a new study found. For a short time, temperatures in some places in the eastern United States, Russia and China were as much as half to two-thirds of a degree (0.3 to 0.37 degrees Celsius) warmer. That’s due to less soot and sulfate particles from car exhaust and burning coal, which normally cool the atmosphere temporarily by reflecting the sun’s heat, Tuesday’s study in the journal Geophysical Research Letters reported.

Overall, the planet was about .05 degrees (.03 degrees Celsius) warmer for the year because the air had fewer cooling aerosols, which unlike carbon dioxide is pollution you can see, the study found.

“Cleaning up the air can actually warm the planet because that (soot and sulfate) pollution results in cooling” which climate scientists have long known, said study lead author Andrew Gettelman, an atmospheric scientist at the National Center for Atmospheric Research. His calculations come from comparing 2020 weather to computer models that simulated a 2020 without the pollution reductions from pandemic lockdowns.

Cleaner air during COVID19 pandemic caused brief temperature spike Study

A civic worker, wearing an anti-pollution mask, sweeps the road amid heavy smog, in New Delhi, Friday, Nov. 15, 2019. A thick layer of toxic smog engulfed Delhi as the pollution level continued to remain in the 'severe' category for the fourth consecutive day in the capital. Image: PTI/Arun Sharma

This temporary warming effect from fewer particles was stronger in 2020 than the effect of reduced heat-trapping carbon dioxide emissions, Gettelman said. That’s because carbon stays in the atmosphere for more than a century with long-term effects, while aerosols remain in the air about a week.

Even without the reduction in cooling aerosols, global temperatures in 2020 already were flirting with breaking yearly heat record because of the burning of coal, oil and natural gas — and the aerosol effect may have been enough to help make this the hottest year in NASA’s measuring system, said top NASA climate scientist Gavin Schmidt, who wasn’t part of this study but said it confirms other research.

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

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