How pandemic lockdowns cleaned the air but resulted in a warmer planet

Earth spiked a bit of a fever in 2020, partly because of cleaner air from pandemic lockdowns, a new study has found.

For a short time, temperatures in some places in the eastern United States, Russia and China were as much as 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 0.03 degrees Celsius warmer for the year because the air had fewer cooling aerosols, which is pollution that you can see that normally blocks incoming sunlight, 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 the study's lead author, Andrew Gettelman, an atmospheric scientist at the National Center for Atmospheric Research.

WATCH | 2020 ties 2016 for the warmest year on record:

2020 reached record temperatures despite emissions reduction during pandemic

4 years ago

Duration 1:55

Despite reduced emissions during the pandemic, annual climate reports from NASA and the NOAA have declared 2020 a virtual tie with 2016 for the warmest year on record, with the Northern Hemisphere seeing the greatest effects.

His calculations come from comparing 2020 weather to computer models that simulated a 2020 without the pollution reductions from pandemic lockdowns.

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 for about a week.

Even without the reduction in cooling aerosols, global temperatures in 2020 already were flirting with breaking yearly heat records because of the burning of coal, oil and natural gas.

The aerosol effect may have been enough to help make this the hottest year in NASA's measuring system, according to 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.