Worldwide economic and social lockdowns due to COVID-19 resulted in cleaner air, but a warmer planet overall, according to new research.
The findings by the National Center for Atmospheric Research are a bit counterintuitive. Most people are taught that pollution in the air leads to higher temperatures - which is accurate, but there is more than that going on in the skies.
Researchers said that their work highlights the influence of airborne particles or aerosols that block incoming sunlight. When emissions in aerosols dropped last spring, more of the sun’s warmth reached the planet, especially in heavily industrialized nations such as the United States and Russia, the study noted.
“There was a big decline in emissions from the most polluting industries, and that had immediate, short-term effects on temperatures,” said NCAR scientist Andrew Gettelman, the study’s lead author. “Pollution cools the planet, so it makes sense that pollution reductions would warm the planet.”
Temperatures over the Earth’s land surface in spring 2020 were about 0.2-0.5 degrees warmer than would have been expected with prevailing weather conditions, the study said. In the U.S. and Russia, where a lot of aerosols are pumped into the atmosphere, the temperature rose by about 0.7 degrees.
At the heart of the study is the difference in how various pollutants impact the atmosphere and weather. While aerosols tend to brighten clouds and reflect heat from the sun back into space, carbon dioxide and other greenhouse gases have the opposite effect, trapping heat near the planet’s surface and elevating temperatures, the study said.
The study looked at the short-term effect of the COVID-19-prompted lockdowns, but the long-term effect could be a slight slowdown of climate change.
To read the full NCAR study, go to news.ucar.edu.
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