Reduction in aerosol emission during lockdown, temporarily raised Earth’s temperature: Study

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While we saw the clear sky and breathed clean air during COVID, there is another aspect of COVID which resulted in slightly warming of the planet for several months last year. According to a recent study by the National Center for Atmospheric Research, changes in the emissions of aerosols during lockdown affected the global surface temperature.

The study titled, ‘Climate Impacts of COVID‐19 Induced Emission Changes’ funded by the National Science Foundation is co-authored by scientists at Oxford University, Imperial College, and the University of Leeds.

According to the study, warming effect was strongest in the mid and upper latitudes of Northern Hemisphere whereas the effect was mixed in the tropics. However, a few effects were seen in Southern Hemisphere where aerosol is not as pervasive.

The study notes that during the lockdown emission of anthropogenic aerosols like black carbon and sulfate (SO4) decreased as transport was impacted. Black carbon and SO4 not only plays a crucial role in scattering and absorption of radiation but also they have an indirect effect on the cloud.

The aerosol changes are the largest contribution to radiative forcing and temperature changes as a result of COVID‐19 affected emissions, larger than ozone, CO2 and contrail effects, the study says. Radiative forcing is the difference between the absorbed and reflected the sun’s radiation.

Temperatures on the earth’s land surface last spring were about 0.1-0.3 degree Celsius- warmer than it would have been expected with lockdown in place, the study claims. The decrease in aerosol resulted in more absorption of incoming sunlight especially in heavily industrialized nations like the United States and Russia.

“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 in a statement. “Pollution cools the planet, so it makes sense that pollution reductions would warm the planet.”