During the past two years of this pandemic, we’ve seen a lot of human suffering, but we’ve also seen the skies over some of the world’s cities clear as cars have stayed parked and factories have slowed or stopped production. Here in small town America, we’ve seen wildlife come into town, with coyotes now hunting neighborhood cats instead of farm chickens. These changes are stark reminders of our effects on the world, but the effects we see with our eyes don’t help us understand if these change local or global temperatures and the weather they moderate.

Understanding that requires satellites and ground stations.

In a new paper in Geophysical Research Letters, researchers led by Zihan Liu, look at data for 300 massive cities in China – cities that sprawl over more than ten square kilometers and include many megacities of more than ten million people.

It was known that cities act as urban heat islands, with human activities and infrastructure raising the temperatures above those of the less developed surroundings. This is especially true in high latitudes during the winter, where heated buildings also heat their surroundings. A/C also pumps inside heat into the environment. Added greenhouse gases from vehicles contribute as well.

During the pandemic lockdowns, however, when fewer vehicles were used and many buildings and public transportation systems were shut down, cooling of a quarter degree Celsius was measured at ground level and closer to half a degree in the atmospheric canopy over the cities.

While fractions of a degree may not seem a lot, these are the kinds of changes that make all the difference in the world with climate change, and this points to how just working from home may be an answer for making a better future.

More Information

“Urban Heat Islands Significantly Reduced by COVID-19 Lockdown,” Zihan Liu et al., 2022 January 11, Geophysical Research Letters