LSA Associate Dean for Natural Sciences Chris Poulsen, along with the rest of the college administration, is approaching COVID-19 with the seriousness it deserves and putting the safety of the U-M community first. Poulsen’s research investigates climate change throughout Earth’s history, and he and his colleagues are fielding questions about the virus’s potential effect on global carbon emissions. 

How is COVID-19 affecting the environment through things like reduced economic activity, people telecommuting to work, etc.?

Chris Poulsen: The total impact of COVID-19 on our environment will not be known for some time and will depend on how quickly industrial activities and energy production return to pre-crisis levels.

If the crisis turns into a global recession, reductions in carbon emissions could be substantial and might slow the rise of atmospheric CO2 level.

The larger effect on our environment will be from a reduction in industrial activity and energy production—which account for more than 70 percent of global CO2 emissions—as the world economy responds to the crisis. Economic slowdown and a decline in consumption of goods and services will reduce emissions of carbon and other greenhouse gases. This happened last month in China, where industrial output is estimated to have declined by 15 to 40 percent, leading to a decrease in carbon emission of about 25 percent over a four-week period and a 37 percent decline in nitrous oxide levels. This also happened during the Great Recession of 2007-2013 and contributed to an 11 percent decrease in fossil fuel CO2 emissions in the United States during that period.

Reduced travel and telecommuting is likely to improve environmental conditions by reducing emissions of greenhouse gases that warm the climate and other pollutants that dirty our air and water. However, the impact of air travel and telecommuting might be relatively modest. 

As COVID-19 reduces air travel, could there be a measurable decrease in temperature or carbon?

CP: Yes, a reduction in air travel could lead to both cooling and a decrease in carbon emissions. The research shows that contrails—clouds produced by engine exhaust—have a net warming effect on climate by trapping heat that would otherwise escape to space. A significant decrease in air travel and contrails could lead to slight temporary cooling. Because contrails last only for hours or possibly a couple of days before dissipating, the cooling effect would be localized and persist only as long as air travel is down.

The reduction in air travel, especially if sustained, would reduce carbon emissions and slow the rise of atmospheric CO2 levels in the atmosphere and slow global warming. This could potentially have a much longer lasting and widespread effect on temperature than a reduction in contrails. Estimates indicate that air travel declined by about 4.3 percent in February 2020. As the pandemic spreads, we expect to see a deeper decline in air travel. But even if that happens, the effect on global carbon emissions will be modest—a reduction of less than 0.1 percent of total carbon emissions using February’s estimates—and less than the annual rate by which emissions have been increasing. In other words, the reduction in air travel alone—even if sustained—will have a measurable but relatively small effect on global carbon emissions.

If telecommuting means a reduction in car or train travel, could that have a similar perceptible effect on carbon emissions?

CP: Possibly. This is a hard question to answer because it depends on human behavior, which is difficult to predict.

If there were a large-scale movement towards telecommuting and a decrease in transportation, total emissions could decrease substantially. Road and rail transportation make up more than 70 percent of the total emissions due to transportation (including air travel), and transportation is responsible for over 20 percent of total CO2 emissions. This reduction could be significant, especially if the COVID-19 crisis led to a sustained shift to telecommuting.

On the other hand, if the COVID-19 crisis pushes people away from public transportation and toward automobile travel or if telecommuters substantially increase their residential energy use and home deliveries, then carbon emissions might not decrease and actually increase. At least one study has shown that telecommuters actually drive more miles than non-telecommuters by running more non-work-related errands.

One outcome of the crisis will be the ability to have a better answer to this question for the future.