Stay-at-home orders haven’t just curbed the spread of COVID-19. They’ve briefly cleared the air.
Daily global carbon dioxide emissions dropped 17 percent, from about 100 million metric tons to about 83 million metric tons, in early April compared with average daily emissions in 2019, researchers report May 19 in Nature Climate Change. Among other changes, the lock-downs grounded planes, reduced traffic and changed peoples’ patterns of energy consumption (SN: 5/14/20).
Quantifying the impact of those changes on global CO2 emissions in real time is tricky; most emissions data are reported annually, not day by day or even month by month. So climate scientist Corinne Le Quéré of the University of East Anglia in Norwich, England, and colleagues used daily data such as electricity demand, city congestion and readouts from smart meters in homes to estimate emissions for 69 countries. Then, the researchers created a “confinement index” based on the stringency of government-imposed policies in different locations and over time.
During the most stringent confinement periods, when only essential workers were permitted to commute, daily aviation activity shrank by 75 percent, the team reports. Surface transportation was reduced by about 50 percent, while power use shrank by about 15 percent.
If the world returns to a pre-pandemic level of activity by mid-June, the researchers say, 2020’s emissions will be about 4 percent lower than in 2019. If some restrictions remain through the end of the year, 2020 emissions could be as much as 7 percent lower.
This COVID-19–related decline in emissions isn’t sustainable, and comes at a very high cost, says coauthor Rob Jackson, an environmental scientist at Stanford University. However, it highlights the depth of the cuts needed to reach emissions targets set by the 2015 Paris Agreement (SN: 11/26/19). To limit warming to 1.5 degrees Celsius by 2100, nations would need to reduce emissions by 7.6 percent each year over the next decade, scientists say.
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