Emission Reductions From Pandemic Had Unexpected Effects on Atmospherehttps://www.jpl.nasa.gov/news/emission-reductions-from-pandemic-had-unexpected-effects-on-atmosphereThe most surprising result, the authors noted, is that while carbon dioxide (CO2) emissions fell by 5.4% in 2020, the amount of CO2 in the atmosphere continued to grow at about the same rate as in preceding years. “During previous socioeconomic disruptions, like the 1973 oil shortage, you could immediately see a change in the growth rate of CO2,” said David Schimel, head of JPL’s carbon group and a co-author of the study. “We all expected to see it this time, too.”
the researchers identified several reasons for this result. First, while the 5.4% drop in emissions was significant, the growth in atmospheric concentrations was within the normal range of year-to-year variation caused by natural processes. Also, the ocean didn’t absorb as much CO2 from the atmosphere as it has in recent years – probably in an unexpectedly rapid response to the reduced pressure of CO2 in the air at the ocean’s surface.
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Nitrogen oxides (NOx) in the presence of sunlight can react with other atmospheric compounds to create ozone, a danger to human, animal, and plant health. That’s by no means their only reaction, however. “NOx chemistry is this incredibly complicated ball of yarn, where you tug on one part and five other parts change,” said Laughner.
As reported earlier, COVID-related drops in NOx quickly led to a global reduction in ozone. The new study used satellite measurements of a variety of pollutants to uncover a less-positive effect of limiting NOx. That pollutant reacts to form a short-lived molecule called the hydroxyl radical, which plays an important role in breaking down long-lived gases in the atmosphere. By reducing NOx emissions – as beneficial as that was in cleaning up air pollution – the pandemic also limited the atmosphere's ability to cleanse itself of another important greenhouse gas: methane.