Earth entering 'uncharted territory' as heat records quickly shatter

[dalton99a]

24. +1. During the pandemic, carbon dioxide increased at the same rate despite lower emissions

https://magazine.caltech.edu/post/atmospheric-co2-covid-pandemic

A Climate Conundrum: Why Didn’t Atmospheric CO2 Fall During the Pandemic?

...

“During previous socioeconomic disruptions, like the 1973 oil shortage, you could immediately see a change in the growth rate of CO2,” says 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 study also examined atmospheric nitrogen oxide (NOx) levels. In the presence of sunlight, nitrogen oxides can react with other atmospheric compounds to create ozone, a gas that is a danger to human, animal, and plant health. Although the study found that COVID-related drops in nitrogen oxides led to a reduction in ozone in most places around the world, its satellite measurements uncovered a less positive effect of limiting NOx. Nitrogen oxides react 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.

Molecule for molecule, methane is far more effective than carbon dioxide at trapping heat in the atmosphere. Estimates of how much methane emissions dropped during the pandemic are uncertain, but one study calculated the reduction at 10 percent. However, as with carbon dioxide, the drop in emissions did not decrease the concentration of methane in the atmosphere. Instead, methane grew 0.3 percent faster in the past year than in the previous four—a faster rate than at any other time in the last decade. With less NOx there was less hydroxyl radical to scrub methane away.

Notably, emissions returned to near pre-pandemic levels by the latter part of 2020, despite reduced activity in many sectors of the economy.

“This suggests that reducing activity in these industrial and residential sectors is not practical in the short term” as a means of cutting emissions, the study noted. “Reducing these sectors’ emissions permanently will require their transition to low-carbon-emitting technology.”