Earth’s Atmosphere Reacted in Surprising Ways to Emission Reductions From COVID Pandemic

Almost-Empty Highways in Colombia During COVID Pandemic

Worldwide restrictions during the COVID-19 pandemic caused huge reductions in travel and other economic activities, resulting in lower emissions. Seen here, almost-empty highways in Colombia during the pandemic. Credit: International Monetary Fund

Earth’s atmosphere reacted in surprising ways to the lowering of emissions during the pandemic, showing how closely climate warming and air pollution are linked.

The COVID-19 pandemic and resulting limitations on travel and other economic sectors by countries around the globe drastically decreased air pollution and greenhouse gas emissions within just a few weeks. That sudden change gave scientists an unprecedented view of results that would take regulations years to achieve.

A comprehensive new survey of the effects of the pandemic on the atmosphere, using satellite data from NASA and other international space agencies, reveals some unexpected findings. The study also offers insights into addressing the dual threats of climate warming and air pollution. “We’re past the point where we can think of these as two separate problems,” said Joshua Laughner, lead author of the new study and a postdoctoral fellow at Caltech in Pasadena, California. “To understand what is driving changes to the atmosphere, we must consider how air quality and climate influence each other.”

Published Nov. 9 in the Proceedings of the Natural Academy of Sciences, the paper grew from a workshop sponsored by Caltech’s W.M. Keck Institute for Space Studies, led by scientists at that institution and at the Jet Propulsion Laboratory in Southern California, which is managed by Caltech. Participants from about 20 U.S. and international universities, federal and state agencies, and laboratories pinpointed four atmospheric components for in-depth study: the two most important greenhouse gases, carbon dioxide and methane; and two air pollutants, nitrogen oxides and microscopic nitrate particles.

Carbon Dioxide

The 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.”

Using data from NASA’s Orbiting Carbon Observatory-2 satellite launched in 2014 and the NASA Goddard Earth Observing System atmospheric model, 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.

Air Pollutants and Methane

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 the coronavirus pandemic slowed global commerce to a crawl in early 2020, emissions of nitrogen oxides (NOx) – which create ozone, a danger to human health and to climate – decreased 15% globally with local reductions as high as 50%, according to a study led by scientists at NASA’s Jet Propulsion Laboratory. Credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio

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.

Molecule for molecule, methane is far more effective than CO2 at trapping heat in the atmosphere. Estimates of how much methane emissions dropped during the pandemic are uncertain because some human causes, such as poor maintenance of oilfield infrastructure, are not well documented, but one study calculated that the reduction was 10%.

However, as with CO2, the drop in emissions didn’t decrease the concentration of methane in the atmosphere. Instead, methane grew by 0.3% in the past year – a faster rate than at any other time in the last decade. With less NOx, there was less hydroxyl radical to scrub methane away, so it stayed in the atmosphere longer.

Lessons From the Pandemic

The study took a step back to ask what the pandemic could teach about how a lower-emissions future might look and how the world might get there.

Notably, emissions returned to near-pre-pandemic levels by the latter part of 2020, despite reduced activity in many sectors of the economy. The authors reason that this rebound in emissions was probably necessary for businesses and individuals to maintain even limited economic productivity, using the worldwide energy infrastructure that exists today. “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.”

4 Comments on "Earth’s Atmosphere Reacted in Surprising Ways to Emission Reductions From COVID Pandemic"

  1. “… 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.”

    Other estimates are that the average for the year was 7-10% lower, with reduction of over 18% in April 2020. Actually, the growth curve for 2020 was almost identical to 2019. That suggests that something else is driving the CO2 response. Indeed, the CO2 growth during the hot El Nino year, 2016, was much higher than any others.

    “During previous socioeconomic disruptions, like the 1973 oil shortage, you could immediately see a change in the growth rate of CO2,” In the 1970s people were concerned about an impending Ice Age, not warming.

    “Also, the ocean didn’t absorb as much CO2 from the atmosphere as it has in recent years ..” More probably because 2020 was about as warm as usual.
    https://wattsupwiththat.com/2021/06/11/contribution-of-anthropogenic-co2-emissions-to-changes-in-atmospheric-concentrations/

    • “…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.”

      First off, the first part of the quote is misleading. The graphs of the ramp-up and drawdown phases of the seasonal variation for 2019-2020 are almost indistinguishable from the preceding year! There is no obvious evidence that there was reduced absorption in the oceans.

      The second part of the quote is double talk. He is basically saying that the CO2 concentration did not go down because it went down. He is perhaps trying to convey the idea that as the partial pressure of CO2 in the atmosphere declined, as a result of anthropogenic emission reductions, the oceans compensated by a net increase in outgassing CO2. If that is what he meant, and it is true (questionable), the implication is that any purposeful reductions of human emissions will be thwarted by that feedback loop! We are being asked to turn our world economies on their heads and make sacrifices to accomplish something for which there is no empirical evidence will happen.

  2. Purebloodpatriot | November 11, 2021 at 10:58 am | Reply

    While the MSM condemns the use of ivermectin, the most populated state in India just declared they are officially COVID free after promoting widespread use of the safe, proven medicine. In addition to this, Ivermectin attaches to covid spikes and prevents them from binding to ACE2.

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