Forced lockdowns across the world due to the coronavirus pandemic had a direct impact on the effect on ozone pollution, a NASA study has found.

As the lockdowns slowed global commerce, emissions of nitrogen oxides (NOx) decreased 15 percent globally, with local reductions as high as 50 percent, according to a study led by scientists at NASA’s Jet Propulsion Laboratory in Southern California.

As a result of the lower NOx emissions, by June 2020, global ozone levels had dropped to a level that policymakers thought would take at least 15 years to reach by conventional means, such as regulations.

NOx creates ozone, a danger to human health and to climate.

The study, published in Science Advances, shows that innovative technologies and other solutions intended to decrease NOx locally have the potential to rapidly improve air quality and climate globally.

Ozone protects the earth from destructive solar radiation when it’s high above in the stratosphere. Closer to the ground, though, it has other lasting impacts. Ozone at the surface was estimated to cause 365,000 deaths globally in 2019 by damaging the lungs of vulnerable people, such as young children and those with asthma. Similarly, it damages the breathing systems of plants – reducing their growth and crop yields. And at the top of the troposphere, it’s a potent greenhouse gas, increasing global temperatures.

When the world went into lockdown, scientists had an unprecedented opportunity to study how human activity interacts with natural Earth system processes at regional and global scales. A team of international researchers led by JPL scientist Kazuyuki Miyazaki found that the more stringent the lockdown a nation imposed, the greater the reduction in emissions. For example, China’s stay-at-home orders in early February 2020 produced a 50 percent drop in NOx emissions in some cities within a few weeks, while most U.S. states achieved a 25 percent drop later in the spring.

The total result of the reduced NOx emissions was a 2 percent drop in global ozone – half the amount that the most aggressive NOx emission controls considered by the Intergovernmental Panel on Climate Change were expected to produce over a 30-year period.

Ozone reductions from the reduced NOx emissions quickly spread both around the globe and from the surface upward more than 10 kilometers. “I was really surprised at how large the impact on global ozone was,” said JPL scientist Jessica Neu, a co-author of the new study.

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