Ozone Increased in the Northern Hemisphere Over the Last Two Decades

Phys.org reports:
In a first-ever study using ozone data collected by commercial aircraft, researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder found that levels of the pollutant in the lowest part of Earth's atmosphere have increased across the Northern Hemisphere over the past 20 years. That's even as tighter controls on emissions of ozone precursors have lowered ground-level ozone in some places, including North America and Europe...

In a study published today in the journal Science Advances, the team found an overall increase in ozone levels above the Northern Hemisphere. "That's a big deal because it means that as we try to limit our pollution locally, it might not work as well as we thought," said Audrey Gaudel, a CIRES scientist working in the NOAA Chemical Sciences Laboratory and the study's lead author...

In the so-called "lower troposphere," which is closer to Earth's surface, ozone has decreased above some mid-latitude regions, including Europe and the United States, where ozone precursor emissions have decreased. The researchers found those reductions were offset by increases higher in the troposphere — with the net result being an overall ozone increase from the surface to 12 km... The model showed that increased anthropogenic emissions in the tropics were likely driving the observed increase of ozone in the Northern Hemisphere.

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