NOAA scientists contribute to WMO report on COVID-19 and air quality

NOAA scientists contribute to WMO report on COVID-19 and air quality

September 14, 2021

Human-caused emissions of air pollutants fell during last year's COVID-19 economic slowdowns, improving air quality in some parts of the world, while wildfires and sand and dust storms in 2020 worsened air quality in other places, according to a new report from the World Meteorological Organization (WMO). The report's authors included scientists from two National Oceanic and Atmospheric Administration (NOAA) laboratories.

Owen Cooper with NOAA Chemical Sciences Laboratory (CSL) is lead editor of the first edition of the WMO Air Quality and Climate Bulletin, which was released on September 3, and Irina Petropavlovskikh with NOAA Global Monitoring Laboratory (GML) is a co-author. NOAA also provided long-term ozone monitoring data from atmospheric baseline observatories in Barrow, Alaska; Mauna Loa, Hawaii; and South Pole, Antarctica.

The bulletin highlights the connections between air quality and climate change, including how persistent weather patterns amplified 2020 wildfire conditions, leading to increased regional-scale particulate matter pollution; the impact of COVID-19 travel restrictions on air quality worldwide; and estimates of human mortality due to long-term exposure to ozone and particulate matter pollution. The launch of the report coincides with the United Nations International Day of Clean Air for Blue Skies.

"Climate change, caused by the accumulation of greenhouse gases in the atmosphere, is happening on a decades-long timescale and is driving environmental changes worldwide," the authors wrote. "The impacts of air pollutants including ozone and particulate matter occur near the surface, on timescales of days to weeks and across spatial scales ranging from local to regional. Despite these differences, air quality and climate change are strongly interconnected." For example, human activities that release long-lived greenhouse gases into the atmosphere can also increase concentrations of shorter-lived ozone and particulate matter in the atmosphere.

According to the new report, the 2020 wildfire season was marked by extreme fires in Siberia and the western U.S., exacerbated by persistent weather patterns that produced hot and dry conditions, including a historic high-latitude heatwave in Siberia. Fires in the U.S. contributed to unhealthy levels of air pollution affecting 20–50 million people in the West and in regions downwind of the fires.

By contrast, COVID-19 pandemic triggered worldwide travel restrictions that reduced emissions of many air pollutants in 2020, although impacts on ground and atmospheric levels of ozone, particulate matter, and other pollution varied widely. The report concluded that average PM2.5 concentrations decreased by 30% to 40% during the most stringent restrictions in 2020 compared with the same periods in 2015-2019, although PM2.5 increased in some places because of long-range transport of African dust and/or biomass burning.

Changes in ozone concentrations also varied greatly across urban areas, ranging from no overall change to small increases, as was the case for Europe, and larger increases in East Asia and South America. The report notes that the ozone response is complicated, with preliminary results showing unusual ozone decreases of 10 to 15 percent in rural regions of Europe during summer.

The bulletin also summarizes the latest estimates, from the 2019 Global Burden of Disease report published in The Lancet, of human mortality due to long-term exposure to outdoor ozone and particulate matter pollution. According to that assessment, global mortality increased from 2.3 million in 1990 (91% due to particulate matter, 9% due to ozone) to 4.5 million in 2019 (92% due to particulate matter, 8% due to ozone).

WMO will issue this report annually, with updates on the state of air quality and its connections to climate change.

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