Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

First Annual Report Highlights Links Between Air Quality and Climate Change

Fires, dust storms, COVID impacted air quality in 2020

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). Two CIRES scientists working in NOAA laboratories contributed to the WMO’s first-ever Air Quality and Climate Bulletin, released on September 3. 

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 today’s United Nations International Day of Clean Air for Blue Skies.

Owen Cooper, a CIRES scientist working in NOAA’s Chemical Sciences Laboratory, is lead editor of the first edition of the WMO Air Quality and Climate Bulletin, and Irina Petropavlovskikh, a CIRES scientist in NOAA’s Global Monitoring Laboratory, is a co-author. For the new report, NOAA provided long-term ozone monitoring data from atmospheric baseline observatories in Barrow, Alaska; Mauna Loa, Hawaii; and South Pole, Antarctica. 

“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 impacts of air pollutants occur near the surface, on shorter timescales. Despite these differences, air quality and climate change are strongly interconnected,” the report’s authors stated. 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, 2020 was marked by extreme fires in Siberia and the western United States, exacerbated by persistent weather patterns that produced hot and dry conditions, including a historic high-latitude heatwave in Siberia. Fires in the United States contributed to unhealthy levels of air pollution affecting 20-50 million people in the U.S. West and in regions downwind of western 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 30-40 percent 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 during 2020 also varied greatly across urban areas, ranging from no overall change to small increases (in Europe) and larger increases (in East Asia and South America). The report noted that the ozone response to COVID-19-related slowdowns was 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 percent due to particulate matter, 9 percent due to ozone) to 4.5 million in 2019 (92 percent due to particulate matter, 8 percent due to ozone).

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

A WMO animation on the connections between air quality and climate is here:

CIRES at CU Boulder has partnered with NOAA since 1967.


Owen Cooper
CIRES and NOAA scientist
Karin Vergoth
CIRES communications

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