Climate Change Feedback Loop: Extreme Heat and Air Quality Must Be Tackled Together, WMO Says

According to a new report from the World Meteorological Organization (WMO), extreme heat waves resulting from human-caused climate change are significantly and measurably impacting air quality, so the two must be addressed at the same time.

This year’s WMO Air Quality and Climate Bulletin focuses on heat waves, highlighting the fact that high temperatures aren’t the only danger of the climate crisis, but heightened pollution and its impacts are consequences as well, a WMO press release said.

“Heatwaves worsen air quality, with knock-on effects on human health, ecosystems, agriculture and indeed our daily lives,” said professor Petteri Taalas, WMO secretary-general, in the press release. “Climate change and air quality cannot be treated separately. They go hand-in-hand and must be tackled together to break this vicious cycle.”

The report discusses how wildfires in the northwestern U.S. were triggered by heat waves, and how heat waves along with desert dust in Europe resulted in hazardous air quality last year. It also highlights Brazilian case studies on the ability of urban parks and tree-covered spaces to lower temperatures, absorb carbon dioxide and improve air quality.

“This Air Quality and Climate Bulletin relates to 2022. What we are witnessing in 2023 is even more extreme. July was the hottest ever month on record, with intense heat in many parts of the northern hemisphere and this continued through August,” Taalas said. “Wildfires have roared through huge swathes of Canada, caused tragic devastation and death in Hawaii, and also inflicted major damage and casualties in the Mediterranean region. This has caused dangerous air quality levels for many millions of people, and sent plumes of smoke across the Atlantic and into the Arctic.”

The intensity and frequency of heat waves has been exacerbated by climate change, and WMO said this is expected to continue.

The mounting consensus among scientists is that heat waves will increase the severity and risk of wildfires.

“Heatwaves and wildfires are closely linked. Smoke from wildfires contains a witch’s brew of chemicals that affects not only air quality and health, but also damages plants, ecosystems and crops – and leads to more carbon emissions and so more greenhouse gases in the atmosphere,” said Dr. Lorenzo Labrador, a WMO scientific officer in the Global Atmosphere Watch, the program that compiled the Bulletin, in the press release.

Today is the United Nations’ International Day of Clean Air for blue skies, and the WMO report was released to coincide with it and this year’s theme: Together for Clean Air, which focuses on the necessity of partnerships, shared responsibility and increased investment to address and overcome air pollution.

WMO points out that climate change is a long-term threat, while air pollution has more local effects that last from days to weeks.

Climate and air quality are intertwined due to the types of contaminants involved — biogenic volatile organic compounds, nitrogen oxides and particulate matter (PM) — frequently being emitted by the same polluters, and because the changes they cause feed into each other.

“For example, the combustion of fossil fuels emits carbon dioxide (CO2) and nitrogen oxide (NO) into the atmosphere, which can lead to the formation of ozone and nitrate aerosols. Similarly, some agricultural activities are major sources of the greenhouse gas methane and also emit ammonia, which then forms ammonium aerosols which negatively impact air quality,” the press release said.

Ecosystem health is affected by air quality, as plants absorb pollutants like sulfur, nitrogen and ozone, causing environmental damage and reduced crop yields.

Last summer’s heat wave increased concentrations of ground-level ozone and PM. There was also an abnormally high amount of desert dust over Europe and the Mediterranean. The combination of high amounts of aerosol, which led to high PM content, and high temperatures affected human health.

Dry conditions and heat waves also create conditions conducive to wildfires, which grow rapidly when they encounter dry vegetation. The wildfires can then lead to increased aerosol emissions.

The long heat wave in September of last year, along with increased burning of biomass, led to unhealthy air quality in a large part of the northwestern U.S., the U.S. Environmental Protection Agency reported.

Nitrogen-containing compounds deposited downwind of wildfires affect drinking water, air quality and biodiversity.