According to a new report from the World Meteorological Organization (WMO), the quality of air on earth will likely worsen due to an anticipated rise in frequency, intensity, and duration of heatwaves and wildfires.
The WMO report indicates that heatwave duration this century is likely to worsen air quality, harming human health and ecosystems and hence altering the interaction between pollution and climate change.
The annual WMO Air Quality and Climate Bulletin which reports on the state of air quality on Earth and its close interlinkages with climate change indicated that there will likely be an additional “climate penalty” for hundreds of millions of people.
The bulletin basically explores a range of possible air quality outcomes under high and low greenhouse gas emission scenarios, but the 2022 bulletin focuses particularly on the impact of wildfire smoke in 2021.
In 2020, hot and dry conditions exacerbated the spread of wildfires across western North America and Siberia, producing widespread increases in particulate small matter (PM2.5) levels harmful to health.
WMO Secretary-General Professor Petteri Taalas said, “As the globe warms, wildfires and associated air pollution are expected to increase even under a low emissions scenario. In addition to human health impacts, this will also affect ecosystems as air pollutants settle from the atmosphere to Earth’s surface.”
“We have seen this in the heatwaves in Europe and China this year when stable high atmospheric conditions, sunlight and low wind speeds were conducive to high pollution levels,” said Professor Taalas.
“This is a foretaste of the future because we expect a further increase in the frequency, intensity and duration of heatwaves, which could lead to even worse air quality, a phenomenon known as the ‘climate penalty,’” he said.
Climate penalty pivotal theme in air quality and climate Bulletin
Asian countries were identified as centers for climate change amplification, accounting for approximately one-quarter of the world’s population where climate change could exacerbate surface ozone pollution episodes.
Climate penalty refers specifically to the climate change amplification effect on ground-level ozone production, which negatively impacts the air people breathe, leading to detrimental health impacts for hundreds of millions of people.
The Air Quality and Climate Bulletin, the second in an annual series—and an accompanying animation on atmospheric deposition—were published ahead of the International Day of Clean Air for blue skies on September 7th.
The theme of this year’s event, spearheaded by the UN Environment Programme, is The Air We Share, focusing on the transboundary nature of air pollution and stressing the need for collective action.
Based on input from experts in WMO’s Global Atmosphere Watch network, which monitors air quality and greenhouse gas concentrations, it can quantify the efficacy of the policies designed to limit climate change and improve air quality.
Air quality and climate are interconnected because chemical reactions that lead to a degradation in air quality are normally co-emitted with greenhouse gases. Hence, changes in one inevitably cause changes in the other.
The combustion of fossil fuels, which is a major source of carbon dioxide (CO2) also emits nitrogen oxide (NO), which can react with sunlight, leading to the formation of ozone and nitrate aerosols.
Air quality, in turn, affects ecosystem health via atmospheric deposition (as air pollutants settle from the atmosphere to Earth’s surface). The Deposition of nitrogen, sulfur, and ozone can negatively affect the resources, such as clean water, biodiversity, and carbon storage, provided by natural ecosystems and can impact crop yields in agricultural systems.
On a global level, observations of the annual total burned area show a downward trend over the last two decades as a result of decreasing numbers of fires in savannas and grasslands (2021 WMO Aerosol Bulletin).
New WMO Air Quality and Climate Bulletin: Anticipated rise in the frequency, intensity and duration of heatwaves this century➡️increase in wildfires.🔥
This is likely to worsen air quality, harming human health and ecosystems.https://t.co/toYtCl29j8#WorldCleanAirDay pic.twitter.com/nwChjeoBSy
— World Meteorological Organization (@WMO) September 7, 2022
Future scenarios on air quality evolution
Western North America’s annual total emissions were ranked amongst the top five worst years when considering the period 2003 to 2021 with PM2.5 concentrations well above limits recommended by the World Health Organization.
However, at continental scales, some regions are experiencing increasing trends, as are parts of western North America, the Amazon, and Australia.
The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) includes scenarios on the evolution of air quality, as temperatures increase in the 21st century.
It was determined that the probability of catastrophic wildfire events—like those observed over central Chile in 2017, Australia in 2019, and the western United States in 2020 and 2021—is likely to increase by forty to sixty percent by the end of this century under a high emissions scenario, and by thirty to fifty percent under a low emissions scenario.
If greenhouse gas emissions remain high, such that global temperatures rise by 3° Celsius from preindustrial levels by the second half of the 21st century, surface ozone levels are expected to increase across heavily polluted areas, particularly in Asia.
This includes a twenty percent increase across Pakistan, northern India, and Bangladesh and ten percent across eastern China. Most of the ozone increase will be due to an increase in emissions from fossil fuel combustion.
Roughly a fifth of this increase will be due to climate change, most likely realized through increased heatwaves, which amplify air pollution episodes. Thus, heatwaves, which are becoming increasingly common due to climate change, are likely to continue leading to a degradation in air quality.
Carbon neutrality can limit ozone air pollution
The bulletin indicated that a worldwide carbon neutrality emissions scenario would limit the future occurrence of extreme ozone air pollution episodes.
This is because efforts to mitigate climate change by eliminating the burning of fossil fuels (carbon-based) will also eliminate most human-caused emissions of ozone precursor gases, particularly nitrogen oxides (NOx), Volatile Organic Compounds, and methane.
Particulate matter, commonly referred to as aerosols, have complex characteristics which can either cool or warm the atmosphere. High aerosol amounts—and thus poor air quality— can cool the atmosphere by reflecting sunlight back to space or by absorbing sunlight in the atmosphere so that it never reaches the ground.
The Intergovernmental Panel on Climate Change suggests that the low-carbon scenario will be associated with small, short-term warming prior to temperature decreases.
This is because the effects of reducing aerosol particles, i.e., less sunlight reflected into space, will be felt first while temperature stabilization in response to reductions in carbon dioxide emissions will take longer.
However, natural aerosol emissions (e.g., dust, wildfire smoke) are likely to increase in a warmer, drier environment due to desertification and drought conditions. This may cancel out some of the effects of the reductions in aerosols related to human activities.
A future world that follows a low-carbon emissions scenario would benefit from reduced deposition of nitrogen and sulfur compounds from the atmosphere to the Earth’s surface, where ecosystems might be damaged.
Stations of WMO around the world would monitor the response of air quality and ecosystem health to propose future emissions reductions, and this could quantify the efficacy of the policies designed to limit climate change and improve air quality.