How Climate Change May Impact Ozone Pollution and Public Health through the 21st Century

Published February 15, 2022

Climate researchers are learning that warming temperatures and heat waves resulting from greenhouse gas (GHG) emissions could adversely affect air quality in the United States and increase deaths from air pollution exposure. This effect is referred to as the “climate penalty.”

Higher levels of GHG emissions from vehicles, power plants, and other human-made sources are contributing to warming, which will increase ozone. Exposure to this pollutant can aggravate asthma, cause heart attacks, and exacerbate other respiratory and cardiovascular conditions. Air quality managers need to know how climate change will affect air quality and public health throughout the 21st century.

New modeling approaches by EPA are providing this information for states as they work to implement the National Ambient Air Quality Standards. In one modeling simulation, researchers showed that full implementation of enacted air pollution regulations could reduce the increase of ozone despite warmer temperatures, thus reducing potential deaths from exposure. 

Exploring Changes to Ozone and Impacts on Health Using Model Simulations

EPA researchers conducted an extensive modeling study of the impacts of climate change on air quality in the United States and the implications for public health. They first used data from two global climate models and produced more localized and detailed climate projections over North America for five 11-year periods. They found that summer average daily maximum temperatures across the contiguous United States are projected to increase 2–7 degrees Fahrenheit by 2050 and 4–13 degrees Fahrenheit by 2095 under one climate model, while the other climate model simulated increases of 4–13 degrees Fahrenheit by 2050 and 7–20 degrees Fahrenheit by 2095.

The researchers then ran both of the climate projections in EPA’s Community Multiscale Air Quality (CMAQ) model to simulate what would happen to air pollutants under two air pollution emissions scenarios. The first scenario replicated the 2011 emissions in the U.S., while the second scenario was a 2040 projection accounting for the full implementation of current air regulations.

“This is the most extensive study conducted to date of the climate penalty and its implications for human health,” said Chris Nolte, an EPA physical scientist who is the lead researcher and author of the study. “It allows us to assess the impact of widely varying atmospheric chemical and physical conditions on seasonal average pollutant concentrations and consequent mortality effects.”

The impacts of climate change on air quality varied depending on the region of the country and the air pollutant emissions scenario. For example, in the 2011 emissions scenario, the largest ozone increase was in the central Great Plains and Midwest with a 1–5 parts per billion (ppb) increase by 2050 and more than 10 ppb by 2095. Ozone remained unchanged or decreased for the Gulf Coast, Maine, and parts of the Southwest. In the 2040 emissions scenario that included the new emissions controls, the ozone increases were considerably lower. The study demonstrated that current air pollution control measures can lower ozone concentrations even with climate warming and assist states with meeting the air quality standards to protect public health.

Using the CMAQ future scenarios, another analysis led by EPA health scientist, Neal Fann, found a projected increase in deaths that could be attributed to climate impacts on air pollution. The analysis estimated 21,000 additional deaths from exposure to the air pollutant, fine particulate matter (PM2.5), and 4,100 additional deaths from ozone exposure from 2000 to 2095, using the 2011 emissions scenario. These projections decreased, however, to an estimated 15,000 additional PM2.5-related deaths and 640 additional ozone-related deaths from 2000 to 2095 under the 2040 emissions scenario accounting for planned emissions controls.

This suggests that reducing future air pollutant emissions also could reduce the number of deaths due to climate-driven increases in air pollution by thousands of persons per year, according to the published analysis by Fann.

“Both the modeling and mortality risk studies support the broader goal of providing guidance to state regulators on air quality and health impacts from climate change,” Nolte said.

The work also advances the capacity to estimate air quality and health impacts for various climate scenarios by using the comprehensive modeling studies as baselines to develop more efficient models that can be applied for a broader range of scenarios.

Learn More:

• Regional Temperature-Ozone Relationships Across the U.S. Under Multiple Climate and Emissions Scenarios.
• Associations Between Simulated Future Changes in Climate, Air Quality, and Human Health. JAMA Network Open, Chicago, Illinois,  4(1):e2032064, (2021).
• CMAQ: The Community Multiscale Air Quality Modeling System