A/C Cools Us in a Warmer World but Dirties Air, Harms Health
As temperatures worldwide soar because of climate change, so will demand for electricity to keep people cool and safe from sweltering heat. That’s the finding of a new study published today by researchers at the University of Wisconsin-Madison in PLoS Medicine, which concludes that increased use of air conditioning in response to climate change could increase air pollution, sickening hundreds of Americans every year.
New Research to Connect the Dots
Heating and cooling account for almost half of the energy use in a typical American home, and we now use roughly as much energy to cool our buildings as we did for all purposes in 1955. This demand for energy has a harmful side effect on air quality, because of our heavy reliance on polluting fossil fuels for generating the electricity used to cool our homes, schools, and office buildings when it gets hot outside. The electricity sector is one of our country’s largest sources of polluting greenhouse gas emissions, and coal-fired power plants are also major sources of air pollution that disproportionately harm the most vulnerable among us. This work shows that, if the United States plans to adapt to climate change by using more fossil fuel energy to stay cool, we could worsen both air pollution and climate change itself—and more people will die as a result.
The research team at the University of Wisconsin-Madison, of which I was a part, deployed a toolbox of climate, energy demand, air quality, and health impact assessment models in sequence to quantify how climate change-driven warmer weather affects human adaptive behavior (e.g., increased demand for air conditioning to cool buildings in the summer), and how this extra energy demand, when met by our current fossil fuel-reliant energy infrastructure, could worsen air quality and human health.
Higher Energy Demand in Warmer Summers
We began our study with a mid-century scenario of climate change effects in the eastern United States using models from the National Center for Atmospheric Research. This future scenario represents a plausible warm summer corresponding to a business-as-usual trajectory in which we continue to deploy fossil fuels to meet most of our energy needs.
By the middle of the century, in our scenario the maximum ambient summer temperature across the eastern United States increases from 90.3° to 101.3°F. Correspondingly, summer demand for energy also rises about 28 percent (213 to 274 GWh) and carbon dioxide emissions jump by about 18 percent (169,000 to 200,000 metric tons).
Summer Air Pollution Could Worsen Significantly
Our research found that the effects of climate change on air quality are substantial partly because our country’s dirtiest power plants are activated on the hottest days. By the middle of this century, we found that climate change and increased energy demand could worsen summer air pollution from fine particulate matter (PM2.5) by about 60 percent and ground level smog by about 16 percent, compared to current pollution levels. Overall, extra energy demand for air conditioning, if met largely by today’s fossil fuel-heavy mix, would constitute about 4 percent of the increase in PM2.5 pollution and about 7 percent of the increase in smog. We anticipate current trends toward greater adoption of renewable fuels and a cleaner grid will continue and that will dampen this effect. While millions of Americans already breathe unhealthy air, climate change threatens to make this problem even worse unless we act to stem the problem.
A/C Cools Us Down, But Worsens Air Pollution
Using a health impact assessment model developed by the U.S. Environmental Protection Agency, we calculated that by the middle of the century, higher levels of air pollution from extra air conditioning demand cause about 650 future PM2.5-related deaths and about 300 ozone-related deaths each year in the summer. Clearly, the public health threat posed by this unintended, side effect of air conditioning on air quality is substantial.
We focused our analysis on the eastern United States, from roughly Minnesota to Maine, because this area already faces a range of air pollution health risks and is the most highly populated region of the country. This work was funded by the National Institutes for Environmental Health Sciences and quantified, for the first time, the relationship between climate change, air quality, adaptation (via air conditioning demand) and risks to public health.
Skyrocketing Demand for A/C in Developing Countries
The nexus of climate change, energy demand, air quality, and health is an important area for future studies, since demand for air conditioning may triple by 2050. This issue is especially important in developing countries in Asia in Africa which often have even more extreme climates and where air conditioner sales are growing exponentially due to rising middle classes. India, for example, struggles with some of the world’s worst air pollution, and also skyrocketing demand for air conditioning as a form of partial relief from hotter and hotter summers. The UN Environment’s program called United for Efficiency is working to improve the energy efficiency of new air conditioners to be sold in developing countries.
Making Smarter Energy Choices to Protect Public Health
Last year was one of the hottest years on record and extremely hot days are becoming more intense and frequent worldwide. Our study shows that while using air conditioning to adapt to increasingly warmer weather will relieve exposures to extreme heat, this response will harm public health if we continue to rely on fossil fuels to meet our cooling needs.
The good news? The United States has minimum energy efficiency standards for air conditioners being installed, as well as building energy codes that require new buildings and major retrofits to be energy efficient. NRDC is actively involved in updating national and state building codes in the United States and air conditioner efficiency standards in the United States and around the world. Together, these policies can dramatically improve a customer’s level of comfort, while at the same time reduce the amount of energy and pollution caused by their use of air conditioners.