The coronavirus-climate-air conditioning nexus

This summer, America will be hemmed in by a climate emergency on one hand and a continuing deadly pandemic on the other. Meanwhile, humming away in the background, aggravating our plight, will be that longtime summer friend: air conditioning.

Climatic models are projecting that heat waves will be more frequent and more intense than usual across the United States this summer. As pandemic-induced restrictions are relaxed, severe heat likely will drive most social gatherings and group activities into the air-conditioned indoor world. There, the risk of coronavirus spread will be much higher than it is in a park or on a porch. 

These days, it’s always riskier to gather indoors than outdoors. Research says that indoor spaces can be made somewhat safer simply by opening windows for ample ventilation. That won’t work in air-conditioned buildings, which must be zipped up tight.   

Air conditioning raises the risk further by lowering the indoor relative humidity. Studies show that coronaviruses in general, including those that cause the common cold, SARS and MERS, remain viable and infective longer when humidity is low, whether the viruses are in the air or on surfaces. 

There’s more. When humidity is high, virus particles are carried inside bulky saliva droplets that fall to the floor or other surfaces within seconds. But with low humidity, they are in much smaller droplets called aerosols that stay airborne far longer, ready to be inhaled. 

Some types of cooling systems also serve to circulate droplets very efficiently and potentially could infect large numbers of people. A widely cited case study found that in January, one customer at a restaurant in Guangzhou, China, infected nine other diners sitting at three different tables with COVID-19. The breeze from an air conditioner near one of the tables had efficiently distributed virus-laden droplets along a 20-foot-long path. 

There are numerous cases in which air conditioning has caused health problems by spreading bacteria and mold spores, which can be associated with so-called “sick building syndrome.” Studies in North and South America and Europe have found that people employed in air-conditioned workplaces generally have more health problems than those who work in non-cooled spaces.

Despite such impacts, air conditioning is customarily viewed as a net health benefit, because it can help prevent deaths during heat waves. However, research shows that when people die of heat stress, it is largely because they are living in marginalized, economically stressed urban areas with too much concrete and too little vegetation, often in communities of color who have inadequate access to services, especially health care. 

Those who die in heat waves also are often elderly and/or have preexisting health problems, and they may be unable to afford the electricity to run an air conditioner. Not coincidentally, these communities and individuals who are most vulnerable to heat waves are also the most vulnerable to the coronavirus. 

To be clear, air conditioning indeed can help keep people alive under harsh conditions, and that is no small thing. Nevertheless, it is important for us to acknowledge that in that role, the air conditioner is an “in case of emergency break glass” tool. It’s not designed to fix the underlying social and economic injustices from which people need to be rescued, whether it’s from extreme heat or a viral pandemic. 

Air conditioning increasingly is viewed as an adaptation to climate change, but it also accelerates greenhouse warming. It accounts for 17 percent of year-round home electricity consumption and the resulting emissions; furthermore, the Energy Information Agency predicts that U.S. energy use for air conditioning will grow faster than any other use of energy in buildings of all kinds in coming decades. 

The chain of causation forms a perfect circle. Greenhouse emissions from past decades — including billions of tons of carbon dioxide emitted by air conditioning, aircraft and other technologies that also happen to be implicated in the pandemic — may make this summer the hottest ever, prompting even more air conditioning use, which will further increase greenhouse emissions. Those emissions will help ensure that future summers are even hotter and future air-conditioning systems are pushed even harder. 

I believe that ending the climate emergency will require the rapid, mandatory reduction of fossil fuel use to zero and a complete overhaul of our built environment — including good, affordable housing and a healthy environment for all. 

Meanwhile, we at least can curb the short-term damage. Home air conditioning should be turned off on those many summer days when shade and fans can provide sufficient comfort. Offices should never be so frigid that workers resort to wearing sweaters or keeping space heaters under their desks in July. Every building should have windows that can be opened and that stay open as much as possible.

And, at least for the rest of this summer, let’s all get together outdoors.  

Stan Cox, author and plant scientist, began his career at the U.S. Department of Agriculture and now is the lead scientist at The Land Institute. His new book is “The Green New Deal and Beyond: Ending the Climate Emergency While We Still Can” (City Lights Books, 2020). Follow him on Twitter @CoxStan.