Why air-conditioning is a climate change nightmare
Heat is entropy. Heat is chaos. The hotter something gets, the more kinetic energy it has: molecules vibrate, relationships change, life overheats, things die.
You can see that out west right now. Last week, a heat dome formed over the Great Plains all the way out to the California coast. Salt Lake City boiled at 107°F, the hottest temperature ever recorded there. In Las Vegas, it was more than 100 degrees at night. Phoenix hit at least 115°F five days in a row, setting a new record for the city. The health impacts of heat waves are difficult to track in real time, but public-health officials in the Phoenix area are already investigating the heat-related deaths of nine people in a single day (June 17th). More heat is forecast for this week, this summer, and, as long as the world keeps burning fossil fuels, many years to come. Brutal as it seems, this is just heat bootcamp compared to what we will be facing in the not-so-distant future.
Heat creates a cascading catastrophe of climate chaos. It sucks the moisture out of soil; dry land leads to less evaporation, which leads to fewer clouds and more sun, which equals more heat and evaporation. Lake Mead, the reservoir on the Arizona-Nevada border that provides drinking water to 25 million people and generates electricity for eight million more, is at its lowest point since the 1930s. With heat and drought comes fire. On the first day of summer, wildfires were burning in California, Utah, New Mexico, Arizona, and Montana. Heat changes the movement of insects that carry diseases. It melts away the last of the snowpack. And in us humans, heat causes your heart to beat faster, shunting blood toward your skin, where it can be cooled as you sweat. If you get too hot too fast, your heart can’t keep up, the proteins in your body unfold, your gut leaks nasty stuff into your fast-warming blood, and if you don’t cool off quickly, you die.
But long before that, the most obvious impact of extreme heat is that it pushes people to turn on – and turn up – their air-conditioning. With cool air, you can feel the chaos within you subsiding. But it comes at a cost: AC sucks up huge amounts of electricity, which strains the grid and increases the risk of blackouts. More electricity also means burning fossil fuels, which means more CO2 pollution (President Biden has promised a 100 percent clean electricity grid by 2035, but that’s still a long way off). In addition, hydrofluorocarbons (HFCs), the human-made chemicals inside of air-conditioners used to cool the air, are super greenhouse gases, up to 3,000 times more potent than CO2 at trapping heat in the atmosphere. What it comes down to is this: By cooling ourselves off, we risk cooking ourselves to death.
In fact, that’s pretty much what’s happening right now. The heatwave that is melting pavement out west is indisputably linked to the climate crisis. While the Earth as a whole has warmed up a little more than 1°C already, over land, where we all live, it has warmed up close to 2 °C. According to Michael Wehner, a senior scientist at Lawrence Berkeley National Lab, today’s heat waves are 3° to 5°F hotter than they would be without the additional warming from CO2 pollution, which largely comes from burning fossil fuels. And the more CO2 we dump into the atmosphere, the hotter it is going to get.
And it’s pretty much a given that as the planet heats up, the demand for air-conditioning will grow fast, especially in the developing world, where air-conditioning is still a luxury that few people can afford. There are just over 1 billion single-room air conditioning units in the world right now – about one for every seven people on Earth. By 2050, there are likely to be more than 4.5 billion units, making them as common as cellphones today.
The consequences of this are enormous. A small unit cooling a single room can consume more power than running four refrigerators. The U.S. already uses as much electricity for air conditioning each year as the UK uses in total. The International Energy Agency projects that as the rest of the world reaches similar levels, air conditioning will use about 13 percent of all electricity worldwide, and produce 2 billion tons of CO2 a year – about the same amount as India, the world’s third-largest polluter, emits today.
The HFCs in AC units just amplify the problem. Right now, HFC emissions account for around 1 percent of global greenhouse gas emissions and as much as 3 percent in many developed countries. According to the IEA, if left unchecked, these emissions will increase to 7-19 percent of all greenhouse gas emissions by 2050 and offset most, if not all, mitigation actions pledged by countries to date.
As AC use rises, so too does the risk of brownouts and blackouts. During heatwaves, the demand for power surges, putting the stability of the entire grid at risk. And when power goes out on a hot day, people die. “[In 2018] in Beijing, during a heatwave, 50 percent of the power capacity was going to air conditioning,” John Dulac, an analyst at the IEA, told the Guardian. “These are ‘oh, shit’ moments.”
Even without blackouts, higher temperatures mean bigger electric bills as AC units struggle to keep up with the heat. “If you want to cool your house to 75°F and the outside temperature increases from 95°F to 98°F, that *small* change means you need 1.3x more energy to cool,” Andrew Dessler, a climate scientist at Texas A&M, tweeted recently. That’s 30 percent more power, which means a 30 percent higher electricity bill, just for a 3-degree increase in temperature.
What’s the solution to this cascade of heat-driven chaos? The most obvious one: Stop burning fossil fuels. For all intents and purposes, when carbon emissions reach zero, warming will stop and the temperature in the atmosphere will level-out (they will stay at that level until CO2 levels fall, which, barring the massive deployment of some new technology that can suck CO2 out of the atmosphere, will take many hundreds of years). But since we are obviously not going to be living in a zero-carbon world anytime soon, increasing the efficiency of AC units can help, as can developing and commercializing new technologies to cool the air without destroying the planet (in the U.S., new efficiency standards for AC units will take effect in 2023). In some places, heat pumps, which both heat and cool buildings, can be a smart option. And earlier this year, the winners of a $1 million Global Cooling Prize were announced, showcasing new technology that promises to have five times less climate impact than traditional AC units.
But there are simpler solutions, too. Last week, the respected medical journal Lancet published a largely overlooked paper about humble technology that can do a lot to help solve the problems of extreme heat: the electric fan.
As everyone knows, fans have been used for centuries to move air around and help you feel cooler (in China, hand fans date back to the 8th century). But in recent years, electric fans have gotten a bad rap. The Environmental Protection Agency warns, “portable electric fans are not the simple cooling solution they appear to be.” From the World Health Organization: “In severe heat, fans can add to the level of heat stress, in particular when ambient humidity is high.” Also from the WHO: “There is no scientific consensus on the efficacy of fans.”
The fear is that fans create what amounts to a convection oven for people. As hot air blows across body, it can increase heat stress. The gist of most public health recommendations that are in place today is that when it gets above 95°F, fans do more harm than good.
But Nate Morris, a researcher at the University of Copenhagen and the lead author of the Lancet paper, argues in the new study that these guidelines are not based on sound science. In fact, Morris and his co-authors make the case that in most circumstances and for most people, fans are a cheap, easy, low-power relief from extreme heat.
In the study, researchers used biophysical models to create combinations of temperature and humidity to see when using a fan would worsen heat stress for three groups of people: healthy young adults (aged 18–40 years), healthy older adults (aged 65 years and older), and older adults taking anticholinergic medication, a class of drugs used to treat Parkinson’s Disease and other conditions. These age groups were selected because the ability to sweat is reduced by 25 percent in older adults, and is decreased by a further 25 percent in people on anticholinergic medication. Heat stress thresholds for these three groups were then compared with hourly hot weather data for 108 cities around the world between January 1st, 2007, and December 31st, 2019.
The study found that the effectiveness of fans depends on both temperature and humidity. Basically, in hot, humid conditions, the fan helps more because the blowing air helps sweat evaporate faster, which accelerates cooling. In hot, arid climates, sweat evaporates easily, so fans are less helpful and, at extreme temperatures, can indeed increase heat stress. Nevertheless, during the 12-year period the study covered, it found that electric fan use would have provided cooling benefits for 96.6 percent of all hot weather days for young adults, and 94.9 percent of days for healthy older adults and older adults taking anticholinergic medication.
In addition, the paper pointed out that electric fans reduce demand for electricity by 30 times compared with traditional AC units, thus greatly easing strain on the grid and reducing risk of blackouts. They also have the potential to greatly reduce carbon pollution. “As a crude estimate,” the authors of the study wrote, “if young people [i.e., under 65] were to switch from air conditioning to fan use for their cooling needs, when fan use would be beneficial, this would yield a 59 percent reduction in global hydrofluorocarbon emissions and a 9 percent reduction in global CO2 emissions.”
Electric fans are not going to solve the climate crisis. But it’s good to know that there are simple ways to cool ourselves off that don’t make the crisis a lot worse. Given all we know about the risks we face right now, cooking ourselves to death is not our destiny. It is our choice.