How Heat Waves Work (and Why They’re Getting Worse)
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Publishing a report on the danger of heat waves during the tail end of 2019’s worst one yet had a bitter sort of irony for Rachel Licker. Talking to Popular Mechanics from Washington, D.C, the senior climate scientist with the Climate & Energy Program at the Union of Concerned Scientists (UCS) had just faced temperatures hovering around 100 and a heat index around 115.
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“It was a pretty poignant moment,” Licker says, referring to the the release of “Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days,” the 2019 report by the UCS. While hurricanes and wildfires have gotten a lot attention (and rightfully so) for being strengthened by climate change, the seemingly more mundane heat wave will likely become more familiar in the coming years—and more deadly.
Since that report came out, heat waves have become an annual occurrence. July 2022 is bringing scorching temperatures across Europe, where around 750 people are reported dead due to consequences of the unusually extreme heat, including wildfires. Parts of Spain and Portugal rose to 117 degrees. The United States is experiencing its own temperature spike once again this summer.
How Heat Waves Work
Heat-trapping greenhouse gases are part of what makes life on Earth livable. Gases like methane, water vapor, nitrous oxide, ozone, and carbon dioxide filter out much of the sun’s harmful radiation while trapping its heat, allowing a temperate climate to emerge.
Through activities as varied as transportation to farming, humans make several of these gases in tremendous quantities, especially carbon dioxide and methane. As these gases increase in the atmosphere, they supercharge what’s known as the greenhouse effect. That increases heat across the planet. In the Arctic, that means ice melting. But on land, it can be harder to track.
Climate scientists, like Licker, are often loathe to directly finger climate change as the cause of a specific weather event. “Whereas weather refers to short-term changes in the atmosphere, climate describes what the weather is like over a long period of time in a specific area,” explains the National Oceanic And Atmospheric Administration.
“Obviously, there’s a difference between weather and climate,” Licker says. “But we’re projecting that these kind of events are likely to increase in the near term, and there’s evidence to show that some of these extreme events are already affected by climate change.”
Heat waves form when “high pressure aloft, from 10,000 to 25,000 feet (3,000 to 7,600 meters), strengthens and remains over a region for several days up to several weeks,” explains the National Weather Service. “This is common in summer (in both Northern and Southern Hemispheres) as the jet stream ‘follows the sun.’”
The jet streams are crucial to their existence. Jet streams are skinny bands of strong wind that move in the upper levels of the atmosphere. They meander around the globe, blowing west to east but often shifting to move north to south. The problem is that greenhouse gases, which human activity pumps into the air, makes jet streams act weird.
Greenhouse gases increase temperature, which plays a role in melting the icy Arctic. In studies, scientists have observed the faster warming of the Arctic alters the jet stream, creating what they’ve mapped as an “unprecedented hemisphere-wide pattern,” according to Pennsylvania State University climate scientist and study lead author Michael Mann.
That pattern is already starting to affect weather today.
“It played a key role in the large-scale jet pattern we saw in late July [2018], associated with deep stagnant high pressure centers over California and Europe,” Mann said in 2018.
Working in the Heat
The report has sobering statistics on recent heat waves. A 2018 heat wave hit Quebec, which doesn’t have a tradition of air conditioners, and killed over 70 people. In early 2019, a heat wave hit Japan and killed 57 people and sent 18,000 to the hospital. But even in the U.S., where air conditioners are often known commodities (and are also contributing to climate change), heat waves could affect a wide variety of workers.
Outdoor workers were some of the people the UCS were most concerned about. That’s a large group containing a wide variety of jobs, including mail carriers, house painters, construction workers, farm workers, open pit miners, solar panel installers, soldiers, and more, The number workers in this group easily exceeds 10 million, but less than half of U.S. states have heat-related labor standards that protect both private sector and state and local government workers. This is an improvement from 2019, when only two states—California and Washington—had such standards.
The UCS report breaks down the dangers into the likely increases in heat indexes of 90 degrees Fahrenheit, 100 degrees, 105 degrees, and “off the charts.”
“Outdoor workers are one of the most vulnerable groups to extreme heat, given their exposure,” says Licker. “We chose [90 F] because that’s the threshold above which OSHA [the federal Occupational Safety and Health Administration] says conditions can become dangerous for outdoors workers and they start to begin to issue guidance to employers. We looked at 100 and 105 because those are thresholds above which the National Weather Service advises different parts of the United States should issue heat advisories.”
Heat rising through a greenhouse effect might sound like one of the most fundamental aspects of a trend called global warming, but that ubiquity renders it less visible alongside other threats. “We often talk about things in terms of global average temperature change,” Licker says, citing the famous Paris Agreement goal of keeping temperature from rising over 2 degrees.
“We wanted to unpack how that will actually play out,” she says. The abstract goal of the Agreement is “really hard for people to relate to, so we wanted to what that would show in terms of your community.”
?? If you’re forced to be outside during extreme heat, there are a few safety precautions you can take to help yourself out. The Red Cross has some good tips. Having a water bottle at home will make it easier to take water on the go, and hydrate regularly. Wear loose, lightweight clothing that is on the lighter side. If it is possible to postpone outdoor activities, do it.
Not Just a Human Problem
The answers vary across the country, with Florida having a different climate than Minnesota. The UCS has produced a digital map that outlines a rise in heat waves for all 433 of America’s Congressional districts.
Of particular interest to Licker was the fate of Wisconsin’s 4th district, where she just finished several years at the University of Wisconsin-Madison and lived for 11 years. UCS predictions for the state overall show that it will likely have 51 days over 90 degrees Fahrenheit per year by mid-century, and 21 days above 100 degrees, plus 11 days above 105 degrees. The number of unbearably hot days are predicted to rise even more by the end of the century.
“That’s a lot,” she says, “for a state that’s often so cool. That’s a part of the country, like a lot of other northern parts of the country, that is not adapted for extreme heat at the moment. I can speak anecdotally and say that the only place I ever got heat illness was in Wisconsin, because I didn’t have air conditioning at home, we didn’t get hot temperatures. And when a heat wave hit, I was home amidst the heat and got sick from it, because I didn't have the infrastructure to keep safe.”
While northern states might not have the most startling numbers on the map, Licker says, they “have a special vulnerability.” And while air conditioners could provide short term cooling indoors, heat waves don’t just affect humans. They could easily ruin harvests of crops like wheat.
There’s also the challenge of infrastructure, including, the report lists, “road surfaces and airport runways melting, railway tracks buckling, homes and other buildings becoming dangerously hot, electricity being disrupted because of power grid equipment failures or increased power demand.” Power outages during the summer can become frustrating situations, as New Yorkers learned during outages in the summer of 2019.
It’s worth taking some time to say that if you’re forced to be outside during extreme heat, there are a few safety precautions you can take to help yourself out. The Red Cross has some good tips.
Having a water bottle at home will make it easier to take water on the go, and hydrate regularly. Wear loose, lightweight clothing that is on the lighter side. If it is possible to postpone outdoor activities, do it.
Is There a Fix?
The report has multiple suggestions for future actions that can be taken. As it acknowledges that at least some global warming is an inevitability, it suggests investing in cooling infrastructure including cool roofs and pavements, urban forestry, cooling centers, and retrofitting schools. Other structural recommendations include an increasing of American reliance on renewable energy, energy storage, and microgrids.
Under the UCS recommendations, energy utilities like California’s powerful and controversial Pacific Gas and Electric Company (PG&E), would try to move demand away from times of peak energy consumption to help prevent failures during extreme heat event. They would also invest in the resilience of the system itself to prevent failures like the ones in New York.
It’s a lot to take in, but the UCS thinks drastic actions are necessary. During the recent heat have, Licker had an 11-year old nephew visiting her in Washington. During the 115 heat index, he asked her, “Aunt Rachel, is this what climate change is going to feel like?”
“It was kind of heartbreaking,” she says.
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