Summer has only just begun, but much of the world is already experiencing extreme heat. Over the past two weeks, extreme heat waves have hit many parts of the United States, Europe and China, threatening lives, increasing the risk of wildfires and testing the limits of power grids.
Temperatures soared above 100 degrees Fahrenheit in Minnesota earlier this week, causing curving streets and shattering car windows. Thousands of cattle died in Kansas. Meanwhile, France reached nearly 110°F and set or matched more than 200 monthly high temperature records nationwide.
And that’s all before summer technically begins — Tuesday is the summer solstice — raising concerns among climate scientists that heat waves will arrive earlier as the planet warms. Meteorologist Bob Henson said: “It’s especially impressive (and disturbing) to see Europe set all-time high temperature records ahead of the summer solstice.” wrote on Twitter over the weekend.
Heatwaves in Europe are starting to subside. But extreme heat in the U.S. — the country’s deadliest weather-related phenomenon — is still lingering, moving east from the Great Plains into the southeastern U.S. A staggering 70 percent of the U.S. population could see temperatures in the 90s next week, including residents of major cities like Atlanta, New Orleans and Dallas. Tens of millions of Americans received heat advisories on Tuesday. Looking further afield, the National Weather Service is forecasting above-average temperatures for July, August and September — with little hope of relief.
Compared to past averages, this is not normal for any time in June or summer. This is an extreme. But as fossil fuels continue to warm the planet, “normal” has become a useless word in meteorology — and “extreme” is a mundane one.In the next few years, heat waves like this could worse, not better. So while this summer may be unbearably hot, it could be one of the coolest for decades to come.
Where does this heat come from?
According to the National Weather Service, a “heat wave” is a technical term that refers to an extended period of time (at least two days) where temperatures remain significantly warmer than the local average. Typically, they start where high pressure builds up in the atmosphere, writes Vox’s Umair Irfan:
This creates a sinking column of air that compresses, heats up and often dries out. The high-pressure system also pushes out cooler, fast-moving airflow and squeezes clouds away, allowing the sun to see the ground unobstructed. The ground—soil, sand, concrete and asphalt—is then baked in the sun, and heat builds up rapidly during the long summer days and short nights, raising temperatures.
These high-pressure systems have contributed to recent heat waves in North America and Europe, reports Axios’ Andrew Freedman. All the pressure in the atmosphere acts like a pot lid, trapping the heat so it cannot dissipate. That’s why these heat waves are often referred to as “heat domes” — heat trapped beneath a pressure dome.
When these domes linger, they put human lives at risk. Without air conditioning or cool public spaces, people — especially those young or old with underlying health conditions — are at risk for conditions such as heat stroke and heat exhaustion. It is estimated that in the United States, more than 1,300 people die each year from extreme heat. (Check out this helpful chart detailing symptoms and what to do if you have them.)
Heat waves also threaten the natural world. They can kill livestock and wild animals. For example, scientists estimate that a heatwave in the Pacific Northwest killed hundreds of millions of marine life last summer. During the recent European heatwave, water temperatures in the Mediterranean were 9°F warmer than average.
“Heatwaves now occur regularly, exceeding physiological thresholds for some species,” wrote the authors of a recent report from the Intergovernmental Panel on Climate Change. In other words, heat waves have become yet another threat to flora and fauna, many of which are already at risk of extinction.
Summer is only getting hotter and starts faster (in a bad way)
The world has warmed by 1.1°C (roughly 2°F) since the beginning of the Industrial Revolution. While this increase may not sound like much, it makes extreme cases more likely – just check out the chart below.
Heat waves are becoming more common, they last longer and they bring more extreme temperatures. According to the U.S. Environmental Protection Agency, in the 1960s, there were an average of about two heat waves a year, compared with an average of six in the last decade.
Either one can be devastating. Just last month, severe heatwaves triggered by climate change hit India and Pakistan, home to 1.5 billion people.
Of particular concern, according to climate experts, is that these events occurred earlier this year, when people, cities and the infrastructure they depend on may not be ready for extreme heat. “Heatwaves that occur early in the spring or late in the fall can catch people off guard and increase the health risks associated with heatwaves,” the EPA wrote. (As the seasons get hotter, people’s bodies can physically adapt a little to deal with the heat, but that process takes time.)
The good news is that meteorologists can predict extreme weather to some extent, and climate models are improving. A report from the National Weather Service in May indicated that June will be hot.
The problem is that much of the world’s infrastructure, policy and planning is based on historical averages – it’s clear that the future will not be like the past.
Umair Irfan contributed reporting.