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It’s not your imagination, US summers are hotter than ever before | climate science

From Texas to California, most of the US south-west is experiencing scorching heat this week, with temperatures soaring above 100F (38C) in dozens of locations, putting millions of people at risk of “dangerously hot conditions”.

This is part of an alarming trend. American summers are hotter than ever, according to new research, with most of the country experiencing increased summer averages over the last half century.

1. Almost every location measured has higher summer temperatures since 1970

A map of the United States showing increased average 2021 summer temperatures across the country.

Climate Central, a non-profit that analyzes and reports on climate science, shows 235 out of 246 US locations have seen an increase in their summer average temperature since 1970. More than half of the locations have warmed by 2F (1C) or more. And 37 locations had 30 or more summer days that were hotter than normal.

“This trend is a signal of all the extra heat that we’ve accumulated on the planet,” says Andrew Pershing, director of climate science at Climate Central, which released the research. “Globally, this blanket of extra carbon dioxide in the atmosphere is radiating heat back at us.”

2. Spikes are highest in the US west and south-west

The west and south-west region have experienced the greatest temperature shifts over the last five decades, with cities such as Boise, Idaho (+5.6F), and El Paso, Texas (+5.3F), all posting higher temperatures.

But the largest increase was in Reno, Nevada.

Average summer temperature shifts in Reno, Nevada. Between 1970 and 2021, average summer temperatures increased by 10.9F

“In the past, you’d not expect to have such high record-breaking temperatures so early in the season,” said Juan Declet-Barreto, climate vulnerability researcher at the Union of Concerned Scientists. “Now, those things which had seemed anomalous are starting to become commonplace.”

The rising heat poses challenges the human body. More than 11,000 people in the US died from heat-related illnesses between 1979 to 2018, and a recent study concluded that heat-related deaths may be “substantially larger than previously reported”.

“Heat is not just an inconvenience, it’s a severe health threat, especially to people with pre-existing conditions,” says Vijay Limaye, senior scientist at the Natural Resources Defense Council.

3. Rising heat is affecting people in the US unevenly

People age 65 and above are more likely to die from heat-related cardiovascular disease than the general population. Native Americans had the highest rate of heat-related deaths, followed by non-Hispanic Black people. Most heat-related mortality is observed among people living in cities and metropolitan areas.

“This urban environment tends to amplify heat,” Pershing says. Across the country, industrial zones, treeless expanses of asphalt, are concentrated in low-income areas and neighborhoods of color. This is rooted in historical discrimination. “Communities that had been redlined are hotter than the ones that hadn’t been,” Pershing adds. A 2020 study found that in the US, previously redlined neighborhoods are approximately 5F (3C) hotter than non-redlined areas, while having half the tree canopy.

Another alarming trend identified in the report is the nighttime temperature warming. These overnight highs can disrupt the crucial time when our bodies recover from the daytime heat.

“We’re seeing these nighttime temperatures elevated in a way that seems to be driving an increase in sleep-related mental health problems,” said Limaye.

With inflation driving higher energy prices and utility costs, experts are concerned about people’s ability to afford air conditioning.

“Air conditioning is life-saving,” Limaye said, adding that federal programs to help with the costs of utilities are a partial solution in ensuring adequate access to affordable cooling. Local mitigation efforts are an important part of the picture. Last year, Miami-Dade county in Florida and Phoenix, Arizona, appointed chief heat officers who are working on adaptation strategies for growing heat hazards.

“The way we’ve built our cities and designed policies, those were under the assumption of a stable climate,” Limaye added. That is no longer the presumption.

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