If you thought this summer felt hotter than normal, you were right. Temperatures around the world were unusually warm, surpassing several heat records, including in the U.S.
The National Oceanic and Atmospheric Administration this week announced that for the Lower 48 states, this summer– from June to August– was the warmest in 132 years of record-keeping.
Globally, August ties with July 2023 as the hottest month on record, according to the European climate service, Copernicus Climate Change Service.
In August, global temperatures exceeded 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels, according to Copernicus. That's a key climate threshold agreed to by countries in 2015. Record high sea surface temperatures were also seen across the Pacific Ocean as the climate pattern El Niño began to develop.
Francesca Guglielmo, a senior scientist at the Copernicus Climate Change Service, said while "every record is always shocking in a way," the numbers are not a surprise. It's a trend scientists have been observing for years.
"Measures need to be undertaken to try to mitigate as much as possible," Guglielmo said.
Global temperatures in August averaged 62.53 degrees Fahrenheit, Copernicus data shows.
"What we're feeling is not some regional heat anomaly, but a hotter climate all over the globe," said Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography at UC San Diego. "We're not the only ones who are feeling it: ask the Europeans, the Japanese, everybody is feeling the heat this summer."
August averaged 75.6 degrees Fahrenheit in the Lower 48 states, making it the warmest August on record. Daytime maximum temperatures also reached 88.6 degrees Fahrenheit on average, another record, according to the National Oceanic and Atmospheric Administration. Drought also covered almost 60% of the U.S. this summer.
"We're just going to continue to hear about record-breaking heat, record- shattering heat over and over and over again," said Daniel Swain, a climate scientist with the University of California Agriculture and Natural Resources. "We're going to become a little bit numb to it — maybe we already have."
Guglielmo said these numbers have real-time impacts – an increase in demand for energy and cooling, more droughts, hotter oceans and greater wildfire risk.
"There is a chain of events from larger to smaller scale, the impacts of which are felt by people every day across the world," Guglielmo said.
What is causing the heat?
The main driver behind record-breaking heat is human-caused climate change.
"The number one reason is climate change. Full stop," said Swain. "The earth is warming. It's been warming. It continues to warm."
Scientists, like Swain, are increasingly able to make the connection between heat and climate change.
"Whenever there is an extreme or record breaking heat wave, there is a human-caused climate change contribution to that heat wave," Swain said.
El Niño started to develop over the summer against this backdrop of climate change. It's a natural climate pattern that happens every few years where the Pacific Ocean along the equator gets abnormally warm, and then heat gets released to the atmosphere. This heat has large impacts on weather patterns and temperatures.
"[El Niño] is a natural pattern that's occurring in an unnaturally warming world," said Gershunov, the UC San Diego researcher.
How does heat impact people?
This summer's heat brought devastating consequences to Europe, where French officials recorded thousands of deaths. Western Europe marked its hottest summer on record, according to Copernicus data.
In the U.S., tens of millions of Americans were under extreme heat advisories or warnings from the National Weather Service.
Swain said it's not just heat during the day that's the problem. Overnight temperatures also aren't cooling down. NOAA reported above-average nighttime temperatures across most of the contiguous U.S. this summer.
A study from the research organization Climate Central found in July that people around the world lose about 56 hours, or seven full nights, of sleep every year due to heat.
"That's when your body is going to otherwise recover," Swain said. "The overnight heat can actually be even more dangerous than daytime heat because you never get that reset cycle."
Scientists expect temperatures in September to also be above average, the NOAA report said, with significant potential for wildfires across parts of the Northwest and Southern U.S. Swain and other climate scientists say these record-breaking temperatures are not going away without cuts to fossil fuel emissions – the primary driver of climate change.
"We [have] got to bend that carbon curve," Swain said. "Although we've made progress with green energy, we've not made enough progress in other sectors. We are not on the path that we need to be on."
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