July 4 was earth’s hottest day on record

Tuesday was the hottest day on Earth since records began in 1979, with the global average temperature reaching 62.92 degrees Fahrenheit (17.18 degrees Celsius), according to data from the U.S. National Centers for Environmental Prediction.

As a result, scientists believe July 4 may have been the hottest day on Earth in around 125,000 years, due to a dangerous combination of climate change causing global temperatures to soar, the return of the El Niño pattern and the start of summer in the northern hemisphere.

In the United States, 57 million people were exposed to dangerous heat on Tuesday, according to The Washington Post’s extreme heat tracker. At the same time, China was gripped by a sizzling heat wave, the Antarctic is hotter than usual during its winter and temperatures in the north of Africa reached 122F, Reuters reported.

Tuesday’s global average air temperature was calculated by a model that uses data from weather stations, ships, ocean buoys and satellites, Paulo Ceppi, a climate scientist at London’s Grantham Institute, explained in an email Wednesday.

“This is our ‘best guess’ of what the surface temperature at each point on earth was yesterday,” he said.

Instrument-based global temperature records go back to the mid-19th century, but for temperatures before that scientists are dependent on proxy data captured through evidence left in tree rings and ice cores. “These data tell us that it hasn’t been this warm since at least 125,000 years ago, which was the previous interglacial,” Ceppi said, referring to a period of unusual warmth between two ice ages.

The last time the record was broken was on Monday, when the temperature was 62.62 degrees Fahrenheit, according to the same data. Before that, the highest recorded average temperature in history was 62.46 degrees Fahrenheit as measured on Aug. 14, 2016, during the previous El Niño cycle.

Unless action is taken to combat carbon emissions, temperatures are likely to get even hotter, experts say.

“When’s the hottest day likely to be? It’s going to be when global warming, El Niño, and the annual cycle all line up together. Which is the next couple months,” said Myles Allen, a professor of geosystem science at Oxford University, in a phone interview Wednesday. “It’s a triple whammy.”

Much of Tuesday’s record is explained by climate change causing the world to heat up, Allen said, adding that global temperatures are already 1.25 degrees Celsius (2.25 degrees Fahrenheit) above their preindustrial average. “It’s warming 0.25 degrees Celsius a decade,” he said. “That’s why we see records broken continuously, rather than just as one-offs.”

“Looking to the future, we can expect global warming to continue and hence temperature records to be broken increasingly frequently, unless we rapidly act to reduce greenhouse gas emissions to net zero,” Ceppi added.