Visitors wear sun hats and carry umbrellas as they leave the Forbidden City on a hot day in Beijing, Thursday, June 29, 2023. The entire planet sweltered for the two unofficial hottest days in human recordkeeping Monday and Tuesday, according to University of Maine scientists at the Climate Reanalyzer project. The unofficial heat records come after months of unusually hot conditions due to climate change and a strong El Nino event. (AP Photo/Andy Wong)

The planet’s temperature spiked on Tuesday to its hottest day in at least 44 years and likely much longer, and Wednesday could become the third straight day Earth unofficially marks a record-breaking high, the latest in a series of climate-change extremes that alarm but don’t surprise scientists.

The globe’s average temperature reached 62.9 degrees Fahrenheit (17.18 degrees Celsius) on Tuesday, according to the University of Maine’s Climate Reanalyzer, a common tool based on satellite data and computer simulations and used by climate scientists for a glimpse of the world’s condition. On Monday, the average temperature was 62.6 degrees Fahrenheit (17.01 degrees Celsius), breaking a record that lasted only 24 hours.

While it is not an official National Oceanic and Atmospheric Administration record, “this is showing us an indication of where we are right now,” NOAA chief scientist Sarah Kapnick said. Even though the dataset used for the unofficial record goes back only to 1979, she said that given other data, it’s likely the hottest day in “several hundred years that we’ve experienced.”

The previous hottest day was in August 2021, Kapnick said.

“A record like this is another piece of evidence for the now massively supported proposition that global warming is pushing us into a hotter future,” said Stanford University climate scientist Chris Field, who was not part of the calculations.

With many places seeing temperatures near 100 degrees Fahrenheit (37.8 degrees Celsius), the new average temperatures might not seem very hot. But Tuesday’s global high was nearly 1.8 degrees Fahrenheit (a full degree Celsius) higher than the 1979-2000 average, which already tops the 20th- and 19th-century averages.

Higher temperatures translate into brutal conditions for people all over the world. When the heat spikes, humans suffer health effects — especially young and elderly people, who are vulnerable to heat even under normal conditions.

“People aren’t used to that. Their bodies aren’t used to that,” said Erinanne Saffell, Arizona’s state climatologist and an expert in extreme weather and climate events. “That’s important to understand who might be at risk, making sure people are hydrated, they’re staying cool, and they’re not exerting themselves outside, and taking care of those folks around you who might be at risk.”

The highs come after months of “truly unreal meteorology and climate stats for the year,” such as off-the-chart record warmth in the North Atlantic, record low sea ice in Antarctica and a rapidly strengthening El Nino, said University of Oklahoma meteorology professor Jason Furtado.

Scientists generally use much longer measurements — months, years, decades — to track the Earth’s warming. But the new figures are an indication that climate change is reaching uncharted territory, even if the data aren’t quite the type used by gold-standard climate measurement entities such as the National Oceanic and Atmospheric Association.

The figures legitimately capture global-scale heating, and NOAA will take them into consideration for its official record calculations, said Deke Arndt, director of the National Center for Environmental Information, a division of NOAA.

High-temperature records were surpassed this week in Quebec and Peru. Beijing reported nine straight days last week when the temperature exceeded 35 degrees Celsius (95 degrees Fahrenheit). Cities across the U.S. from Medford, Oregon to Tampa, Florida have been hovering at all-time highs, said Zack Taylor, a meteorologist with the National Weather Service.

Wednesday may bring another unofficial record, with the Climate Reanalyzer again forecasting record or near-record heat. Antarctica’s average forecast for Wednesday is a whopping 4.5 degrees Celsius (8.1 degrees Fahrenheit) warmer than the 1979-2000 average.

In the U.S., heat advisories are in effect this week for more than 30 million people in places including portions of western Oregon, inland far northern California, central New Mexico, Texas, Florida and the coastal Carolinas, according to the National Weather Service Weather Prediction Center. Excessive heat warnings are continuing across southern Arizona and California.