Earth keeps breaking global heat records

Earth now is hotter than it’s been at any time in recorded history.

Average global temperatures shattered records on two consecutive days last week, reaching 17.09° Celsius on July 21 and then inching up still more the next day, to 17.15° C, or nearly 63° Fahrenheit. That’s almost an entire degree Celsius hotter than the planet’s average temperature of 16.25° C for every July 22 from 1990 to 2020.

Those new heat records come amid 13 months in a row of record-breaking temperatures on Earth — not just over land, but in the oceans too (SN: 4/29/24). Before 2023, the record highest temperature was 16.8 °C, set in August 2016. Since mid-2023, the planet has broken that 2016 threshold 58 times.

It makes you wonder: Just how hot could Earth get? Is there a theoretical highest global average temperature? Well, we wondered that.

And so Science News has launched a project to regularly note Earth’s climate extremes — and answer your questions about how to navigate our changing planet.

First up, extreme heat.  

Theoretically, it could get a lot hotter. Right after Earth formed nearly 4.6 billion years ago, the planet was still molten rock, with surface temperatures perhaps 1900° C.

Earth’s temperature during the Neoproterozoic Era, between about 800 million and 600 million years ago, careened between frigid and boiling, with the average planetary temperature perhaps reaching as high as 32° C. There have been similar just as hot or nearly as hot episodes in Earth’s history: 250 million years ago, when Earth had one massive continent called Pangaea; about 92 million years ago, during the Cretaceous Hothouse; around 55 million years ago, during the Paleocene-Eocene Thermal Maximum (SN: 1/11/17; SN: 10/4/06; SN: 5/7/15).

All of those times were largely ice-free on Earth, with high sea levels and forested polar regions. Not exactly ideal for humans.

Since preindustrial times — before about 1850 — Earth’s average surface temperature has increased by about 1.1 degrees C. The planet, on average, is now as warm as it was 125,000 years ago, at the peak of the last interglacial period, researchers say, based on data gleaned from ice and sediment cores. Back then, the sea level was also much higher — at least seven meters higher than today.  

As for the future, a lot depends on ongoing greenhouse gas emissions, of course. Under high emissions scenarios, some climate simulations pushed all the way out to 2500 suggest that the world’s average temperature could be 5 degrees C hotter than currently — but in some places, including in the Arctic, those temperatures could be as much as 8 degrees C higher than today (SN: 11/19/21).

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OK, your turn. Bring it on. What are some of your burning questions about Earth’s extreme heat? We’ll do our best to answer. Send us your questions here, and we’ll see you next week.