Aurelia Butler

Australia’s Great Barrier Reef faces critical danger from back-to-back bouts of extreme ocean heat.

Ocean heat in the Coral Sea is at its highest in four centuries, scientists report in the Aug. 8 Nature. The researchers drilled into coral skeletons from in and around the region and analyzed the chemical makeup of those samples to reconstruct sea surface temperatures from 1618 to 1995, alongside modern instrumental sea surface measurements spanning 1900 to 2024.   

Before 1900, ocean temperatures in the region were relatively stable. But from 1960 to 2024, those temperatures have climbed relentlessly. That upward climb is linked to humans’ greenhouse gas emissions, the team found.

Five of the six hottest years in the record were in the last decade: 2016, 2017, 2020, 2022 and 2024, with temperatures as much as 1 degree Celsius hotter than average. Each year had a mass bleaching event during the warmest months, from January to March (SN: 4/29/24).

Scientists drilled into corals in the Great Barrier Reef (shown) to collect core samples. The chemical makeup of the corals reveals changing water conditions, including temperature, over the corals’ lifetime.Tane Sinclair-Taylor

Researchers have long sounded the alarm about mass bleaching, in which corals stressed by extreme heat or pollution expel symbiotic algae living in their tissues, leaving them stark white (SN: 8/9/23). Corals can bounce back, given time. But back-to-back bleaching can ultimately kill a reef.

“The Great Barrier Reef is iconic,” climate scientist Benjamin Henley of the University of Melbourne in Australia said at an Aug. 6 news conference. UNESCO designated the reef as a World Heritage Site in 1981. More

Il fait trop chaud. The Paris Olympics officially opened on July 26, just in time for athletes to compete in a hellish heat wave.

Last week, Olympians in the French capital faced daytime temperatures reaching 35° Celsius (95° Fahrenheit), and in southern France temperatures climbed up to 40° C (104° F). Other countries in the Mediterranean region also felt the heat wave. In Spain, the city of Barcelona recorded its highest-ever temperature — 40° C — on July 31. And in Italy, the sweltering weather helped fuel a wildfire in the Monte Mario natural reserve in Rome. 

This extreme heat would not have happened without climate change, researchers from the World Weather Attribution Network reported on July 31.  “If the atmosphere wasn’t overloaded with emissions from burning fossil fuel, Paris would have been about 3 [degrees] C cooler and much safer for sport,” said climatologist Friederike Otto of the Imperial College London in a statement. 

“Yesterday, climate change crashed the Olympics.“The world watched athletes swelter in 35°C heat. If the atmosphere wasn’t overloaded with emissions from burning fossil fuel, Paris would have been about 3°C cooler and much safer for sport” – @FrediOtto— World Weather Attribution (@WWAttribution) July 31, 2024

Other parts of the world sweltered, too. In California, Death Valley set the record for the hottest month ever recorded on Earth, averaging 42.5° C (108.5° F) across July. A major heat dome also settled in over the southern United States (SN: 6/21/24). The extreme heat swept across much of the country by the end of the week, with the National Weather Service placing more than 150 million people under extreme heat advisories on August 1. Antarctica’s eastern region also experienced a major heat wave, with ground temperatures rising beyond 28° C. More

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. More

Abby Wallace is the digital engagement producer at Science News. She has an undergraduate degree in biology from George Washington University in Washington, D.C., and a master’s degree in journalism from the University of Maryland — College Park. More

Earth’s plants aren’t holding onto carbon as long as we thought.

A new analysis of pulses of radioactive carbon-14 from 20th-century bomb tests reveals that plants stock more carbon in short-lived tissues such as leaves than previously estimated, scientists report in the June 21 Science. That means that this carbon is probably more vulnerable to re-release to the atmosphere — potentially altering estimates of how much anthropogenic carbon the biosphere can hold, the team says. More