Wednesday, January 08, 2025

Is Global Warming Speeding Up?

From Nature magazine. (Might be paywalled, I get free access so I'm not sure what permissions are set for me.)

"Earth shattered heat records in 2023 and 2024, with temperatures rising further than expected on the basis of previous trends and modelling. A mysterious reduction in cloud cover, combined with an El Niño weather pattern, could be responsible for temperature increases in 2023. However, scientists expected temperatures would decrease again in June 2024 when the El Niño subsided, which didn’t happen. Now they are racing to work out whether this sudden spike is just a blip in the climate data, or an early indicator that the planet is heating up at a faster pace than they thought.

"...Some scientists argue that the spike can be mostly explained by two factors. One is the El Niño event that began in mid-2023 — a natural weather pattern in which warm water pools in the eastern tropical Pacific Ocean, often leading to hotter temperatures and more-turbulent weather. The other is a reduction over the past few years in air pollution, which can cool the planet by reflecting sunlight back into space and seeding low-lying clouds. Yet neither explanation fully accounts for the temperature surge, other researchers say.

"Clouds clearly played a part, according to a study published in Science in December, just before the AGU meeting1. A research team identified a reduction in low-lying cloud cover across parts of the Northern Hemisphere and the tropics that, combined with El Niño, was large enough to explain the temperature spike in 2023. But the cause of this decrease — and whether it can be chalked up to normal climate variations — remains a mystery, the authors say. Decreased air pollution alone doesn’t seem to explain it. They suggest that global warming itself could be causing some reduction in cloud coverage, creating a feedback loop that could accelerate the rate of climate change for decades to come.

"'I would be very careful about saying this is clear evidence [of acceleration], but there might be something going on,' says co-author Helge Goessling, a climate physicist at the Alfred Wegener Institute in Bremerhaven, Germany.

"Another reason is that last year was also much warmer than expected. Scientists projected that early 2024 would be hot owing to El Niño. But they also anticipated that temperatures would fall after the weather pattern subsided and conditions in the equatorial Pacific returned to normal last June.

"'That didn’t happen,' says Zeke Hausfather, a climate scientist at Berkeley Earth, a non-profit organization in California that tracks global temperatures. Instead, global temperatures remained elevated, shattering more records and probably making last year the warmest on record by a sizeable margin. “All of us who made projections at the start of the year underestimated just how warm 2024 would be.'"There's more, including about a possible decrease in shipping aerosol emissions."
2025 will be interesting. But then all years are interesting now.
 

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