The number of low clouds decreased significantly in 2023
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Changes in cloud cover may mean that global temperatures over the past two years have exceeded climate model predictions.
Temperature records were repeatedly broken in 2023 and 2024, and both years now show average temperatures About 1.5°C above pre-industrial levels. Climate change and El Niño weather patterns are partly to blame, but neither factor fully explains the extraordinary warmth.
Now, researchers believe the answer lies in a major decline in lower cloud cover in 2023. This change reduced the Earth’s albedo – the planet’s ability to reflect solar radiation back into space – causing temperatures to rise.
The Earth’s albedo has largely been declining since the 1970s melting of polar ice capswhich help reflect sunlight back into space. But the analysis of satellite data Helge Goessling At the Alfred Wegener Institute in Germany and colleagues revealed that the planetary albedo of 2023 was a record low.
Goessling and his colleagues then used a combination of weather observations and modeling to understand the reasons for this decline, and found that in 2023 there was a sharp drop in the number of low-lying clouds. The change was particularly noticeable in the Atlantic Ocean. what he experienced some unusual temperature extremes in 2023
“We were able to indicate where the cloud is actually changing, at what altitude in the atmosphere it is,” says Goessling. “What’s really striking is that this, this reduction in cloud cover, is happening mostly at lower levels.”
The findings could explain the missing heat scientists struggle to account for the extra 0.2°C, counting the impacts of background climate change and the 2023 El Niño. “It’s another piece of the puzzle, and I think it’s pretty important,” says Goessling. Although the study only evaluated data from 2023, the findings may also explain why global temperatures remained very high through 2024. Despite fading El Niño at the beginning of the year
Paulo Ceppi At Imperial College London, he says the study is timely as climate scientists are keen to understand the drivers of recent record-breaking warmth. “I think they make a pretty compelling case that changes in albedo, particularly in low clouds, have had a significant impact on changes in the radiation budget and therefore temperature,” he says.
The next question is why the low clouds disappear. In general, there are three explanations. It could be due to a reduction of global aerosol pollutionwhich helps clouds form and persist. Alternatively, it could be the result of global warming changing how clouds behave. Or it could simply be the natural variability of the climate.
Understanding which of these three factors is dominant is essential because it affects how sensitive the Earth’s climate is to greenhouse gas pollution. If the lack of clouds is due to a climate change feedback, then the effect will accelerate in the coming years, pushing global temperatures higher than expected. “The answer has pretty profound implications for what we expect about future climate change,” Ceppi says.
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