Reduced low-altitude cloud cover allows Earth to absorb more solar radiation. This change could be one of the main reasons for the 0.2°C extra warming that scientists have been trying to explain recently. The increase in solar radiation to the earth’s surface not only causes it to heat up more, but may also have long-term effects on the climate of the earth.
According to New Scientist, temperature records were broken several times in 2023 and 2024, and both years now show average temperatures about 1.5 degrees Celsius above pre-industrial levels. While climate change and the El Nino weather pattern have both contributed to the rise in temperatures, neither factor alone can explain the extreme heat we’ve been experiencing.
The reduction of cloud cover has reduced the albedo of the earth and it has increased the temperature
Now, researchers believe that the cause of the extreme temperatures of the last two years is a sharp decrease in low-altitude cloud cover in 2023. Changes in the amount of clouds caused a decrease in the Earth’s albedo (the planet’s ability to reflect sunlight into space) and resulted in an increase in temperature.
The Earth’s albedo has decreased since the 1970s, mainly due to the melting of the polar ice caps, which helps reflect sunlight back into space. However, Helge Goslingclimatologist from the Alfred Wegener Institute in Germany and his colleagues analyzed satellite data and found that in 2023, the Earth’s albedo reached its lowest point.
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Gosling and his colleagues then used a combination of climate observations and modeling to understand the causes of the Earth’s albedo drop, and found that in 2023, the number of low-altitude clouds decreased. This change was particularly evident in the Atlantic Ocean, which experienced some of the most unusual temperature swings in 2023.
“We were able to get an indication of where and how high clouds are changing in the atmosphere,” Gosling says. It is very noticeable that this decrease in cloud cover occurs mostly at low levels.
The findings could explain the extra 0.2 degrees Celsius of warming that scientists were trying to figure out after taking into account the effects of background climate change and the 2023 El Niño. Gosling says:[یافتهها] Another piece of the puzzle, and I think it’s very important.” Although the new study only evaluated data from 2023, the findings may explain why global temperatures remained so high through 2024 despite El Niño disappearing earlier this year.
Paolo SeppiA researcher from Imperial College London says the new study is timely; Because climatologists are eager to understand the factors behind the recent record-breaking heat. Seppi believes that the strong evidence presented in the new study shows that changes in albedo, especially in low-altitude clouds, have made a major contribution to changes in the planet’s radiation budget and thus temperature.
Perhaps the cause of the increase in temperature is explained, but the next question is why the low-altitude clouds have disappeared. Broadly speaking, there are three explanations. It is possible that the global decrease in aerosol pollution in the air, which helps in the formation and persistence of clouds, has caused the decrease in clouds. On the other hand, global warming may change how clouds behave. Or the simpler answer is that all of these events are natural variability in the climate.
It is very important to understand which of the three possible factors is dominant; Because it affects the sensitivity of the Earth’s climate to greenhouse gas pollution. If the lack of clouds is due to climate change, the impact will accelerate in the coming years, driving global temperatures higher than expected. Sepi says: “The answer [دلیل کمشدن ابرها] “It has very profound implications for our expectations of future climate change.”
The study was published in the journal Science.
