Where did the low clouds go? Their decline contributed to record 2023 temperatures

Recent research indicates that a decline in low-altitude clouds may be accelerating global warming. Scientists from the Alfred Wegener Institute analyzed satellite data and found that the Earth's albedo, or reflectivity, was at its lowest level since at least 1940. This decrease in albedo allows more solar radiation to reach and warm the planet's surface.

According to Phys.org, the researchers identified a significant reduction in low-altitude cloud cover in 2023, particularly in the northern mid-latitudes and tropics. This decline intensified the trend of decreasing planetary albedo, contributing to a previously unexplained warming of 0.2 degrees Celsius for the year. Despite accounting for factors such as greenhouse gases and the El Niño phenomenon, scientists were unable to fully explain the temperature rise.

"If there are fewer low clouds, we lose only the cooling effect, so it gets warmer," explained Helge Gößling, a climate researcher at the Alfred Wegener Institute, as reported by T-Online. The reduction in low clouds means the planet absorbs more sunlight, leading to increased warming. "The 0.2-degree-Celsius 'explanation gap' for 2023 is currently one of the most intensely discussed questions in climate research," Gößling stated, according to Futura Sciences.

The decline in low clouds could be linked to several factors. One possibility is the reduction of aerosols in the atmosphere due to stricter regulations on shipping emissions. Aerosols act as condensation nuclei for cloud formation, and their reduction means fewer low clouds. Phys.org reported that decreased aerosol concentrations have contributed to warming trends during the last year. Another potential cause is natural climate variability. NBC News reported that natural fluctuations in the oceans could contribute to the reduction in low-level clouds. However, Gößling and his team consider it unlikely that these factors alone are sufficient to explain the observed changes.

Some scientists suggest that global warming itself may be reducing the number of low clouds, creating a feedback loop that accelerates future warming. "If this is indeed responsible for the reduction of albedo, we should expect strong warming in the future," Gößling said, according to Die Welt. This feedback between global warming and clouds could lead to stronger future warming than previously predicted.

"We may already be closer to a global temperature increase of over 1.5 degrees Celsius than previously thought," Gößling stated, according to Die Zeit. Scientists emphasize the urgent need for further research to understand the causes of the decline in low clouds.

"The measures to combat the effects of the expected extreme climate events are becoming even more urgent," Gößling emphasized.

Other experts echo the need for caution. Zeke Hausfather, a climate researcher with Berkeley Earth, told Science that the findings raise as many questions as they provide answers. "We still do not know for sure that these changes in cloud behavior are not due to short-term variability—which would return to more normal conditions with time—or if they represent a new ongoing change to the climate system," he said, as reported by ABC News Australia.

The reduction in low clouds and the resulting decrease in the Earth's albedo could have significant implications for future warming projections.

Understanding the role of clouds in the climate system is critical, as "small changes in cloud cover can drastically change Earth's albedo," noted Mark Zalinka, emphasizing that clouds act as Earth's sunscreen, according to CNN.

This article was written in collaboration with generative AI company Alchemiq