Global warming is happening faster than scientists previously predicted, with new records for global temperatures set in 2023 and, according to predictions, 2024. Now a new study has revealed the reason: low clouds are disappearing, making the planet “go dark” and absorb more heat.
What the team found was that the record temperatures the planet has experienced over the last decade coincide with a rapid decline in low-lying cloud cover, particularly over the North Atlantic. Clouds are bright compared to the Earth’s surface and therefore they reflect sunlight and heat away – a phenomenon known as albedo. When that shield of clouds disappears, the planet absorbs more light and heat, accelerating global warming.
Why are low clouds disappearing?
The research, published on 5 December 2024 in Science journal by a team from Germany’s Alfred Wegener Institute for Polar and Marine Research and the European Centre for Medium-Range Weather Forecasts, was based on analysis of NASA satellite data, weather data and climate models.
Identifying the drivers behind the loss of cloud cover is “a complex beast and so hard to disentangle,” said Helge Goessling, one of the report’s lead authors. But contributory factors include, ironically, a drop in shipping pollution. New rules have improved air quality by cutting sulphur emissions from shipping but in the short-term the sulphur was brightening clouds, making them more reflective. Now that the sulphur has been reduced, so has its cooling effect. Some people have even called for a return to atmospheric sulphur pollution as a temporary measure to limit climate change.
In addition to the loss of sulphur, other natural weather variations and cycles, such as El Niño or changing ocean currents, can contribute to cloud formation, or the lack of it. And, in a perfect example of a vicious cycle, global warming itself also makes clouds thin and disappear. Put simply clouds are formed in cool, damp air. So, the warmer the planet, the warmer its air, the thinner the cloud, the warmer the planet and so on.
Expect “rather intense warming” in the future
Under these circumstances, Goessling warned, some climate change modelling may not be accurate, explaining why the global mean temperature is rising faster than previously anticipated. As a result, “We should expect rather intense warming in the future,” he said.
Mark Zalinka, an independent climate expert from the Lawrence Livermore National Laboratory confirmed to CNN “the fact that clouds play a key role in the story makes sense, as they essentially act as Earth’s sunscreen”, with even seemingly small drops in cloud cover able to “drastically change Earth’s albedo.”
With more intense warming, come more intense global consequences, which means more violent and frequent storms, flooding, heatwaves and wildfires, a loss of Arctic sea ice (which also acts as a shield through its albedo), and loss of habitats for many species, from plankton to polar bears to humans.
