One big question mark in climate research is how cloud formation will affect global warming. A new study gives a disappointing message.
Current climate models offer very different answers to the defining question of our time: How much greenhouse gases can be emitted before global warming has such dire consequences?
The uncertainty is largely due to the clouds. They serve as a kind of annoying nuisance in advanced calculations for climate models, because clouds can have both a cooling and a warming effect depending on how dense they are and the altitude at which they form. These characteristics, in turn, are affected by global warming.
stops heat radiation
Simply put, thin, high, feather-like clouds have a warming effect, as they allow short-wavelength sunlight and thus prevent long-wave heat radiation from bouncing back into space. Instead, cumulus cauliflower-like clouds at lower altitudes have a cooling effect, because they reflect more of the sunlight directly.
But piecing this together into a combined effect of the entire Earth was thus difficult to crack.
Now, researchers at Imperial College London and the University of East Anglia have used a new method in which the AI has been looking for patterns in nearly 20 years of global satellite observations of clouds, linked to meteorological data, among other things, temperature and air. pressure, wind conditions and humidity.
The results, published in the Journal of the American Academy of Sciences PNAS, show that total cloud formation on Earth is likely to enhance the greenhouse effect, and thus contribute to an increase in global warming.
“Our results mean we can make more reliable predictions, and get a clearer picture of how severe climate change will be in the future,” one of the researchers commented in a press release.
The researchers believe their results make it possible to more accurately calculate the so-called climate sensitivity, a measure of how much Earth’s average temperature would be expected to increase if the carbon dioxide content of the atmosphere doubled compared to pre-industrial times. times. According to the latest report from the United Nations Climate Committee IPCC, climate sensitivity ends somewhere in the range of 1.5-4.5 degrees Celsius. In their new study, the researchers circle the climate sensitivity to 3.2 degrees Celsius, writing that it is “very unlikely” that the climate sensitivity is below 2 degrees Celsius.
Today, the average carbon dioxide content in the atmosphere is about 420 parts per million (parts per million). Under pre-industrial it was about 280 ppm. The research group wrote that if the current rate of emission had not slowed significantly, this level could have already doubled by the middle of this century.