Changes in cloud cover amplify global warming

June 21. () –

Scientists have discovered increasingly asymmetric changes in cloud cover -decreases more during the day than at night- that amplify global warming.

This asymmetry means that the cooling effect of clouds is decreasing during the day and their warming effect is increasing at night. A team of researchers led by Professor Johannes Quaas of the University of Leipzig and Hao Luo and Professor Yong Han of Sun Yat-sen University in China publish results in the journal Science Advances.

During the day, clouds reflect sunlight back into space, cooling the Earth’s surface. At night, however, they act like a blanket, trapping heat. This keeps the Earth’s surface warm. “This is why clouds play a decisive role in the Earth’s climate,” says meteorologist Quaas.

In their study, the scientists used satellite observations and data from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), which provides complete climate models and scenarios. These models cover historical data from 1970 to 2014 and projections to the year 2100.

“As cloud cover decreases more during the day than at night on a global scale, this leads to a decrease in the shortwave albedo effect during the day and an increase in the longwave greenhouse effect during the night”, Explain it’s a statement Hao Luo, lead author of the study.

Climate models are essential for understanding and predicting the complex processes and interactions within the climate system. They help scientists develop possible future scenarios and analyze the impact of various factors such as greenhouse gases, aerosols and clouds on the climate.

Quaas emphasizes: “The asymmetry in the way cloud cover changes is an important recently discovered factor. Our study shows that this asymmetry causes a positive feedback loop that amplifies global warming.“.

According to the researcher, clouds are changing as a result of climate change. Overall, there is slightly less cloud, which means more global warming.

This daily asymmetry in cloud cover can be attributed to several factors. One of the main causes is the increasing stability of the lower troposphere as a result of increasing greenhouse gas concentrations. This stability means that the clouds are less likely to form during the day, while remaining stable or even increasing during the night.

Yong Han, co-author of the study, explains: “The change in cloud cover is not evenly distributed throughout the day. During the day, when solar radiation is strongest, we see greater reduction in clouds. At night “When the Earth’s surface normally cools, cloud cover traps heat and therefore amplifies the greenhouse effect.”

“Our findings show that there is an even greater need to reduce greenhouse gases, as cloud cover not only responds to warming, but also amplifies it through this new effect“warns Quaas.

Scientists believe more studies are needed to better understand changes in cloud cover. Ongoing studies at the University of Leipzig also look at changes in vegetation and its biodiversity, for example, as well as the role of decreasing air pollution.