Study warns clouds will further exacerbate climate change as Earth warms

The researchers found that it is very likely (< 97.5% probability) that clouds will amplify global heating, by both reflecting less solar radiation and enhancing the greenhouse effect. The findings also suggest that at double atmospheric carbon dioxide (CO2) concentrations above pre-industrial levels, the climate is unlikely to warm below 2-degree celsius, and is more likely on average to warm more than 3-degree celsius.

Clouds are very likely to enhance global heating over the long term, further exacerbating climate change, according to new research by scientists at Imperial College London and the University of East Anglia.

The researchers developed a new method to quantify relationships between state-of-the-art global satellite observations of clouds, and the associated temperature, humidity and wind conditions. By observing their relationships, they were then able to better constrain how clouds will change as the Earth warms.

"Over the last few years, there's been a growing amount of evidence that clouds probably have an amplifying effect on global warming. However, our new approach allowed us for the first time to derive a global value for this feedback effect using only the highest quality satellite data as our preferred line of evidence," said the study co-author Dr Peer Nowack, from the School of Environmental Sciences and Climatic Research Unit at the University of East Anglia and Imperial's Grantham Institute and Data Science Institute.

The researchers found that it is very likely (< 97.5% probability) that clouds will amplify global heating, by both reflecting less solar radiation and enhancing the greenhouse effect. The findings also suggest that at double atmospheric carbon dioxide (CO2) concentrations above pre-industrial levels, the climate is unlikely to warm below 2-degree celsius, and is more likely on average to warm more than 3-degree celsius.

According to the researchers, the largest uncertainty in climate sensitivity - the amount of global surface warming that will occur from a doubling of atmospheric CO2 concentrations - predictions is the influence of clouds, and how they may change in the future.

"The value of the climate sensitivity is highly uncertain, and this translates into uncertainty in future global warming projections and in the remaining 'carbon budget' - how much we can emit before we reach common targets of 1.5°C or 2°C of global warming," said co-author Dr Paulo Ceppi, from the Grantham Institute - Climate Change and the Environment at Imperial.

The findings are published in Proceedings of the National Academy of Sciences, a peer-reviewed multidisciplinary scientific journal.