Clouds dominate uncertainties in predicting future Greenland melt
New research by climatologists from the University of Bristol and the University of Liege (ULiège) suggests that the representation of clouds in climate models is as important or even more important than the uncertainties related to the amount of greenhouse gas emissions when it comes to projecting the melting of the Greenland ice sheet
Recent research shows that the entire Greenland ice sheet could disappear within a thousand years, raising sea levels by more than seven metres if global warming exceeds 4°C for 1000 years. However, most future projections of the future of the Greenland ice cap focus on the impact of different greenhouse gas emission scenarios on its evolution.
A new study published today in the journal Nature Climate Change shows, using the MAR model developed at ULiège, that cloud microphysics plays an important role as an additional natural greenhouse gas and, in the case of high emission scenarios, dominates the uncertainties associated with the projection of ice sheet melting.
The difference in melting potential caused by changes in cloud cover is mainly due to the ability of clouds to control infrared radiation on the surface of the ice cap. They act as a cover, potentially amplifying the melting by a factor of two if the clouds become twice as thick "optically".
Uncertainties related to the melting of Greenland's ice, due to clouds, could represent up to 40,000 gigatonnes of additional melting in 2100. This is equivalent to 1500 years of domestic water supply from the United States or a sea level rise of 11 cm.
Stefan Hofer, PhD from the University of Bristol and post-doctoral fellow at the Laboratory of Climatology directed by Xavier Fettweis at ULiège, is the main author of the new study.
Xavier Fettweis: "Until now, we thought that the differences in the modelled projections of the future evolution of the Greenland ice cap were mainly determined by the amount of our future greenhouse gas emissions."
Stefan Hofer: "However, our study clearly shows that the uncertainties in our projections of the melting of Greenland also depend on how we represent clouds in these models (here the MAR model)."
"Until the end of the 21st century, clouds could increase or decrease the sea level rise from the Greenland ice cap by 11 cm. »
"The main message of this research is that clouds are the main source of uncertainty in modelling Greenland's future melting and its contribution to sea level rise."
Stefan Hofer adds: "Observations of cloud properties in the Arctic are expensive and can be difficult. There are very few long-term observations of cloud properties in the Arctic, making it very difficult to represent cloud properties in our climate models such as the ULiège MAR."
"The next logical step would be to increase the number of long-term observations of cloud properties in the Arctic, which can then be used to improve our climate models and thus our projections of future sea level rise. »
Cloud microphysics and circulation anomalies control differences in future Greenland melt, S. Hofer, A. Tedstone, X. Fettweis and J. Bamber dans Nature Climate Change - http://dx.doi.org/10.1038/s41558-019-0507-8
Laboratory of Climatology and Topoclimatology, Department of Geography, University of Liège (ULiège)
Xavier FETTWEIS, FNRS Research Associate
Stefan HOFER (only in English)