Preliminary results from global modelling of Cirrus Cloud Thinning in the Geoengineering Model Intercomparison Project

Cirrus clouds have a net positive radiative forcing effect on the climate, leading to the suggestion of cirrus cloud thinning (CCT) as a means to ameliorate global warming. By deliberately thinning cirrus clouds, more longwave radiation is able to escape the Earth system into space, cooling the planet. CCT has been modelled as part of the Geoengineering Model Intercomparison project in the G7cirrus experiment. Given the complexities of cirrus cloud modeling, to obtain similar results across different models this experiment simulates CCT by increasing the fall seed of ice crystals in cirrus clouds. This is carried out against a SSP5-8.5 scenario background, beginning in 2020 and ending in 2100. So far, G7cirrus has been run in two Earth System Models: UKESM1 and IPSL. Here, we look at some preliminary results from this experiment, such as analysing the intervention’s effective radiative forcing and its impact on different climate variables such as air temperature and precipitation.