Recent trends in global warming are incompatible with very high climate sensitivity

Research published this week in Earth system dynamics reports that the most sensitive climate models overestimate global warming over the past 50 years.

Three scientists from the University of Exeter have studied the results of complex climate models and compared them to temperature observations since the 1970s.

Recent developments in cloud modeling have produced models that exhibit a very high sensitivity to increasing concentrations of greenhouse gases.

A subset of models even showed that a doubling of CO₂ could lead to more than 5 ° C of warming, questioning whether the goals of the Paris agreement are achievable even if nations are doing all they can.

Lead author of the study, Ph.D. Candidate Femke Nijsse from the University of Exeter, said: “By evaluating climate models, we were able to exploit the fact that through air regulation Pure air pollution in the form of climate-cooling aerosols has stopped increasing around the world, thus allowing signal greenhouse gases to dominate recent warming. “

The amount of warming that occurs after CO₂ the concentrations in the atmosphere are doubled, this is called the equilibrium climate sensitivity.

The study found that, based on the latest generation of climate models, the equilibrium climate sensitivity is likely to be between 1.9 and 3.4 ° C.

Co-author Mark Williamson, Global Systems Institute, Exeter, added: “Global warming since 1970 also provides even better indications of the pace of climate change in the future.

“We find a probable range for the ‘transient climate response’ of 1.3 to 2.1 ° C, whether we are using the latest models or the previous generation of models.”

The new study is only one piece of the puzzle.

A recent review article found that low estimates of climate sensitivity can be excluded because they are, in general, not compatible with the climate changes of Earth’s past.

Co-author Prof Peter Cox explains the importance of these results: “It is good to see that studies are now converging towards a range of climate sensitivity at equilibrium, and that high and low values ​​can be excluded. .

“For over forty years climatologists have tried to determine this quantity and it seems that we are finally getting closer.”