The Brewer Dobson circulation climate feedback

Abstract:

Climate models consistently simulate an increase in the strength of the Brewer Dobson circulation under climate change. Despite this being a ubiquitous feature in climate projections, the mechanisms underlying this dynamical response have received relatively little attention. We analyse data from an ensemble of chemistry-climate models and show that the strengthening of tropical lower stratospheric upwelling over the 21^st century is strongly correlated with the magnitude of tropospheric warming. However, the magnitude of the increase in upwelling for a given warming differs amongst models. This spread in 'dynamical climate sensitivity' is important for understanding projected trends in tropical lower stratospheric ozone and water vapour, which have been highlighted as important climate feedback mechanisms. The strong relationship between tropospheric warming and the change in tropical upwelling offers insights into the possible underlying mechanisms.