Weakening of the global atmospheric circulation with global warming
This study finds that the global atmospheric circulation weakens, i.e. transports less mass, by about 5 % per degree of global warming as a result of anthropogenic emissions. This is found by calculating a global thermodynamic mass stream function and diagnosing long-term changes in a set of climate-model simulations in the Intergovernmental Panel on Climate Change 5th assessment report. The global atmospheric circulation also expands in thermodynamic coordinates due to increased dry static energy and latent heat in the tropical troposphere. The surface warming and moistening follows a Clausius–Clapeyron relation and tropical moist ascent remains nearly moist adiabatic. Furthermore, the meridional overturning circulation is found to only weaken slightly suggesting that the dominant change is in the zonally asymmetric circulation, i.e. the Walker circulation. The total poleward energy transport increases while the poleward mass transport decreases. The results are found to be robust across the climate models studied