How will global warming change the coupling between the troposphere and stratosphere?

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Please see our new paper exploring the impact of global warming stratosphere-troposphere coupling, just submitted to the Journal of Geophysical Research: Atmospheres.

This study, lead by Blanca Ayarazuguena and Andrew Charlton, investigates changes in extreme events in the coupled stratosphere-troposphere system (Sudden Stratospheric Warmings, or SSWs) under extreme global warming (quadroupled CO2). The key findings are:

  • The tropospheric impact of Sudden Stratospheric Warming events in the North Atlantic region will not change with extreme global warming. We can expect the same poleward shift of the jet stream and storm systems following an SSW, as we observe in today’s climate.

  • There is high uncertainty in the change of SSW frequency under extreme warming. Some models predict that the rate of events will be cut in half; others predict a doubling in their number!

  • The boreal polar vortex will form earlier and disappear later under increased CO2, extending the season of stratosphere-troposphere coupling.

While we are interested in understanding these changes in the atmospheric circulation, it is important to stress that these would be the least of our problems if we don’t curb green house emissions. Our world would be radically different if we allow CO2 to reach these levels, perhaps 6-10 degrees warmer with sea level a meter+ higher than today … if not worse. For those of us in New York, that would mean that your run-of-the-mill winter storm would pack the effective storm surge of Hurrican Sandy. Let’s not go there!

This is the first study of the CMIP6 climate models organized through the DynVarMIP. Our field has too many acronyms: the Coupled Model Intercomparision Project, Phase 6, is set of climate simulations by the the world’s best climate prediction systems, organized to support the Intergovernmental Panel on Climate Change’s (IPCC) 6th assessment report. The Dynamics and Variability MIP is a sub-project within the CMIP6 focussed on atmospheric dynamics and stratosphere-troposphere coupling.