Thread by @DrAHButler

1-How will the stratospheric #polarvortex respond to #climate change? Bottom line: we have no idea. A 🧵on a new paper out by Alexey Karpechko, @HillaA1, me, @Domeisen_D, @Marlene_Climate, @zd1awrence, E. Manzini, @michaelsigmond, @IslaSimpson4, and Z. Wu: agupubs.onlinelibrary.wiley.com/doi/10.1029/20…

2- There is no agreement across #CMIP6 models in the magnitude or even sign of the polar vortex response to climate change, though the magnitude of any individual model response tends to increase with the magnitude of climate warming.

3- Individual models tend to show the same signed response of the #polarvortex regardless of greenhouse gas scenario. This implies that differences in the model physics/configurations are likely causing the disagreement across models.

4- In fact, by the end of the century, model uncertainty dominates over internal variability as the main source of uncertainty in the #CMIP6 #polarvortex response.

5- While the response of the strength of the polar vortex is completely disparate across models, surprisingly almost all models (>95%) show an eastward shift of the #polarvortex that scales with GHG scenario.

6- Why does it matter that we don’t know whether the #polarvortex will strengthen or weaken in the future? Because the uncertainty in the polar vortex response is associated with significant uncertainty in the #climate response at the surface.

7- After regressing out the global mean temp response, up to 20% of the spread in projected 2m temps over the western US and up to 30% over Northern Eurasia can be associated with the uncertainty in the projected #polarvortex strength.

8- Thanks again to Alexey Karpechko for leading this analysis, which was a collaboration brought forth by the @WCRP_SPARC DynVar initiative.

Just realized I should have been more specific- these results are for the Northern Hemisphere!