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.

(1/n) One measure I pay close attention to in winter is the "eddy heat flux". What does that mean? Eddy heat flux is basically referring to the heat transported from the tropics to the poles by weather fronts (otherwise, the tropics would be much hotter and the poles colder!). (2/n) Mathematically, it’s defined as v’T’, where the prime is a deviation from the zonal-mean, v is meridional wind, and T is temperature. Usually it’s averaged over the mid-latitudes.