Revisiting observed trends in the jet streams and their link to tropical warming

We revisit observed zonal wind trends using 40 years of satellite-era reanalysis products and find evidence that general poleward shifts are emerging, often with low significance but notable similarity across different seasons and hemispheres. While much recent work has focused on the jet response to amplified Arctic warming, the observed trends are more consistent with the known sensitivity of the circulation to tropical warming. The circulation trends are within the range of historical model simulations but are relatively large compared to the models when the accompanying trends in upper tropospheric temperature gradients are considered. The balance between tropical warming and jet shifts should therefore be closely monitored in the near future. We also present a new hypothesis concerning the sensitivity of the circulation response to tropical heating which may be one factor affecting this balance.