nuovo lavoro che fornisce qualche evidenza per una maggiore risposta (rispetto ai modelli) del jet stream al riscaldamento dell'alta troposfera tropicale (nonostante il riscaldamento stesso sia meno forte):

Trends in the atmospheric jet streams are emerging in observations and could be linked to tropical warming | Communications Earth & Environment

Much attention has recently focused on the amplified warming of the Arctic, which weakens the meridional temperature gradient in the lower troposphere4. In isolation, this is widely predicted to shift the northern hemisphere jet stream equatorwards, in particular by weakening the baroclinicity on the poleward flank of the associated storm tracks5,6. In the upper troposphere, however, predicted warming is strongest in the tropics and hence a competing effect acts to push the jets poleward instead7,8. The opposition of these two effects leads to a relatively small projected poleward shift of the jet in response to tropical warming, which is partially offset by the effects of Arctic amplification9,10,11,12,13.
Despite the apparent dominance of tropical forcing in model projections, confidence in these projections has been limited by uncertainty over the strength of tropical warming14. The amplified Arctic warming is a striking feature of observed trends, associated with a range of processes including poleward heat transport and local feedbacks15. The enhancement of warming in the tropical upper troposphere is expected as a consequence of the moist adiabatic structure of the tropical atmosphere, but in contrast to the Arctic there remains uncertainty over its strength16, with some observational estimates remaining weaker than the warming in model simulations17.
One possibility (amongst several) is that the jet streams in reality may be more sensitive to the tropical upper tropospheric warming than those in many climate models. One of the physical mechanisms thought to be important in the circulation response to localised heating is the transport of heat by atmospheric eddies33, which then in turn leads to anomalous momentum fluxes6,34. Such an eddy-mediated response would be consistent with the equivalent barotropic structure in the observed wind trends. Hence, we hypothesise that the observed trends could be explained by a relatively strong increase in poleward eddy heat flux in the upper troposphere, which would act to weaken the meridional temperature gradient while simultaneously driving a strong circulation response.