Some warmists such as Jennifer Francis and Katherine Hayhoe instead want you to believe that recent record-cold winters due to dips of the polar vortex are your fault, due to your evil CO2 emissions and the CO2 universal control knob of climate. This false assumption has been thoroughly shot down in the peer-reviewed literature by fellow warmists, even including Kevin Trenberth et al. Climate models robustly predict the opposite of fewer jet stream and polar vortex dips due to global warming.
This new paper provides a start to explain how natural forcings and feedbacks [some of which are linked to solar activity] combine chaotically and unexpectedly with "the opposite sign to the forcing" to govern the polar vortex. The paper also joins others finding links between solar activity and the polar vortex.
Climate Dynamics [full paper open access]"The demonstration that the steady state stratospheric response to a forcing may have the opposite sign to the forcing (Sect. 3.1) has important implications for studies of the mechanisms by which external forcings influence the polar vortex—in principle it could be the case that the direct effect of a forcing has the opposite sign to the long-term mean response. As far as we are aware, this possibility has not been considered in any previous studies of the effect on the [polar] vortex of forcings such as the QBO, ENSO and the solar cycle. Feedbacks may greatly modify the response from what is expected based on simple arguments. It also highlights the difficulties of using diagnostics such as composite differences to understand forcing mechanisms, since these may be dominated by the effects of feedback processes (Watson and Gray 2014). [i.e. chaos]The implication that the extratropical stratospheric response to an external forcing is affected by the climatology may be relevant for understanding non-linearity in the way different forcings combine to affect the polar vortex, such as the suggested non-linear combined influence of the QBO and ENSO (Garfinkel and Hartmann 2007; Wei et al. 2007) and of the QBO and solar cycle (e.g. Labitzke 1987; Matthes et al. 2004). When one forcing affects the background circulation, this would be expected to change the circulation response to other forcings, and this effect may contribute to the reported non-linearities."
The stratospheric wintertime response to applied extratropical torques and its relationship with the annular mode
The response of the wintertime Northern Hemisphere (NH) stratosphere to applied extratropical zonally symmetric zonal torques, simulated by a primitive equation model of the middle atmosphere, is presented. This is relevant to understanding the effect of gravity wave drag (GWD) in models and the influence of natural forcings such as the quasi-biennial oscillation (QBO), El Ninõ-Southern Oscillation (ENSO), solar cycle and volcanic eruptions on the polar vortex. There is a strong feedback due to planetary waves, which approximately cancels the direct effect of the torque on the zonal acceleration in the steady state and leads to an EP flux convergence response above the torque’s location. The residual circulation response is very different to that predicted assuming wave feedbacks are negligible. The results are consistent with the predictions of ray theory, with applied westerly torques increasing the meridional potential vorticity gradient, thus encouraging greater upward planetary wave propagation into the stratosphere. The steady state circulation response to torques applied at high latitudes closely resembles the Northern annular mode (NAM) in perpetual January simulations. This behaviour is analogous to that shown by the Lorenz system and tropospheric models. Imposed westerly high-latitude torques lead counter-intuitively to an easterly zonal mean zonal wind (u¯) response at high latitudes, due to the wave feedbacks. However, in simulations with a seasonal cycle, the feedbacks are qualitatively similar but weaker, and the long-term response is less NAM-like and no longer easterly at high latitudes. This is consistent with ray theory and differences in climatological u¯between the two types of simulations. The response to a tropospheric wave forcing perturbation is also NAM-like. These results suggest that dynamical feedbacks tend to make the long-term NH extratropical stratospheric response to arbitrary external forcings NAM-like, but only if the feedbacks are sufficiently strong. This may explain why the observed polar vortex responses to natural forcings such as the QBO and ENSO are NAM-like [Northern annular mode]. The results imply that wave feedbacks must be understood and accurately modelled in order to understand and predict the influence of GWD and other external forcings on the polar vortex, and that biases in a model’s climatology will cause biases in these feedbacks.
Cool step-by-step animation of the stratospheric polar vortex forming over the south pole as the southern hemisphere transitions from summer to winter during the first half of this year.ReplyDelete
The same is happening right now over the north pole!
As first author of this paper, firstly thanks for taking an interest in our work. However, I think there has been some confusion - our work relates to the polar vortex in the *stratosphere*, roughly between altitudes 10-50km, and is not directly related to the extremes of last winter's weather at the surface.ReplyDelete
Thanks very much for your reply.Delete
Isn't the polar vortex in the stratosphere indirectly or directly related to the polar vortex in the troposphere?
There is some interaction between the two - the size of the interaction is a matter of research. But they are very different phenomena dynamically. I don't think our work really says anything about the extreme weather of last winter.Delete