The connection between global warming and severe outbreaks of cold winter weather has suddenly become a hot topic for media outlets everywhere, deservedly so because the relationship is not just unclear, but counterintuitive. Reporters are giving us a chance to hear opinions from the best scientific minds about what they think is going on that can explain a phenomenon like the one we have just experienced. I will re-post two of the more broadly-based stories I have seen, starting with this one from VOX, containing a number of individual observations while stressing the lack of strong consensus among scientists: https://www.vox.com/22287295/texas-uri-climate-change-cold-polar-vortex-arctic. Some excerpts: “Winters can warm up over the long term while the polar vortex may spill over more frequently in the near term…..Maybe we can’t say for sure there’s a connection, but it’s a matter of how soon that connection will become clear and how big that connection will be…..Scientists do expect to get a better handle on what to expect with cold weather extremes as they gather more data.”
Bob Berwyn has also written a lengthy piece for Inside Climate News, entitled “Warm Arctic, Cold Continents? It Sounds Counterintuitive but Research Suggests it’s a Thing,” which makes it clear that current climate models are unable to make good use of events of this type that we have seen to date, by way of adjustments into projections of the future—a possible weakness. “….one weakness in the models might be that they can’t accurately show a specific mechanism that makes the warming Arctic affect the mid-latitudes……The models are constantly being updated, every winter and the divergence between their projections and the observations is striking….. By contrast, the model predictions for summers are nearly perfect…..Cohen said he considers complex atmospheric movements involving the polar vortex to be a key link between the warming Arctic and extreme cold events in North America and Eurasia…..That disruption happens, he said, when the warm Arctic air works its way high into the upper atmosphere, where it crests like a wave to break through the vortex…..It’s getting increasingly difficult to get severe winter weather into the mid-latitudes without a polar vortex disruption, and amplified Arctic warming is favorable for disrupting the polar vortex.” This is a view that sounds correct as far as it goes, but what about the full mechanism behind events that follow? Some other attempts to find a mechanisms are also described.
None of the stories I have seen have anything to say about a possible role being played by precipitable water (PW), or about how alterations in the normal pattern of high-altitude air air pressure configuration might be an integral part of the physical mechanism. Both of these, linked together by the organization and behavior of jetstream winds, are visible today in modes that are basically quite extraordinary, with relevance to their having a direct effect on the unusual way that global temperatures are currently distributed. This entire sequence has been discussed in detail in recent letters. Today I will just show three key maps with coincidental imagery effects that provide supporting evidence. Be sure to take note of the sharp contrast between the upper parts of the two hemispheres in all three.
Carl