observation of Hadley Cell expansion into Arctic
I'm not qualified enough to know whether it's rare for specific storm systems to get slurped up like that, but I suspect it happens from time to time.
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I read this to indicate that the mode of atmospheric circulation is exceptionally stable and we would not expect any of the relevant variables to be affected by global warming.
I'm definitely willing to be proven wrong, but I remain skeptical about the claims.
Well, we have 2 years worth of pretty compelling observational evidence of storms being "shlurped" far more than "time to time".
You need to keep in mind the baseline temperatures in the Arctic, and just how far they currently are off that baseline - consistently 10C above normal, with some areas skyrocketing to 30+C above normal. That would be the equivalent here in Seattle of us suddenly getting a 40C heat wave.
It's persistent and consistent - if you look at last year's (2015) DMI graph over winter and check the spikes against weather maps, you will see a fairly major storm associated with each one. This year, there isn't even a pause.
As a Geologist, I have a fundamental problem with your "exceptionally stable" assertion. That position is based in the paradigm of incrementalism - as my old Zoology prof once put it "Natura Non Facit Saltum" - Nature does not make leaps.
Given everything else being equal, that is the correct assumption - that the variables driving climate - insolation, chemistry, topology - will vary slowly and the corresponding behavior of systems will follow similarly in train.
Only they *aren't*, or specifically chemistry is not.
To a great degree topology is not either - as we have massively changed forestation and made other changes which affect heat uptake and albedo. We have literally drained seas (the Aral) and by way of that utterly and probably permanently changed the climate over vast stretches of central Asia.
So, your variables on which your incrementalist conclusion is based... have already slipped their leashes and are running off with the controls to the system.
There is massive hysteresis in our climate right now; the last time CO2 levels were this high, (3.6 MYA), Average summer temps around the shores of the arctic were 15C; we've got a long way to go before the inputs from that extra CO2 reach a stable relationship with the net enthalpy in the system. Until then, it will be attempting to equilibrate, in increasingly dramatic ways. Even after that, the relative "stability" that will return will be far more enegetic - that's determined purely by the mechanics of water and how much bigger a load of moisture the atmosphere will be capable of carrying.
So, I'd say, if you think atmospheric circulation will remain stable in the face of increasing levels of CO2, you need a more convincing argument than something dug out of a Wikipedia article.