Monday, January 06, 2014

Polar Vortex vs. Global Warming

Global warming skeptics are quick to claim any cold day anywhere as "proof" of the validity of their skepticism, so that the polar vortex currently gripping much of the US is a late Christmas for them. So it's only fair to point out that the opposite explanation is at least equally valid, namely that our current encounter with the polar vortex could actually be a consequence of global warming and such events might become more common as the planet warms.

That word "global" often seems to be a problem for our skeptical friends, as does the fact that changes in one place might be anti-correlated with changes in others. Polar vortices are so-called because they form and tend to hang around the pole in Winter. One of the factors that tends to keep them polar is the temperature difference between the pole and the rest of the planet. One of the demonstrated features of our current global warming is that the far North is warming far faster than the rest of the planet - that's actually one of the signatures of CO2 driven warming. It's at least plausible that the consequent decrease in temperature gradient makes the current sort of arctic breakout "easier" and more frequent.

Note that all that polar air moving south means an equal amount of warmer air moved north. Anchorage Alaska will be quite a bit warmer than Atlanta today.

Bryan Walsh has a news article, with appropriate caveats, on the subject here:

What does that have to do with climate change? Sea ice is vanishing from the Arctic thanks to climate change, which leaves behind dark open ocean water, which absorbs more of the heat from the sun than reflective ice. That in turn is helping to cause the Arctic to warm faster than the rest of the planet, almost twice the global average. The jet stream—the belt of fast-flowing, westerly winds that essentially serves as the boundary between cold northern air and warmer southern air—is driven by temperature difference between the northerly latitudes and the tropical ones. Some scientists theorize that as that temperature difference narrows, it may weaken the jet stream, which in turns makes it more likely that cold Arctic air will escape the polar vortex and flow southward. Right now, an unusually large kink in the jet stream has that Arctic air flowing much further south than it usually would.

Still, this research is fairly preliminary, in part because extreme Arctic sea ice loss is a fairly recent phenomenon, so scientists don’t have the long data sets they need to draw more robust conclusions about the interaction between Arctic warming and cold snaps. In fact, the most recent report from the Intergovernmental Panel on Climate Change concluded that it was likely that the jet stream would shift towards the north as the climate warmed, and that the polar vortex would actually contract, even as a 2009 study found that sudden stratospheric warming events are becoming more frequent, which in turn seems to be driven by the rapid loss in Arctic sea ice.

And while a muddle like that would seem to make the science less rather than more reliable, it’s actually one more bit of proof that climate change is real. Global warming is sometimes thought of more as “global weirding,” with all manner of complex disruptions occurring over time. This week’s events show that climate change is almost certainly screwing with weather patterns ways that go beyond mere increases in temperature—meaning that you’d be smart to hold onto those winter coats for a while longer.

Read more: Climate Change Could Be the Cause of the Record Cold Weather | TIME.com http://science.time.com/2014/01/06/climate-change-driving-cold-weather/#ixzz2peC9KsGY