The question arises: how might temperature variation have changed? We all know (if you don’t already, then read this blog!) that things like temperature show a combination of trend and fluctuation. We almost always focus on the trend, because that’s what shows the most obvious changes over time. But those fluctuations … the “noise” that we add to “signal” to get “data” … the “variation” we add to “average” to get the “weather” … are they changing too? Or are they just doing the same old same old kind of fluctuation they’ve been doing all along? This is a very different question than we usually hear about in discussion of climate change, not about a change in the average temperature, but whether or not the fluctuations have somehow changed.
They’re prominent in today’s news on two continents. The great plains of the USA are shivering through some of their coldest temperatures on record as the “polar vortex” invades from the north. Meanwhile, Australians suffer through their hottest month and worst heat waves ever, hell on earth for a place already known for it’s heat.
But mainly, it’s that polar vortex thing. Some have suggested that the rapid warming of the Arctic compared to the rest of the world, plus the dramatic decline of Arctic sea ice, have changed things in a fundamental way. It has thrown a monkey wrench into the jet stream, and during winter it can cause the polar vortex to fragment, part of it diving southward and bringing the deep freeze with it.