Snow now possible in all 50 states

Negative phase of the Arctic Oscillation is back — with a vengeance

Just as strange, temperatures in parts of Greenland are reaching 40 degrees — and in one spot even 50.  There’s also a 30 percent chance of rain — not snow — forecast for the southeastern part of the island. (To check the weather in various locations in Greenland, see this Weather Underground page.)

Sound familiar? That’s because the topsy turvy temperatures are a replay of what happened in December and January, with frigid temperatures gripping much of North American while parts of the Arctic warmed to a bizarre degree, and rain fell on the Greenland coast. Now, as then, the likely cause is a phenomenon known as the Arctic Oscillation. And here is the news: Just as in December and January, the AO index is now extremely low, a condition that usually brings abnormally warm temperatures to the Arctic and abnormally cold temperatures further south.

Here’s a diagram charting the AO index:

It reached record lows back in December and January, and it looks like it’s back down in that territory once again.

So as climate skeptics claim that the freak snowstorm spreading across the South proves that global warming is bunk, and climate activists parry that it’s actually evidence that global warming is happening, try to keep this in mind: Weather is different from climate. Weather happens over the course of days. Climate is measured in terms of decades.

Moreover, mother nature probably isn’t conforming to the simplistic arguments of partisans. Something quite unusual is certainly going on. And I suspect that aside from the observations of what’s happening to the AO index, we don’t know exactly what it is.