DAVID GREENE, HOST:
All right. Here are the voices of some meteorologists around the country. This was in Indianapolis.
UNIDENTIFIED MAN: This is the coldest wind chill I've ever reported in on the Weather Channel. It's 41 below zero. The air temperature is 13. In fact, it has dropped eight degrees in four hours this morning, as that wind just eats right through you.
GREENE: And no surprise, it is also cold in Green Bay, Wisconsin.
UNIDENTIFIED WOMAN #1: Could be so cold the National Weather Service is calling them life threatening, saying wind chill temperatures could dip as low as negative 50 today.
GREENE: It is cold as far South as Baton Rouge.
UNIDENTIFIED WOMAN #2: I don't know if we've ever really talked about having a wind chill advisory in effect in our area, but indeed...
GREENE: The bitter weather is a result of the ominous sounding polar vortex. And joining to explain this vortex is Andrew Freedman, senior science writer for Climate Central, an independent non-profit organization that researches and reports on the science and impact of climate change. Andrew, welcome to the program.
ANDREW FREEDMAN: Thanks for having me.
GREENE: So, let me start with the question that's on the minds of a lot of Americans right now, and that is why is it so cold?
FREEDMAN: Well, it's so cold because we have this polar air, this polar vortex, which is this area of low pressure and fast-moving winds over the Arctic that normally stays pretty friendly and up over Canada.
GREENE: Friendly to us, at least. Not to Canada, I guess.
FREEDMAN: Friendly to the U.S., at least. This is air that is circulating the Arctic. And in the last couple of days, it's sort of become lopsided, sort of like a figure skater that has extended their arms, and then tripped. You know, when a figure skater pulls their arms in, they spin tighter and tighter and faster and faster. But when they put their arms out, they are a little bit slower and a little bit more wobbly and more prone to fall or stop skating at the end of their routine. And what's happening now is that a piece of it is down on the other side of the globe, and a piece of it kind of got lopsided and came down on top of us. It just is a weather pattern that we don't see very often.
GREENE: Well, I wanted to ask you: How often do we see it? How rare is it for one of these things to come down onto the lower 48 of the U.S.?
FREEDMAN: Well, it's not all that rare to get pieces of the polar vortex to break off and affect parts of the U.S. What's rare is that this is sort of a huge part of the vortex that has descended on us and a huge area of the U.S. that's being affected. We have single-digit temperatures, overnight lows all the way from the Deep South near the Gulf Coast to the U.S.-Canadian border, all the way up to Maine and Minnesota. I mean, this is a huge expanse. You can say that it's the coldest that it's been since at least the early '90s, and in some places since the early '80s and late '70s. Thankfully, it's kind of this brief taste of how bad it can get, and then we go back to average, to slightly above average temperatures.
GREENE: I mean, is climate change playing some sort of role here in the cold we're seeing this week?
FREEDMAN: We actually have these possible connections between the Arctic - which is warming rapidly, and which is losing sea ice - and these perturbations, these shifts in the jet stream over North America and over Europe. And many scientists are convinced that there's enough circumstantial evidence to potentially convince a jury that there is this link, and that the weather patterns are becoming more and more suspicious as being influenced by human activities. But the physical connections, the actual smoking gun that would link Arctic warming to weather patterns that we see right now - like this one - isn't quite there yet. It hasn't quite been proven. So whether or not it would convince a jury of scientific peers in this case is unclear. And I think in the next few years, we'll know a lot more. But certainly, climate change is influencing every weather pattern that occurs today, in some ways large and small.
GREENE: Andrew Freedman, stay warm and thanks so much for talking to us.
FREEDMAN: Thank you.
GREENE: Andrew Freedman is a senior science writer for the nonprofit Climate Central. Transcript provided by NPR, Copyright NPR.