ARI SHAPIRO, HOST:
And I'm here in Washington, D.C., where people have been outside, walking around in shorts and flip-flops. We've got Mike Halpert on the line. He's deputy director of the Climate Prediction Center at the National Oceanic and Atmospheric Administration. And Mr. Halpert, what temperature should it be in Washington in the middle of December?
MIKE HALPERT: Middle of December, we oftentimes see highs roughly in the mid-40s, lows - somewhere just below freezing.
SHAPIRO: The other day, I saw lilacs blooming.
HALPERT: Well, it certainly a - been a very warm period that we've had here in December. I know. I was talking with other colleagues - certainly quite unusual.
SHAPIRO: Well, then, the next question is, why?
HALPERT: There's a couple of factors at play here. I think everybody's well aware that we have a strong El Nino that's kind of started back last spring, and El Nino is known to exert a pattern that oftentimes favors warmer-than-average temperatures. There's another factor that seems to maybe have been playing even a larger role over the last four to six weeks. It's something that we call the Arctic oscillation.
SHAPIRO: Explain what the Arctic oscillation is. We don't hear as much about that as we do about El Nino.
HALPERT: Yeah. It's an atmospheric pattern, and it relates basically the pressures at the polar regions to the pressures in the mid-latitudes where we live. It becomes much more newsworthy, typically, when we're very cold here because that's associated with the negative phase of the Arctic oscillation oftentimes. And what that means, is that the polar vortex, which may be surprising to some but not to a meteorologist - the polar vortex, which is located around the pole, weakens and allows cold air to spill out. This year, we're seeing the opposite. So we've had a strong polar vortex, and it's cold up at the polls but not really anywhere else.
SHAPIRO: OK. So El Nino plays a roll. The Arctic oscillation plays a role. What about climate change? Is that playing a role?
HALPERT: If it is, it's probably fairly insignificant at this point. If it were to play a role, it would be more likely if, somehow, climate change is impacting either the Arctic oscillation or El Nino, and we're not really aware that it is at this point. If you think about, maybe - the high temperature over the weekend was 70, so maybe without climate change, it would've been 69. I think it's a fairly insignificant role, if any role at all.
SHAPIRO: Is this just the kind of winter we're going to have, or could everything snap back to normal tomorrow or next week?
HALPERT: Well, it won't snap back in the next couple of weeks, but winter still has a long way to go. Certainly El Nino would favor, probably, a milder winter for the remainder in January and February. But the Arctic oscillation is something that's really not predictable at long lead times. And so, you know, could that become strongly negative at some point later this winter? You know, that possibility is something we would never rule out. You know, it's probably not the favored solution, but you know, for those snow lovers out there, maybe I wouldn't give up all hope just yet.
SHAPIRO: Mike Halpert is deputy director of NOAA's Climate Prediction Center. Thanks for talking with us.
HALPERT: You're very welcome. Transcript provided by NPR, Copyright NPR.