ROBERT SIEGEL, HOST:
On this first day of winter - a heat wave at the North Pole - well, relatively speaking. Tomorrow, temperatures at the North Pole are expected to approach freezing.
ZACK LABE: In Fahrenheit, It's nearly 40, maybe 50 degrees above normal.
ARI SHAPIRO, HOST:
That's Zack Labe, a doctoral students studying Arctic climate at the University of California, Irvine. Over Skype, he explained what's going on. He said warmer than usual air temperatures and even warmer ocean temperatures have kept Arctic waters from refreezing as much as they normally do this time of year.
LABE: So when you have more ocean water that's open, it kind of acts - you can think of it as a buffer to the air temperature - prevents the air temperature from getting very, very cold.
SIEGEL: Now, Zack Labe says it is normal to see great variability in arctic temperatures. Some days are much colder or warmer than others.
LABE: And when we looked back at previous years, we do see these strange spikes in temperatures that occur every so often. However, when you look over the longer term trend of the last several decades, ignoring those spikes and just focusing on the trend, you see a gradual warming over time and a gradual decrease in the amount of sea ice.
SHAPIRO: And human-induced climate change is a big contributor to that trend. This winter, Zack Labe will be watching to see where the Arctic sea ice forms and where it doesn't. He'll also look at how thick the sea ice gets. He's concerned it will remain thin, but he hasn't ruled out the opposite.
LABE: Maybe in a few weeks we'll have a very unusual cold spell, and that will really help the sea ice to refreeze a bit more and become thicker and maybe prevent some of the melt going into next summer. Or next summer we could have a cooler-than-normal summer, and there would be less melt than normal.
SIEGEL: The weather, after all, can vary quite a bit. But planetwide, things are continuing to warm up. Today the World Meteorological Organization announced that 2016 is on track to be the hottest year on record. Transcript provided by NPR, Copyright NPR.