tonight, a conversation with usc law professor edwin smith about the fallout from the nsa leaks which detail the effects of our government surveillance at home and abroad and whether or not edwards noted should now be considered a whistleblower or brought to trial as a traitor. should he be convicted, snowden could face 30 years in prison. then we will turn to a conversation with bela fleck, who, as the world's premier banjo player, has been nominated for 30 grammys. excerptg a performance from his new cd, "the imposter". we are just -- we are glad you can join us for those conversations and a performance by bela fleck, coming up right now. ♪ >> and by contributions to your pbs station from viewers like you. thank you. tavis: edward snowden is a hero to some and a traitor to others after leaking secret information about government surveillance programs at home and around the world. snowden remains in russia, where he refuses to return to this country to stand trial. the intelligence data he revealed just how extensive the nsa's data collection was and continues to be. here to talk abo

we have assembled an a-list panel, gaven smith is a climateologist, josh marks is ceo of mass flight, edwinamerica's future, contributor for msnbc. gaven, let's start with you. for all of us shivering our behinds off, what is the science here? >> it's wintertime. we have a number of really cold fronts come through this year. mostly associated with meandering of the jet stream. you can see it on the weather maps. you get this big dip going down. that's bringing cold air down from canada and the arctic where it normally sits and bringing it down to us. >> is that what is making this year so unusual? >> we've had an unusual set of patterns. but it's not that unusual. new york city in decades past has seen much, must have worse. 1934, we got down to minus 19 fahrenheit. we've seen far more snow. if you actually look at the statistics, on average, the winters have been getting warmer. so this is a bit of an aberration going against the trend. but it doesn't keep you any warmer. >> it's that darn groundhog. he saw his shadow. now how much longer of this? >> slightly more reliable than small ferre