I think it depends on whose temps you are talking about. What happens globally may not be reflected regionally or locally. We can still get colder than average winters in the Midwest no matter what is going on elsewhere. But for the sake of argument, let's say Detroit starts seeing a significant warming trend in winter temps. Snowfall is fickle but that would probably start to eat into the snowfall average eventually. Josh or someone can check it out but if you look at Detroit's snowiest 10 or 20 winters, I bet you aren't going to find that many warmer than average ones in there... especially more than 1F above avg. And the warmer than average winters probably lean toward mediocrity or worse for total snowfall. Of course the farther north you are, the more you can get away with warming.