One season (or half a season) doesn't make much of a trend, but the Daily Yomiuri today has an article on how warm things are in parts of Japan that are normally covered by snow this time of year. In Niigata, it's raining. In Gunma, ice fishing hasn't started yet because the lake hasn't frozen over. In parts of Niigata, they're golfing instead of skiing. In Aomori, they've had to postpone a series of ski competitions because there's no snow (and it's too warm to make any).
Most of those parts of Japan are generally just below freezing in the winter, getting lots of snow but not really being bitterly cold. The paper says temperatures are 0.8 to 1.0C higher than average, but that sounds like an underestimate to me; 2-3C is what I would expect it to take to completely kill snow in those parts, but maybe it's more marginal than I think.
And on the news last night, they said that Moscow is 10C warmer than typical this time of year.
The article attributes the warming to El Nino. Make of it what you will...