Data: Climate Central; Note: Winter temperature threshold based on the coldest 90-day window; Map: Jacque Schrag/AxiosThis winter has been brutally cold, snowy and icy for millions of Americans — yet winters are getting shorter across most U.S. cities amid climate change.That's per a new analysis based on temperatures rather than calendar dates from Climate Central, a climate research group.Driving the news: Compared to the 1970-1997 period, winters are now shorter in 80% of the 245 U.S. cities...