Two new reports show that winter low temperatures and the number of warm days are both on the rise due to human-caused climate change. The group Climate Central has been tracking the warmest and coldest winter days over the last five decades. What they’ve found is that 86 percent of some 240 sites across the country now have more very warm days than in the 1970s, and that the coldest day of the year has gone up by 7 degrees.