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.
Changes in high temperatures were more modest across much of our region, but some of the most dramatic swings in cold days were found in the West. Winter lows jumped nearly 16 degrees since 1970 in Boise, and by 14 in Reno.
But Judah Cohen, seasonal forecasting director at Verisk Atmospheric and Environmental Research, said this trend doesn’t mean extreme cold is going away. That’s due in part to disruptions in the polar vortex, which have brought frigid temperatures in recent weeks.
“Then a few days later, a week later, the polar vortex snaps back to its normal shape or configuration and the record warm temperatures return,” he said. “So that's why we're seeing this increase in weather volatility.”
“Weather whiplash,” is one of the terms used to describe the sense the swings provoke, he said.
A debate about the impact of climate change on the polar vortex is ongoing, according to Cohen.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
