Icy weather highlights open questions about climate change effects

Arctic blasts and heavy snow affected more than 30 U.S. states in late January and early February and were linked to over 120 deaths, while numerous daily low-temperature records were broken. Scientists report ongoing uncertainty about how rapid Arctic warming and sea ice loss influence the jet stream and outbreaks of frigid air.

Thousands gathered for Groundhog Day in Punxsutawney as another Arctic blast brought freezing temperatures, ice and snow to much of the eastern United States. A winter storm and polar air between Jan. 23 and 26 affected more than 30 states and was linked to over 120 deaths. Dozens of daily and monthly low-temperature records were broken, though only a small number of all-time record lows were set. Scientists say they have not reached consensus on how rapid Arctic warming, sea ice loss and other factors are affecting the jet stream and cold-air outbreaks. Key facts: - A Jan. 23–26 winter storm and polar air mass affected more than 30 states and was associated with more than 120 deaths, according to reporting. - Many daily and monthly low-temperature records were broken across a wide swath of the country; about 15 new all-time record lows were recorded in preliminary NOAA data. - Researchers report active debate and unresolved questions about how Arctic warming and sea ice loss interact with the polar jet stream and the stratospheric polar vortex. - Climate modelers and some scientists say long-term trends still show overall winter warming and a projected decline in cold extremes even as episodic severe cold events continue. Summary: The recent sequence of Arctic blasts produced widespread cold, snow and multiple record low readings, which has prompted renewed public and scientific discussion about links between extreme winter weather and climate change. Undetermined at this time.