WASHINGTON — We've become weather wimps.
As the world warms, the United States is getting fewer bitter cold spells like the one that gripped much of the nation this week. So when a deep freeze strikes, scientists say, it seems more unprecedented than it really is.
An Associated Press analysis of the daily national winter temperature shows that cold extremes have happened about once every four years since 1900. Until recently.
When computer models estimated that the national average daily temperature for the Lower 48 states dropped to 17.9 degrees on Monday, it was the first deep freeze of that magnitude in 17 years, according to Greg Carbin, warning meteorologist for the National Oceanic and Atmospheric Administration. That stretch — from Jan. 13, 1997, to Monday — is by far the longest the United States has gone without the national average plunging below 18 degrees, according to a database of daytime winter temperatures starting in January 1900.
"These types of events have actually become more infrequent than they were in the past," said Carbin, who works at the Storm Prediction Center in Norman, Okla. "This is why there was such a big buzz because people have such short memories."
Said Jeff Masters, meteorology director of the private firm Weather Underground: "It's become a lot harder to get these extreme (cold) outbreaks in a planet that's warming."
And Monday's breathtaking chill? It was merely the 55th coldest day — averaged for the continental United States — since 1900. The coldest day for the Lower 48 since 1900 — as calculated by the computer models — was 12 degrees on Christmas Eve 1983, nearly 6 degrees colder than Monday.
Nine of 11 outside climate scientists and meteorologists who reviewed the data for the AP said it showed that as the world warms from heat-trapping gas spewed by the burning of fossil fuels, winters are becoming milder. The world is getting more warm extremes and fewer cold extremes, they said. And the scientists dismiss global warming skeptics who claim one or two cold days somehow disproves climate change.