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“We expect to see a lengthening of time between cold air outbreaks due to a warming climate, but 17 years between outbreaks is probably partially due to an unusual amount of natural variability,” or luck, Masters said in an email. “I expect we’ll go far fewer than 17 years before seeing the next cold air outbreak of this intensity.

And the scientists dismiss global warming skeptics who claim one or two cold days somehow disproves climate change.

“When your hands are freezing off trying to scrape the ice off your car, it can be all too tempting to say, ‘Where’s global warming now? I could use a little of that!’ But you know what? It’s not as cold as it used to be anymore,” Texas Tech University climate scientist Katharine Hayhoe said in an email.

The recent cold spell, which was triggered by a frigid air mass known as the polar vortex that wandered way south of normal, could also be related to a relatively new theory that may prove a weather wild card, said Rutgers University climate scientist Jennifer Francis. Her theory, which has divided mainstream climate scientists, says that melting Arctic sea ice is changing polar weather, moving the jet stream and causing “more weirdness.”

Ryan Maue, a meteorologist with the private firm Weather Bell Analytics who is skeptical about blaming global warming for weather extremes, dismisses Francis’ theory and said he has concerns about the accuracy of Carbin’s database. Maue has his own daily U.S. average temperature showing that Monday was colder than Carbin’s calculations.

Still, he acknowledged that cold nationwide temperatures “occurred with more regularity in the past.”

Many climate scientists say Americans are weather weenies who forgot what a truly cold winter is like.

“I think that people’s memory about climate is really terrible,” Texas A&M University climate scientist Andrew Dessler wrote in an email. “So I think this cold event feels more extreme than it actually is because we’re just not used to really cold winters anymore.”