It happens every winter.
Sometime between Santa's squeeze down the chimney and the Groundhog's peek out of his hole, a cold snap or big snowstorm gives climate-change skeptics another chance to suggest that global warming isn't happening.
Some examples this week: Radio talk show host Rush Limbaugh said the "polar vortex" the cold was blamed on is a new term invented by the media to link the cold wave to man-made climate change. The term has been around for decades.
Donald Trump took to Twitter to write: "Record snowfall & freezing temps throughout the country. Where is Global Warming when you need it?!"
So if it's very cold, then global warming isn't real? Scientists say no: "This week's brutal cold wave was a 1-in-20-year type of event," says meteorologist Jeff Masters of the Weather Underground, "and we will continue to see such cold waves in the future, even as the planet warms."
Meteorologist Cliff Mass of the University of Washington agrees, writing on his blog: "This individual event says nothing about the impacts of global warming. Global warming will occur over the coming century ..... One event proves nothing. Furthermore, the real warming is in the future."
This short blast of cold remains a blip in an onslaught of warm records: In the past four years, the USA has set more than 90,000 record high temperatures and about 38,000 record low temperatures, according to data from the National Climatic Data Center. Additionally, in the past 40 years, winters have steadily gotten warmer (by about 0.61 degree per decade) over the contiguous USA, the climate center reports.
Globally, the decade of the 2000s was the warmest since record-keeping began in the 1880s.
Although it was very cold over parts of North America this week, it was unusually warm elsewhere: Australia is smashing heat records, with temperatures reaching 118 degrees, according to meteorologist Bob Henson, a science writer at the National Center for Atmospheric Research.
Henson also says many Eurasian cities are seeing well above-average temperatures this week. Moscow temperatures will reach the 30s and Warsaw is expecting 40s.