The record-crushing cold that rang in 2018 was like a blast from the past that will become increasingly rare.

For much of the Eastern United States, the polar vortex unleashed the coldest start to a calendar year in recorded history. The punishing cold was exceptional for both its strength and duration, shattering scores of records and persisting two weeks after its invasion on Christmas Eve.

The frigid spell was particularly noteworthy for occurring when the planet is steadily warming because of the accumulation of greenhouse gases in the atmosphere. Climate warming from the increase in these heat-trapping gases does not eliminate cold waves, but it tends to weaken them.