This weird winter was one of the warmest — and coldest — on record. It’s a glimpse of our future

By Andrew Freedman, CNN

(CNN) — There was a decisive winner to the Lower 48 states’ split screen winter — a battle between frigid cold in the East and record warmth in the West. Anyone in the East who shivered through this winter could be in for a shock at the outcome.

In the end, the warmth won out, and this winter will likely be ranked among the warmest such seasons for the contiguous US. In fact, two data sets preliminarily show that the Lower 48 states saw its 2nd-warmest winter on record.

It’s an astonishing demonstration of how climate change works. Even our coldest colds can no longer make a dent in record-setting heat.

That may come as a surprise to the tens of millions of people who trudged through severe cold, snow and ice for weeks on end in the Midwest and East, with new terms like “snowcrete” — sleet-encrusted snow resistant to melting — taking hold.

But at the end of meteorological winter, which ran from December through February, few observing stations in the East had recorded a record-breaking cold winter, while dozens in the West and Southwest saw their warmest.

The Western U.S. as a region had its warmest winter on record, and one with a paucity of snow cover. Many areas are now facing a potentially dire summer drought and wildfire season.

The split screen was visible at the local scale, as well as regional. Numerous cities in the West set records for their hottest winter. In the East, however, while many locations ranked this winter among their top 25 coldest, no station with a long period of weather records had its most frigid.

For example, Salt Lake City, Phoenix, Las Vegas and Cheyenne, Wyo. had their warmest winters on record this year, and that was not compensated for by record cold in the East. Denver even had more 60-degree days during the winter months than did Myrtle Beach, South Carolina.

The fact is that winters used to be colder than this, and in many places in the US, winter is now the fastest-warming season.

Another way of looking at the temperature battle this past winter is by tracking the aerial extent of what meteorologists refer to as the Northern Hemisphere’s “cold pool.” This is, essentially, where snow is born — a layer of air, about 5,000 feet up, cold enough to support the formation of snowflakes.

Jonathan Martin, a meteorologist at the University of Wisconsin-Madison, has been tracking the size of this cold pool, tracing it back to when such reliable data began in the 1940s. He found that this past meteorological winter had the smallest cold pool in the entire data set. That’s consistent with an overall contraction in the pool’s size during the past several decades.

But because the frigid air that did exist sat on top of some of the most heavily populated land in the world, it gave the impression that it was an unusually cold winter more broadly. Martin said the cold pool was centered over two areas — one of which was adjacent to Hudson Bay, Canada, including most of the eastern U.S. And that same region also saw repeated outbreaks of Arctic air as lobes of the polar vortex split off and dove south.

Martin views the long-term cold pool data as a unique indicator of human-caused climate change.

“It’s one of the first free atmosphere, that is, away from the surface … measurements that conclusively show that the hemisphere is warming during the wintertime,” he said.

“The dice are loaded,” Martin said. As the world warms, it’s clear that cold pools are likely to keep shrinking and winters of the future are more likely to keep breaking warmth records.

The-CNN-Wire
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