Snow in Spring? Why a Cold March Doesn't Disprove Global Warming

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Kenneth Libbrecht, a professor of physics at California Institute of Technology, photographs snowflakes in the field and in his lab. Studio-type lighting, even outdoors, brings out angles, texture and color that are otherwise hard to spot. (Image credit: Credit: Kenneth Libbrecht, Caltech/ www.snowcrystals.com)

It's the first week of spring, and yet many East Coasters woke up this morning to freshly fallen snow. Isn't that counter to the fact that the Earth is experiencing a warming trend?

"People make the mistake of equating weather in their location with global warming or climate change," said David Easterling, chief of the Scientific Services Division at the National Oceanic and Atmospheric Administration's National Climatic Data Center. "But the answer is that even with a warming planet, you're always going to have some places that are unusually cold for a day, or even a month, while at the same time other areas are unusually warm."

"What we're dealing with now is weather as opposed to climate," Easterling told Life's Little Mysteries. Even by 2050, when the Earth is projected to be warmer, we'll still get an occasional cold air outbreak in the eastern states. "It just won't happen as frequently," he said.

So, then, why is it snowing in Times Square on March 23?

Just about any time it's unseasonably cold on the East Coast, it's because the jet stream — the fast-flowing upper air current that runs west to east over the U.S. — is acting funny.

Right now, a high-pressure system in the western part of the country has nudged the jet stream north in that area. When that happens, the jet stream will dip southward in the east, creating a low pressure trough.

"Cold air from Canada moves into this trough," Easterling said. "This will last for the next 10 days or so, and it will be cold in the east." After that, though, the jet stream ridge will likely be over the east coast, bringing warmer air with it. Which is another reason not to get worked up over snow in the spring.

"It's a transition season, spring, and we'll still get the occasional blast of cold or warm air," Easterling said. "By May, things will settle into a more reliable pattern."

Life's Little Mysteries is a sister site to LiveScience. Follow Bjorn Carey on Twitter @thebjorncarey

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Bjorn Carey
Bjorn Carey is the science information officer at Stanford University. He has written and edited for various news outlets, including Live Science's Life's Little Mysteries, Space.com and Popular Science. When it comes to reporting on and explaining wacky science and weird news, Bjorn is your guy. He currently lives in the San Francisco Bay Area with his beautiful son and wife.