Understanding Snowfall Trends and Climate Change: It’s Not What You Think

Climate change in New York City is palpable. It’s in small things, like backyard hydrangeas blooming in July instead of August. It’s in big things, like a record-setting 8.05 inches of rain falling in a single day in September, turning streets into rivers. And it’s in momentous things, like 2012’s Superstorm Sandy, which destroyed beaches, neighborhoods and subway lines, and caused blackouts lasting for days. 

But it’s not just freak storms that endanger us: Since 1900, sea levels have risen here by 1.2 inches a decade. Mean annual precipitation has risen 8 inches, and mean annual temperatures are up 4.4 degrees, according to the city’s Panel on Climate Change. The city is wetter, and it’s hotter. 

Here’s the surprise, though: We’ve had more snow overall in recent decades, not less. 

“Snowfall is a bit of a controversial topic,” said climatologist Judah Cohen, director of seasons forecasting at AER (Atmospheric and Environmental Research). In the 1990s, conventional wisdom projected that as the globe warmed, “winter might be the season that would warm the fastest,” with temperate regions like New York City seeing “less snow because more days would be above freezing.” 

But it turns out to be “more of a zigzag than a straight line,” Cohen said, in which “some places are getting more snowfall, not less.” 

National Weather Service statistics show that the city’s snowiest decade was the one ending in 2018, averaging nearly 38 inches a year. The 30-year average ending in 2018 also set a record: 29.68 inches annually — or nearly 5 inches more than the 24.9-inch annual average in the previous 30 years. 

One theory says the increase is random, due to weather’s natural variability. But Cohen believes “it wasn’t an accident.” He thinks “there’s a physical connection between the Arctic getting warmer and this increase in severe weather.” 

He and other scientists propose that while the oceans and the globe are warming overall, that warming “is not uniform, but rather it’s focused in the Arctic region,” where warming has accelerated relative to the rest of the planet. That Arctic warming can disrupt the jetstream, leading to severe periods of winter weather and disruptive snowfall in regions like New York that are “mid-latitude,” or halfway between the Earth’s poles and the equator. 

At the same time, seasons are shifting. Summer and fall are warmer, winters are “shrinking,” spring comes earlier and more aggressively, Cohen observed. September is now so warm, it “should not be considered a fall month anymore,” he said. 

As for winters, even when they’re snowy, they’re starting later. “My joke,” he said, “is that the first official day of winter should be Martin Luther King Day.”