Seven of D.C.’s top 10 snowstorms since 1889 have occurred since 1979. Storms that unload at least 16 inches of snow are now happening every five or six years, nine times as often as they did before 1979 when they only occurred once every 45 to 50 years.
As Capital Weather Gang’s Ian Livingston put it: “It seems the tempo of big storms for the city has increased.”
The flurry of recent blizzards is even more impressive farther north:
- Baltimore has witnessed seven of its top 10 biggest snows since 1979, and four of its top five since 1996.
- All of Philadelphia‘s top five snowstorms have occurred since 1983, and its top three since 1996.
- In New York City, seven of its top nine biggest snowstorms have occurred since 1996, six of them since 2003. Three of its top five have occurred since 2006.
- Five of Boston‘s top 10 snowstorms have occurred since 2003, and eight of its top 10 since 1978.
In all of the above megalopolitan cities, historical records date back to the late 1800s, yet the overwhelming majority of blockbuster snowstorms have occurred in the last 40 years.
This increase in such crippling events is incredibly consequential for society. These events often turn into multi-billion-dollar disasters, shutting down businesses and commerce for days, and restricting travel. They also frequently have auxiliary effects, such as costly coastal flooding and severe weather in the South.
More blizzards, but less snow?
While blizzards are booming, we note a paradox. D.C.’s annual average snowfall is steadily declining. In the early 1900s, D.C. averaged about 21 inches of snow per year. Today, it averages just 15.4 inches.
In this era of megastorms, the frequency of small snow events has decreased dramatically. Livingston, who has analyzed historical snowfall statistics, found that in the late 1800s and early 1900s, D.C. averaged more than six snow events of at least one inch per winter. Today, that number is down to about three.
As temperatures have risen, November and April snow events have practically vanished from the D.C. area. All five of D.C.’s latest measurable snows on record (in April) occurred before 1960. And D.C. has not experienced accumulating snow in November in the last 18 years, the longest stretch on record.
Climate change connections
Climate scientists say this new era of more blizzards but less snow is symptomatic of a warming world. Overall snow amounts decline because the cold season shortens and marginal situations for snow turn rainy. But, when big storms come along and the cold air supply is adequate, more snow falls as they draw increased moisture from a warmer ocean and atmosphere.
“For most conditions at sea level, there’s a rule of thumb that says the atmosphere can hold four percent more moisture per one degree Fahrenheit increase in temperature,” climate scientist Kevin Trenberth has written.
An MIT study conducted in 2014 found that while average snowfall could decrease by 65 percent by the late 21st century, amounts in extreme events would decrease little on balance and even increase in some cases.
“Shorter snow season, less snow overall, but the occasional knockout punch,” Princeton University climate scientist Michael Oppenheimer told the Associated Press’s Seth Borenstein in 2013. “That’s the new world we live in.”
Climate scientists have also identified changes in the circulation of the atmosphere and ocean, linked to climate warming, that may be feeding into bigger East Coast snowstorms.
Rutgers professor of meteorology Jennifer Francis has proposed the idea that declining sea ice in the Arctic has set off a ripple effect that slows down the jet stream and more frequently positions it for monster East Coast storms.
The Post’s Chris Mooney recently wrote about a suggestion put forth by German climate scientist Stefan Rahmstorf — that the meltwater from Greenland is slowing the North Atlantic ocean circulation, causing warm waters to accumulate off the East Coast, where big storms can draw moisture from.
Both the Francis and Rahmstorf hypotheses are new and must stand the test of time. But they suggest the planet may be changing in multiple ways to help intensify the most severe East Coast snowstorms, even as the climate warms and becomes less hospitable for snow.
Random chance probably plays some role as well, and climate scientists will surely work toward untangling the manic behavior of East Coast storms as we both trudge through knee-deep snow and leap over puddles of rainwater into a warmer future.