While it’s still too soon to say whether or not this winter will end up looking like the last, snow fanatics should rest assured that extreme snowfall events are here to stay, even in a warming world. That is the finding of an MIT study that was published in the journal Nature this week.
Paul O’Gorman, a professor at MIT’s Department of Earth, Atmospheric, and Planetary Sciences, used model simulations to investigate the impact of global warming on both average, day to day snowfall amounts as well as the extreme snowfall events. He found that while average daily snowfalls could decrease by 65 percent by the late 21st century, the extreme snowfall events only decreased by eight percent in the model simulations. In fact, in some high-latitude cases, the models suggested that extreme snowstorms could deposit 10 percent more snow.
While there is always some uncertainty in studies using computer models, the results make sense with what we know about the physical nature of the atmosphere.
As the planet warms, the atmosphere is able to hold more moisture, and more water is evaporated into the air from oceans and lakes. In the same way that more moisture in the air has the potential to cause heavier downpours and more serious flooding, the added moisture also plays an important role in the intensity of winter storms, when they happen.
In addition, the temperature range at which extreme snowfall events happen is on the warm end, closer to the freezing point. As O’Gorman puts it, “people may know the expression, ‘It’s too cold to snow’ — if it’s very cold, there is too little water vapor in the air to support a very heavy snowfall, and if it’s too warm, most of the precipitation will fall as rain.”
It’s not hard to imagine a situation where the temperature is being pushed into this “sweet spot” for winter storms, whereas without the warming, they would have been too cold to see a heavy snowfall event. And as the study points out, the small change in extreme snowfall events has “corresponding implications for the detection and public perception of climate change.” A raging snowstorm appears to fly in the face of global warming, when in fact the two events are not necessarily unrelated.
O’Gorman’s results are in agreement with what we have seen here in Washington D.C. over the past few decades: our snowiest winters are getting snowier. In a post in February 2013, Jason Samenow writes:
In the 30 winters since 1984 … only five winters have had above average snowfall in D.C. – compared to 25 winters with average to below average amounts (15.4 inches or less). In 4 of the 5 winters with above average snowfall, the total was 2 to more than 3 times normal – or 30.1 to 56.1 inches (in 1987, 1996, 2003, and 2010). Or, put another away, the 25 snow-deprived winters averaged 9 inches of snow, the 5 snowy winters averaged 40 inches.
In an extensive analysis of D.C. snowfall events, Ian Livingston notes that while it’s increasingly difficult to get run-of-the-mill snows, the historic events have been left pretty much in-tact:
10 inch or greater storms, as well as categories down to 5 inches or so, are generally rather steady or even slightly up over time. They’re not necessarily coming with the same consistency in smaller winter-to-winter stretches, but they’re still coming, and possibly in larger groupings in big winters.
The last three decades, or since the 1980s, the city has recorded six of its current top 20 snowstorms. That’s as high as any other period in history of snow around the city, and up from decades prior that often featured more in the way of regular smaller events.