If the globe is warming, shouldn’t
there be less snow?
This a common question. So last winter, as
another intense snowstorm blanketed a large part of the US, the New York Times
put it to Kevin Reed, an associate professor at the School of Marine and
Atmospheric Sciences at Stony Brook University on Long Island.
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It is true, he said, that in a
warming world, less snow is falling overall, and covering less area. But higher
temperatures also allow the atmosphere to hold more water, which creates more
precipitation and makes it more likely to fall quickly.
“That means there are still times and cases
where that precipitation increase comes in the form of snow,” Reed said. “We
know that to be true.”
Summers have always been more humid than
winters because warmer air absorbs more moisture. As the moisture condenses,
warm air rises faster, bringing even more moisture in a feedback loop that can
create sudden,
fast-falling downpours.
Higher temperatures also allow the atmosphere to hold more water, which creates more precipitation and makes it more likely to fall quickly
Overall, Reed said, a few degrees of global
warming means that some storms that would have brought snow on a below-zero day
will end up as rain at 0.5 degrees. But on the other hand, more snow falls when
temperatures are just below freezing than during extreme cold.
“So a storm that’s a little warmer but
still below freezing, a storm that might’ve been a (
negative-four-degree) storm
but ends up as a (negative-one-degree storm), means it will snow more,” he
said.
Flash floods are generally more likely
during warm-weather downpours. But freezing temperatures bring their own
flooding risks, Reed said: Ice can block drainage systems, and if rain or
warmer temperatures follow snow, the melting can cause flooding.
“That’s the worst-case scenario when we’re
right around the freezing line: Rain and snow melt and (cause) blockages all at
once,” he said.
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