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Don Paul: What could climate change mean for lake-effect snow?

Don Paul

As of this writing on Dec. 3, Buffalo has had 13.5 inches of snow for the season, 3.5 inches above average. Most of that has been snow from widespread/synoptic low pressure storm systems, rather than lake-effect. We will probably pick up some limited lake snow later this week, ahead of a milder pattern for mid-December. Despite a cold and exceptionally cloudy November, the Lake Erie temperature is at 44 degrees, one above average for the date.

Lake-effect snow, as we all know, has very uneven distribution. It is dependent on temperatures at the surface up to at least 5,000 feet decreasing sharply with height, precise wind direction in the lower atmosphere, absence of too much wind shear, moisture availability and topography. Here is a National Weather Service snowfall map for the harsh winter of 2014-15 which, of course, included the infamous Snovember event. The accumulations reflect all of the factors I mentioned.

February 2015 was a stark reminder that even in a warming climate, very harsh winter weather will still occur at times. That month was the coldest month on record for Buffalo, with a mean temperature of 10.9 degrees. (The following February, in a very strong El Nino, the mean temperature was 29.4 degrees, well above average.)

With all that in mind, I bring to you what climate modelers have come up with as scenarios for future lake-effect seasons later in the century.

The model factors in the additional warming on tap for decades to come. Keep in mind these graphics are the mean for all five Great Lakes. We are not yet at a point where climate models can project for small regions, though that day will come. Weather models can do that owing to high resolution data; climate models can’t … yet. Here is the Great Lakes lake-effect trend since 1930.

The lake snow mean has been slowly climbing. The authors imply this is due to less lake ice resulting from warming, allowing more evaporation. My problem with this graphic is that while that has probably been happening since the early 1980s, that does not really account for the upward trend back in the '30s through the '70s. Some of those earlier increases were related more to abundant arctic air and broadly harsh winters before the onset of accelerated warming since the '80s.

In this era of warming, here is what one model projects based on warmer lakes and longer periods of open waters.

The length of the peak season contracts due to fewer incursions of arctic air in a warmer climate, but still allows plenty of room for major lake snows when such incursions occur for some decades to come.

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As for warming lakes, that is a very gradual process. It takes much longer to warm large bodies of water than it does to warm land. The average highest temperature for Lake Erie is 73 degrees, with records going back to 1927.

In this century, 13 of 18 summers have seen peak summer temperatures exceed the 73 degree mark, with larger margins occurring more often in the last eight to 10 years. Despite that, last year and this year both saw peaks of just 74 degrees, which is not much of an excess.

The marine air over the Great Lakes is slower to respond to a warming climate in general. The marine layer is why Buffalo, Miami Beach and Tampa have never hit 100 degrees. But if arctic incursions grow fewer in number and eventually less cold than in the past, later this century, lake-effect snow will gradually decline due to the absence of the necessary sharp drop-off in temperature from the lake surface up to 5,000 feet to make lake-effect precipitation. The lower volume of water in Lake Erie than in the other five lakes may allow it to warm a bit more rapidly than those lakes.

At least in the meantime, for winter recreation there is no indication the reduction in lake-effect precipitation will be precipitous.

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