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Climate change is shrinking winter snow in the South, and in fall and spring over much of nation, report shows


During the 1970s, Nashville averaged just under a foot of snowfall each winter. Nowadays, Music City is lucky to see half that in a season.

The same is true in Knoxville, El Paso and Albuquerque; all have seen their typical wintertime snowfalls slashed by half in the past 50 years. And they’re not alone. A broad swath of the United States is seeing changing snowfall patterns, many of which are commensurate with those expected as a result of climate change.

In much of the South, the Plains and the interior Mid-Atlantic, seasonal snow totals are dwindling. That’s according to Climate Central, a nonprofit group specializing in climate change research and communication. A report released Wednesday reveals where snow hopes are beginning to melt away, while a select few locations may actually be seeing more snow thanks to climate change.

Where seasonal snowfall is diminishing

Snowfall was seen to be decreasing especially rapidly in the South. These are largely areas that pick up their snow in marginal environments anyway, so any subtle warming can tip the scales and favor temperatures above freezing. That can cut back on snowfall.

This was also prevalent in parts of the Rockies and interior Appalachians, as well as the central and southern Plains in between. Springfield, Mo.; Evansville, Ind.; and Lubbock, Tex., all saw a greater than 40 percent decline in annual snowfall between in the 2010s compared with the 1970s. Even State College, Pa., saw about 20 inches per year less during the 2010s.

When it’s decreasing

Perhaps the most telling aspect of the report wasn’t necessarily where snowfall is decreasing, but rather when.

“In the shoulder seasons, when we look at the nationwide average, in the fall and the spring, we’re starting to see a tendency for the amount of snow to decrease,” Climate Central meteorologist Sean Sublette said.

That’s because the “shoulder seasons” on either side of winter — spring and fall — are warmer than winter. By nature of being transitional seasons, their snowfall events typically occur at warmer temperatures closer to the freezing mark. Any climate warming would nudge spring and fall snow events above freezing first, before affecting any trends in the wintertime.

In the South, 13 out of 14 cities saw a decrease in fall snowfall, while 71 percent experienced a drop in spring snowfall. Each of the five stations in the Southwest recorded a drop in fall and spring snowfall. And in central regions, three-quarters of stations witnessed a decline in fall and spring snowfall.

And in the Northeast, 71 percent saw a decline in the fall, but less than half did in springtime.

In the dead of winter, Sublette says the trends “are much more piecemeal.”

Snowfall increasing in some areas

In a few spots, snowfall is actually increasing — particularly in the wintertime. According to the report, this occurred in some Northeast cities as well as several communities in the Upper Midwest. Why?

For every degree Fahrenheit the air temperature increases, the atmosphere can hold 4 percent more water. That means that, as long as temperatures stay below freezing, an increase in temperature could lead to a juicier storm and actually produce more snow. For areas that are already plenty cold, such as the Upper Midwest and Interior Northeast, that could be a trend going forward — until, down the road, rising temperatures push some storms over the freezing line.

With a greater atmospheric moisture content, Sublette said, we would expect to see “more snow when the temperature is sufficiently low.”

The report also mentioned that lake-effect snow off the Great Lakes will probably increase because of climate change. With warming temperatures, ice cover is dropping. That leaves comparatively warmer waters exposed, which are source for lake-effect snow bands.

“With open lakes, you get much more heat and moisture flux off the lake, and again if it stays below freezing, you have more snow in that time frame” Sublette said.

Bigger storms for the Northeast

In recent years, there has been a demonstrable trend in many East Coast cities, during which some winters will feature booming blockbuster storms while others pass with hardly a flake. The “feast or famine” nature of the snowfall may have a climate explanation behind it.

“It gets back to the fundamentals of the physics of these systems,” said Dave Robinson, a professor of atmospheric sciences at Rutgers, who runs the university’s Global Snow Lab. “You can develop stronger storms over warmer seas. And with more moisture in the air and a greater temperature contrast.”

As long as you can still be “dynamically cold enough to snow … they’re powerful systems. We’re seeing some suggestion of more large storms, more impactful storms, up in the north,” Robinson said.

How they did it

The team reviewed snowfall data from 244 locations between 1970 and 2019. After whittling down the count based on which met their stringent continuity requirements, 145 data sets remained. They then performed “endpoint analysis,” comparing average snowfall for each location during the 1970s vs. the 2010s. The results reported focused primarily on contrasting those two decade-long blocks in each city.

Thereafter, the scientists sorted their results geographically into nine regions nationwide. The West did not offer enough observation stations to discern a meaningful trend. In the Southwest, it was marginal.

Limitations

Endpoint analysis is at times useful. By virtue of design, however, it “skips over” anything that is happening in between endpoints. Given how much snowfall amounts change year to year and even decade by decade, a more rigorous analysis would be needed to see how those “endpoints” fit into context.

“The point is that snowfall is so variable year to year and even decade to decade,” Robinson said.

He pointed out that, if the report’s analysis had started in the 1960s, snowfall reductions in the East would have appeared even more impressive. “Here in the Mid-Atlantic, the ’60s were the most snowy [decade] on record.”

Overall, though, Robinson found it to be a “very respectable study,” stating that the results fall in line with what should be expected thanks to climate change. He noted that the report’s authors were wise to only review stations with more than 5 inches of snow annually, appreciating the regional breakdown as well.

Across the board, atmospheric scientists wish that more data was available, particularly for a longer time series. “I’m one who is very data driven,” said Robinson.

Sublette agrees. “You always want to have more data.” But a variety of factors “make it very difficult to get strong data.”

Takeaways

While the report’s analysis aims to explore several topics in greater detail, the trends indicated by its results are in clear agreement with what the science predicts should be associated with climate change.

“The take home is that what we have seen with the limited data is consistent with a warming climate,” said Sublette.

As the seasons continue to compress, with more mild/less snowy autumns and springs, there’s the chance that winter’s duration in many areas will continue to narrow. But that doesn’t mean a decline in snowfall everywhere, as results showed.

“They’re very complex issues,” Robinson said.

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