Lauren R. Stevens: Winter numbers add up to change
For instance, how severe was the winter of 2016-17? Do we exaggerate its severity because it followed on the mild winter of 2015-16? How does our recent bout with snow and cold compare with others through time?
Hopkins Forest, Williams College's 2,500-acre experimental parcel in the corner of Massachusetts, New York and Vermont, maintains its own weather station, which has tracked temperatures going back to 1892 and snowfall back to 1993. Thanks to Jay Racela, Environmental Lab Manager, for this information — misinterpretations are mine.
Hopkins Forest averages the daily, monthly and yearly temperatures and also records the overall daily, monthly and yearly high and low. The long-term winter average is 23.7 degrees F. Although there were warmer periods in the `30s and `40s, and a colder period in the `60s and `70s, since then the temperature averages have been steadily rising. Five of the top-ten warmest winters (December-February) recorded in Williamstown have occurred since 1997 and 12 of the top 25 since 1990.
The winter of 2015-16 was the warmest winter on record, averaging 31 degrees F. The average December-February temperature for 2016-17 was the eighth highest on record, averaging 29 degrees. (Those who feel that the past winter was more rugged can point out that February was unusually mild — but that's what averages are all about.)
Hopkins Forest also keeps track of total snow, about 86 inches in 2016-17, compared to 21 inches for 2015-16. The most recent winter, although snowier than the year before, was not a record, with five other years since 1993 posting higher totals. The record: over 100 inches in 2011.
More helpful, perhaps, in terms of how snowfall impacts our lives, Hopkins Forest tracks the number of days in a given winter with over one inch of snow on the ground. Those numbers display the interplay of temperature and precipitation. On that scale, as with snow totals, 2015-16 is the lowest and 2016-17 is middling high with something less than 65 days, about half that of the record year (2000-01). Half the years since 1993 have been higher.
Do these numbers say anything about the local effects of climate change? Well, I guess, although they represent a very small data point in a very large, global set. Concerning precipitation, the decline in snowfall and snow cover is not as pronounced as temperature change. These numbers only go back to `93, however, and any trend may not yet be obvious.
Concerning temperature, we have seen the growing season lengthen locally and we have seen the introduction of species, such as ticks, moving north as warmth allows. Eight of the top 25 warmest years (all seasons) in Williamstown have occurred since 1990. Those numbers and the last 40 years of climbing winter temperature averages would certainly be consistent with climate change — change as dramatic as the snap of a whip.
At least, that's how it looks from the White Oaks.
A writer and environmentalist, Lauren R. Stevens is a regular Eagle contributor.
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