UMass Amherst Climate Center Considers the Mild Winter of 2001-02

AMHERST, Mass. - It wasn’t your imagination: last winter really was one of the mildest on record, says Frank Keimig, a climatologist and manager of the Climate System Research Center at the University of Massachusetts. Keimig recently compiled information on last year’s winter weather, and compared those statistics with the numbers from anaverage winter in western Massachusetts.

"Most people living in the Connecticut River Valley would probably say that our recent winter was unusually mild," said Keimig. "They might point to the minimal snow shoveling they had to do, the few (or no) snow days called for area schoolchildren, and lower-than-usual heating bills. They might point out the short periods of time that ponds or lakes were frozen, or the dry conditions that helped to spur the current drought. Some might even suggest a connection to global warming."

Residents’ observations have been borne out by the scientific data, according to Keimig, who considered a range of weather factors collected from a National Weather Service site in Amherst, from November through March. His results show that the area saw a record-breaking winter in terms of warmth: "In the context of our historical data, the Northeast saw the warmest winter on record, along with winter precipitation amounts that were below normal in most areas. In the Amherst daily data, what was remarkable was not just the overall warmth, but the persistence of the warmth from mid-November through mid-March, along with below-normal precipitation and well-below normal snowfall."

The warmth experienced in Amherst was indicative of a much larger regional warmth, Keimig added. "All of the New England states, except Maine, experienced their warmest December through February in 107 years of record-keeping, and Maine had its second-warmest."

Whether the markedly mild winter signals a climate change in the region will require a longer perspective, Keimig said. "If the remarkable statistics we saw this winter had been part of a significant trend from earlier years or decades, then we might be able to make some conclusions about climate change. But, on their own, these statistics may simply be a notable blip in the climate record."

In conducting the study, Keimig considered daily temperatures (both maximum and minimum), precipitation, and snowfall. He compared these daily statistics with an "average" Amherst winter, based on weather records from the past 75 years.

Temperatures were warmer-than-average this past winter, on a startling 74 percent of days. "The only cold period, as indicated by maximum temperatures, is in the second half of March, but that’s not strongly apparent in the minimum temperatures," he said. "The graphs are remarkable, not only in the number of days with temperatures above normal, but also in the number of days with very high temperatures. There were no extensive periods of cold days, or ‘cold snaps,’ but there were several warm spells."

The extremely low amount of snowfall is equally stunning. Snowfall ran well below normal: 25 inches for the five-month period, compared with a 75-year average of 44 inches. There was only one snowfall before January 7, and just 2.5 inches of snow fell between January 21 and March 17, Keimig points out. "The precipitation plot shows that our largest precipitation deficits occurred in November and in late December, through the beginning of February," Keimig said. "This five-inch precipitation deficit, combined with a 4.5-inch rainfall deficit for July through October, led to the present drought watch."

The study of the Amherst data, taken from November through March, also offers some eyebrow-raising percentages:

* 28 percent of days had a maximum temperature 10 degrees or greater than the long-term average;

* 56 percent of days had a minimum temperature above average;

* there were only nine snowfalls as opposed to the average of 16;

* there weresix snowfalls of greater than one inch, as opposed to the average of 10;

* there was one snowfall greater than five inches, compared with the average of 2.

Also, the following percentages for December through February underscore the mild winter:

* Only five days had a maximum temperature of less than 32 degrees, (with an average of 28);

* 19 days had a maximum temperature greater than 50 degrees, (the average is 6);

* Seven days had a minimum temperature lower than 10 degrees, (the average is 25);

* No days had a minimum temperature lower than zero (the average is 8).