Tapping Into a Changing Climate
by: Robert Lee Hotz 23 April 2006
JEFFERSONVILLE, Vt. — Sitting in his son's sugarhouse, Rex Marsh, 71, can recall winters so cold that no one in northern Vermont ever thought of tapping a sugar maple before town meeting day on the first Tuesday of March.
The winter snow routinely drifted 6 feet deep. Every sluggish step was in snowshoes. Even if the trees thawed, the sap would freeze in the bucket, bursting its metal seams.
"I've been doing this since I was big enough to carry a bucket," Marsh said. "Tapping in January? Never. Never. Never."
For the last two years, however, the Marshes have tapped their maples in January, the earliest they can recall in the family's five generations of sugar making.
By mid-April — usually their busiest time — Marsh and his son Rick, 46, had boiled the last of their maple sap into syrup and were shutting down their oil-fired evaporator for the season.
Nestled in a grove of 9,000 maples among the sugarbush foothills of Mt. Mansfield, the Marshes' clapboard-and-concrete sugarhouse is an unassuming outpost on the frontier of climate change.
By analyzing decades of records kept by regional maple sugar producers, climate researchers are finding clear evidence here of what Rex Marsh can feel in his bones.
The weather just isn't what it used to be.
In Ohio and New York, through New England and into Canada, the maple sugaring season starts and ends earlier than a generation ago, University of Vermont researchers and other experts say.
Moreover, the daily temperature cycle of frost and thaw on which sap production depends also has been disrupted.
While officials argue over carbon emission controls and global warming treaties, tree farmers such as the Marsh family, along with gardeners, anglers and bird-watchers, sense the change in the air.
In response to rising global temperatures, spring comes as much as 13 days earlier in many parts of North America and 15 days earlier in Europe than 30 years ago, scientists say.
"The spring is getting earlier at a rate of a little bit more than a day per decade," said Mark D. Schwartz, who studies the interaction between plants and climate at the University of Wisconsin in Milwaukee.
Winter is retreating as average temperatures in the U.S. have risen about 1 degree during the last century and as levels of greenhouse gases such as carbon dioxide have steadily increased to record levels, global warming studies show.
Spring and winter are becoming milder, according to the National Climatic Data Center. From 1950 to 1993, the coldest winter temperatures rose by 5 degrees, and the warmest spring temperatures rose 2.5 degrees.
On average, the temperature difference between cold nights and warm days is narrowing even more quickly.
Climate is like a pointillist composition, however, made up of myriad points of local variation — just as the advent of spring is a collection of responses that vary by altitude and longitude, rather than a single day marked on the calendar.
Until recently, the natural variations of weather made it difficult to discern the early effects of climate change. Only now are scientists beginning to understand the interlocking gears of weather, climate, solar cycles, ocean currents and the global effects of greenhouse gases.
Searching for reliable clues, scientists turned to those who for generations have kept a precise weather eye on the seasons. Researchers have combed personal diaries, bird-watchers' ledgers, herbarium files, museum collection notations, old photographs and naturalists' field notes.
From these records, some encompassing centuries of observations, researchers have tracked tiny alterations in lifetime routines. The shifts reveal the imprint of climate change among hundreds of plant and wildlife species — and among people, such as Rick and Rex Marsh, whose livelihoods are intimately tied to them.