Feeling Minnesota, Looking Nebraska

The magnitude and frequency of high dewpoint episodes are increasing, indicating that the air is more saturated with water. An increase in water vapor may be linked to the trend of what appears to be more violent weather in Minnesota. The state set a record for number of tornadoes in 1998 with 57, only to have it broken again with a record 73 tornadoes in 2001. Floods expected once in 500 years hit the Red River in 1997; and flooding levels expected once in 100 years overran the banks of the Mississippi in 1993 and 2001. Hail, heavy rains, and tornadoes were the major cause of the record $1.5 billion in insurance damage Minnesota incurred in 1998, a payout that topped the previous 49 years combined.

Meteorologist Paul Douglas, who has affixed his well-recognized mug to a dire climate-change report put out by Minnesotans for an Energy-Efficient Economy, says all of these occurrences are either “the mother of all coincidences,” or that “some very distinct trends are emerging, with troubling consequences for daily weather and longer-term climate.”

If you remember your Earth science coursework, you know that Minnesota is at an impressive naturally occurring crossroads. We are a nexus of air streams, biomes, and water, which helps explain how excitable our local newscasters seem to get about the weather. (Paul Douglas has claimed that despite his national prospects, he thinks this is the most challenging place to be for a skilled meteorologist.) Three air masses converge on the state—dry air from the Pacific, wetter air from the Gulf of Mexico and polar air from the north. Three major biomes, basically large biological communities of a type, follow roughly the same contours as the air masses: prairie to the west and south, and northern coniferous forest to the north and east, transected from the northwest to the southeast by a swath of hardwood forest.

The Department of Natural Resources, in its eternal quest for accuracy, calls these three biomes prairie parkland (now mostly cropland), Laurentian mixed forest (mixed hardwood and coniferous trees, including the boreal forest of balsam fir, white cedar, and white spruce), and eastern broadleaf forest (sugar maple, basswood, oak and ash). According to John Tester, professor emeritus of ecology at the University of Minnesota and author of a natural history of Minnesota, the state has one of the greatest climate changes in North America, outside alpine zones. That’s true across time, with the dramatic change of seasons—the painfully obvious 60-degree divergence in mean temperatures between July and January. It’s also true across distance, with sharp changes in climate within less than 50 miles. That variability, due to our location at the edge of three distinct environments, also makes the state more susceptible to climate change.

Near Itasca State Park, for example, along the gradual rise of a glacial moraine, the land changes from prairie to hardwood forest to mixed pine forest within a distance of 40 miles. Tester found that the average temperature from the prairie to the pines consistently differed by 4 degrees in the summer months, and annual precipitation varied by 5 inches, leaving the forest cooler and wetter. If such relatively minor weather differences correlated so strongly to different landscapes, Tester wonders, what happens to the landscape if the entire region warms up and dries out?

Duluth biology professor John Pastor looks at the interaction of trees and soils, and he agrees that Minnesota is at “the bullseye of big changes,” when it comes to global warming. Over the past two decades, he has spent many hours in church basements and libraries across the northern part of the state, giving talks about climate change.

“I used to describe the changes we will likely see in the next fifty years here in northern Minnesota, and people would be interested. But they would look at the time frame and say, ‘So what, I have to go pick my kid up at hockey.’” Pastor says. “Now I speak in terms of generations, as in ‘I am the last generation of my family who will be able to live out my life in the north woods.’ That gets their attention. And I go further, and ask them what it will mean if the family cabin—the one they want to pass down from generation to generation—what will it be as a legacy if the pines and firs are gone, the loons pass it by, the water’s too warm for walleye or trout, and the wolves have moved farther north? Then we’re not Minnesotans anymore, it seems to me.”

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