Sunday, July 02, 2006
Michigan is losing its cool
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. . . This summer, look around that "pleasant peninsula'' celebrated in our state motto: Changes have started, and more are in store as global warming becomes a phenomenon we can't help but notice. That's the verdict from scientists who study how Earth's buildup of carbon dioxide and other gases in the atmosphere will affect the Great Lakes region.
So pack some friends in your most fuel-efficent vehicle - to shrink, however slightly, your contribution to greenhouse gases - and ponder what scientists say we're in for. Winters like Missouri's by the end of the century. Declines in whitefish, lake trout and brook trout in waters that have lost the needed chill. Heavier rainstorms, summers with thirsty crops and lawns during hot, dry spells and more days when the mercury hits 97 or higher. By century's end, scientists project Detroiters will swelter through five to 10 times as many of these extreme heat days, which currently run about five or fewer a year.. . .
Some expected changes won't be noticeable for many decades: Cold-loving trees like spruce, fir and sugar maple will recede north from where they are now, but very slowly.
But other changes are having an impact now. Michigan's cherry orchards around Grand Traverse Bay bloom on average a week earlier now than they did 30 years ago, says Jim Nugent, an Michigan State University Extension horticultural agent who's worked that long with the region's cherry growers. When warm spells have made the trees bloom early - a now-frequent occurrence many scientists attribute to global warming - the result has been sometimes severe damage to the state's important cherry crop, because frosts have still hit at the usual times. In 2002, farmers lost nearly their entire crop of tart cherries, which supply most of the nation's cherry pies. . . .
Ice records for more than 150 years kept by the Traverse City Chamber of Commerce offer a fascinating look at winters then and now. They are "a strong piece of evidence to show winters are becoming milder,'' says the Extension's Nugent, who has analyzed the records. In each decade from 1851 to 1971, Grand Traverse Bay froze in at least 70 percent of winters, but in the 1970s, '80s and '90s, the number of winters in which the bay froze plummeted to 20 percent. Since 2001, the bay has frozen one time.
With more days of open water, more water evaporates from the lakes. So scientists expect water levels in the Great Lakes to drop more, continuing a trend from the late 1990s to the present. Consequences of those years range from wider beaches sprouting vegetation to freighters carrying lighter loads to reduce draught. . . .
Summer temperatures in Michigan are expected to rise 7 to 13 F by the end of the century. Heavy rainstorms are expected to occur far more frequently, perhaps twice as often. . . .
More frequent and more intense thunderstorms could increase the risk of outbreaks of waterborne illnesses. In Milwaukee in 1993, more than 400,000 people became ill when torrential rains caused cryptosporidium, a protozoan that can cause diarrheal illness, to wash from farm lots and contaminate the municipal water supply. Some Michigan communities are among those in the nation with combined wastewater systems that can allow this to happen, Bierbaum says.
A growing season eight to 10 weeks longer could be the norm in less than 100 years. That, along with faster plant growth spurred by more carbon dioxide, might seem at first like good news for Michigan farmers. But recent projections show that heavy spring rains, long dry spells, crop damage from ground-level ozone and shifts in pests may offset those advantages. Raising crops could become a riskier business, especially for smaller farms. . . .Scientists project there may be 30 to 50 90-degree-plus days in Detroit later this century. The most alarming of these days are the ones when the mercury hits 97 or higher. Cities with their paved expanses become "heat islands,'' with serious impacts on people's health. . . .
In extreme heat events people too poor to have air-conditioning are vulnerable. "We have laws that keep power companies from turning off the heat (in winter), but no laws preventing shutoffs for air-conditioning. How are we going to deal with that socially?'' askes Kling. . . .
Another change will affect fish: Lakes will tend to remain stratified longer in summer, allowing deep-water dead zones to form. Fish and other organisms can die, sometimes in large fish-kills, in these zones for lack of oxygen. On the other hand, shallow lakes where winterkill now occurs will be spared if their waters no longer freeze solid.
When the state motto was written in 1835, Michigan was practically covered in mature forests. The increased burning of fossil fuels that led to global warming is the latest of changes humans have caused: The mass removal of all that timber by the logging industry in the 19th century had dramatic effects too. The north woods of today are relatively recent regrowth.
Myers says the species shifts he studies are startling signs the new round of changes is under way. "This is not something that's happening in the future, it's happening now,'' he says.