A change in climate: Global Warming in Wisconsin
By Lee Berquist and Thomas Content
Milwaukee Journal Sentinel
Posted March 24, 2007
Second part in an occasional series
Town of Fairfield - On a warm winter day, Nina Leopold Bradley walked nimbly along a trail to a weather-beaten cabin that figures prominently in modern environmental history.
Bradley is 89 years old, and using a pair of hiking poles, she pointed out places where she has recorded the arrival of spring for the last 30 years. Her father, the famed ecologist and pioneer of wildlife management Aldo Leopold, had done the same before her.
But spring's advance has been so dramatic that if Leopold were alive today, he'd have to rewrite parts of his seminal book, "A Sand County Almanac."
Take, for example, the Canada geese. Leopold wrote that they "tumbled out of the sky like maple leaves" in March.
But records by his daughter show that migratory geese are returning home more than a month sooner - now arriving about Feb. 19.
The differences chronicled by father and daughter along the Wisconsin River in Sauk County mirror hundreds of studies worldwide that show that the climate is changing.
If many of the predictions about global warming come true, it will create a new climate for Wisconsin and pose sweeping social, economic and environmental challenges.
So far, scientists have seen quicker-blooming plants, the invasion of non-native insects and nature simply getting out of kilter - and it's happened with a seemingly small increase in the thermometer.
"The main thing is that we are pushing on the system at a much faster rate than we understand," said Stephen Schneider, a climatologist at Stanford University. "The faster you push on the system, the more things are going to happen."
Wisconsin's temperature rose 0.7 degrees during the 20th century, according to the State Climatology Office. Globally, the average increase was 1.5 degrees.
In the climate world, these are big leaps.
Since 1920, global temperatures have risen at a faster rate than any time in at least 2,000 years, according to the National Academy of Sciences.
In Milwaukee, the average temperature over the past 30 years has jumped 2 degrees from the same 30-year period a century ago, according to the State Climatology Office.
The higher temperatures coincide with rising levels of carbon dioxide, most of which is the result of burning fossil fuels.
But there are additional explanations for the Earth's warming. Some scientists believe the natural cycles of cooling and the current warming trend have been overlooked.
Edward Hopkins, assistant state climatologist, believes that these natural cycles and rising levels of carbon dioxide are both at work.
"Nobody wants to say that we just don't know," Hopkins said. "I am willing to say that we don't know completely."
Today the majority of scientists believe that an increase of carbon dioxide in the atmosphere is the key reason for why the Earth has warmed so quickly in the past 50 years.
And Wisconsin plays a small, but not insignificant role in the emissions of carbon dioxide: Each state resident generates five times more carbon dioxide on average than the typical person around the world.
Only 12 states rely more on coal as a percentage of their fuel source to generate power.
By the end of the century, the most accepted prediction is that the Earth will warm by 3.2 to 7.2 degrees. This would be two to five times as high as the change in temperature we've experienced since 1900.
The assessment came last month from the Intergovernmental Panel on Climate Change, which surveyed the latest findings in climate research. The predicted temperature increases would dwarf those that have been experienced in thousands of years.
In Wisconsin, winters by 2100 could be more like Missouri's today, and Lake Michigan water levels could drop as much as 5 feet in the next 100 years, according to a study by the Union of Concerned Scientists.
Already, Wisconsin winters lack the consistent punch of a few decades ago.
The American Birkebeiner drew 6,700 skiers to Hayward last month for the largest ski marathon in North America. In one weekend, the event generates $4 million for the local economy, said Ned Zuelsdorff, executive director.
Poor snow conditions this year cut the length of the course in half. The same thing happened in 1998. The race was canceled in 2000.
Snowmobile sales, meanwhile, have fallen every year but one since 1997, according to the International Snowmobile Manufacturers Association. Domestic sales have fallen 46% to 91,670 units in 2006, association figures show.
Less ice cover, earlier blooms
But perhaps the hardest evidence of global warming is the dwindling ice cover on our lakes.
The duration of ice on Lake Mendota in Dane County has slipped from an average of four months between 1850 and 1870 to nearly three months for the 20 years ending in 2005, according to research at the University of Wisconsin-Madison.
John Magnuson, a lake researcher at UW, said less ice cover could harm the health of some lakes.
For shallow lakes, less ice means more evaporation, which could reduce water levels.
The water in deeper lakes is divided by different temperature zones. If lakes stay warmer for a longer period, they could lose their ability to recirculate water and deprive bottom-dwelling fish of oxygen.
Outside his office in January, waves on Lake Mendota licked the shoreline. The lake didn't freeze until Jan. 20 - the second latest date in 152 years.
Scientists found similar results on other Wisconsin lakes, across Canada and as far away as Lake Baikal in Russia.
"The studies from other places made it clear that this was not just a local phenomenon," Magnuson said. "You didn't need a theory. You didn't need a computer model. You didn't even need a thermometer."
Other changes documented in Wisconsin include the earlier bloom of the pussy willow - a tree with silky buds and favored by many nature lovers as an early sign of spring.
Mark D. Schwartz of UW-Milwaukee found that the plant and a flowering herb called scilla bloomed nearly three weeks earlier in southwestern Wisconsin in 1998 than in 1965. Other regions of the state showed less change, but the trend "sticks out like a branch," Schwartz said.
"It's the sort of thing where you look at an alternative explanation, but given the amount of change we are seeing, the balance of evidence points to human events as a key factor," he said.
Some insects also appear to be affected by higher temperatures and are moving northward.
Eggs of the praying mantis - a non-native species introduced as a predator to other insects - have begun to make it through Wisconsin winters in the past five years and are hatching on their own, according to entomologist Phil Pellitteri of UW-Madison.
"I see this as the tip of the iceberg," observed botanist Don Waller of UW-Madison, who has studied the effects of climate change for 25 years.
"I never thought I would see definitive biological and physical evidence of global warming just a few years after most of us woke up to it."
One concern, he said, is that plants and cold-blooded animals, in particular, "can't just turn up the thermostat like we can" and adapt quickly to changes.
Sand County saga
At his cabin near Baraboo, Aldo Leopold charted changes in the natural world until shortly before he died fighting a neighbor's grass fire in 1948.
His local observations were the foundation of "A Sand County Almanac," a classic in environmental writing that was published after his death.
Nina Leopold Bradley and her late husband, Charles Bradley, resumed her father's work in 1976.
The results show how spring has advanced for selected species in Wisconsin.
On average, plants bloomed and birds returned along the Wisconsin River 7.6 days sooner during the period of 1994 to 2004 than they had between 1935 and 1945, according to Bradley and an analysis of the data by UW-Madison graduate student Sarah D. Wright.
Among the findings: The cardinal sang its first song four weeks earlier, and the sentinel of spring, the robin, arrived three weeks earlier.
How would Leopold, who wrote so movingly about the relationship between man and nature, react to the changing landscape?
"I think it would be extremely distressing to him," his daughter said.
A global trend
The Leopolds' research was one of 866 peer-reviewed studies analyzed by Camille Parmesan of the University of Texas in 2006.
Parmesan concluded that spring was advancing around the globe and that some plants and wildlife were moving northward or to higher elevations, presumably in search of cooler conditions.
"These are adaptations that humans can make, but nature can't always do that," said Schneider, the Stanford climatologist.
Indeed, scientists are worried that warming is causing mismatches in the ecosystem - when a change in temperature alters the traditional pattern of one species and harms another that depends on it.
"The $64 question," said UW's Waller, is whether this is happening yet in Wisconsin.
Near the Leopold cabin, the fly-catching eastern phoebe has started to return home sooner in spring, apparently to catch up with the skunk cabbage, which it depends on. The plant now blooms about two weeks earlier than during Leopold's day.
"We are seeing life becoming uncoupled, and what we are talking about next is life unraveling," Waller said.
Schneider told an audience in Madison last fall that policy-makers have responded to global warming faster where the signs are more visible.
It's why California, under Republican Gov. Arnold Schwarzenegger, passed a law in September to cut carbon dioxide emissions by 25% by 2020, effectively rolling back emissions to 1990 levels.
In California, "water really matters," Schneider said.
Californians are worried that higher temperatures will melt mountain snow too early, when water isn't needed, and leave reservoirs without adequate supplies later.
Most climate models predict the Midwest will be marked by more heat waves, more rain and intense storms by the end of the century.
Models are imperfect, however, and researchers say the models need to become more accurate in making local assessments.
"It's very difficult at this point to offer specifics" on the regional effects of global warming, said Thomas Karl, director of the National Climatic Data Center in Asheville, N.C.
Still, findings so far predict longer growing seasons and greater yields. In many cases farmers will be able to adapt to the changes, according to an assessment co-sponsored by the U.S. Environmental Protection Agency and led by University of Michigan scientist Peter Sousounis.
But the 2000 study also predicted a retreat of the red pine from northern Wisconsin by the end of the century as higher temperatures spur more disease. The change could devastate the state's paper industry.
Evaporation, brought on by higher temperatures, is expected to trump the effects of more rainfall. This could harm breeding habitat for water-dependent species such as ducks. Computer models from the study predict as much as a 39% reduction in duck numbers by the 2030s.
Some fish, such as bass, will respond well to higher temperatures, but there are worries about trout.
The summer temperature of many Wisconsin trout streams is about 70 degrees.
A degree or two rise "is going to be very stressful for them," said John Lyons, a research scientist at the Wisconsin Department of Natural Resources.
As for the Great Lakes, a key finding showed water levels would fall 2.5 feet by 2030.
By 2090, Lake Michigan and Lake Huron could drop by 2 to 5 feet, the study found.
Falling lake levels could favor owners of lakefront property where beaches are too narrow.
But if Lake Michigan dropped 5 feet, ships would have to reduce loads by 23% to get into ports, said Glen Nekvasil, a spokesman for the Lake Carriers' Association in Cleveland.
"It would mean a major challenge for the shipping industry," he said. "I don't think the industry could continue."
As she keeps her eye on life along the Wisconsin River, Nina Leopold Bradley has found something for the record book.
Sandhill cranes didn't leave for Florida until Jan. 15 - an observation confirmed by the International Crane Foundation of Baraboo.
Bradley flipped through her notebook and found that the average departure date based on the Leopolds' field work is Nov. 13.
"You gradually put all of these things together, and it's kind of scary," she said.