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Don Baker

Donald Baker has made his mark on climatology, including a long-term record of soil temperatures and finding the windiest spots in Minnesota.

Digging deeper pays off

Donald Baker's 43-year experiment to take the Earth's temperature is just one of his contributions to his field and to the state

By Deane Morrison

March 10, 2006

In science as in other walks of life, a little dash of competitive spirit can yield surprising dividends. Back in 1963, Donald Baker decided to take the temperature of soil at various depths. A University professor interested in the agricultural impacts of climate, Baker wanted to know the soil temperatures at various rooting depths. He also knew that a fellow over at Argonne National Laboratory in Illinois was already measuring temperatures as deep as 25 feet below the surface. "So I thought, let's go him one better and go beyond the depth of the annual heat wave," says Baker, now a retired climatology professor in the department of soil, water and climate (SWC) in the College of Agricultural, Food and Environmental Sciences. It took all the equipment and skills of a professional well driller, but Baker got what he wanted: a hole 42 feet deep, dug in the midst of agricultural test plots on the St. Paul campus. He quickly installed sensors at 10.5, 21, and 42 feet and replaced the soil and gravel from the hole. Since that day, Baker has amassed both a unique long-term record of soil temperatures and one of the world's most solid pieces of evidence that global temperatures are rising. In his experiment, soil temperatures have been rising slowly and at nearly identical rates at every depth. After the first 37 years, the warming amounted to 3.6 degrees F. In a paper published in 2002, Baker and colleague John M. Baker (no relation) reported their data and warned that such a rise in temperature "does not need to be carried too far forward to generate biologically important warming."

"This study shows the importance of long-term research. There are few studies anywhere that have this kind of long-term measure of an environmental variable."

It wasn't what Donald Baker had been expecting. He had not been a believer in global warming, nor in global cooling, for that matter; the issue was clouded by too little hard data and too much sales talk by proponents of certain theories. Some climatologists, for example, were proclaiming the imminent arrival of a cold period. "They convinced the CIA that cooling could be bad for crops and, therefore, for political stability," says Baker. "News people, including Time magazine, had people believing we were facing the coming of a new ice age. I got tired of people accepting everything they read." It's hard to pick out warming or cooling trends from data taken at the land's surface, which is subject to dramatic daily and seasonal temperature swings. But subsurface soil is buffered by its sheer mass and insulating quality; therefore, the deeper the soil, the less it is affected by short-term phenomena and the more closely it mirrors long-term changes. This gives Baker confidence that his experiment is a reliable indicator of global change. Still, being a scientist to the core, he keeps an open mind about global warming, remembering how people who predicted cooling "made such a big thing of it." The experiment stands as a landmark in climate research, says Ed Nater, current SWC head. "It clearly demonstrates significant climate warming in this region," says Nater. "... this research method is independent of other research methods used to assess global warming. That's important when one is trying to measure a property as complex and variable as the earth's 'temperature.' The more independent studies that come to the same conclusion, the more credibility it has, much like independent sources in journalism. "This study shows the importance of long-term research. There are few studies anywhere that have this kind of long-term measure of an environmental variable. The longer the observed trend, the more likely it represents a general trend in the data and not just a short term reversal or anomaly." Warming soils could have several effects down the road. John Baker, now research leader for the Agricultural Research Service's Soil and Water Management unit in the SWC, says warmer-and thus drier-conditions may lead annual crops like corn to send roots deeper in search of moisture. Deeper roots could improve the plants' drought tolerance. Warmer soils may also protect some pipes from freezing in winter. But warmth could also stimulate soil microorganisms to speed up their respiration, a term biochemists use to mean the burning of food for energy. "To the extent that soil warming increases microbial respiration, it would mean more carbon dioxide given off," says John Baker. Also, Mark Seeley, a climatologist and professor in SWC, says warmer soils may speed up the production of nitrates by bacteria. Nitrate can evaporate and form nitric acid, a constituent of acid rain, or leach into water supplies. Current warming trends have been linked to fossil fuel burning, and Baker has made his mark in efforts to reduce their use. His studies of wind strength around the state as part of the Wind Resources Assessment program identified Buffalo Ridge, Minnesota, as a prime site for wind turbines. The wind farm there, along with a wind turbine-based alternative energy project in Morris, Minn., are direct offshoots of Baker's work, according to Seeley. Baker retired in 1984, but he has continued to work and publish scientific papers. Besides his scientific work, he established the graduate program in climatology, a joint program of SWC and the geography department in the College of Liberal Arts. He also turned the site of the temperature experiment into a weather station that for many years measured more weather items than any other station between Chicago and Los Angeles. And last but not least, he did it all while maintaining a sterling reputation among his colleagues. "He's a guy I've looked up to ever since I got here," says Seeley. "He's the godfather of climatology. In the '80s and '90s, he was known as Dr. Baker, even to senior colleagues, and as 'the Don.'" Baker credits his success largely to the support and freedom he received from people like William P. Martin, his longtime department head; William E. Larson, Martin's successor; and administrator William Hueg, who helped him obtain the plot of land for the temperature experiment and weather station. The weather station, which helped shape the state's responses to droughts and floods, has always been an object of curiosity to young people. "If I saw kids there on bikes, I'd speak to them and show them around," recalls Baker. But in the wake of vandalism, the station is now surrounded by a chain-link fence that alters the flow of wind and the pattern of snowfall around the station, much to Baker's regret. One concern he has is for the increasing amount of rainfall in the region since 1950. In the Twin Cities, the annual average has risen from 27.5 inches in 1950 to 34.7 inches in 2000-what Baker calls "an amazing rise." It is worrisome, he says, because precipitation patterns could revert, leaving urban populations in the lurch. And warming only makes things worse. "The higher temperature implies that water will evaporate and crops will require the extra moisture," he explains. "The timing is extremely important. Even if precipitation is low, if the timing is right, crops do all right. "But as a result of the pavement and sewers we've put in cities, water will be removed much more quickly." With less water in the air and soil to absorb solar heat, plants will have a hard time of it and temperatures of air and earth will rise more than if the climate were moist. Last year the University gave Baker an Outstanding Achievement Award, its highest award to alumni. The honor crowned a career that began formally when he received bachelor's, master's, and doctoral degrees from the University and has yet to end. Baker says he greatly appreciates the award, which he categorizes as "a wonderful surprise." But, says Baker with typical modesty, "I felt it was undeserved." His colleagues and friends beg to differ.

To read about recent University research that uncovered another piece of evidence for global warming, click here.