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Dylan Millet, Tracy Twin, Peter Snyder

Tracy Twine, Peter Snyder, and Dylan Millet (left to right) are new faculty members in the Department of Soil, Water and Climate.

A welcoming climate

Three new faculty find the U a good place to study climate change

By Deane Morrison

April 25, 2008

Some of the biggest players in global climate change are living right in your own back yard. All kinds of plants both respond to and affect the climate. Yet their roles, especially those of crops, have been given short shrift in even the most widely used computer models of climate change. But that situation, too, is changing, with help from the University. In carving out a niche as a powerhouse in this field, the U has just hired three young atmospheric scientists who are already making waves. In luring Dylan Millet from Harvard and Peter Snyder and Tracy Twine from the University of Illinois, the U's Department of Soil, Water and Climate has given the new assistant professors an interdisciplinary environment where they can flourish to the benefit of both the U and the science of climate change. Their work will help Midwestern farmers anticipate and weather the shifting climactic conditions of the 21st century. "They fill a longterm need to integrate individuals studying various aspects of atmospheric science," says Ed Nater, department head. "We had major searches and pulled some fantastic hires, the best of the bunch." All three study how the atmosphere and the land surface interact to influence temperature, precipitation, and vegetation. For example, Snyder has shown how vegetation changes in remote areas can affect climate close to home. "In general, tropical deforestation on a large scale can have a big effect on amplifying warming in high latitude areas like ours," he says. Living plants work against global warming by taking up carbon dioxide and storing it in their tissues, but they can also lower air quality by emitting carbon-containing compounds. One, says Millet, is isoprene, a byproduct of photosynthesis. But in the presence of sunlight and nitrogen oxides--an ingredient of car exhaust--isoprene breaks down to form smoglike particles and ozone. "Ozone, when high up in the atmosphere, shields us, but in air near the ground it's a pollutant and a greenhouse gas," says Millet. The widespread planting of crops provide us with food and fiber, but it also alters the flow of energy, water, and carbon between land and the atmosphere. Twine studies these aspects of cropping systems and how they respond to and contribute to climate change. For example, more carbon dioxide seems to spur plant growth, but ozone, which hurts crops like soybeans, may tend to cancel that benefit, she says. Also, a warmer climate could dry out soil.

Less-than-model models

As patterns of land use and vegetation change worldwide, the need for better data becomes even more acute. But Twine has found shortcomings in models of climate change used by scientists worldwide. In climate modeling, scientists feed climate-related data into computers, which crunch the data and predict how, for example, temperature will change in response to rising carbon dioxide or scantier vegetation. Models must be accurate because many governments base climate-related policies on their predictions.

"Crops are part of the 40 percent of the Earth's land surface that's managed by humans, yet large models don't take [cropping systems] into account."

"The model I'm using is like those used by the Intergovernmental Panel on Climate Change [IPCC], except that mine models crops," she explains. "Crops are part of the 40 percent of the Earth's land surface that's managed by humans, yet large models don't take [cropping systems] into account. Progress is being made, however, and I hope my work contributes to it." Millet also finds certain climate change models lacking. Recently, he has used satellite data to test models of isoprene emissions based on ground-level measurements. "We found those models overpredict emissions for some trees and underpredict for others," he says. "For example, satellites showed that oak trees are the strongest emitters of isoprene, but not as strong as we thought." This kind of information may influence people in their choices of which trees to plant or how to fight ozone pollution, Millet says.

What happens in the Arctic doesn't stay in the Arctic

Warming of the Arctic is also a prime concern. "Some studies say a warmer Arctic is a source of carbon dioxide, and some say it's a sink," says Snyder. "Lusher vegetation will store carbon, but an immense amount of carbon dioxide is locked up in permafrost and may be released by thawing. We have a project to look at land cover changes induced by rapid warming and their effects. It's crucial to properly represent Arctic land-atmosphere interactions in climate models used in IPCC reports. "Also, there's a big concern because biofuel crops need ample water." Snyder studies how large-scale planting of biofuel crops may affect precipitation and other aspects of water cycling near and far. "For example, corn growing in Iowa really shot up after World War II, and areas in southwestern Wisconsin, northeastern Iowa and southern Minnesota have seen a more humid environment," he says. "We can relate that partially to corn because it [gives off] more water than the native grasses it replaced [and the water vapor blows into other regions]." Twine is examining the effects of converting Minnesota's trees, grasses, corn, soybeans, and wheat to biofuel crops like switchgrass and a giant grass called Miscanthus. "Miscanthus sucks up a lot of water," she says. "With our model, we can simulate growing Miscanthus over the whole state and ask what would happen to carbon and water, and where the best places to grow these biofuel crops are." Studies like these please University meteorologist Mark Seeley, a professor of soil, water and climate. "A pet peeve of mine is that the area we understand least is atmospheric water vapor," he says. "But with this lineup of scientists, we should better understand the feedback loop between landscape and water vapor, including the vapor that migrates here. Minnesota might contribute to the global community by clearing this up."