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Modeling with impact

Winter/Spring 2013

A close-up view of climate change

Climate models, one could argue, speak in generalities. These powerful computer simulations support confident assertions about future global trends, but their resolution is too coarse to allow detailed projections at the local level. To a global climate model, most of Wisconsin looks the same.

View the full Center
for Climatic Research
series:

  1. Scientific (r)evolution
  2. Climate archivists
  3. Carbon capacity
  4. Modeling with impact

Scientists at the Nelson Institute Center for Climatic Research (CCR) have solved that problem. They’ve developed a technique that can bring the output from global models into sharp focus.

“We’re producing climate information that is both state of the art in climate science and useful to people who are trying to understand climate impacts on various systems,” says Dan Vimont, an associate professor of atmospheric and oceanic sciences and Nelson Institute faculty affiliate. Vimont and CCR scientists Michael Notaro and David Lorenz developed an innovative statistical technique to “downscale” global models, producing high-resolution climate projections on an eight-kilometer grid.

They initially produced the downscaled data for the Wisconsin Initiative on Climate Change Impacts (WICCI), a statewide project co-founded by the Nelson Institute and the Department of Natural Resources.

Projected Change in the Frequency of 90°F Days Per Year from 1980 to 2055 in Wisconsin
CCR researchers initially produced
downscaled data for the Wisconsin
Initiative on Climate Change Impacts.

Vimont says these localized projections allow biologists to evaluate the potential effects of climate change and variability on the state’s ecosystems, and the DNR is incorporating them into its management plans.

Other users include public health officials, educators and water managers like the Milwaukee Metropolitan Sewerage District.

The CCR group has applied its downscaling technique to most of the lower 48 states, and the client list for its services has grown well beyond Wisconsin’s borders. The U.S. Department of the Interior is using the data to support resource management decisions across much of the northern tier of the country, and the National Park Service has commissioned CCR to provide high-resolution temperature and precipitation projections for all of the national parks.

The downscaling process is complex, but in simple terms, it ties local weather on any particular day to large-scale climatic processes happening at the same time – “phenomena we may not recognize in our everyday lives,” says Vimont.

-Steve Pomplun

Canary in a cold spell

During hot summer months when drought creeps in, grasses turn brown and lake levels fall. Less noticeable, though equally important, is the impact on native bird populations. During extreme weather events such as droughts, cold snaps or heat waves, local bird populations often diminish.

According to Steve Vavrus, a senior scientist at the Center for Climatic Research, extreme weather events can affect birds in a number of different ways, often causing death, reduced reproduction or migration.

Vavrus and a team of UW-Madison scientists are studying this phenomenon to learn why die-offs occur and where the surviving bird populations “ride out the storm,” he says.

One likely possibility is migration to national forests or wildlife preserves. If threatened birds use certain habitats as a buffer when things get tough at home, these areas will be an especially important conservation priority – particularly as more extreme weather events are fostered by climate change, Vavrus explains.

The findings are expected to help scientists and land managers better coordinate to protect birds and improve wildlife management strategies.

The impacts of extreme weather are increasingly more visible, but these events are not always explicitly tied to climate change. Vavrus hopes this research will help bridge extreme weather impacts and climate models.

“Climate models tell us that we are going to have a very different climate in the future, but they can’t tell us directly what kind of impacts that will cause,” Vavrus says. 

-Amanda Lucas

Mixed signals

New research shows that planting a tree may not help mitigate the effects of climate change after all. As it turns out, planting vegetation where none previously existed could have the opposite effect, at least in some scenarios.

sunshine in a forest

Creating forest in a naturally bare region, a process known as afforestation, has been suggested as a potential method to mitigate climate change. Trees and other vegetation take up excess carbon dioxide from the Earth’s atmosphere, reducing the concentration of greenhouse gases and slowing atmospheric warming.

But afforestation efforts must be developed carefully, according to a model developed by the Center for Climatic Research’s Guangshan Chen, Michael Notaro and Zhengyu Liu. Their research simulated the effects of a planned federal project to afforest nearly 18 million acres in the Southeast and Midwest by 2020.

Through climate model simulations, the team discovered that afforestation sometimes backfires due to uncertain feedback loops between vegetation and climate.

Over the short term, according to their model, increased vegetation in the Southeast led to a lower surface air temperature and increased total precipitation – the ideal outcome of climate change mitigation.

In the long-term, however, the researchers found the opposite: surface air temperatures in areas adjacent to the proposed afforestation increased, while precipitation decreased. These remote effects may have severe impacts for both ecology and the economy.

-Amanda Lucas



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