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Models Show Regional-Scale Impacts of Climate Change
Released: 10/22/1997

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Heidi Koehler 1-click interview
Phone: 303-236-5900 x302 | FAX: 303-236-5882

How can climate change modify the appearance of society and the environment?

A team of scientists, led by Robert S. Thompson of the U.S. Geological Survey, will present the potential regional-scale impacts of future climate change at GSA on Wednesday, October 22 at 10:30 a.m. in Room 151. These findings are based on a combination of global and regional climate models linked to other models that estimate the effects of climate change on vegetation and water resources.

Thompson and his colleagues have employed the results of a National Center for Atmospheric Research (NCAR) global future climate simulation to initialize a regional model with 60 km resolution. The latter model provides a more realistic view of the topography and regional-scale climatic processes than the global model. Output from the regional model was interpreted by models of hydrologic and vegetation change to simulate how the landscape and environment would be impacted on a 15km resolution under this "greenhouse" climate simulation. The simulated climate is warmer than today across the western United States, with the degree of warming varying across the region and with the seasons.

"Under the simulated climate the northern Great Plains is 5° C warmer than today in the winter, but only 3° warmer in the summer," said Thompson. "In contrast, the desert Southwest is modeled to be less than 2° C warmer than today in the winter, but as much as 5°C warmer in the summer. Rainfall patterns vary even more on a regional basis, with the southern part of the region becoming generally drier than today, and the northern part wetter."

Global climate has varied greatly since the height of the last Ice Age 21,000 years ago. If current projections from numerical climate models are correct, then the Earth’s climate may undergo similarly large changes in the next few centuries due to human-caused changes in the chemistry of the atmosphere, the so-called greenhouse effect. Most current climate models operate on a very coarse geographic and topographic scale, making it difficult to judge how the modeled future changes may impact society and the environment on a regional scale. This is especially true for temperate mountainous regions such as the western United States. The hierarchy of models employed by Thompson and his colleagues provides one means of exploring the potential impacts of climate change in such regions.

Lakes and streams of the western United States would be strongly affected by the simulated regional changes in climate. As a result, the life cycles of many native fish species would be disrupted, and spawning might not be possible for some species. The potential ranges of plant species would also greatly change under the "greenhouse" climate scenario, and many important forest trees such as Douglas fir and Engelmann spruce could lose much of their modern geographic ranges. Other plants, such as the warmth and dry-loving Joshua Tree, could greatly expand their ranges under this scenario. However, not all possible future climates would necessarily have such strong environmental impacts. This strategy provides a means of assessing the impacts of a range of possible climatic changes on national lands and resources and may serve to identify processes and regions that are most vulnerable to these changes.

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