Topography of mountains could complicate rates of global warming

Oregon State University: A new study concludes that the future effects of global warming could be significantly changed over very small distances by local air movements in complex or mountainous terrain - perhaps doubling or even tripling the temperature increases in some situations.

In an article to be published in the International Journal of Climatology, researchers from Oregon State University used the unique historical data provided by Oregon’s H.J. Andrews Experimental Forest to study potential variations in temperature caused by steep hills and valleys.

Based on a regional temperature increase of about 5 degrees projected for western Oregon by 2100, the study concluded that some locations, such as mountain ridge tops, could actually increase as much as 14 degrees at some times, while cold air pools in the valleys below them with temperature increases similar to the regional average.

“Even if the predictions for average temperature changes are accurate, there’s been very little work done on what that may mean in specific locations and situations,” said Chris Daly, an OSU professor of geosciences, director of OSU’s PRISM Climate Group and expert on the effects of elevation and topography on localized climatic effects.

“We are finding that there’s a potential here for tremendous disparities in local effects that we need to learn more about,” Daly said. “Some locations may get much warmer than the average while others nearby are affected less, with associated impacts on their ecology, the plant and animals species that live there.”

….Similar forces could be found in many Mediterranean climates around the world, such as in Europe, South America and parts of the western U.S., which have climates that are controlled by the seasonal movement of high pressure belts, Daly said. “There is more we need to be concerned about than overall warming, and we really haven’t given these localized issues much consideration,” he said...

This graphic indicates December daytime temperature differentials that might be expected from future global warming, in the H.J. Andrews Experimental Forest near Blue River, Ore. Weather conditions that cause ridgetops to warm and cold air to pool in valleys may become more frequent - magnifying global warming on the ridgetops but not in the valley bottoms. (Image courtesy of Oregon State University)