Penn State Live - Climate change study foresees a warmer, wetter Pennsylvania

Climate change study foresees a warmer, wetter Pennsylvania

Wednesday, July 15, 2009

James Shortle

A Penn State study of climate change projects a warmer, wetter Pennsylvania, with a longer growing season and significantly less snow by the middle of the current century.

Conducted by the Environment and Natural Resources Institute in the College of Agricultural Sciences for the state Department of Environmental Protection, the study was mandated by the Pennsylvania Climate Change Act 70 of 2008. A report titled "Pennsylvania Climate Impact Assessment" was recently released by DEP and can be found on the Web at http://www.depweb.state.pa.us, keyword: Climate Change.

The report presents climate projections for Pennsylvania at mid-century and at the end of the century, according to James Shortle, distinguished professor of agricultural and environmental economics and director of the Environment and Natural Resources Institute. "Our conclusions are based on the best available information and science about future climate," he said.

"The study uses models to reach conclusions, and our analysis is based on two scenarios for future emissions. Nobody knows how carbon emissions will change, which depends on how fast economies will grow and what global agreements and national initiatives may be instituted to control greenhouse gases, so we developed plausible scenarios based on a high-emissions scenario and a low-emissions scenario."

Because the global climate system changes very slowly, Shortle explained, reductions in greenhouse gas emissions now won't have an immediate impact on climate. "But the important message is that what we do today has important ramifications -- we just won't see the results of those changes for a long period of time," Shortle said.

Climate change over the next few decades will be driven mostly by emissions that have already occurred, according to Shortle.

"Changes in emissions now won't make much difference for the next 40 years or so. But changes now will have a large impact on the climate we experience in the second half of this century, and those decisions need to be made today."

"We can be pretty confident that Pennsylvania's climate will be warming, and although it is a little less certain, it is very likely to become wetter as well, especially in the winter," said Shortle. "However, additional precipitation will come in the form of more rain and less snow."

Climate change in Pennsylvania is likely to produce "winners and losers," Shortle said. For example, winter sports that depend on snow will be greatly diminished. Species, such as brook trout, that have long thrived in the state's cold, mountain headwater streams will suffer and disappear from some streams as warming occurs. On the other hand, warm-weather activities will be enhanced by longer seasons.

Making predictions about the impact of climate change is complex, Shortle pointed out. For example, a warmer, wetter Pennsylvania would have a longer growing season and may be more productive agriculturally, but the change in climate may limit some crops that do well in the commonwealth now and might promote the growth of pest populations and diseases not currently common in the state.

The study examined the effect of projected climate change on the following sectors: water resources, forests and wildlife, aquatic ecosystems and fisheries, agriculture, energy, human health, tourism and outdoor recreation, insurance and economic risk, and economic barriers and opportunities for Pennsylvania.

The following projections were included in the Pennsylvania Climate Impact Assessment report:

-- By the end of the century, depending on greenhouse gas emissions levels, temperatures will rise an average of 3 to 7 degrees.

-- Annual precipitation will increase in Pennsylvania, especially in winter, but it is expected to be more rain and less snow.

-- Warming will lead to growing season that is three to five weeks longer -- depending on emissions levels.

-- Precipitation events will become more extreme, with longer dry periods in between -- fewer storms but with increases in intensity.

-- Forests will change. The state will become increasingly unsuitable for many of the tree species that are now present, especially those generally associated with northern hardwood ecosystems.

-- As a consequence of warming and less snowfall, the number of days when conditions are suitable for skiing or snowmobiling in Pennsylvania is projected to greatly decrease.

-- Increased temperatures will reduce the number of stream miles that can support wild-trout populations.

-- Higher summer temperatures will result in higher ozone concentrations in cities, with negative impacts on respiratory health.

Study co-authors included David Abler, professor of agricultural, environmental and regional economics and demographics; Seth Blumsack, assistant professor of energy policy; Robert Crane, professor of geography and director of the Alliance for Earth Science, Engineering, and Development in Africa; Zachary Kaufman, graduate research assistant; Marc McDill, associate professor of forest resource management; Raymond Najjar, associate professor of meteorology; Richard Ready, associate professor of agricultural and environmental economics; Thorsten Wagener, assistant professor of civil engineering; and Denice Wardrop, associate professor of geography and assistant director of Penn State Institutes of Energy and Environment.