Pennsylvania will get hotter. Precipitation will increase with fewer but more violent storms and less snow cover. Expect adverse impacts on cool-weather crops, air quality, certain tree and wildlife species, including the state bird and fish.
And there will be a human impact, especially for those whose health is affected by heat or people who enjoy skiing, snowmobiling and ice fishing.
By midcentury, the number of days exceeding 90 degrees Fahrenheit will rise from an annual total of 10 to 40. The number of 100-plus degree days could jump from two to 24 in coming decades.
Those are some of the findings of the 2008 report, "Climate Change Impacts and Solutions for Pennsylvania," compiled by the Union of Concerned Scientists, with general agreement from the 2009 Pennsylvania Climate Impacts Assessment that Penn State University prepared for the state Department of Environmental Protection.
"Overall the reports are very complementary," said James Shortle, director of the Environmental and Natural Resources Institute in Penn State's Department of Agriculture.
The impact on Pennsylvania agriculture is difficult to gauge. Although there will be a longer growing season, the benefits could be offset by too much heat.
"The conclusion in our [PACIA] report is that warming to a certain level will have benefits for some [agricultural] commodities and costs. But if we get beyond 3 degrees [Celsius], it's hard to identify any beneficial impacts," said Mr. Shortle.
Temperature has been projected to rise by 1 degree Celsius if greenhouse-gas emissions are reduced significantly, but up to 6 degrees Celsius if they continue unabated, or a range of 2 to 11 degrees Fahrenheit.
Pennsylvania scientists and economists have joined more than 1,700 other Ph.Ds in calling for reductions in heat-trapping emissions that cause global warming, the 2008 UCS report states.
"The scientists warn policy-makers of the growing risks of climate change, including sea-level rise, heat waves, droughts, floods, disease and species extinctions," the report states, noting that quick action could limit the cost to 1 to 2 percent of Gross Domestic Product but costs could burgeon to 10 to 20 percent of GDP if greenhouse gas emissions are allowed to continue unabated.
Pennsylvania, at a minimum, will develop a climate similar to current-day southern Virginia, with a worst-case scenario of a climate similar to current-day Alabama, the report states.
With rising heat, growing seasons will lengthen. But that advantage soon would give way to lower yields for apples, sweet corn and Concord grapes, along with reduced dairy production. Air pollution, pollen and insect problems will worsen. Skiing and snowmobiling will be bygone activities with significant reductions in snow accumulation. Even snow-making at resorts would become impossible, according to the report.
Sugar maple, black cherry and American beech trees will diminish, even disappear, from Pennsylvania forests, the report states, although the PACIA says state forests could benefit as well.
"Warming climate and shifting distributions and quality of forest habitat is expected to cause substantial changes in bird life," the UCS report says. "Species at greatest risk include the ruffed grouse, white-throated sparrow, magnolia warbler and yellow-rumped warbler."
Population of the ruffed grouse, the state bird, is declining in its southern range from the Georgia mountains to Pennsylvania. While habitat management is cited as the reason, studies suggest that as one impact of climate change.
Decline in the American beech tree will affect the ruffed grouse, whose favorite food is beechnuts. Ruffed grouse experts say better management of bird habitats is needed for the species to survive in the state.
"We are aware of the [climate change] problem that's a contributing factor, but the exact factor is hard to differentiate," said Linda Ordiway, a Ruffed Grouse Society biologist for the Mid-Atlantic and Southern Appalachian region. "We're not ignoring it, but the impact is hard to pinpoint. We can manage habitat, but how do you manage climate change?"
The state fish, the brook trout, also could be a victim of climate-change impact in Pennsylvania.
"As global warming drives up air temperatures and changes precipitation patterns, altered seasonal stream flows, higher water temperatures and diminished shade along stream banks may follow," the UCS report states. "The native brook trout and smallmouth bass are particularly sensitive to such changes."
The UCS says climate change also will affect the state's "economy, character and quality of life."
Air quality, as a result of heat, will deteriorate substantially, with exacerbation of allergies, asthma and other respiratory diseases.
"Pennsylvania's climate has already begun changing in noticeable ways," the report states. "Over the past 100 years, annual average temperatures had increased by a half degree with annual average rainfall increasing in all regions but the central southern area of the state."
Winters have warmed the most, with expectations that the usual 30 days of snow each winter will drop by half. Precipitation is expected to rise by at least 5 percent, with PACIA predicting fewer but more violent storms. The decrease in snow cover statewide will continue accelerating.
"Each of these changes is consistent with the effects expected from human-caused climate change," the UCS report says. "As the state continues to warm, even more extensive climate-related changes are projected, with the potential to transform aspects of Pennsylvania as we know it."
If Pennsylvania and the rest of the world take action and reduce greenhouse-gas emissions dramatically, some of the impacts could be avoided, the UCS said. "However, as many of the impacts are now unavoidable, some adaptation will be essential."
David Templeton: email@example.com or 412-263-1578. First Published April 22, 2012 6:30 AM