Yellowstone and Grand Teton national parks, like Glacier National Park, will endure hotter summers, and less snowy winters, in the coming decades due to climate change, according to projections made by the Rocky Mountain Climate Organization.

In a 55-page report issued Tuesday, Greater Yellowstone In Peril, The Threats of Climate Disruption, the climate organization, along with the Greater Yellowstone Coalition, warned that impacts from these climatic changes will sweep across the landscape, impacting wildlife, forests, fisheries, and local economies.

Under projections RMCO built specifically for the greater Yellowstone ecosystem from federal climate data, summer temperatures in Yellowstone and Grand Teton could increase, on average, as much as 9.7 degrees Fahrenheit by the end of the century, depending on the level of future greenhouse-gas emissions.

"Nine-point-seven degrees of additional heat in the Yellowstone area would totally transform the ecosystems and the experiences for visitors coming there," said Stephen Saunders, a former deputy assistant Interior secretary over the National Park Service and U.S. Fish and Wildlife Service who now heads the climate organization. "The best comparison is that would mean future summers in Yellowstone National Park would be as hot as those of the Los Angeles metro area have been in recent years.

"Another perspective on this is that the summer temperature increases that we've already seen are just a small measure of what these projections say could be coming. If we had 9.7 degrees, as is projected with a medium-high future emissions, that would be seven-and-a-half times the increase in summer temperature that happened in the last decade. So we have just barely begun to do the things that could be done to this ecosystem if we let emissions go up at a medium-high rate."

The report, released during a national media teleconference, mirrors many of the scenarios laid out in other climate-change forecasts for national parks presented over the past year by an array of groups and organizations:

* An April 2010 a report by RMCO and the Natural Resources Defense Fund said that under current emission loads Glacier could see "wholesale changes in species composition" and that the park could see a 70-day reduction per year in terms of snowcover;

* Whitebark pine trees, a species critical for Yellowstone area grizzly bears that feast on its protein-rich nuts, are suffering so greatly from climate change that they are in need of Endangered Species Act protection, according to the U.S. Fish and Wildlife Service.

* Researchers at the University of California, Merced, predicted this past July that by mid-century a new regime of wildfire in the Rockies will change the face of Yellowstone;

* In April, an Interior Department report said climate change is leading to a sizeable decrease in stream flows in the major river basins of the Southwest, declines that could impact recreation and wildlife in national parks such as Arches, Canyonlands, Grand Canyon, and Big Bend.

In Yellowstone and Grand Teton, meanwhile, the latest report said unchecked greenhouse-gas emissions could lead to climate changes that would:

* Lead to less snow and, as a result, earlier peaks in spring runoff and less water in summer for wildlife and vegetation;

* Continued declines in Grand Teton's glaciers;

* Ongoing declines in both whitebark pine and aspen stands in the ecosystem;

* More wildfires, many of greater intensity. One model highlighted by the report predicts that fire seasons on the scale of the summer of 1988, when blazes of historic proportion swept through Yellowstone, will occur at least five times between 2011 and 2050;

* A change in forest composition, with the arrival of "Gamble oak, western larch, ponderosa pine, and western red cedar," as well as a decline in wildflowers;

* Loss of wildlife, particularly snow-dependent species such as Canada lynx and wolverine.

Along with damaging the natural resources of the region, unchecked climate change could damage local economies, the report said.

In 2010, 6.3 million people visited Yellowstone National Park and Grand Teton NP; the year before, visitors to the parks spent nearly $700 million, responsible for over 10,000 local jobs. The six national forests in 2009 drew 8.7 million visitors, who spent more than $515 million. These and other economic benefits could be at risk, though, as a changing climate threatens the special resources that draw both vacationers and residents to the region.

 All that said, significant inroads into reducing greenhouse-gas emissions in the years to come could prevent some of the most dire effects from taking hold, according to Mr. Saunders.

"There are many things we can do to hold down emissions, and holding down emissions will reduce the extent of the climate change," he said. "Even the much more modest change that has already occurred has been enough to begin transforming ecosystems. Forests are dying, whitebark pine has been found to be eligible for protection under the Endangered Species Act, that is in very large part because of the hotter temperatures that have already happened.

"Wildfire acreage burned has gone up in the ecosystem. We've had restrictions on fishing for trout. All these restrictions are likely to get worse, and the more we let emissions go up the worse they are likely to be," continued Mr. Saunders. "Threads are already being pulled out of the glorious tapestry that is greater Yellowstone, and some of the luster is coming off already. It is up to us to preserve this marvelous, special, magical place for future generations."

At the Greater Yellowstone Coalition, Scott Christensen, the organization's climate change program director, said there are ways to reduce the effects of climate change on the landscape and its resources. One way, he said, is to reduce existing stressors to habitat and species, such as water pollution that impact fisheries and the heavy pressure Wyoming's elk winter feeding grounds place on the landscape and the animals themselves.

Protecting water quality and quantity can have beneficial effects on native species such as Yellowstone's four native cutthroat trout subspecies, Mr. Christensen added. Critical winter range and migration routes for wildlife also should be secured and protected, he said.

"Managing collaboratively at an ecosystem level is likely to be very important in the future," he added. "This is a very large and complex landscape, with many different landowners and jurisdictions. And to the extent that we can get together and manage the landscape in a way that works for wildlife, so that they're able to move across the landscape, access their important seasonal ranges, both summer and winter range, and deal with shifting conditions will be a very important tactic in approaching the issue of climate change."

Of course, paying for many of these strategies will not be easy under current funding outlooks. With that in mind, Mr. Saunders suggested that the National Park Service be allowed to divert some of its entrance fees to climate change mitigations.

"One of the things that my organization has advocated, and I have testified before the Congress, is that we let the land-management agencies begin to use some of their entrance fees and recreation fees for dealing with climate change," he said. "What we used to call the fee demonstration program was created to give parks and forests the flexibility to use that money locally to deal with backlog of maintenance issues. Which we used to call the greatest threat to ever to face the national parks.

"Now, we have said, and the National Park Service now says, that climate change is the geratest threat ever to the national parks. We think they should have the flexibility to begin using some of that money so they can reduce emissions within parks, tell the story of what they're doing and why to visitors, which can be enormously important."

The Interior Department, however, already has outlined a program to address climate change on public lands. One aspect of that plan was to create regional "climate science centers" "to provide climate change impact data and analysis geared to the needs of fish and wildlife managers as they develop adaptation strategies in response to climate change."