Isle Royale in Lake Superior used to be too cold for deer ticks. But not anymore.

The ticks, which carry Lyme disease, have been found for the first time on the island off the coast of northern Minnesota. And by the end of the century, nesting loons may disappear altogether from most of the Great Lakes.

Those are some of the findings of a report on the effects of climate change on the Great Lakes' five largest national parks, made public Wednesday by two environmental groups, the Natural Resources Defense Council and the Rocky Mountain Climate Organization.

It was the latest in a series of studies they have conducted on the current and future effects of a warming global climate on national parks from California to Virginia.

The report, the authors said, provides an early look at what's to come if the Republican-led Congress continues to thwart federal efforts to curb greenhouse gas emissions. Republicans this week tried and failed to repeal new standards for more energy efficient lightbulbs, and are resisting the new federal rules regulating greenhouse gas emissions expected later this summer. They say the rules are unnecessary intrusions on freedom, and job-killers.

"We have an increasing partisan divide on this," said Stephen Saunders, president of the Rocky Mountain Climate Organization and a former national parks official with the Department of the Interior. "If people pay attention to how the places they know and love respond to climate change, I hope that makes people aware of what we should be doing differently."

The authors analyzed a century's worth of temperature trends for the Great Lakes area drawn from two weather stations on Lake Michigan, and found that both show more rapid change than the global averages. The one near the Indiana Dunes National Lakeshore, near Chicago, showed that in the last decade average temperatures have increased by 1.6 degrees, and the one near Picture Rocks National Lakeshore in Michigan showed an average increase of 2.7 degrees.

Lee Frelich, a University of Minnesota researcher who studies the effects of climate change in the Upper Midwest, said the analysis used widely accepted climate models and data, and the findings are right on the mark.

"Climate changes are more extreme in the mid continents," said Frelich, who was not involved in the report. "If you are fairly far north you will see bigger magnitudes of climate change than other places."

Water temperatures in Lake Superior have increased 4.5 degrees between 1979 and 2006, twice the rate of land temperatures, the report found. Between the 1970s and 2009, winter ice cover over the lakes shrunk 15 percent.

The report also documented a 31 percent increase in rain falling during big storms, and a 12 percent increase in wind speeds. Combined with less ice during the winter, those changes lead to faster erosion along the shores, putting fragile landscapes like the Sleeping Bear Sand Dunes in Michigan at risk. Frelich said that he's already seen the effect on his family's cabin in Door County, Wis., where winter storms have taken out trees on the edge of his property.

The report found that temperature changes are having a sometimes dramatic effect on wildlife. A growing number of botulism outbreaks, linked to higher water temperatures, have killed hundreds to thousands of birds in recent years in the Sleeping Bear Sand Dunes. Meanwhile, Isle Royale used to be free of deer ticks, which can only survive in average winter temperatures of 19 degrees or higher. But a park service employee this year reported finding a deer tick on his body after he'd been there for a month, meaning he had picked it up while on the island.

The report projects that average temperatures at Isle Royale and the Apostle Islands would increase by an average of 3.6 and 4.6 degrees by 2040 to 2069, depending on the rate of future air emissions -- warm enough to squeeze nesting loons into the northwest corner of Lake Superior.

Mark Seeley, Minnesota state climatologist, said it's difficult to make projections about Lake Superior using data from two weather stations in Lake Michigan. But he said the report accurately documented the extreme upward shift in minimum temperatures in the winter. "The winter season is showing more dramatic increase in temperatures than summer," he said.

The authors said that the five parks in the study draw 3.7 million visitors per year, generate $200 million in spending and support close to 3,000 jobs. "We face the financial reality that climate change may bring tremendous economic challenge," said Larry McDonald, the mayor of Bayfield, Wis., a tourist town on the edge of the Apostle Islands. He joined the authors of the report in a telephone news conference. "We need to respect and protect Lake Superior," he said.

Josephine Marcotty • 612-673-7394