The climate in the nine states _ from New Jersey and Pennsylvania up to Maine _ could become like that of the South with longer, much hotter summers and warmer winters with less snow, the report by the Union of Concerned Scientists said.
"This has enormous implications for human health. It puts a lot of stress on the energy system. It could lead to blackouts," said Katherine Hayhoe, an associate professor of geosciences at Texas Tech University and a lead author of the two-year study.
If power plant and auto emissions of carbon dioxide _ considered the main culprit in global warming _ continue unabated, average temperatures in the Northeast could rise between 6.5 degrees and 12.5 degrees by the end of the century, she said. A shift to cleaner, renewable energy sources would cut that increase in half, she said.
The study said Boston could see its number of 90-degree-plus summer days jump from one to 40 if no changes are made. New York City could have 70.
Doug Inkley, senior science adviser at the National Wildlife Federation, said the report was done by top-tier scientists and backs up his group's research showing a warmer climate in the Northeast will push out temperature-sensitive species from sugar maple and northern pine trees to songbirds and trout.
"This report is yet another wake-up call we cannot ignore," Inkley said.
The report targeted the Northeast because it is the world's seventh-largest source of emissions, behind the U.S. as a whole and five other nations, and because the region's leaders have taken steps to reduce emissions and could spur efforts elsewhere.
Mike MacCracken of The Climate Institute, a former head of the interagency group that did climate assessments under a Clinton-era research program, called the report "a high-quality job" that gives "pretty reliable indications of the amount of change."
John R. Christy, director of the Earth System Science Center at University of Alabama-Huntsville, said regional analyses he's done indicate the latest climate models can't predict well for a region, especially for rain and snow.
He said the report's recommendations _ mostly centered on replacing or upgrading buildings, cars and appliances with more energy-efficient ones _ won't have much effect on the total amount of carbon dioxide going into the atmosphere, partly because energy demand will keep growing.
Source: Union of Concerned Scientists report: http://www.ucsusa.org