New England’s ski industry could be threatened by warm winters decades from now. Regional milk production will probably decline and lobster populations will shift toward the north, looking for cooler water.

Those are some of the predictions for the Northeast in a sweeping new national report on climate change released Tuesday afternoon by top scientists and agencies in the Obama administration.

The report, “Global Climate Change Impacts in the United States,” was released in Washington by the interagency Global Climate Research Program. Key authors include Jane Lubchenko, the new administrator of the National Oceanic and Atmospheric Administration, and Jerry Melillo, director of the Ecosystems Center at the Marine Biological Laboratory in Woods Hole, Mass.

The report comes as Congress struggles over legislation designed to reduce emissions of greenhouse gases that cause climate change, with some legislators denying climate change is a problem.

It is based on research generated during Republican and Democratic administrations and was produced by experts from 13 government agencies and several major universities. At 190 pages, it reaches sweeping conclusions and focuses on different projections for different parts of the country.

And unlike many positions taken during the Bush administration, it pulls no punches on what scientists believe is happening with the climate, and why.

“Observations show that warming of the climate is unequivocal,” says the report’s summary. The warming “is due primarily to human-induced emissions of heat trapping gases.”

Most of the emissions come from the burning of coal, gas and oil, the report says, and important contributions come from the clearing of forests, agricultural practices and other activities.

Focusing on New England, the report says that if warming continues throughout this century, people in New Hampshire will experience summers similar to what occurs today in North Carolina.

Change has already happened in the Northeast, the report says.

Since 1970, the annual average temperature in the Northeast has increased by 2 degrees Fahrenheit, the report says, and winter temperatures have risen twice as much. Average temperatures are expected to increase several more degrees in the next few decades.

Already in the Northeast, the report says, there is less snow in the winter and more rain, precipitation is heavier, there are more days with temperatures above 90 degrees and a longer growing season, rising sea surface temperatures and earlier breakups of ice on lakes and rivers.

If trends continue, the report predicts the length of the winter snow seasons in northern New England will be cut in half, 100-degree days in the summer could become common, and droughts would occur frequently throughout the region. Rising sea levels could double the occurrences of coastal flooding.

The report was welcomed by many who have been fighting over climate change policies.

“This is exactly the comprehensive scientific assessment America needs to effectively respond to climate change,” said Kevin Knobloch, president of the Union of Concerned Scientists.

Adam Markham, CEO of a New England advocacy group called Clean Air–Cool Planet, said the report found even more alarming warming trends than his group outlined in its 2005 report, “Indicators of Climate Change in the Northeast.”

To see the report on the Web, go to www.globalchange.gov

plord@projo.com