The Northeast is bearing the brunt of climate change in the nation, assaulted by heat waves, torrential rains, and flooding that are the result of human action, according to a federal report released Tuesday.
Over the past century, temperatures in Northeastern states have risen by 2 degrees Fahrenheit, and if heat-trapping gases increase at current rates, warming could spike as much as 10 degrees by the 2080s, prolonging bouts of extreme heat, taxing electrical systems, and disrupting ecosystems.
In the same time, the region’s precipitation has risen by more than 10 percent, and the worst storms here have brought significantly more rain and snow — a surge of more than 70 percent over the past 50 years and significantly more than other parts of the country.
As Northeast sea levels have climbed by a foot over the past century, coastal flooding has caused billions of dollars in damage and could get much worse as seas are projected to rise 1 to 4 feet by 2100, leaving much of Boston at risk of flooding.
“Heat waves, coastal flooding, and river flooding will pose a growing challenge to the region’s environmental, social, and economic systems,” the authors of the 841-page federal report wrote. “This will increase the vulnerability of the region’s residents, especially its most disadvantaged populations.”
The report provides a detailed look at how the United States is already experiencing grave impacts from increased carbon emissions. It also provides a thorough description of the coming challenges for the 64 million people living in the 12 states of the Northeast.
Congress in 1990 first ordered that scientific reports on climate change be conducted at least every four years. But this is only the third such report, because some administrations failed to comply.
“A lot has changed since the US government released their last report in 2008,” said David Wolfe, a Cornell University professor and lead author of the report’s section on the Northeast. “Many climate impacts that were once projected for the future are happening now.”
A team of more than 300 specialists guided by a 60-member federal advisory committee produced the report. It was reviewed by federal agencies and a panel of the National Academy of Sciences.
The report concluded that while climate change had once been an issue considered in the distant future, it has “moved firmly into the present.”
“Summers are longer and hotter, and extended periods of unusual heat last longer than any living American has ever experienced,” the report’s authors wrote. “Winters are generally shorter and warmer. Rain comes in heavier downpours. People are seeing changes in the length and severity of seasonal allergies, the plant varieties that thrive in their gardens, and the kinds of birds they see in any particular month in their neighborhoods.”
The report comes after decades of debate over climate change, but with few significant national policies to address it. Congress has been unable to pass broad legislation to regulate greenhouse gases, blocked by Democrats from coal-producing states and Republicans who question the science behind climate change.
President Obama has made several changes using executive authority, and the Supreme Court last week ruled that the Environmental Protection Agency could regulate emissions that cross state lines.
In an interview with NBC News on Tuesday, Obama said: “We want to emphasize to the public, this is not some distant problem of the future. This is a problem that is affecting Americans right now.”
While temperatures in the Northeast increased by almost 2 degrees between 1895 and 2011, the rise is now projected to become far more dramatic, according to the report.
If carbon emissions continue to increase, warming in the Northeast is projected to increase by 4.5 to 10 degrees by the 2080s. If emissions are reduced substantially, the warming would increase 3 to 6 degrees.
“The frequency, intensity, and duration of cold air outbreaks is expected to decrease as the century progresses,” the report says.
In the coming years, the report says, heat-related deaths are projected to increase as heat waves become prolonged and higher concentrations of ground-level ozone exacerbate asthma and other conditions, especially among the young, elderly, and infirm. The southern states of the Northeast, by midcentury, are projected to experience more than 60 additional days per year of temperatures above 90 degrees and heat-related deaths in New York could rise as much as 90 percent by the 2080s.
The changing climate has already increased the potency of plant allergens such as ragweed, the report says, and warmer winters will make Lyme disease, West Nile Virus, and additional diseases linked to ticks, mosquitoes, and other insects more pervasive.
Despite the increased precipitation, the report notes that hotter summers will speed evaporation and probably lead to more droughts. As a result, a range of crops and species are unlikely to survive and will be displaced by those that now thrive to the south.
The changing climate has also hurt coastal marshland in New England. Since the early 1800s, marshlands have faced an estimated 39 percent decline, with fewer than 20 percent of marshes left in metropolitan Boston that existed at the time of the Revolutionary War, according to the report.
“The report highlights the enormous financial impacts that climate change is going to have and it describes a lot of the adaptation mechanisms that we need to start implementing, including building sea walls to deal with rising sea levels, methods to drain floodwaters, conserving water, and shifting our crop species,” said Richard Primack, a Boston University biology professor who studies the effects of climate change on plants and animals.
Professor Raymond Bradley, director of the Climate System Research Center at the University of Massachusetts Amherst, called the report “sobering.”
He added, “The US Congress needs to follow the strong example set by Massachusetts to move the country away from a carbon-based economy toward renewable energy, efficient energy distribution systems, and energy conservation measures.”
The report urges other regions to follow the example of the Northeast, where most of the states take part in a program known as cap and trade that uses economic incentives to reduce greenhouse gases. It also notes that Massachusetts was the first state to mandate that all environmental reviews consider potential impacts of climate change.
State officials noted Governor Deval Patrick recently announced a $50 million plan to improve the state’s preparedness for climate change.
In Washington, reaction to the report was mixed.
Senator Lindsey Graham, a South Carolina Republican who has worked on climate change legislation in the past, said he doubted an approach like the Northeast’s Regional Greenhouse Gas Initiative would be viable on a national level.
“I think cap and trade as a solution to climate change is dead on arrival,” he said.
He added: “I do believe that the planet is heating up, that man-made emissions are contributing. How much, I don’t know. There ought to be ways of becoming energy independent as well as creating clean air.”
Senator Richard Blumenthal, a Connecticut Democrat, said that while he does not expect Congress to pass legislation in the near future, he hopes the report will spur action.
“I have to be hopeful,” he said. “Because the alternative is unacceptable that we would allow the greatest nation in the history of the world to continue to pollute the planet in a way that destroys it.”