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WASHINGTON – The effects of climate change driven by human activity are spreading through the United States faster than had been predicted, increasingly threatening infrastructure, water supplies, crops and shorelines, according to a review of climate science and its effects by a federal-advisory committee.

A draft of the Third National Climate Assessment delivers a bracing picture of environmental changes and natural disasters that mounting scientific evidence indicates is fostered by climate change: heavier rains in the Northeast, Midwest and Plains states that have overwhelmed storm drains and led to flooding and erosion; sea-level rise that has battered coastal communities; drought that has turned much of the West into a tinderbox.

“Climate change, once considered an issue for a distant future, has moved firmly into the present,” the report says. “Americans are noticing changes all around them. Summers are longer and hotter, and periods of extreme heat last longer than any living American has ever experienced. Winters are generally shorter and warmer.”

The draft report — more than 1,000 pages compiled by more than 300 experts during the past three years — sums up what has become increasingly apparent: The country is hotter than it used to be, rainfall is becoming both more intense and erratic, and rising seas and storm surges threaten U.S. coasts.

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It arrives days after the National Oceanic and Atmospheric Administration (NOAA) issued its annual State of the Climate Report, which noted that 2012 was the hottest year on record.

Together, the two major reports and a year of drought, wildfires, floods and freak storms have teed up for President Obama the chance to take substantial steps on climate change, environmentalists said.

The report explicitly addresses the most controversial question in climate change, saying that consumption of fossil fuels by humans is the main driver of climate change.

The report adds that the changes are already exacting an economic toll: “Infrastructure across the U.S. is being adversely affected by phenomena associated with climate change, including sea-level rise, storm surge, heavy downpours and extreme heat.”

The report details 13 airports that have runways that could be inundated by rising sea level. It mentions that thawing Alaskan ground means 50 percent less time to drill for oil.

And overall it says up to $6.1 billion in repairs need to be made to Alaskan roads, pipelines, sewer systems, buildings and airports to keep up with global warming.

Sewer systems across America may overflow more, causing damages and fouling lakes and waterways because of climate change, the report said.

With the White House working on so many economic, foreign and domestic policy fronts, it remains unclear if the president will use the scientists’ findings and the evidence to speak up more on climate.

The White House declined to comment on the climate report because it had not had a chance to review it. It also would not comment on specific on any specific efforts Obama might make to address climate change.

The National Climate Assessment report does not offer policy proposals to reduce greenhouse-gas emissions or to help specific communities adapt to climate change.

Instead, it details the risks they face.

The final assessment will be issued in early 2014, and public comment on the draft will be accepted until April 12.

Material from The Associated Press and The Washington Post is included in this report.

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