The federal government released its best prediction of the effects of climate change in the United States in the coming decades. It’s no surprise that it’s not good: more extreme weather events, more heat, drought, flooding and warmer winters.

The report comes out just days after the National Oceanic and Atmospheric Administration (NOAA) announced that 2012 was the hottest year on record.

“Climate change is already affecting the American people,” stated the draft 2013 National Climate Assessment. “Certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts. Sea level is rising, oceans are becoming more acidic, and glaciers and arctic sea ice are melting. These changes are part of the pattern of global climate change, which is primarily driven by human activity.”

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That’s a pretty strong opening statement for the 400-page report, which was put together over the past four years by 240 scientists from the U.S. Global Change Research Program with input from 13 federal agencies. Here are a few highlights:

– Human influence on the climate has already roughly doubled the probability of extreme heat events like the record-breaking summer of 2011 in Texas and Oklahoma.

– In the Southeast, coastal infrastructure, including roads, rail lines, energy infrastructure, and port facilities — including naval bases — are at risk from storm surge that is exacerbated by rising sea level. Sea level is projected to rise by another 1 to 4 feet in this century. The stakes are high, as nearly five million Americans live within 4 feet of the local high tide.

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– The past climate is no longer a sufficient indicator of the future. For example, building codes and landscaping ordinances will likely need to be updated not only for energy efficiency, but also to conserve water supplies, protect against insects that spread disease, reduce susceptibility to heat stress, and improve protection against extreme events.

– Some of these changes can be beneficial, such as longer growing seasons in many regions and a longer shipping season on the Great Lakes. But many more have already proven to be detrimental, largely because society and its infrastructure were designed for the climate of the past, not for the rapidly changing climate of the present of the future.

The full report, available here (PDF), also breaks down the effects into various regions of the United States. The Northeast corridor from Washington, DC, to Boston, for example, faces 15 additional days of 95-plus degree heat by 2041.

The report is backed by existing observations, computer models of future trends and the best science available.

“Long-term, independent records from weather stations, satellites, ocean buoys, tide gauges, and many other data sources all confirm the fact that our nation, like the rest of the world, is warming, precipitation patterns are changing, sea level is rising, and some types of extreme weather events are increasing,” the report stated. “These and other observed climatic changes are having wide-ranging impacts in every region of our country and most sectors of our economy.”

The draft report goes out for public review and comment through April 12. It’s likely that the new Congress will also get a chance to quiz the scientists behind the report – although chances for a climate change bill that would cut carbon emissions, for example, remain doubtful.

The report notes that carbon emissions in the United States have leveled as the country has shifted from an economy based primarily on coal, to one that runs more on natural gas. The biggest growth in carbon emissions comes from developing nations such as China and India.

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