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The United States has had “some quiet years while the rest of the world was quite wild,” but that’s not the case this year, Arndt said. Insurance giant Munich Re in a report this fall concluded: “Nowhere in the world is the rising number of annual natural catastrophes more evident than in North America.”

In 2011, the United States set a record with 14 billion-dollar weather disasters. The National Oceanic and Atmospheric Administration has a preliminary count of 11 such disasters this year. And NOAA’s official climate extreme index, which tallies disasters and rare events like super-hot days, is on pace to set its own record.

Arndt points to the geographic heart of America, the Mississippi River, as emblematic.

On May 6, 2011, the Mississippi River at New Madrid, Mo., crested at its highest point on record. Less than 16 months later on Aug. 30, 2012, the same spot on the river was more than 53 feet lower, hitting an all-time low water mark.

The U.S. went through the same lurching extremes on tornadoes. Those storms killed 553 people last year, Furgione said. This year began with many tornadoes, then in April they just stopped. April to November, normal tornado season, saw the fewest F1 or stronger tornadoes in the U.S. ever.

“Every year is bringing different types of extreme weather and climate events,” NOAA chief Jane Lubchenco said. “All storms today are happening in a climate-altered world.”

Not everything is connected to man-made global warming, climate scientists say. Some, like tornadoes, have no scientifically discernible connection. Others, like the East Coast superstorm, will be studied to see if climate change is a cause, although scientists say rising sea levels clearly worsened flooding. They are more convinced that the heat waves of last summer are connected to global warming.

These are “clearly not freak events,” but “systemic changes,” said climate scientist Stefan Rahmstorf of the Potsdam Institute in Germany. “With all the extremes that, really, every year in the last 10 years have struck different parts of the globe, more and more people absolutely realize that climate change is here and already hitting us.”

In 1988, NASA scientist James Hansen, sometimes called the godfather of global warming science, ran computer models that predicted the decade of the 2010s would see many more 95-degree or hotter days and much fewer subfreezing days. This year made Hansen’s predictions seemed like underestimates. For example, he predicted that in the 2010s Memphis would have on average 26 days of more than 95 degrees. This year there were 47.

Scientists _ both those studying global warming and those studying hurricanes _ have warned for more than a decade about a hurricane with big storm surge hitting New York City and flooding the subways. That happened with Sandy. Though it was never a major hurricane, it stretched across nearly 1,000 miles in the U.S., bringing storm surges, power outages to millions and even snow. Sandy killed more than 125 people in the United States and at least 70 in the Caribbean.

For decades, scientists have predicted extensive droughts from global warming. This year, the drought of 2012 was so extensive that nearly 2,300 counties _ in almost every state _ were declared agriculture disasters. At one point this summer more than 65 percent of the Lower 48 was suffering from drought.

And with lack of water, came fire, something also mentioned as more likely in scientific reports about global warming. Fire season in the United States came earlier than normal and lasted longer, officials said. Nearly 9.2 million acres _ an area bigger than the state of Maryland _ have been burned by wildfire, the third most since accurate recordkeeping began in 1960.

“Take any one of these events in isolation, it might be possible to yell `fluke!’ Take them collectively, it provides confirmation of precisely what climate scientists predicted would happen decades ago if we proceeded with business-as-usual fossil fuel burning, as we have,” Pennsylvania State University climate scientist Michael Mann said in an email. “And this year especially is a cautionary tale. What we view today as unprecedented extreme weather will become the new normal in a matter of decades if we proceed with business-as-usual.”

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Seth Borenstein can be followed at http://twitter.com/borenbears