NOAA Makes It Official: 2011 Among Most Extreme Weather Years in History

Just past the halfway point, 2011 has already seen eight weather-related disasters in the U.S. that caused more than $1 billion in damages
By Lauren Morello and ClimateWire | June 17, 2011 | 1

The devastating string of tornadoes, droughts, wildfires and floods that hit the United States this spring marks 2011 as one of the most extreme years on record, according to a new federal analysis.

Just shy of the halfway mark, 2011 has seen eight $1-billion-plus disasters, with total damages from wild weather at more than $32 billion, according to the National Oceanic and Atmospheric Administration. Agency officials said that total could grow significantly, since they expect this year's North Atlantic hurricane season, which began June 1, will be an active one.

Overall, NOAA experts said extreme weather events have grown more frequent in the United States since 1980. Part of that shift is due to climate change, said Tom Karl, director of the agency's National Climatic Data Center.

"Extremes of precipitation are generally increasing because the planet is actually warming and more water is evaporating from the oceans," he said. "This extra water vapor in the atmosphere then enables rain and snow events to become more extensive and intense than they might otherwise be."

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http://www.scientificamerican.com/article.cfm?id=noaa-makes-2011-most-extreme-weather-year

They seemed to be saying that, "I don't know" was a more appropriate answer.