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(CBS News) On Tuesday, for the first time, government scientists are saying recent extreme weather events are likely connected to man-made climate change. It's the conclusion of a report by the National Oceanic and Atmospheric Administration.

The report says last year's record drought in Texas was made "roughly 20 times more likely" because of man made climate change, specifically meaning warming that comes from greenhouse gasses like carbon dioxide. The study, requested by NOAA, looked at 50 years of weather data in Texas and concluded that man-made warming had to be a factor in the drought.

The head of NOAA's climate office, Tom Karl, said: "What we're seeing, not only in Texas but in other phenomena in other parts of the world, where we can't explain these events by natural variability alone. They're just too rare, too uncommon."

Aside from the Texas drought, NOAA called the entire year of 2011 the year of extreme weather events, starting in Joplin, Missouri.

All told, there were seven tornado outbreaks in America last year that caused a billion dollars or more in damages. There were increased hurricanes in the North Atlantic, unprecedented flooding in Australia but widespread drought in East Africa, and all of that was caused by La Nina. Typically La Nina is marked by a sharp cooling in the Pacific, but last year's La Nina was the warmest ever, and again the government concluded that global climate change played a role.

"What's happening is, these normal fluctuations between El Nino and La Nina events that lead to some of the extreme conditions, become more extreme, more intense than they otherwise might have been because we've got increased greenhouse gases in the atmosphere leading to a warmer planet," Karl said.

NOAA made a point of saying in their study that the climate change they've identified is man-made.

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