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Global Warming = Early Spring?

In the nation's capital, people are contemplating 80 degree winter days. More than a dozen big cities in the east set record highs this winter. For the season, every state in the country is now warmer than normal. And that's not all.

The last three winters are the three warmest on record. The December, January, and February which just passed were the warmest ever in the United States.

CBS News Correspondent Jim Axelrod reports scientists are pointing fingers at the La Nina effect and an overall rise in global temperatures due to global warming.

Residents of some of the areas that baked Thursday have also seen their share of snow this winter

For that, scientists blame La Nina, the unpredictable pacific weather maker that creates ice breaking just north of New York City one week and ice skating in a T-shirt the next.

"A La Nina type will give you both extremes," said National Oceanic and Atmospheric Administration head James Baker. "Both the very cold times and the very warm but it will give you more warm than cold. And so when you average you get the warm."

But while the shorts-and-frisbee weather is a nice break from winter's doldrums, the high temperatures may signal larger, more dangerous changes in the earth's climate

Alden Meyer of the Union of Concerned Scientists told CBS Newsit's more than just La Nina. In the climbing temperatures, he sees damage done by factory and automobile emissions.

"I think it's one of the most fundamental challenges that faces us in the 21st century," said Meyer.