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National Academy: Earth's Cimate History Mixed

The National Academy of Sciences weighs in on a feud over global warming. At issue is a study that found the earth is hotter now than it's been in a thousand years. Some use that as an argument that global warming has already pushed the world into extreme climate territory.

The academy panel does not dispute that humans are changing the climate, but it said the Earth's climate history isn't as certain as it is sometimes portrayed.

The focus of the debate is a graph, which has become an icon in the political fight over global warming. It's called the hockey stick, because that's what it's shaped like. It starts out as a long straight line, the handle, and then it turns steeply upwards as temperatures rise in the 20th Century. But the Academy today looked askance at that long handle.

Committee chair Gerald North of Texas A&M says they have high confidence that the last few decades have been the warmest in 400 years. But if you ask whether the past few decades have been the warmest in a thousand years, the committe uses a much weaker word: "plausible."

And "plausible" is another way of saying it doesn't meet the scientific standards of certainty. That's because it's also possible there were major warm periods long ago that don't show up in the hockey stick data.

Members of Congress called upon the National Academy of Sciences to assemble an expert panel to review the science. The committee's report was released today.

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Award-winning journalist Richard Harris has reported on a wide range of topics in science, medicine and the environment since he joined NPR in 1986. In early 2014, his focus shifted from an emphasis on climate change and the environment to biomedical research.