MILES O’BRIEN:

Yes, William, this was an attempt to call a bluff, I think. ExxonMobil authored a blog two years ago, daring its critics to analyze its publicly available documents on climate science. They said, read all of these documents. Make up your own mind

The challenge came in the wake of some great investigative reporting by "Inside Climate News," and it found ExxonMobil years ago acknowledged climate change privately, it is caused by humans and is a serious problem, but it did not acknowledge it publicly.

The study co-author, Naomi Oreskes, is a professor of history of science at Harvard.

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NAOMI ORESKES, Professor of History of Science, Harvard University: We see a picture where the company is aware of evolving science, and saying things that pretty much any climate scientist who would have been working at the time would have basically agreed with more or less. But in contrast, when ExxonMobil turned to the public and published advertorials, there we see a very different picture. There we see a very consistent picture emphasizing doubt, implying that we don't really know, that the science is unsettled. And, therefore, it's either too soon to act or it would be too expensive to act or the problem is too difficult to solve.

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