Climate scientists have spent much time on the question and have discovered the causes for differences. Those causes include calibration of different instruments and differences between satellite orbits and platforms.

This effort resulted in scientists "actually reconciling all these differences we see in the data sets," he said.

Scientists have formed a consensus that global warming is taking place and it is caused by humans, Reichler said. He cited the scientific journals that he regularly peruses and said he does not know of more than a handful of reports out of thousands "that disagree on global warming."

Josh Dorner, national Sierra Club spokesman for global warming and energy issues, said that the United Nations Intergovernmental Panel on Climate Change issued a report last year stating it is unequivocal that humans are responsible for global warming.

"This is basically all the world's scientists" working on the issue, he said.

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