The report from the intergovernmental panel was the second of three due this year.
Climate change may have serious repercussions for human health, said the intergovernmental panel.
The growing season is longer, and the intergovernmental panel says that some of the arctic may eventually open up to farming.
The intergovernmental panel, in a draft report, said there would be at least two replacement cycles over the next century.
But for every benign impact, according to the intergovernmental panel, there would be at least one negative counterpart.
He also served on other governmental and intergovernmental panels.
The intergovernmental panel, he said, "is telling us that the signal is here."
Until now, each of the four intergovernmental panels has had to review its predecessor's estimates of the speed at which climate change is taking place.
The role of the intergovernmental panel, which consists of about 2,500 experts around the world, is to advise the treaty parties.
One recent piece of evidence suggesting a strong human influence, which seems likely to carry some weight with the intergovernmental panel, appeared recently in the journal Nature.