Global warming: it's not just the heat -- it's the humidity!

By SETH BORENSTEIN, AP Science Writer

WASHINGTON - With global warming, the world isn‘t just getting hotter — it‘s getting stickier, due to humidity. And people are to blame, according to a study based on computer models published Thursday.

"This humidity change is an important contribution to heat stress in humans as a result of global warming," said Nathan Gillett of the University of East Anglia in the United Kingdom, a co-author of the study.

Humidity increased over most of the globe, including the eastern United States, said study co-author Katharine Willett, a climate researcher at Yale University. However, a few regions, including the U.S. West, South Africa and parts of Australia were drier.

To show that this is man-made, Gillett ran computer models to simulate past climate conditions and studied what would happen to humidity if there were no man-made greenhouse gases. It didn‘t match reality.

Gillett‘s study followed another last month that used the same technique to show that moisture above the world‘s oceans increased and that it bore the "fingerprint" of being caused by man-made global warming.

"This story does now fit together; there are now no loose ends," said Ben Santer, a scientist at Lawrence Livermore National Lab and author of the September study on moisture above the oceans. "The message is pretty compelling that natural causes alone just can‘t cut it."

It will only feel worse in the future, Gillett said.