This U.S. summer is 'what global warming looks like'

Since Jan. 1, the United States has set more than 40,000 hot temperature records, but fewer than 6,000 cold temperature records, according to the National Oceanic and Atmospheric Administration. Through most of last century, the U.S. used to set cold and hot records evenly, but in the first decade of this century America set two hot records for every cold one, said Jerry Meehl, a climate extreme expert at the National Center for Atmospheric Research. This year the ratio is about 7 hot to 1 cold. Some computer models say that ratio will hit 20-to-1 by midcentury, Meehl said.

"In the future you would expect larger, longer more intense heat waves and we've seen that in the last few summers," NOAA Climate Monitoring chief Derek Arndt said.

The 100-degree heat, drought, early snowpack melt and beetles waking from hibernation early to strip trees all combined to set the stage for the current unusual spread of wildfires in the West, said University of Montana ecosystems professor Steven Running, an expert on wildfires.

While at least 15 climate scientists told The Associated Press that this long hot U.S. summer is consistent with what is to be expected in global warming, history is full of such extremes, said John Christy at the University of Alabama in Huntsville. He's a global warming skeptic who says, "The guilty party in my view is Mother Nature."

But the vast majority of mainstream climate scientists, such as Meehl, disagree: "This is what global warming is like, and we'll see more of this as we go into the future."

The Intergovernmental Panel on Climate Change report on extreme weather:

http://ipcc-wg2.gov/SREX/

U.S. weather records set:

http://www.ncdc.noaa.gov/extremes/records/

Seth Borenstein can be followed at http://twitter.com/borenbears