"Greenhouse gases are the steroids of weather," says climate projection expert Jerry Meehl of the National Center for Atmospheric Research, at a briefing held by the report's expert reviewers. "Small increases in temperature set the stage for record breaking extreme temperature events." Overall, says the report, higher temperatures tied to global warming, about a one-degree global average temperature rise in the last century, have widely contributed to recent runs of horrible weather:
•In 1950, record breaking hot weather days were as likely as cold ones. By 2000, they were twice as likely, and in 2011 they are three times more likely, so far. By the end of the century they will be 50 times more likely, Meehl says.
•With global warming's higher temperatures packing about 4% more water into the atmosphere, total average snow and rainfall has increased by about 7% in the past century, says the study. The amount of rain falling in the heaviest 1% of cloudbursts has increased 20%, leading to more flooding.
•Early snow melt, and more rain rather than snow, has led to water cycle changes in the western U.S. in river flow, winter air temperature, and snow pack from 1950 to 1999. The effects are up to 60% attributable to human influence.
Climate report links extreme weather events to global warming