Human-driven climate change is to blame for this year's extreme heat and drought seen through much of the United States and Europe, according to one of NASA's top scientists.
NASA Goodard Institute Director James Hansen, in an editorial written for the Washington Post, added that even his "grim" predictions of a warmer future were too optimistic when he first addressed the U.S. Senate in 1988.
"I have a confession to make," wrote Hansen. "I was too optimistic. My projections about increasing global temperature have been proved true. But I failed to fully explore how quickly that average rise would drive an increase in extreme weather."
In 2012, the continental U.S. has thus far been the hottest since modern record-keeping started in 1895, according to the National Oceanic and Atmospheric Administration.
Hansen's analysis was based not on models or predictions, "but actual observations of weather events and temperatures that have happened." The peer-reviewed study showed global temperature had steadily risen because of a warming climate, about 1.5 degrees Fahrenheit in the past century, leading to more frequent extreme events.
Meanwhile, a former skeptic of global warming, University of California Berkeley Professor Richard Muller, last week made a very public turnaround, saying that a close look at the data had convinced him that his beliefs were unfounded.
"Call me a converted skeptic," Muller wrote in an op-ed in The New York Times.