(The Blaze/AP) -- The relentless heat that has blistered the United States and other parts of the world in recent years is so rare that it can't be anything but man-made global warming, a top government scientist says.
The research by a man often called the "godfather of global warming" says that the likelihood of such temperatures occurring from the 1950s through the 1980s was rarer than 1 in 300. Now, the odds are closer to 1 in 10, NASA scientist James Hansen claims. He says that statistically, what's happening is not random or normal, but pure and simple climate change.
"This is not some scientific theory. We are now experiencing scientific fact," Hansen told The Associated Press in an interview.
Hansen is a scientist at NASA's Goddard Institute for Space Studies in New York and a professor at Columbia University. But he is also a strident activist who has called for government action to curb greenhouse gases for years. While his study was published online Saturday in the Proceedings of the National Academy of Science, it is unlikely to sway opinion among the remaining climate change skeptics.
In a blunt departure from most climate research, Hansen's study is reportedly based on statistics, rather than the "climate modeling" that is sometimes found to be manipulated. In the report, the taxpayer-funded scientist blames these three heat waves purely on global warming:
-Last year's devastating Texas-Oklahoma drought.
-The 2010 heat waves in Russia and the Middle East, which led to thousands of deaths.
-The 2003 European heat wave blamed for tens of thousands of deaths, especially among the elderly in France.
Also unique about Hansen's survey is that it doesn't bother with the usual caveats about individual weather events having numerous causes. In his opinion, something like the Texas-Oklahoma drought was caused by global warming, period.
Extreme weather, Hansen explains, "is happening often enough, over a big enough area that people can see it happening."
Hansen hopes his new study will shift people's thinking about climate change and goad governments into action. He wrote an op-ed piece that appeared online Friday in the Washington Post.
"There is still time to act and avoid a worsening climate, but we are wasting precious time," he wrote.
The science in Hansen's study is excellent "and reframes the question," said Andrew Weaver, a climate scientist at the University of Victoria in British Columbia who was a member of the Nobel Prize-winning international panel of climate scientists that issued a series of reports on global warming.
"Rather than say, `Is this because of climate change?' That's the wrong question. What you can say is, `How likely is this to have occurred with the absence of global warming?' It's so extraordinarily unlikely that it has to be due to global warming," Weaver said.
White House science adviser John Holdren, who co-authored a book that said the government might have to put sterilants in the drinking water to control the population, praised the paper's findings in a statement. But he also said it is true that scientists can't blame single events on global warming: "This work, which finds that extremely hot summers are over 10 times more common than they used to be, reinforces many other lines of evidence showing that climate change is occurring and that it is harmful."
Skeptical scientist John Christy of the University of Alabama at Huntsville said Hansen shouldn't have compared recent years to the 1950s-1980s time period because he said that was a quiet time for extremes.
But Granger Morgan, head of engineering and public policy at Carnegie Mellon University, called Hansen's study "an important next step in what I expect will be a growing set of statistically-based arguments."
In a 1988 study, Hansen predicted that if greenhouse gas emissions continue, which they have, Washington, D.C., would have about nine days each year of 95 degrees or warmer in the decade of the 2010s. So far this year, with about four more weeks of summer, the city has had 23 days with 95 degrees or hotter temperatures.
Hansen says now he underestimated how bad things would get.
And while he hopes this will spur action including a tax on the burning of fossil fuels, which emit carbon dioxide, a key greenhouse gas, others doubt it.
Science policy expert Roger Pielke Jr. of the University of Colorado said Hansen clearly doesn't understand social science, thinking a study like his could spur action. Just because something ought to happen, doesn't mean it will, he said.
In an email, he wrote: "Hansen is pursuing a deeply flawed model of policy change, one that will prove ineffectual and with its most lasting consequence a further politicization of climate science (if that is possible!)."