(CNN) -- What do the 2010 heat wave in Russia, last year's Texas drought, and the 2003 heat wave in Europe have in common?
All are examples of extreme weather caused by climate change, according to a new study from NASA scientist James Hansen.
"This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened," he wrote in a Washington Post opinion piece meant to accompany the study.
"Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change."
The study, which was published by the Proceedings of the National Academy of Sciences, looks at the past six decades of global temperatures and finds what Hansen described as a "stunning" rise in the frequency of extremely hot summers.
It compared what is happening now to what was happening between 1951-1980. In those years, extremely hot temperatures covered less than 0.2% of the planet. Now, those temperatures cover about 10% of the land area, the study said.
It dismissed the idea that specific weather patterns are by themselves sufficient to explain today's extreme anomalies. Phenomena like La Nina have always been around, but large areas of extreme warming have only come about with climate change, the study said.
"The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills," wrote Hansen.
Hansen directs research at the NASA Goddard Institute for Space Studies in New York and is a longtime environmental activist.