” A stunning increase in the frequency of extremely hot summers”

That's James Hansen and other researchers' conclusion after looking at the past 60 years of thermometer readings from Mother Earth. They use last year's $5 billion drought here in Texas as a vivid example of the kind of thing that used to be rare, but no longer is, and they lay the blame squarely on human-made pollution.

"This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened. 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."