PNAS lifts embargo early on Hansen et al extreme weather-climate change study after he publishes WaPo op-ed on it

The Proceedings of the National Academy of Sciences (PNAS) has just lifted the embargo early on a paper by climate change scientist and activist Jim Hansen after an op-ed describing the findings ran in today’s Washington Post:

PLEASE NOTE: Due to the publication of an op-ed by James Hansen in Saturday’s Washington Post, the PNAS News Office has lifted the embargo on Article #12-05276: “Perception of climate change,” by Hansen, et al.

All other PNAS articles will retain a strict embargo time of Monday, August 6, 2012, at 3:00 PM EST.

Here’s how PNAS described the study in a press release:

The study concludes that the recent extreme summer climate anomalies would likely not have occurred in the absence of global warming. Continued warming could potentially make extremely hot summers the norm and possibly contribute to extreme droughts and floods, according to the authors.

Hansen specifically cites the study in his op-ed, “Climate change is here — and worse than we thought“:

In a new analysis of the past six decades of global temperatures, which will be published Monday, my colleagues and I have revealed a stunning increase in the frequency of extremely hot summers, with deeply troubling ramifications for not only our future but also for our present.

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.

PNAS tells Embargo Watch they didn’t know about the op-ed ahead of time. I’ve emailed Hansen for comment and will update with anything I learn.