"As you can see, the 2 degrees C “guardrail” that separated acceptable from dangerous in 2001 is, in 2009, squarely inside several red zones. Today, the exact same social and political considerations that settled on 2 degrees C as the threshold of safety by all rights ought to settle on 1 degree C [1.8 degrees F]. After all, we now know 2 degrees C is extremely dangerous."
The brutal logic of climate change / 2011