Your Climate Change Probability Score

From Andrew Gelman:

What probability do you assign to the following statement: increasing the atmospheric carbon dioxide concentration above 800 ppm will change the global average surface temperature by more than 2.5 degrees C (4.5 F)? This would imply a climate sensitivity somewhat below the extreme low end of what the Intergovernmental Panel on Climate Change says is credible.

I think I'm a 0.95 (or a 95-percent-er). What's your number?