James,
>
> Um....if you really need a citation, some are mentioned in
>
> http://www.clim-past.net/5/803/2009/cp-5-803-2009.html
>
Thanks for this. This part of your paper jumped out at me:
>For the doubled CO2 experiment a number of the ensemble
>members with higher control temperature and high sensitivity
>became unstable once the global mean surface temperature
>exceeded 296 K.
That 296K seems close to the ~300K mentioned above by hgerhauser
(post of 7th January). I also found this: magic number
of 300K (27 degrees C) appears again...
http://earthobservatory.nasa.gov/Newsroom/view.php?id=22423
And again here...
http://geo.arc.nasa.gov/sgp/radiation_aug01/rad7.html
>Surprisingly, above 300K the outgoing radiation emitted to space >actually
>decreases with rising SST. Less energy to space implies >that more energy is
>available to heat the surface, leading to a >potentially unstable situation.
>This behavior is a signature of >the runaway greenhouse effect on Earth.
The overall picture seems consistent here.
- Combination of high CO2 or high sensitivity, or
carbon/methane feedbacks, or all three, could
take us up to 300K
- At that temperature, runaway warming is a real danger
- We don't know exactly what the end-point is like
(models blow up), but it's not pretty: Earth doesn't
look habitable anymore.
Hansen might be wrong in the details, but he's right to get the
discussion out of the closet.
Nick
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