> Ishiwatari M., Takehiro S.-I., Nakajima K., Hayash Y.-Y., 2002:
> A numerical study on appearance of the runaway greenhouse state of a
> three-dimensional gray atmosphere.
> Journal of Atmospheric Sciences, 59, 3223-3238.
> DOI:10.1175/1520-0469(2002)059<3223:ANSOAO>2.0.CO;2
http://dennou-q.gfd-dennou.org/arch/prepri/2002/jas/bousou/pub/runaway.pdf
Looking at the paper I see that with initial temperatures below 300K
there's no runaway, with temperatures around 300K and higher there is.
It's very simplified and all, but still it's an interesting result.
Looking at past temperature history, we think that the Earth was up to
around 10C warmer in the past. I am not sure what the uncertainty on
that is, but it looks like 300K is very much at the high side of
what's credible.
What do we need to get to around 300K? Of the order of 10 to 15 K on
top of pre-industrial. With a climate sensitivity of around 3C, that's
of the order of 10 to 20 W/m2.
So, I can see where Hansen gets that ballpark figure from.
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