I have not read his book yet but from what I can see so far it is indeed
difficult to justify his level of certainty (from his lecture):
"All Coal ->?? (Runaway Possible)
Coal + Tars ->!! (Dead Certainty)"
With all due respect to James Hansen (and I do have tremendous respect for him
as a scientist), it is hard not to take this view as an outlier amongst the
climate scientists.
I wonder if he is using the same approach here as in his paper on sea level
rise "Scientific reticence and sea level rise"?:
http://www.iop.org/EJ/article/1748-9326/2/2/024002/erl7_2_024002.html
"Is my perspective on this problem really so different than that of other
members of the
relevant scientific community? Based on interactions with others, I conclude
that there is
not such a great gap between my position and that of most, or at least much, of
the
relevant community. The apparent difference may be partly a natural reticence
to speak
out, [...]"
That may be the case with the sea level rise but has any climate scientists
come out to support him in his views on the possibility of the Venus-type
runaway greenhouse effect here on Earth?
PS: According to one of the links cited by Robbo
(http://humanknowledge.net/Thoughts.html):
"Global Warming. Accumulation of greenhouse gases is causing a rise in global
temperature of a few degrees celsius. This may by 2050 melt enough antarctic
ice to raise sea levels by a few feet and cause some coastal flooding. Warming
may make weather cycles more extreme but may also make land more useful in the
northern expanses of Asia and North America. Projected greenhouse warming is
not severe enough to lead to runaway effects like on Venus."
So, that is OK then :-)
The next quote though casts some doubt over the credibility of this site (as
far as climate science is concerned at least):
"Ice Age. When Earth's next ice age arrives in 10,000 years or so, [...]."
Yeah, right...
A few more quotes for your entertainment:
"Timeline
...
2020Almost all overt tyranny has been eliminated.
...
2030Radio astronomers have discovered signals from extraterrestrial
intelligence."
________________________________
From: Kooiti MASUDA <[email protected]>
To: globalchange <[email protected]>
Sent: Mon, 4 January, 2010 11:00:23
Subject: [Global Change: 3410] Re: Hansen on runaway warming
On Jan 3, 8:52 am, Igor Samoylenko <[email protected]> wrote:
> Hansen mentioned the Venus syndrome in his Bjerknes Lecture he gave at AGU in
> December 2008:
>
> http://www.columbia.edu/~jeh1/2008/AGUBjerknes_20081217.pdf
>
> What he said is this:
...
In the chapter 10 'Venus syndrome' of his book 'Storms of my
Grandchildren',
Hansen says similar thing.
But, as far as I understand, he does not properly formulate here
what is the condition for runaway greenhouse effect, or 'Venus
syndrome'.
What he shows with good scientific support is that the climate system
is
more sensitive to radiative forcing (either solar constant or CO2)
at both warmer and colder extremes, due to greenhouse effect of water
vapor
and ice-albedo feedback, respectively. I think this is reasonable.
Then he suggests that even CO2 level of 1000 ppm may be dangerous
(this corresponds to "10-20 W/m2" in the Bjerknes lecture, I guess),
perhaps first triggering such an event like Paleocene-Eocene Thermal
Maximum
and then Venus-like runaway greenhouse (evaporation of the ocean).
But he does not tell how likely will it be, or how confident he is.
(This is a complaint a la Stephen Schneider. I know it is a tall
order.)
As far as I understand, the value 1000 ppm is just an estimate of the
maximum
level of CO2 in the atmosphere in the Cenozoic era except PETM.
I could not grasp why he considers this level is near the runaway
situation.
So I am tempted not to use Hansen's book as a reliable source about
climate
change (though it is still a very interesting book).
*****
By the way, some attempts to simulate runaway greenhouse condition in
GCM
are here (information for experts of climate dynamics):
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
Ishiwatari M., Nakajima K., Takehiro S., Hayashi Y.-Y., 2007:
Dependence of climate states of gray atmosphere on solar constant:
From the runaway greenhouse to the snowball states.
J. Geophys. Res., 112, D13120, doi:10.1029/2006JD007368.
http://www.agu.org/pubs/crossref/2007/2006JD007368.shtml
(subscription needed for full text)
Note that their formulation of radiative processes was crude.
Probably they wanted to focus in dynamics.
Ko-1 M. (Kooiti Masuda)
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