One could make an argument that the most troubling potential effect of
global warming is not sea level-rise or drought. The most toubling
potential effect of global warming is *more global warming*.
Yet there seems to be little public awareness of this. The public
seems view global warming as a problem that can be dealt with later,
but this might not be true.
"Greenpeace International polled 400 climate scientists during
December 1991 and January '92. The sample included all scientists
involved in the 1990 study of the Intergovernmental Panel on Climate
Change, and others who have published on issues relevant to climate
change in `Science' or `Nature' during 1991. Scientists were asked
whether they thought there would be a point of no return at some time
in the future, if emissions continued at their present rate. By the
end of January 1992, 113 had replied, in the following way: probably -
15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other
words, 45% believe the runaway greenhouse effect to be possible. "
"Runaway global warming" (RGW) is the best term I have found for this
(based on googling). Is there a better term?
What is the status of RGW in the scientific community these days? It
is frige alarmist or mainstream?
Is there any research that might sort out RGW, determine if its a real
probability, put a probability on it?
What are the time frames for RGW? Perhaps it would play out over such
long time frames that it would not scare the public into action even
if the mainstream of scientists considered it probable.
I haven't really followed this issue closely, but I will refer you to
a pertinent paper:
Weaver, C.P., and V. Ramanathan, 1995: Deductions from a simple
climate model: Factors governing surface temperature and atmospheric
thermal structure. J. Geophys. Res. 100, 11,585-11,591
http://www.agu.org/journals/jd/jd9506/95JD00770.pdf
It's pretty dense. In fact it describes an entire analytic infrared
radiative transfer model. One of the points they address is that the
infrared absorption bands of the greenhouse gases have "windows" -
regions of the infrared spectrum where the atmosphere remains largely
transparent (at least for non-cloudy skies). For Earth, a broad
window is present between 8 and 12 microns. One consequence of the
window is the fact that even for a warming surface and atmosphere,
infrared radiation is still permitted to escape to space through the
window. This property puts a limit on the total amount of warming for
increasing CO2 and water vapor, that is the windows save us from a
runaway greenhouse scenario. This was apparently understood as long
ago as the 1920's according to the references in Weaver and
Ramanathan. However, they note that the window may "close" slightly
as the atmosphere warms and the water vapor amount increases. This
occurs because of a process known as "pressure broadening", which
means that IR absorption by water vapor at the edges of the window
will increase as CO2 and temperature increases. They note that the
final amount of equilibrium warming for a given amount of global
warming depends on how much the pressure broadening of water vapor
absorption closes the window, but I don't think there is concern that
the window will completely close.
Another issue, which I don't think Weaver and Ramanathan address is
that IR absorption by clouds blocks the window. So the total amount
of warming for a given increase in CO2 will also depend on how much a
change in cloud cover (particularly high/thin clouds) increases IR
absorption by clouds. But a runaway scenario based on clouds would
require a much larger increase in cloud cover than is expected. In
fact, I believe many models predict a decrease in cloud cover.
-Eric
On Feb 15, 9:06 am, Tom Adams <tadams...@yahoo.com> wrote:
> One could make an argument that the most troubling potential effect of
> global warming is not sea level-rise or drought. The most toubling
> potential effect of global warming is *more global warming*.
> Yet there seems to be little public awareness of this. The public
> seems view global warming as a problem that can be dealt with later,
> but this might not be true.
> "Greenpeace International polled 400 climate scientists during
> December 1991 and January '92. The sample included all scientists
> involved in the 1990 study of the Intergovernmental Panel on Climate
> Change, and others who have published on issues relevant to climate
> change in `Science' or `Nature' during 1991. Scientists were asked
> whether they thought there would be a point of no return at some time
> in the future, if emissions continued at their present rate. By the
> end of January 1992, 113 had replied, in the following way: probably -
> 15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other
> words, 45% believe the runaway greenhouse effect to be possible. "
> "Runaway global warming" (RGW) is the best term I have found for this
> (based on googling). Is there a better term?
> What is the status of RGW in the scientific community these days? It
> is frige alarmist or mainstream?
> Is there any research that might sort out RGW, determine if its a real
> probability, put a probability on it?
> What are the time frames for RGW? Perhaps it would play out over such
> long time frames that it would not scare the public into action even
> if the mainstream of scientists considered it probable.
By the way, I'll further add that Greenpeace's survey of climate
scientists, apart from being pretty out-of-date by now, was probably
undermined by a lack of knowledge among most climate scientists of the
nuances of infrared radiative transfer. That's probably not a
shortcoming of the climate scientists in general - nobody would expect
an expert in ocean circulation or El Nino dynamics to have the
detailed aspects of infrared radiative transfer available on the tip
of their tongue. But I suspect that if they had limited their survey
to 30 or 40 climate scientists with specific expertise in radiative
transfer, they probably would have found substantially fewer who would
agree that a runaway greenhouse scenario is possible.
-Eric
On Feb 15, 9:06 am, Tom Adams <tadams...@yahoo.com> wrote:
> One could make an argument that the most troubling potential effect of
> global warming is not sea level-rise or drought. The most toubling
> potential effect of global warming is *more global warming*.
> Yet there seems to be little public awareness of this. The public
> seems view global warming as a problem that can be dealt with later,
> but this might not be true.
> "Greenpeace International polled 400 climate scientists during
> December 1991 and January '92. The sample included all scientists
> involved in the 1990 study of the Intergovernmental Panel on Climate
> Change, and others who have published on issues relevant to climate
> change in `Science' or `Nature' during 1991. Scientists were asked
> whether they thought there would be a point of no return at some time
> in the future, if emissions continued at their present rate. By the
> end of January 1992, 113 had replied, in the following way: probably -
> 15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other
> words, 45% believe the runaway greenhouse effect to be possible. "
> "Runaway global warming" (RGW) is the best term I have found for this
> (based on googling). Is there a better term?
> What is the status of RGW in the scientific community these days? It
> is frige alarmist or mainstream?
> Is there any research that might sort out RGW, determine if its a real
> probability, put a probability on it?
> What are the time frames for RGW? Perhaps it would play out over such
> long time frames that it would not scare the public into action even
> if the mainstream of scientists considered it probable.
> One could make an argument that the most troubling potential effect of > global warming is not sea level-rise or drought. The most toubling > potential effect of global warming is *more global warming*.
> Yet there seems to be little public awareness of this. The public > seems view global warming as a problem that can be dealt with later, > but this might not be true.
> "Greenpeace International polled 400 climate scientists during > December 1991 and January '92. The sample included all scientists > involved in the 1990 study of the Intergovernmental Panel on Climate > Change, and others who have published on issues relevant to climate > change in `Science' or `Nature' during 1991. Scientists were asked > whether they thought there would be a point of no return at some time > in the future, if emissions continued at their present rate. By the > end of January 1992, 113 had replied, in the following way: probably - > 15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other > words, 45% believe the runaway greenhouse effect to be possible. "
no they don't. "point of no return" is open to many interpretations. you might take it to mean "greenland will melt" for example.
> "Runaway global warming" (RGW) is the best term I have found for this > (based on googling). Is there a better term?
> What is the status of RGW in the scientific community these days? It > is frige alarmist or mainstream?
no-one believes it
-william
> Is there any research that might sort out RGW, determine if its a real > probability, put a probability on it?
> What are the time frames for RGW? Perhaps it would play out over such > long time frames that it would not scare the public into action even > if the mainstream of scientists considered it probable.
----- Original Message ----- From: "David B. Benson" <dben...@eecs.wsu.edu> Newsgroups: gmane.science.general.global-change To: "globalchange" <globalchange@googlegroups.com> Sent: Friday, February 15, 2008 12:30 PM Subject: [Global Change: 2416] Re: The future of runaway global warming
David B. Benson wrote: > but I'll opine that Venus-style runaway is not possible here on earth > (following threads and commentary on Real Climate).
"not possible" is hard to defend IMO.
I have a handful of model simulations which give a reasonable climate under present day conditions but show runaway global warming under 2xCO2 and even 1.4xCO2 in one or two cases (about where we are now!). These models are in the same class as the CPDN ensemble, ie a fully-fledged atmospheric GCM coupled to a slab ocean, so designed for looking at equilibrium climates, based on our detailed understanding of the myriad interacting physical processes.
I suppose I should submit it to Nature :-) But when a Japanese model gives a crazy result, everyone says "that's a crap model". When HadCM3 gives a crazy result, everyone say "ooh that's scary, we're all going to die".
Seriously, the runaway term is used to describe a planet where the water vapor feedback is such that entire ocean evaporates and the planet becomes completely unviable. This is believed to be the story of the evolution of Venus.
I have seen formal calculations about this; apparently we are a bit too far from the sun for this to happen here, but not by a huge margin. If the sun warms up just a little bit it will happen. If the earth were a cylinder and not a sphere, hence tropical everywhere, the oceans would boil away post haste. Unfortunately I didn't track this down on the first attempt.
(It's a Ray P question if there ever was one, though I don't think he was the author of the definitive analysis of the question if I recall right.)
That doesn't mean there aren't exacerbating feedbacks. The clathrates may provide one on a millenial time scale. There are other candidates. But "runaway" isn't the right word for that unless you think the world will tip into complete uninhabitability as a result.
> On 15/02/2008, Tom Adams <tadams...@yahoo.com> wrote:
> > One could make an argument that the most troubling potential effect of
> > global warming is not sea level-rise or drought. The most toubling
> > potential effect of global warming is *more global warming*.
> > Yet there seems to be little public awareness of this. The public
> > seems view global warming as a problem that can be dealt with later,
> > but this might not be true.
> > "Greenpeace International polled 400 climate scientists during
> > December 1991 and January '92. The sample included all scientists
> > involved in the 1990 study of the Intergovernmental Panel on Climate
> > Change, and others who have published on issues relevant to climate
> > change in `Science' or `Nature' during 1991. Scientists were asked
> > whether they thought there would be a point of no return at some time
> > in the future, if emissions continued at their present rate. By the
> > end of January 1992, 113 had replied, in the following way: probably -
> > 15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other
> > words, 45% believe the runaway greenhouse effect to be possible. "
> no they don't. "point of no return" is open to many interpretations.
> you might take it to mean "greenland will melt" for example.
> > "Runaway global warming" (RGW) is the best term I have found for this
> > (based on googling). Is there a better term?
> > What is the status of RGW in the scientific community these days? It
> > is frige alarmist or mainstream?
> no-one believes it
Why not?
I see a couple of arguments in the thread: a bit too far from the sun,
the atmosphere will not refect sufficient IR regardless of any
plausible greenhouse gas concentration.
Those are good arguments since they don't appear to rely on the
biosphere, given our proclivity to screw up the biosphere's regulation
system. An argument against runaway that depended on the biosphere
might not inspire confidence.
BTW, "runaway greenhouse effect" is better term, I think. But, as mt
pointed out, it's ambiguous. Could be either Venus or the major
factor in most or all warm periods in Earth's history. Everyone
believes in the latter.
> > Is there any research that might sort out RGW, determine if its a real
> > probability, put a probability on it?
> > What are the time frames for RGW? Perhaps it would play out over such
> > long time frames that it would not scare the public into action even
> > if the mainstream of scientists considered it probable.
On Feb 16, 4:04 pm, James Annan <james.an...@gmail.com> wrote:
...
> I suppose I should submit it to Nature :-) ...
How much attention does it warrant? How much attention is it getting
from the people funding your modeling work? Anyone take these runs
seriously, or are they the handful in hundreds?
On 17/02/2008, Tom Adams <tadams...@yahoo.com> wrote:
> On Feb 16, 6:22 pm, "William Connolley" <wmconnol...@gmail.com> wrote: > > On 15/02/2008, Tom Adams <tadams...@yahoo.com> wrote: > > > What is the status of RGW in the scientific community these days? It > > > is frige alarmist or mainstream?
> > no-one believes it
> Why not? > ... > BTW, "runaway greenhouse effect" is better term, I think. But, as mt > pointed out, it's ambiguous. Could be either Venus or the major > factor in most or all warm periods in Earth's history. Everyone > believes in the latter.
Fair enough, we all know its been warmer in the past, but RGE doesn't mean that. To me at least it means a discontinuity in forcing-response: past a certain (GHG) forcing the response suddenly jumps to a new state (a tipping point, ha ha, to use a meaningless phrase) that is *much* warmer. I suppose the methane clathrates might satisfy this, but they are on the ocean bed where its deep and cold.
