The future of runaway global warming
Tom Adams
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. "
http://archive.greenpeace.org/climate/database/records/zgpz0638.html
"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.
sploo.laroo
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
sploo.laroo
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.
David B. Benson
http://biopact.com/2008/02/new-study-shows-stabilizing-climate.html
but I'll opine that Venus-style runaway is not possible here on earth
(following threads and commentary on Real Climate).
That said, PETM-warm would be more than enough to extinguish Homo
sapiens...
William Connolley
>
> 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.
> http://archive.greenpeace.org/climate/database/records/zgpz0638.html
>
> "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.
> >
>
--
William M. Connolley | www.wmconnolley.org.uk | 07985 935400
Don Libby
Don't worry, the International Biochar Initiative will save us.
-dl
James Annan
> 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".
James
Michael Tobis
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.
mt
Tom Adams
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.
>
> -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.
>
> --
>
> - Show quoted text -
Hank Roberts
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?
William Connolley
> 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.
-W.
James Annan
>
> 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.)
I doubt there are formal calculations that really *prove* anything,
though there may well be sensible approximations and assumptions that
support this conclusion. After all, we do not *know* bounds on what
the climate sensitivity is with *certainty*, and a high enough
sensitivity would generate this behaviour. It was indeed Ray P who
IIRC expressed some interest and/or surprise at our model results,
when I mentioned them on RC once.
James
James Annan
Not much, not much, no-one, and handful in about 100 :-)
I take it as a salutory reminder of the limitation of this class of
model (experiment). You may not realise, but in these experiments the
atmosphere is "tied" to a sea surface which is forced to have
realistic temperatures and which (crucially) acts as an infinite
source or sink of heat (and freshwater, although this may not matter
so much). So the actual radiative behaviour of the atmosphere may not
be at all realistic when we push parameters to extreme values.
Furthermore, we can only evaluate the model by looking at equilibrium
situations (eg pre-industrial climate) and not explore the transient
response in any quantitative sense, since the model lacks the thermal
inertia of a deep ocean.
The only time I saw someone try a hindcast of the last 100 years with
a model that had a sensitivity of ~10C, it was completely crazy. High
sensitivity means low stabilising radiative feedback so the
temperature oscillated rather wildly, especially in response to
historical volcanic eruptions. In principle one might be able to get
such a model to work passably by adjusting other uncertainties such as
deep ocean heat uptake, but the amount of evidence you have to
handwave away in order to defend this makes the whole process a bit
fantastical...which is why I say that sensitivity is very likely close
to 3C, although it is not possible to formally *prove" that much
higher values are impossible.
James
Tom Adams
was studying it recently:
http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=1386
But perhaps your information post-dates this.
Note that the "Earth's future habitability" link on this page is
dead. I tracked down an old version of the link here:
http://astrobiology.arc.nasa.gov/roadmap/1998/objectives/o15_future_habitability.html
Apparently, "Earth's future habitability" was a objective of study by
NASA till 2005 (inferring from the wayback machine). It has been
replaced by: "Understand the principles that will shape the future of
life, both on Earth and beyond":
http://astrobiology.arc.nasa.gov/roadmap/g6.html
David B. Benson
>... I suppose the methane clathrates might
The bogs did not.
Steve Bloom
David B. Benson
> Is it clear that the clathrates remained stable? Reference?
stating that bogs expressed methane during PETM. Hank Roberts, I
think it was, wrote a comment thanking me for the link and stated that
efforts looking for clathrate instability had not found any. It
appeared this was something of a puzzle and so I suppose, without
actually knowing, remains one.
That said, natural gas cathrates which form in shallower waters have
collapesed and rather spectacularly so, leaving gigantic but shallow
holes on the continental slope. The assumption is that these formed
during or before LGM, when the waters off the Carolinas was much
colder. When the water warmed at the end of the most recent stade,
the clathrates released the gas. This process continued, rather
recently, in the so-called Burmuda Triangle. Rapid expression of
natural gas remains a hazard for drilling in the Gulf of Mexico, but I
don't know the extent to which the natural gas pockets are clathrates.
Sorry, I haven't kept any of the references. :-(
Hank Roberts
On Feb 19, 11:24 am, "David B. Benson" <dben...@eecs.wsu.edu> wrote:
> On Feb 18, 6:54 pm, "Steve Bloom" <spbl...@earthlink.net> wrote:
>
> > Is it clear that the clathrates remained stable? Reference?
> Sorry, I haven't kept any of the references. :-(
http://geosci.uchicago.edu/~archer/reprints/archer.ms.hydrate_rev.pdf
via
http://scholar.google.com/scholar?q=clathrate+methane+PETM
and there's
http://www.realclimate.org/?comments_popup=398#comment-24993
asking about
"in AGU Geophysical research letters an article about methane hydrates
titled Origin of pingo-like features on the Beaufort Sea shelf and
their possible relationship to decomposing methane gas hydrates, sheds
new information about this menace...."
(question not answered before the thread closed, but it was asked by
Tony Noerpel -- 5 February 2007)
Here's the AGU abstract:
http://www.agu.org/pubs/crossref/2007.../2006GL027977.shtml
Yeah, I recall seeing and likely mentioning this one. The Abstract
says:
-----
The Arctic shelf is currently undergoing dramatic thermal changes
caused by the continued warming associated with Holocene sea level
rise. During this transgression, comparatively warm waters have
flooded over cold permafrost areas of the Arctic Shelf. A thermal
pulse of more than 10°C is still propagating down into the submerged
sediment and may be decomposing gas hydrate as well as permafrost. A
search for gas venting on the Arctic seafloor focused on pingo-like-
features (PLFs) on the Beaufort Sea Shelf because they may be a direct
consequence of gas hydrate decomposition at depth. Vibracores
collected from eight PLFs had systematically elevated methane
concentrations. ROV observations revealed streams of methane-rich gas
bubbles coming from the crests of PLFs. We offer a scenario of how
PLFs may be growing offshore as a result of gas pressure associated
with gas hydrate decomposition.
-----
I recall finding imagery somewhere online taken from someone's ROV,
and seismic imaging of the sediment showing how methane was changing
the layers and creating the "pingo" structures; I have the impression,
though I don't recall any survey proving it, that people thought
they're popping up rapidly in current time, not just leftovers from
the end of the last glaciation.
Hmmmmm ... just quickly poking for info, I haven't done any thing
close to a real search on this.
Hank Roberts
coal could:
http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_94450.htm
A CONTINENTAL SCENARIO FOR THE PETM: PEAT/COAL CAPACITOR, OROGENIC/
CLIMATIC TRIGGER
WING, Scott L., Dept. Paleobiology, Smithsonian Institution, MRC121,
Washington, DC 20560, wi...@si.edu
The magnitude of the carbon isotope excursion (CIE) during the
Paleocene-Eocene Thermal Maximum (PETM), and the extent of oceanic
acidification at its onset, suggest >4500 Gt of carbon were released
from a carbon reservoir that was isotopically moderately depleted
(Zachos et al. 2005), possibly from burning or oxidation of Paleocene
peat and/or coal (Kurtz et al. 2003). A continental scenario for the
PETM includes: 1) extensive deposition of peat and coal during the
middle Paleocene, 2) increased oxidation and/or burning of organic
deposits such as those in the northern Rocky Mountain coal basins
during the late Paleocene as uplift of mountains created a rain
shadow, 3) global greenhouse warming and poleward shift of subtropical
high pressure as a result of higher atmospheric pCO2, and, 4) rapid
acceleration of peat/coal oxidation as global and regional climate
change affected major mid- to high-latitude coal basins at the start
of the PETM. The scenario is consistent with the timing of uplift and
the onset of red-bed formation in the northern Rockies, with the
inference of rapid drying at the base of the PETM from fossil leaves,
and with the larger magnitude of the CIE in continental than marine
carbon reservoirs. In contrast to clathrate or thermogenic methane
scenarios for the PETM the continental scenario predicts a faster
onset of the CIE in continental than in marine sections, and increased
evidence for burning and/or oxidation of organic matter in major coal
basins during the late Paleocene, with a peak at the beginning of the
PETM.
J. C. Zachos et al., 2005, Science 308, 1611. A. C. Kurtz, et al.,
2003, Paleoceanography 18, 1090.
Tom Adams
On Feb 21, 11:22 pm, Hank Roberts <ankh...@gmail.com> wrote:
> and there's the argument that methane couldn't explain the PETM but
> coal could:
>
> http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_94450.htm
>
> A CONTINENTAL SCENARIO FOR THE PETM: PEAT/COAL CAPACITOR, OROGENIC/
> CLIMATIC TRIGGER
> WING, Scott L., Dept. Paleobiology, Smithsonian Institution, MRC121,
Robert A. Rohde
> Do they have a good idea of what turned around the PETM?
coal or whatever) was short-lived and then natural processes simply
removed the excess over ~200 thousand years. The principle process
for permanent removal is calcium carbonate formation and burial in the
oceans.
Why the carbon impulse was short-lived is unknown, largely because the
carbon source is still a matter of significant debate. The most
obvious, but unproven, scenario is that whatever carbon source was
being oxidized simply ran out of carbon.
Incidentally, there is some discussion of whether there were
additional smaller carbon excursions during the Early Eocene, like
mini-PETM events, which would imply at least some observations of
recurrence.
-Robert Rohde
David B. Benson
> ... the carbon impulse (whether from methane or
> coal or whatever)
> ... largely because the
Wikipedia page on PETM provided a more balanced view of the source of
the carbon.
Would you care to edit the Wikipedia page?
Tom Adams
> On Feb 24, 6:58 am, Tom Adams <tadams...@yahoo.com> wrote:
>
> > Do they have a good idea of what turned around the PETM?
>
> The observation is that the carbon impulse (whether from methane or
> coal or whatever) was short-lived and then natural processes simply
> removed the excess over ~200 thousand years. The principle process
> for permanent removal is calcium carbonate formation and burial in the
> oceans.
biosphere? Just wondering if humans had been around, could they have
screwed it up? By developing the polar regions, all that.