Guest post by Indur M. Goklany
In the earlier post reporting on the recent greening of the Arctic, some commentators — Crispin in Waterloo, BillD, Jimbo — have alluded to the notion that Arctic thawing could lead to positive feedback by adding to methane emissions to the atmosphere.
This global warming bogeyman is founded on the plausible notion — plausible, at least at first blush — that warming might release methane from methane clathrates (or hydrates) stored in the Arctic permafrost which would increase its concentration in the atmosphere.
But methane has a “global warming potential” averaged over 100 years of 25, that is, methane, ton-for-ton, is 25 times more powerful a greenhouse gas than carbon dioxide (AR4WG1 Technical Summary: 33). Thus, such releases of methane would constitute a positive feedback for global warming.
The initial concerns about methane stemmed from the fact that by the 1990s the atmospheric concentration of methane, which had been growing rapidly, had exceeded 1,730 parts per billion (ppb), almost twice the maximum amount measured over the past 650,000 years in ice cores (AR4WG1: 3).
Concern of runaway methane feedback was also stoked by a number of modeling studies which suggested rapid disintegration of the permafrost with global warming (e.g., Lawrence and Slater 2005, Zimov et al. 2006). However, in a modeling study which took into consideration the thermal profile of the permafrost, and the fact that the melting effect of warm air surface temperatures on the upper layers of permafrost would be countered by cooling due to colder deeper layers of permafrost, Delisle (2007) showed that “massive releases of methane in the near future are questionable.”
Even more compelling is that the growth in atmospheric concentrations has slowed substantially. As noted by the IPCC AR4WG1 (p. 796):
Recent measurements show that CH4 growth rates have declined and were negative for several years in the early 21st century … The observed rate of increase of 0.8 ppb yr–1 for the period 1999 to 2004 is considerably less than the rate of 6 ppb yr–1 assumed in all the [IPCC] SRES scenarios for the period 1990 to 2000.”
The latest observations indicate that the rate of change is not increasing, and that they “are not consistent with sustained changes … yet” (Dlugokencky et al. 2009: 4). [Dlugokencky’s “yet” seems gratuitous — no matter, I’ll give it a pass.] They also indicate that the geographical pattern and the isotopic signature of methane increases suggests that the major sources are wetlands — probably tropical wetlands —rather than Arctic permafrost.
Petrenko et al. (2009) examined the source of isotopic methane in a glacial ice core from West Greenland to determine the probable source of the large increase in methane during the abrupt warming of +10±4°C that occurred during the transition from the Younger Dryas to the Preboreal (~11,600 years ago) (Grachev and Severinghaus 2005). They concluded that “wetlands were the likely main driver of the [methane] increase and that clathrates did not play a large role,” a finding they noted “is in agreement with findings from previous ice core CH4 isotopic studies” (Petrenko et al. 2009: 508). This study essentially reiterated the results of another paper by many of the same researchers that appeared in Nature the previous year (Fischer et al. 2008). Notably the Petrenko et al. study’s publication was accompanied by an announcement titled, “Ancient Greenland methane study good news for planet, says CU-Boulder scientist” (Eureka Alert 2009).
So it seems that while methane emissions might increase if there is warming, there is no evidence of catastrophic releases from clathrates.
References
1. The above is, for the most part, extracted from:
Goklany, Indur M. (2009). Trapped Between the Falling Sky and the Rising Seas: The Imagined Terrors of the Impacts of Climate Change. Prepared for University of Pennsylvania Workshop on Markets & the Environment, draft, 13 December 2009.
2. Specific references follow:
AR4WG1 ≡ IPCC’s Fourth Assessment Report for Work Group 1 ≡ IPCC (2007). Climate Change 2007: The Physical Science Basis. Cambridge: Cambridge University Press.
Delisle, G. (2007), Near-surface permafrost degradation: How severe during the 21st century?, Geophys. Res. Lett., 34, L09503, doi:10.1029/2007GL029323.
Dlugokencky, E. J., et al. (2009). Observational constraints on recent increases in the atmospheric CH4 burden. Geophysical Research Letters, 36, L18803, doi:10.1029/2009GL039780.
Eureka Alert. 2009. Ancient Greenland methane study good news for planet, says CU-Boulder scientist. PR announcement, 23 April 2009. Available at http://www.eurekalert.org/pub_releases/2009-04/uoca-agm042109.php.
Fischer, H., Melanie Behrens, Michael Bock, Ulrike Richter, Jochen Schmitt, Laetitia Loulergue, Jerome Chappellaz, Renato Spahni, Thomas Blunier, Markus Leuenberger & Thomas F. Stocker (2008). Changing boreal methane sources and constant biomass burning during the last termination. Nature 452: 864 -865.
Grachev, Alexi M. and Jeffrey P. Severinghaus (2005). A revised +10±4 °C magnitude of the abrupt change in Greenland temperature at the Younger Dryas termination using published GISP2 gas isotope data and air thermal diffusion constants. Quaternary Science Reviews 24 ( 5-6): 513-519.
Lawrence, D. M., and A. G. Slater (2005). A projection of severe nearsurface permafrost degradation during the 21st century, Geophys. Res. Lett., 32, L24401, doi:10.1029/2005GL025080.
Petrenko, Vasilii V.; Andrew M. Smith, Edward J. Brook, Dave Lowe, Katja Riedel, Gordon Brailsford, Quan Hua, Hinrich Schaefer, Niels Reeh, Ray F. Weiss, David Etheridge, and Jeffrey P. Severinghaus. 14CH4 Measurements in Greenland Ice: Investigating Last Glacial Termination CH4 Sources. Science 324: 506-508.
Zimov, S. A., E. A. G. Schuur, and F. S. Chapin III (2006). Permafrost and the global carbon budget, Science, 313, 1612–1613.
major says:
October 30, 2010 at 8:29 pm
Why cant we put stake in the heart of the Global Warming Fanatics?? They dont quit and they continue repeating the same dull chant as there there were no other questions to be answered and no possiblity of ever being wrong.
They are like the cult of Landrew; dangerous relentless robotic humanoids.
Why indeed!
Their own words shall be their own undoing. That’s why!
Give them space, and give them time, and soon their story shall unwind, revealing to all its hideous wickedness, and how our deaths they would define.
R. Gates says:
October 30, 2010 at 9:07 pm
Accelerated methane release from various sources as a positive feedback to general global warming remains a subject of intense research and huge unknowns. Furthermore, the fluctuation of atmospheric methane concentrations (while generally going up over the past many decades) is even more variable and the sources and causes less well understood than the the fluctuations of CO2, which, we all know, has been increasing far more steadily. The issue is far from settled on which way atmospheric concentrations will be headed in the short and longer but because of the potency of methane as a greenhouse gas, any growth of atmospheric concentration over the long term represent a serious enough threat to climate stability that in needs close monitoring.
VERY BIG QUESTION FOR YOU: GOT =ABSOLUTE PROOF= OF YOUR ASSERTIONS?
No?
Too bad, eh?
Until then, all you have is conjecture, prognostication, and wishful thinking.
Natsman says:
October 31, 2010 at 2:13 am
Why is EVERYTHING “catastrophic” these days?
It’s the automatic postulate of Post Normal Science’s Method. Except that according to PNS, Climate Catastrophy will be magically avoided if we eliminate the ~”obscence inequality of wealth ” between nations. [Hulme]
Pops says:
October 31, 2010 at 2:21 am
What’s with the Catastrophic? Is it not possible for anyone to present a theory without the use of that word?
Well, you see? In the ‘beginning,’ the term ‘catastrophic’ was intended to impart the idea of, well, ‘catastrophe.’
Now, any human sufficiently knowledgeable in his own native language, would have come to understand the term ‘catastrophe’ as something akin to the worst sort of happenstance.
So, here we are, toiling over relative terms, when the abstract and the absolute come to mean the very same thing.
You see? It’s not the idea, but rather the interpretation: When murder may come to mean mere death, then murder is acceptable.
But isn’t that really what they have in mind for the rest of us?
THINK: Stalin’s murders in the Ukraine were —and are— considered ‘acceptable’ by the current ‘soviet’ of the scientific establishment.
Humans are —according to them— VERMIN on the face of the Earth.
But, will THEY do the rest of us the favor of LEAVING FIRST?
No! Of course not! THEY demand that WE leave first.
Leadership DEMANDS that we follow by example.
Therefore, they are caught-up in their own web: WHY SHOULD WE DIE, WHY THEY WON’T LEAVE FIRST?
Methane is the main constituent of natural gas. So if we can harvest all that nasty methane from the ocean floors we can burn it to heat our homes and in the process reduce it to the much more harmless CO2, thereby rescuing the earth from another disaster du jour. Problem solved!
richard verney says:
The arctic has been warmer in the past (and with correspondingly less ice) and hence if runaway methane release was going to happen, it already would have occurred. When one examines the evidence on a geological time scale, it is apparent that there is no problem here.
This is a fundermental problem with all such “doomesday” senarios involving some positive feedback effect of GHG.
Ferdinand Engelbeen says: October 31, 2010 at 11:48 am
The curve for CO2 and methane in ice cores are similar: both increase very rapidely around 1850, together with the increase of fossil fule use. Methane increased some 100 ppbv in the period starting 6,000 years ago.
Do you have any numbers on fossil fuel use in 1850-1900?
Didn’t think so.
davidmhoffer says:
October 30, 2010 at 9:46 pm
++++++++
Appreciated your humour in that one.
Moving on:
While previous ages may have been warmer and there was no catastrophic release of methane that we know about, it could happen, right? There could be a release of underground oil (Athabaska tar sands), under-sea methane burps (Bermuda triangle), natural gas ‘gas-offs’ through fissures (earthquakes in Africa) – many things could happen that perhaps did not in the Holocene. There are no doubt many things to fear. Stephen Colbert held his rally in Washington last weekend to promote and entrench the idea that we should be fearful “because there are so many things out there we should be afraid of”. I don’t agree with him on his principal point nor the ending of the sentence with a preposition.
Something we do NOT need to be afraid of is that the methane emerging from rotting vegetation will put into the atmosphere, over say 100 or 200 years, so much additional forcing that there will be a run-away greenhouse effect. It is a ridiculous and unscientific idea. There are several reasons why not, but the most obvious is that the methane turns to CO2 quite quickly and is absorbed by growing plants that cannot grow now because they are frozen in that very permafrost. Silly people.
Let’s look at northern Siberia and the Canadian shield between the Mackenzie River and Hudson Bay – a vast area of the globe. There is, straight south of any point across those tracts, a vast forest of evergreens. They grow as far north as possible until the cold stops them. A pine tree 200 years old north of the treeline is about a foot high. When it warms they will immediately grow, one additional day per year whenever possible.
By my calculation it will take about 5 kg of tree to consume all the methane (in fact all the carbon) released by melting the permafrost. Suppose I am wrong by 100%, or 200% or 500%. The entire forest to the south will also grow taller and thicker. It is not just the permafrost area that is affected. The ENTIRE North American evergreen forest will expand upwards if it is a little warmer.
It means there is zero, absolutely no chance whatsoever, that a methane release from the rotting of preserved vegetation in permafrost could spike the global temperature. As that is the main claim regarding permafrost, that should put an end to the hyping of this particular calamity.
The release of methane stored in the ocean is a completely different matter. It has nothing to do with permafrost. It is not so much frozen as it is under pressure. If there is a tiny rise in the temperature of the ocean at great depths, perhaps there will be a release of some of the methane, or more likely, the rate of accumulation of it will decline.
But remember, the sea level will be increasing too. Will the increased pressure from deeper seas all over the world increase the extraction of methane from the atmosphere? Will it exactly compensate for the slight rise in temperature? Will the pressure increase outweigh the temperature increase while the tundra gobbles up the CO2? Will warmer seas enhance the growth of seaweed and more than compensate for the presence of additional carbon in the form of methane?
Stay tuned to this channel….for about a million years.
Tim Clark says:
November 1, 2010 at 7:28 am
Do you have any numbers on fossil fuel use in 1850-1900?
Didn’t think so.
There are only rough estimates of CH4 releases of that period (mostly from increasing livestock, rice growing and far behind as third, coal mining), see:
http://cdiac.ornl.gov/trends/meth/ch4.htm
Livestock and rice still are the major sources, with coal mining still at the third place, but biomass burning (with some methane losses) is coming near.
Fossil fuel use 1750-2003 can be found here:
http://cdiac.ornl.gov/trends/emis/tre_glob.html
Again rough estimates for the earlier period.
In addition: the CH4 data found in ice cores, firn and atmosphere for the period 1000-1997:
http://cdiac.ornl.gov/trends/atm_meth/lawdome_meth-graphics.html
“”””” Leif Svalgaard says:
October 30, 2010 at 6:38 pm
Max Hugoson says:
October 30, 2010 at 5:24 pm
650,000 Years in Ice Cores?
I say B.S. What ice core would have existed that many years ago?
Ice cores extend to about 800,000 years. The snow is compressed into ice and the annual layers are rather thin [4000,000 millimeter/800,000 years = 5 millimeters not 6 inches] as also the Arctic/Antarctic are low precipitation areas to boot. “””””
If my memory serves me, Vostok sits on about 430,000 years of ice, and it is at “Dome C” where the cores go back close to that 800,000 year age.
And the problem at Vostok, is that they now know that they are sitting on top of a huge liquid water lake; so at that point the ice recored would cease. They have quite deliberately stopped drilling at Vostok closer thanba few metres to the lake, because they don’t want to accidently tap into it, and inadvertently completely contaminate the thing, before they figure out how they might safely research the properties of that lake. (or if they can)
This particular panic-attempt is another positive-feedback idea. Intellectually, it makes sense, which makes it a good example of abuse of the intellect that can result in disastrous wrong anwers.
If the net climate modifiers were positive feedbacks, then life on Earth would have vanished eons ago. We may not understand the factors, but the presence of life today, the stability of even the 20th-21st century climate within 3 degrees C, and paleontology research on past temps showing impressive stability overall–all these things PROVE that the real feedbacks are primarily negative.