Guest Post by Willis Eschenbach
Well, Nature Geoscience is on a roll. Their latest “scientific study” makes an old claim in a new way. After ascribing the temperature changes in Lake Tanganyika to human actions, in a new paper they are now ascribing the changes in the climate 12,000 years ago to the actions of humans in changing the methane levels …
Figure 1. The real reason for the ending of the Ice Age
No, that’s not from the Nature Geoscience article. We’ll get to that, but first , a short cruise through the historical methane data.
As usual, the NOAA Paleoclimatology site has the goods. The data shows an interesting thing. This is that, like CO2, the amount of methane in the air is a function of the temperature. Figure 2 shows the relationship.
Figure 2. Relationship between temperature and methane, Vostok ice core data, last half million years. Image Source
As you can see, temperature and methane are tightly coupled. The relationship is that when temperature raises by 1°C, the methane concentration in the atmosphere goes up by about 24 parts per billion by volume (ppbv). The reasons for this are not entirely clear, but the methane mostly comes from natural fermentation in wetlands. And as anyone knows who has made the prison liquor called “swipe” from potato peelings in a mason jar, fermentation increases with temperature … or that’s what I’ve read, at any rate, I wouldn’t know about that myself …
So what did the Nature Geosciences article say about methane? It is entitled “Methane emissions from extinct megafauna”, by Smith et al. (hereinafter S2010). You have to pay them $18 to have the privilege of reading it. My advice is, don’t waste your money.
Their claim is that the drop in temperature about 12,000 years ago known as the “Younger Dryas” is due in part to the loss of methane from the eeeevil humans killing off the large animals of North America. This reduced the amount of methane from the … well, let me call it “spontaneous release of large parcels of intestinal gases” of the extinct “megafauna”, the ground sloths and mastodons and wooly mammoths and the like. Here’s their graphic of the event:
Figure 3. Graphic from the S2010 paper.
Note how they clearly show that humans come to North America, and very quickly the methane concentration dropped. (As an aside, don’t they know that Jim Hansen said that American temperatures are meaningless because America is only a few percent of the planet’s surface area? Also, note that they claim that species loss could be responsible for “12.5 to 100%” of the methane decline. Now that’s what I call a robust confidence interval, a variation of eight to one. But I digress …)
I showed above that methane concentration is driven by temperature changes, and has been for a half-billion years. However, they say that this particular event is unique. Why? Not because suddenly the temperature/methane relationship broke down. After all, the methane concentration during the Younger Dryas event is totally predictable from the temperature, just like the during the rest of the half billion years.
Figure 4. Methane levels in the Younger Dryas, featuring the usual flatulent suspects. Methane data from NOAA, showing Greenland ice core methane levels. Note that the temperature changes correlate very well with the changes in methane. Temperature changes inferred from d18O levels. Difference in dating from Figure 3 is because this chart shows years BC.
So why blame megafaunal methane for the drop? Well, because the methane levels drop so fast. I kid you not. In their words:
Moreover, the changes in methane concentration at this time seem to be unique. A comparison with the five largest drops over the past 500,000 years shows that the Younger Dryas transition was characterized by a methane decrease that was two to four times more rapid than any other time interval (Supplementary Table T3, P < 0.01 to P < 0.001), which suggests that novel mechanisms may be responsible.
Now, they ignore the fact that among the historical drops in methane levels, one has to be the largest, so finding the largest one means nothing. And they ignore the well-known and aptly named “Noah Effect”, whereby the largest of a group of natural phenomena is often much, much larger than the second largest of the same phenomena. These together are more than enough to explain the rapidity of the methane drop at the start of the Younger Dryas.
Instead, following the Rahm Emanuael dictum, “Never let a serious crisis go to waste”, they have blamed the precipitous drop in methane at the start of the Younger Dryas on human meddling with the biosphere. We killed the mammoths, their argument goes, which stopped them from cutting loose with … large spontaneous emissions of biomethane … and that made the atmospheric methane levels plunge off of the proverbial cliff. QED.
Now, I suppose that their claim is theoretically possible, and they do a lot of plain and fancy tap dancing to show that it is so, but I’m just a cowboy, so that gives me the right to ask the dumb questions:
1. If missing mammoth methane was the cause of the extremely rapid drop in methane … then what was the cause of the following extremely rapid rise in methane? I mean, the megafauna didn’t suddenly become un-extinct and start passing gas again. So why did the methane suddenly rise again?
For this one, I have no answer other than the obvious one … both the drop and the rise in methane were caused by a drop and rise in temperature. The authors of S2010, however, show no interest in this important question … if the cause of the rapid drop in methane during the Younger Dryas is not temperature but a deficiency in ground sloth gas, then what is the cause of the rapid rise in methane?
2. Is the change in methane forcing significant enough to create such a large temperature change? The S2010 paper says:
Ice-core records from Greenland suggest that the methane concentration change associated with a 1 °C temperature shift ranges from 10 to 30 ppbv, with a long-term mean of about 20 ppbv (ref. 13).Thus, empirically, the 185 to 245 ppbv methane drop observed at the Younger Dryas stadial is associated with a temperature shift of 9 to 12 °C. The attribution and magnitude of the Younger Dryas temperature shift, however, remain unclear. Nevertheless, our calculations suggest that decreased methane emissions caused by the extinction of the New World megafauna could have played a role in the Younger Dryas cooling event.
Well, yeah … but the IPCC says that methane forcing varies linearly with concentration. It also says that a change in methane of 100 parts per billion by volume (ppbv) leads to a change in forcing of 0.05 Watts per square metre (W/m2). Given the methane change in the Younger Dryas of ~200 ppbv, this would result in a methane forcing change of a tenth of a watt per square metre (0.1 W/m2).
Now, the IPCC says that a forcing change of 3.7 W/m2 (from a doubling of CO2) would lead to a temperature change of 3°C. I think this is way too large, but we’ll let that be and use their figure. This means that the Younger Dryas change in methane forcing of 0.1 W/m2 would lead to a temperature change of 0.08°C …
Eight hundredths of a degree? These people are hyperventilating over eight hundredths of a degree? I spent eighteen buck to read their !@#$%^ paper for eight hundredths of a degree? That trivial change in forcing is supposed to have “played a role in the Younger Dryas cooling event”? … I weep for the death of science.
(And since you ask, yes, I do marvel that I was able to get through this without once saying the dreaded phrase “mammoth far…” … hey, wait a minute, whoa, that was close, you almost got me there …)
[UPDATE] There’s another oddity I just noticed about the paper. They use the following formula to calculate the methane emissions:
(4) DMIe = BMe^0.75 *[ (0.0119*NEma^2 + 0.1938)/NEma] where BMe = body mass in kg, and NEma = estimated dietary net energy concentration of diet in MJ/kg
Now, one of the rules of math that was endlessly drummed into our heads by my high schoo chemistry teacher (thank you, Mrs. Henniger) was that the units follow the same rules as the numbers. For example, here’s the formula relating distance (S), acceleration (A) and time (T)
S = 1/2 A * T^2
With S in metres, A in metres/second^2 and T in seconds, this is
metres = metres/second^2 * second^2
or
metres = metres
So far, so good. Now let’s look at the units in their formula:
kg = kg^0.75 * [ (MJ/kg)^2 / (MJ/kg) + 1/(MJ/kg) ]
Simplifying, we get
kg = kg^0.75 * [ (MJ/kg) + 1/(MJ/kg) ]
kg = kg^-0.25 *MJ + kg^1.75 /MJ
Well, that’s certainly a fascinating combination of units, but it is definitely not kilograms as advertised.
So I looked to see where they got the formula … and as I should have guessed, it is from the IPCC …
Mrs. Henniger would not approve, she used to wield her red pencil like Thor’s own hammer on this kind of nonsense.
Al Gored says:
May 27, 2010 at 11:38 pm
I’m really not sure what you are trying to say. My point was that the changes occurring at the start of the Holocene caused an increase in abundance of the anadromous salmon. This occurred for a variety of reasons including a decline in aridity and the opening of new spawning locations. Salmon have a high percentage of the populations stray and thus take advantage of new habitat quickly and the fact they are tetraploids allow them to adapt within just a few generations to new habitat. Your comment that Fraser salmon were not present to 6,000 years ago is wrong- see P. Thomlinson’s 1987 master thesis “When Cielo was Cielo: An Analysis of Salmon Use During the past 11,000 years” Also see the “Holocene History of Salmon in the Columbia Basin” http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_56999.htmt
Salmon take marine derived nutrients from the ocean and bring them to freshwater. In many regions this drives the entire ecosystem. The point I was making was that this introduction of organic material impacts the production of methane.
My point about the bears and trees in Alaska was an example of how salmon carcasses moved into the terrestrial ecosystem from scavengers- bears, wolves, birds etc and its impact on riparian vegetation And SCAT production. Your claim that this does not occur and is a “green fairy tale” is to be kind – erroneous. (And humans by feeding on the salmon were also moving the nutrients into the terrestrial community and producing scat). Here are some papers:
Fertilization of Riparian Vegetation by Spawning Salmon: Effects on Tree Growth and Implications for Long-Term Productivity
James M. Helfield1 and Robert J. Naiman2
ECOLOGY MANUSCRIPT, IN PRESS
Transfer of Nutrients from Spawning Salmon to Riparian
Vegetation in Western Washington
ROBERT E. BILBY, et al Transactions of the American Fisheries Society 132:733–745, 2003
And some others:
http://www.springerlink.com/content/422781626m348m06/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC156615/
http://www.fish.washington.edu/people/naiman/Salmon_Bear/salmon_veg.html
I wonder if anyone has attempted to model the state of the upper atmosphere during the ice-age periods. Would there have been a lowering of the tropopause as a result of increased IR transparency in the atmosphere or did the temperatures up there get colder for some other unspecified reason?
I assume that typical surface temperatures must be reflect the typical tropopause temperatures by means of the adiabatic lapse-rate as long as the atmosphere between these levels remains in a state of incipient full-column convection. I believe surface heating in excess of that which can be cooled by direct or intermediate radiation to space will assure this condition.
re Pat Moffitt: May 28, 2010 at 10:58 am
Pat, your first link had a small typo. The correct URL is:
Holocene History of Salmon in the Columbia Basin
/dr.bill
“PS – if you don’t follow the unit checking, perhaps you could tell me where I went wrong. Wouldn’t be the first time …”
Just guessing, but maybe its not working out because you assumed the “constants” were dimensionless?
Did the report mention anything about how much methane was produced by the humans after eating their mammoth? Or was it assumed that the humans, who otherwise may have died, produced no methane?
Another peer-reviewed paper worthy to be cited in the next IPCC report.
Excellent as always, even better, Mr Willis.
wills,
your questions are very valid. if one cannot explain the increase in methane, he/she should not be so bullish on the explanation of the decrease in methane. this is just plain arrogance and ignorance of the part of the authors.
as for the constants in that wretched eqn,
DMIe = BMe^0.75 *[ (0.0119*NEma^2 + 0.1938)/NEma]
the coefficients were derived by simple ( most probably simpleminded ) curve fitting using MATLAB or some such tool. The constant 0.1938, SHOULD have the same units, ie. (MJ/Kg)^2, as the other term they are adding to. This kind of garbage eqns generally wind up being BS, in the longrun. there is no theoretical reason for these coefficients to be what they are.
Al Gored says:
May 27, 2010 at 11:45 pm
Willis – re 10:32 pm
That weight loss graph is more consistent with predation by humans than anything else. Optimal foraging theory – kill/eat the biggest ones first.
It depends on the relative sizes between prey and predator. Foxes may go for the biggest rabbits, but lions don’t go for the bull elephants.
So what is the unit for flatulent discharge? I’d think that one wooly mammoth has the same discharge rate as the cast of “Blazing Saddles” during the campfire scene. I therefore propose that this unit be called the Blazing Saddle or BS for short.
If you see another paper on the subject of mammoth flatulence – you’ll be able to see BS through out it.
Willis Eschenbach says:
May 27, 2010 at 9:21 pm
2. Wild animals are only at 2%. Yes, there were many more wild animals back then,
Animals don’t stop producing methane the instant they become “domesticated”. And over 300 million hominids in North America probably do their share too.
Reed Coray says:
May 27, 2010 at 2:49 pm
I want to know who paid for this “stinking study.”
Blame Willis and his $18 burning a hole in his pocket…
Z says:
May 28, 2010 at 3:13 pm
The list was only “natural” (not human-related) sources of methane, which is why there is no “domesticated animal” part of the pie chart.
Louis Hissink says:
May 28, 2010 at 3:22 am
2. The idea that the Clovis people killed the North American pachyderms is a nonsense – even today killing an elephant with wooden spears is not plausible, and in any case why did the Clovis people massacre their pachyderms and the Africans, Indiands and Chinese not?
Sorry Louis, you are incorrect about this “nonsense.”
For starters, these where stone tipped spears. Second, it was simple to kill them but not quickly. You just spear them in the gut and they die slowly from the wound(s), while the hunters follow them at a distance. Not “sporting” but very effective, and for a meal this large it was well worth the time.
They have done tests on African elephants using Clovis technology to demonstrate this.
See this: Frison, G.C. 1991. Prehistoric Hunters of the High Plains. Academic Press.
As for the difference between mammoths in North American and elephants, the latter coevolved with human hunters and had behavioural adaptations to that while the North American mammoths did not. And if you look at the early historical records of Africa you will see that elephant and human populations did not coexist as some might imagine.
In India they were in jungles – harder to find and hunt – and were also domesticated.
With their slow reproductive rates these animals can be readily extirpated.
Pat Moffitt says:
May 28, 2010 at 10:58 am
Re salmon. The Columbia system was different, and further south. For the Fraser system see several papers in Carlson, R.L, and L. Dalla Bona. 1996. Early Human Occupation in British Columbia, University of British Columbia Press.
Here’s one quote (p 59): “it is difficult to conceive of any salmon… attaining full productivity prior to the stabilization of stream gradients about 5000 BP. Some sockeye may have been passing the Fraser Canyon as early as 7500 BP, but they could not have achieved a quantitative development equivalent to that of the historical period until 2500 years later.”
As for the bear-salmon-nutrient story, I am very familiar with the current situation, and the papers written about it. But the current situation is a European creation made possible by the removal of indigenous people.
Look at the historical record. Everywhere you find abundant bears on salmon streams now, you find people in early history. Bears were extremely rare and local in that early record. That is why I call it a fairy tale. Because it portrays a “wilderness” that never existed because it was full of people, whose populations were very high because of the availability of salmon, and who excluded bears.
See this: Birkedal, T. 1993. Ancient Hunters in the Alaskan Wilderness: Human Predation and Their Role and Effect on Wildlife Populations for Resource Management. 7th Conference on Research & Resource Management In Parks and On Public Lands. The George Wright Society.
It looks at two specific areas. One is the Brooks River in Katmai NP, where today one can see dozens of bears on salmon streams and has the highest bear densities in North America. The current streamflow there, which makes catching salmon easy, developed by about 4,000 years ago and, after that, “village followed village to form a vast archaeological complex along the whole length of the river… Nearly 900 house and structural depressions are visible on the surface alone.”
The abundance of bears there now is a recent phenomenon… “brown bears were a rare sight on the river in the 1930s and 1940s… as lates as the 1960s, Professor Don Dumond… primary investigator at Brooks River, seldom saw more than eight individual bears” in a whole summer season. Now you can see 25 at a time in short prime stretches.
Same story almost everywhere along the Pacific coast and tributaries where salmon were available. High human densities excluded bears. Called competitive exclusion. Basic ecology.
Needless to say, the Conservation Biologists who believe in some “pristine wilderness” where Native Americans were rare, primitive and had no impacts don’t like these facts, and do their best to ignore or dismiss them, but that just tells you what kind of pseudoscience that really is.
And you do know that Lewis and Clark saw almost no bears around the Columbia and no grizzly bears west of the Bitterroots, don’t you? Instead they saw lots and lots of people, with salmon-fed populations.
—
Regarding salmon in the Columbia and Fraser systems, Al Gored writes of how “Everywhere you find abundant bears on salmon streams now, you find people in early history. Bears were extremely rare and local in that early record.”
There is a puzzling tendency in modern scholarly and popular writing to exclude Homo sapiens from the “natural” order of things, as if there was no ecological niche into which our own species evolved long before we achieved the widespread capacity for time-binding, recordkeeping, higher-order intellectual function, and the transmission of abstract concepts by way of written language.
(What I find surprising about the industrial revolution is that it took such an astonishingly long time for it to happen. Anybody else a fan of L. Sprague de Camp’s Lest Darkness Fall [1939]? Speculative fiction writers from the time of Mark Twain’s A Connecticut Yankee [1889] have been fiddling with time travel ideas and “alternative histories” based on the transplantation of modern ideas to past situations in which there was objectively fertile ground for those memes to catch on and take effect.)
Al Gored‘s point about the pre-Columbian population of the American and Canadian northwest has to be kept in mind. Though their economic status was that of a Neolithic culture without significant agricultural elements, they were efficient in their exploitation of the resources available for a hunter-gatherer system of sustenance, and their way of life was robust in that it did not appear to “eat itself out of house and home.”
It was only after the autochthonous hominids got shoved out of that salmon-exploiting niche by hominids armed and engined by an industrial and agricultural civilization (and therefore better capable of waging war) that the present populations of ursine megafauna moved in to less efficiently fish these waters.
But human beings were a very natural part of “the natural order of things” in those many centuries prior to the arrival of the Europeans, and cannot simply be dismissed as an extraneous intrusion upon the ecosphere, no matter how fervent is this “only man is vile” romantic sentiment among modern scholars and other bloody fools.
—
Willis,
I see from some of the comments here that you are aware of the comet impact theory that resulted in this most recent mass extinction. There is a great deal of evidence that this impact did indeed occur and that the resulting conflagration resulted in the end of the Clovis as well as the megafauna. As I recall the researchers who first started putting the pieces of this puzzle together were scientists at the Lawrence Berkeley National Lab. The initial inquiry that ultimately led to the theory was what was the cause of a spike of atmospheric C12 concentrations at that same time. Relative to the Younger Dryas, it has been thought that these comet impacts into the great mass of glacial ice in the Hudson Bay and Lake Michigan area resulted in a great meltdown that caused the ocean current changes that resulted in the return to glacial conditions as pointed out in a previous post.
Have you or Anthony thought about putting a post together on this topic? Or has it already been done?
Willis asked “Why do we have to make these decisions in “the next few weeks”? What’s your urgency? If you are right, we won’t see deleterious effects for decades … so why the urgency? Twenty-five years ago James Hansen said we had to act immediately … and now there has been no statistically significant warming for the last fifteen years. You can cry “Wolf!” all you want, my friend … we’ve heard it before.”
Because there is bill in the U.S. Senate that will pass or not in the next view weeks. I should have been more specific.
Also: If x has units then ax+b can only possibly makes sense if a and/or b have units. In this case one can deduce what the units need to be. The paper’s authors assume a certain level of competence in the reader. Your not knowing to do this is an easy mistake for a layperson to make. But it is not the sort of mistake someone qualified to write in this area would make. You are not stupid, but you are not competent in science. Your opinions should weighted accordingly.
Mike says:
May 29, 2010 at 3:13 pm,
Two questions:
1. Have you been published in a scientific peer reviewed journal?
2. Would you like to retract your statement to Willis that “…you are not competent in science.”?
Z says:
May 28, 2010 at 3:05 pm
Al Gored says:
May 27, 2010 at 11:45 pm
Willis – re 10:32 pm
That weight loss graph is more consistent with predation by humans than anything else. Optimal foraging theory – kill/eat the biggest ones first.
It depends on the relative sizes between prey and predator. Foxes may go for the biggest rabbits, but lions don’t go for the bull elephants.
———-
True in general Z. But human hunting groups armed with only stone age weapons were capable of killing anything and everything, including mammoths and elephants.
Mark Nutley says:
May 27, 2010 at 3:27 pm
“The clovis people had arrowheads, look them up…”
Sorry Mark, but this doesn’t make sense, at all. Think you must be confused about this. What is your source?
The almost instant extinction of the majority of NA megafauna caused by a relatively small number (a few tens of thousands?) of human immigrants seemed absurd when I first read about yrs ago. It still does.
The YD impact theory makes more sense given the current evidence, but it’s still not a sure thing. There’s no impact crater, but we already know destructive airbursts can occur without creating them (Siberia). Perhaps shallow crater(s) were produced in the mile-thick glaciers & the evidence melted away.
Someone previously stated that the YD also shows a remarkable change in Carbon14. C14 is produced by cosmic rays. I don’t know how an impact can cause such a change. Did the impact somehow bollix-up the C14 assimilation in the biosphere? Or was there some other astronomical event that caused the disaster? A WAG would be a shock-front from a supernova-like event vastly increasing cosmic-ray exposure (but how would that create nanodiamonds?) But I’d think some evidence of such a recent shock-front would still be detectable today in nearby space.
Eventually the cause of the YD will be figured out, but it may take many yrs. But “we” didn’t cause it or the megafauna extinctions.
Mike says:
May 29, 2010 at 3:13 pm
Thanks, Mike, that make much more sense.
Oh, please. The problem is that they did not correctly copy the units from the source document. The source document clearly states that the units of the answer are in kg^0.75. Smith et al. say that the units of the answer are in kg. That is not my mistake, it is theirs.
In addition, the source document clearly lists all of the units of the constants in their equations. The Smith article did not do so. I did not say that their equations were wrong because of that. I said that I found it worrisome that they would be cavalier about the units … and when I explored the question further, I found that my concerns were justified. I found that they in fact were using the wrong units.
You say “In this case one can deduce what the units need to be.” Sorry, but that is a very naive assumption, particularly in climate science. In this case, we can’t deduce that because the units that they do show are incorrect.
In addition, your claim that I am “not competent in science” is unfounded. I have published several peer reviewed articles in the journals, including a peer-reviewed “Brief Communication Arising” in Nature Magazine … so clearly, they thought I was competent.
Now, I could say that the fact that you didn’t notice that they were using kg when the source document used kg^0.75 indicates that you are a “layman” who is “not competent in science” … but that is not the case for either of us. You merely assumed that what units they did put in were right, so we could deduce the rest … but your assumption was wrong.
The problem with their leaving out the units is that we can’t check their work. As a result, I had to go back to the source document to find that they were using incorrect units. It is very poor practice to leave out the units, because you can’t tell if they balance or not … as any scientist would know. You seem to think that my insistence on the importance of the units was misplaced, or that it was a sign of my ignorance.
But in fact, the lack of the units kept them (and you) from noticing that they ended up with an incorrect final unit. I can’t tell from their paper whether this made a difference in the final answers, but I suspect it did.
So which of us is the layman here? I’d say neither of us … but I’m the one that found the units error, not you. So your arrogant, patronizing attitude is totally inappropriate.
beng says:
May 30, 2010 at 7:46 am
“The almost instant extinction of the majority of NA megafauna caused by a relatively small number (a few tens of thousands?) of human immigrants seemed absurd when I first read about yrs ago. It still does.”
It would seem much less absurd if you would read this:
Martin, P.S. 2002. Prehistoric Extinctions: In the Shadow of Man in Kay, C.E., and R.T. Simmons (eds.) 2002. Wilderness & Political Ecology: Aboriginal Influences & the Original State of Nature, The University of Utah Press.
Great global review. Megafauna extinctions wherever/whenever modern humans showed up, not just in the New World.
Earliest one happened in Australia starting about 40,000 years BP.
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