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.
While working on the EIS for a mining project, I happened upon a veritable treasure trove of “mammoth-sized” weapons–spear points that weighed several pounds, fleshing knives as big as medium saucers, and stationary knife edges against which hunters whacked the bones of their prey to extract the marrow within (these weighed up to 30 lbs so could not possibly be used except as described).
I found a spokeshank that indicated the spear shafts were about 3 inches in diameter, and grooves on the fore and aft positions of both sides of the spear points where leather thongs were wrapped to keep these spear points on the ends of the spear shafts. The favored hunting method for mammoths consisted of chasing the animals through a narrow opening between rocks or trees; brave hunters would be positioned ahead of the thundering herd with their lengthy spears lying next to them on the ground–as the mammoths passed, the hunter would raise the spear and hopefully cause the mammoth to impale itself with a mortal wound. Several hunters working in a line would have a better chance of getting the giant mammoths to squeeze through butt-grounded spears on either side, increasing the chance of a kill (which would feed the clan for quite a while, obviously).
But here’s the stickler–how many mammoth, giant ground sloths, or other sizable animals could be killed with such a technique? These hunters didn’t have horses–why, they didn’t even have bows and arrows (arrows are a relatively recent invention–none are more than 6,000 years old). Besides, a bow and arrow would be practically useless for creatures the size of these.
Nor did these ancient hunters have guns or other meachnized methods of harvesting so vast a number of such animals as this article on reduced methane concentration claims.
I’ve seen the weapons they used–many, many of them (yet not a single arrowhead among them). In my opinion, these weapons are incapable of reducing the megafauna population in a way to cause their own demise, especially in the hands of people that most likely had dinner for days once one was brought down rather than continuing the hunt. (It was probably easier to move camp to the meat rather than the meat to the camp.) Indeed, considering the hunting methodology, it isn’t certain which was killed more often–megafauna or human.
By the way, can you imagine hiding supine behind a bush or a tree waiting for charging mammoths to go by so you can lift the business end of your 20-ft spear while standing on the butt end so it penetrates effectively? Now THAT’s a gutsy hunter! Wound one of those big bruisers and I’m sure the fun would only begin.
Around that time, there was a huge oil spill near Los Angeles which killed millions of mammals – including Sabre Toothed Cats and Mammoths. It is now a museum.
http://www.tarpits.org/
There seems to be no limit to the environmental damage caused by careless humans. Another famous incident was an oil spill in Tennessee in the 1960s, caused by a man named Jed who was out shooting for some food – when up from the ground came a bubbling crude (Oil that is. black gold, Texas Tea.)
Vuk etc. says:
May 27, 2010 at 2:38 pm
OT
Volcanic plumes generate lightning from the electrification of plume particles.
Electrification of volcanic plumes provides a spectacular source of lightning.
……….findings demonstrate that charge exists well within a volcanic plume, the origin of which is not readily attributable either to the eruption directly or subsequent fair weather charging. ….. Charged particles can cause aircraft radio interference and, if introduced into aircraft cabins, charged ash may present an electrostatic hazard to occupants or aircraft systems.
http://iopscience.iop.org/1748-9326/5/2/024004/fulltext#SECTIONREF
From the always incredible Astronomy Picture of the Day site a beautiful shoot of this phenomenon in action
http://antwrp.gsfc.nasa.gov/apod/ap100419.html
If your claim is right and methane always closely follows temperature, then the recent rise in methane would be a definite proof for the recent global warming.
@johnny D
Here’s a thought, Johnny. Why don’t you use your OWN God given ability to reason. Don’t take Willis at his word. Follow his line of thinking critically. If you seem something that doesn’t sit right, call him on it. As for the “scientists, editors, and peers”, just because someone says they know about something, doesn’t mean they really do.
When did a large part of the world acquiesce the ability to think for themselves to the “higher powers”?
If Willis’ synopsis on the paper is anywhere close to correct, then the paper is so flawed there really isn’t a point in critiquing the thought, and one should just go straight to laughing at the authors, editors and reviewers.
Food chain, supply and sources. I’d start there if you want to know why you should be laughing at the authors. Oh, and how methane is produced in mammals. I’d tell you, but then, I’d only be an author of a blog post and can’t possibly be more correct than a “SCIENTIST”.
RockyRoad @ur momisugly May 27, 2010 at 3:06 pm
The clovis people had arrowheads, look them up, they died off at the same time as the mammoths in north america
More problems with their paper. See my update in the head post.
Phew! A breath of fresh air needed here methinks! I’ll shortly be publishing a paper on how polar bear poo is reducing the albedo of arctic ice, and creating a feedback loop.The poor devils (how do they survive in summer when the ice is far to the north?) are the unknowing engineers of their own demise.
Does no-one realise that the Great Lakes were originally formed when Mammoth urine drained from the central plains? IMHO the rapid temperature rise 10,000 years ago was caused by water-vapour feedback from these vast expanses of nutrient-rich waters. I feel a computer model coming on…..
BTW, as a fully paid-up member of the Global Sceptics and Deniers Association, I’m still waiting for my cash from Big Oil. Do I have to fill in a form, or is there a minimum number of posts on sceptical blogs to trigger payment? Any help would be appreciated.
RockyRoad says:
May 27, 2010 at 3:06 pm
My question has always been very similar, Rocky. Why would humans in the new world be able to drive mammoths and mastodons and a host of other species to extinction, while similarly sized mammals (rhinos, hippos, elephants and the like) continue to coexist with humans in Africa and Asia to this day? As a hunter myself, I know that it is hard to stalk and kill any wild animal, much less one that outweighs me by an order of magnitude or two.
In addition, half of the species in their calculations of “megafauna” extinctions weigh less than 375 kg, a quarter of them weigh less than 150 kg, and 10% of them weigh less than 50 kg … megafauna? Don’t think so …
uups says:
May 27, 2010 at 3:19 pm
uups, not sure if you are serious here, but the relationship is that for every degree of temperature rise, methane rises by about ~ 20 — 25 ppbv. So the recent temperature rise is far too small to make a significant change in methane levels.
The hypothesis that it was the Clovis people who exterminated the megafauna is just that. Jared Diamond’s “Guns Germs and Steel” goes out on a limb arguing for it but a lot of animals and even some plants went extinct at that time. How could stone age hunters exterminate a rabbit or a pine tree? The Clovis themselves disappeared too. Evidently the very last saber toothed kitty cat and the very last Clovis went out in a death struggle. Or something else did them both in. There remains a great deal to be learned about what happened at that calamitous time.
Since coastal estuaries, whose ecologies are significantly impacted by sea-level changes, account today for about 80% of Global methane production, did it occur to anyone in Nature that sea-level changes at this time might be important?
Clovis is close to Roswell. Their weapons may have come from this guy.
The only problem is that the science in this paper isn’t quite as good as the Area 51 research.
@johnny D
Use of the authority argument is old, tired and erroneous. Instead of simply believing and trusting in the authorities you list, how about thinking for yourself. Even debating the points raised in the article and comments? No? Can’t do so? Thought not.
Thanks for dropping by though.
OK, so given the rather large number of ruminants, ( domestic and wild ), on the planet now, surely it’s about time we started eating them faster! “Save the planet eat a burger!”
It’s my new slogan.
As someone who has had the fantastic good fortune to witness the wildebeast, ( and many other species eg zebra, eland, springbok and others ), migration through the Masai Mara this paper is demonstrably utter crap.
If you add in that the VAST majority of methane in the atmosphere is from the oceans then it becomes utter crap.
It seems in climate science rent seeking is the only game in town, pathetic really.
“Patrik says:
May 27, 2010 at 1:45 pm
So.. To save us from catastrophic warming, all we have to do is…
Kill all elephants?”
Patrick beat me to it.
But it begs the question, do polar bears fart?
Another theory for the end of the Clovis people, the mammoths and other giant mammals is a meteor crashing near the Great Lakes. There are soot layers from that time period and small diamonds found in the ash as well as on the Greenland ice sheet from that time period. This theory has appeared in two or more programs on PBS including Time Team America and NOVA.
I don’t follow your units checking in Equation (4):
(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
Note that DMIe = kg/day [not stated here]
I get, upon reduction and substitution:
DMIe = kg/day intake = (kg^.75) * [MJ/kg]
The equation is evidently empirical, based on animal husbandry studies. I wouldn’t expect it to have units that balance. Think of it as a model, one that probably has been established by many data sets of field data.
Your observation on dimensional analysis is well made.
Note how there are two numerical constants in the ‘rule’ proposed by the IPCC and the dimensions of these constants could resolve the dimensional question in principle.
But, naturally, the constants would then need to be justified and explained -including their dimensions. It would be very interesting to see how they could seek to justify any physical parameters whose units include kg^-0.75.
Occam’s razor leads me to the conclusion that these people haven’t the slightest clue about what they are talking about. And if they claim to be scientists would be an exterme case of self flattery.
This paper could have been peer reviewed by the author of Ecclesiastes:
‘Vanity and a striving after wind’.
I have done researsh in Paleoclimatology, palinology, and this article is ridiculus…this is not not science.
(The chinese had a teory about the dinossares desapearence, and the cause of death whas the enormous volumes of gases they were putting in the atmosphere, like methane.
but this is a very ancient teory…centuries)
My understanding is that the previous theory for the Younger Dryas cooling period is that during the warming period of the early holocene, when the tw0-mile thick glaciers of North America were melting away, a huge freshwater lake was formed in Canada from the runnoff, blocked by either ice or earth dams. At a certain point, this lake broke free and spilled into the North Atlantic. A great deal of geological evidence exists for this lake and its sudden spill-off. The massive influx of fresh water into the North Atlantic had the effect of shutting down the Gulf Stream, which depends on high saline water sinking near Greenland. This slowing of the Gulf Stream and ocean circulations around the world resulted in a sudden and lasting temperature drop around the word. Hence, the 1700 year Younger Dryas period.
Is there some reason the authors of this paper don’t address this previous theory that has real geological evidence behind it, and a sound cause and effect mechanism that could have resulted in climate changes of this magnitude? Is there some reason the loss of mammoth farts somehow represents a more plausible explanation?
@ur momisugly uups who said: “If your claim is right and methane always closely follows temperature, then the recent rise in methane would be a definite proof for the recent global warming.”
Proof of global warming? But critics don’t dispute “global warming.” The issue is the cause.
See also Willis’ response.
I would look at an aquatic source of methane first. We had complex patterns of ice advance and retreat at about this time with glacial lakes forming and bursting -creating massive outwash plains and possible impact on the the North Atlantic currents causing the Younger Dryas. We had lakes buried under ice for ten of thousands of years- newly opened to the atmosphere and releasing its stored methane load. See: http://www.sciencedaily.com/releases/2007/10/071025174618.htm
We had the formation of swamps where bacterial action would dominate before the the slower adapting macrophytes became part of the equation. The duration of this time lag may be critical to the production of methane.
The importance of pH and alkalinity cannot be ignored in the production of methane. Much of eastern North America is underlain by granite. Glacial flour has a pH of around 8.5. However, the pH and ANC (acid neutralizing capacity) quickly declines as the glacial soil is colonized by bogs and forests. (Bogs do an especially good job driving down pH by actively sequestering Ca–in fact to survive they need to drive the pH below the point where the rooted aquatic plants can compete). The production of organic acids quickly depresses the virgin glacial soil pH to the 4 to 5.5 range depending on the flora succession and fire cycle . (Granite bedrock is very poor at buffering these acids.) The decline in pH and alkalinity would suppress the methane generation rate as methane bacteria do best at a pH between 7 and 8.5 with a relatively high alkalinity.
While the methane generation rate would decline as a result of pH the amount of organic material available, temperature and ice free waters all increased. Some of the new swamps and wetlands created by the interglacial would be in high limestone regions and would see methane production rates continue at higher rates.
How does all this fit- I don’t know- it is complex. But I don’t think the authors of this Nature paper understand how all this fits together either.
One of the issues with the MegaFauna extinctions which is not addressed adequately is CO2 levels themselves.
The C3 plants (mostly grasses) are able to grow reasonably well with low CO2 levels. C4 plants (most other broad-leafed plants but including a few grasses as well) grow very poorly with CO2 levels as low as 200 ppm (and especially in hot conditions and/or dryer conditions when CO2 levels are this low).
CO2 levels during the height of the ice ages were below 200 ppm for long periods of time. This allowed Grasses to take over most of the areas where precipitations levels were low which ocurred in many areas. The planet was a grass, tundra, savanna, small rain-forest area and ice and snow planet.
The MegaFauna were, in fact, Mega-Herbivores who fed on grasses and the small bushes which dominated the ice age vegetation map other than the areas covered by ice and the rain-forest areas. When you have Mega-Herbivores, one also tends to get Mega-Carnivores.
So, at about 14,000 years ago and 13,000 years ago, CO2 levels increased to 240 ppm and the broad-leafed C4 plants could grow again. The vegetation that all the Mega-Fauna relied on, changed considerably at about 13,000 years ago and this along with climate change was the main reason for the extinctions.
http://img260.imageshack.us/img260/8371/transitioniceageco2.png
http://tpittaway.tripod.com/sphinx/climate1.gif
http://upload.wikimedia.org/wikipedia/commons/archive/e/e4/20071126225658!Last_glacial_vegetation_map.png