Climate Craziness of the Week: The AGU peddles a mammoth climate change theory

Yes, our forebears started global warming by hunting the woolly mammoth. Right. Must be the mammoth albedo effect, much like the sheep albedo effect. Oh, wait, no it’s birch trees albedo calculated via pollen proxy. The mammoths stopped eating birch trees, that’s wot did it. And those hunters used cooking fires too. Gosh. I wish I had more time to refute this, travel beckons, but I’m sure readers can lend a hand in comments.

UPDATE: Carl Bussjaeger points out in comments that;

Just last month, USA Today told us that Felisa Smith of the University of New Mexico in Albuquerque discovered that…

Mammoth extinction triggered climate COOLING

File:Woolly mammoth (Mammuthus primigenius) - Mauricio Antón.jpg

Woolly mammoths (Mammuthus primigenius) in a late Pleistocene landscape in northern Spain. (Information according to the caption of the same image in Alan Turner (2004). National Geographic Prehistoric Mammals. Washington, D.C. Image: Wikipedia

Man-made global warming started with ancient hunters

AGU Release No. 10–15 Link here

30 June 2010

For Immediate Release

WASHINGTON—Even before the dawn of agriculture, people may have caused the planet to warm up, a new study suggests.

Mammoths used to roam modern-day Russia and North America, but are now extinct—and there’s evidence that around 15,000 years ago, early hunters had a hand in wiping them out. A new study, accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union (AGU), argues that this die-off had the side effect of heating up the planet.

“A lot of people still think that people are unable to affect the climate even now, even when there are more than 6 billion people,” says the lead author of the study, Chris Doughty of the Carnegie Institution for Science in Stanford, California. The new results, however, “show that even when we had populations orders of magnitude smaller than we do now, we still had a big impact.”

In the new study, Doughty, Adam Wolf, and Chris Field—all at Carnegie Institution for Science—propose a scenario to explain how hunters could have triggered global warming.

First, mammoth populations began to drop—both because of natural climate change as the planet emerged from the last ice age, and because of human hunting. Normally, mammoths would have grazed down any birch that grew, so the area stayed a grassland. But if the mammoths vanished, the birch could spread. In the cold of the far north, these trees would be dwarfs, only about 2 meters (6 feet) tall. Nonetheless, they would dominate the grasses.

The trees would change the color of the landscape, making it much darker so it would absorb more of the Sun’s heat, in turn heating up the air. This process would have added to natural climate change, making it harder for mammoths to cope, and helping the birch spread further.

To test how big of an effect this would have on climate, Field’s team looked at ancient records of pollen, preserved in lake sediments from Alaska, Siberia, and the Yukon Territory, built up over thousands of years. They looked at pollen from birch trees (the genus Betula), since this is “a pioneer species that can rapidly colonize open ground following disturbance,” the study says. The researchers found that around 15,000 years ago—the same time that mammoth populations dropped, and that hunters arrived in the area—the amount of birch pollen started to rise quickly.

To estimate how much additional area the birch might have covered, they started with the way modern-day elephants affect their environment by eating plants and uprooting trees. If mammoths had effects on vegetation similar to those of modern elephants , then the fall of mammoths would have allowed birch trees to spread over several centuries, expanding from very few trees to covering about one-quarter of Siberia and Beringia—the land bridge between Asia and Alaska. In those places where there was dense vegetation to start with and where mammoths had lived, the main reason for the spread of birch trees was the demise of mammoths, the model suggests.

Another study, published last year, shows that “the mammoths went extinct, and that was followed by a drastic change in the vegetation,” rather than the other way around, Doughty says. “With the extinction of this keystone species, it would have some impact on the ecology and vegetation—and vegetation has a large impact on climate.”

Doughty and colleagues then used a climate simulation to estimate that this spread of birch trees would have warmed the whole planet more than 0.1 degrees Celsius (0.18 degrees Fahrenheit) over the course of several centuries. (In comparison, the planet has warmed about six times more during the past 150 years, largely because of people’s greenhouse gas emissions.)

Only some portion—about one-quarter—of the spread of the birch trees would have been due to the mammoth extinctions, the researchers estimate. Natural climate change would have been responsible for the rest of the expansion of birch trees. Nonetheless, this suggests that when hunters helped finish off the mammoth, they could have caused some global warming.

In Siberia, Doughty says, “about 0.2 degrees C (0.36 degrees F) of regional warming is the part that is likely due to humans.”

Earlier research indicated that prehistoric farmers changed the climate by slashing and burning forests starting about 8,000 years ago, and when they introduced rice paddy farming about 5,000 years ago. This would suggest that the start of the so-called “Anthropocene”—a term used by some scientists to refer to the geological age when mankind began shaping the entire planet—should be dated to several thousand years ago.

However, Field and colleagues argue, the evidence of an even earlier man-made global climate impact suggests the Anthropocene could have started much earlier. Their results, they write, “suggest the human influence on climate began even earlier than previously believed, and that the onset of the Anthropocene should be extended back many thousands of years.”

This work was funded by the Carnegie Institution for Science and NASA.

Notes for Journalists

As of the date of this press release, the paper by Doughty et al. is still “in press” (i.e. not yet published). Journalists and public information officers (PIOs) of educational and scientific institutions who have registered with AGU can download a PDF copy of this paper in press.

Or, you may order a copy of the paper by emailing your request to Maria-José Viñas at Please provide your name, the name of your publication, and your phone number.

Neither the paper nor this press release are under embargo.


“Biophysical feedbacks between the Pleistocene megafauna extinction and climate: The first human‐induced global warming?”


Christopher E. Doughty, Adam Wolf, and Christopher B. Field, Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA


Readers, I urge you to write to newspapers and magazines that carry this story.


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Green Sand

“Readers, I urge you to write to newspapers and magazines that carry this story.”
and may I respectfully suggest writing to two other organisations:-
“This work was funded by the Carnegie Institution for Science and NASA.”

To about the same degree that a four-year-old contributes to global warming by peeing in the ocean.

Nolo Contendere

Sigh. This would be funny if it weren’t so pathetic.


Whether or not it stays within them, post normal science has no necessity to heed the boundaries of reality. Yes, anything is possible.

But wait! Aren’t people also arguing that cow flatulence is a cause of global warming? Presumably, mammoth farts were, well, fairly mammoth. We must immediately fund a study to determine whether the elimination of mammoth farts offset the effect of increased birch tree cover.

John Trigge

But….but….more trees would sequester more CO2 to counteract the mammoth flatulence.
And, if both mammoths and birch trees are natural, more or fewer of either (or both) would have ‘some’ effect on the climate so can we blame Nature for destroying her/himself?

Rob R

Regardless of whether there is any substance to the conclusions one would have to ask “so what”. The effect, if any, occurred about 15,000 years ago, and surely by now the various affected species have adapted to the lack of Mamoths and the slight change to the climate.
Yet another non-event in the history of climate-science.

Olaf Koenders

I wonder if the Carnegie Institute will fund a dull study on my backyard if I tag on the word “climate” or “global”..

My neighbors have a tree overhanging my driveway with hundreds of birds in it. They are making a mess out of my car, which is normally white.
The bird poop is decreasing the albedo of my car, and thus causing Polar Bears to suffer. For the good of the planet, I’d like to take a 12-gauge to the birds – but city ordinances prevent me from rescuing the planet.

Layne Blanchard

I was digging a posthole in the backyard, and discovered an ancient record of beetle dung. Studying this find, I learned I could monitor the beetle diet from traces in the dung. This became a proxy for climate, the entire history of plants and animals, and the advance of civilization. I began digging furiously, proceeded back thru time, past the ice ages, and discovered to my shock that an entire human civilization lived on earth before even the dinosaurs. Studying carefully the bits of writing in documents in the beetle dung, I determined this society exterminated itself to save the planet.

Back in the ’80’s, before academics became HOPELESSLY MIRED IN POLITICS AND VIEWPOINTS, there was an anthropology professor at the University of Minnesota.
He would start his class on “Food supply and population of primative cultures” by asking, “About how many ‘Native Americans’ were in north American before the ‘white man’ arrived?” As I recall, answers varied from 6 million to 60 million. He then would say, “There were less than 1 million, TOTAL…probably closer to 300,000 to 500,000..on the basis of food supply, gathering, and storage techniques.”
He then spent the rest of the quarter, taking young heads filled with mush, and trying to make it a little more solid. As I recall, he came up with a number akin to 1 square mile of “capable” land needed for every “Native American” family to survive. Yes, some of the Native American groups were cultivators. But the remains from these people tend to show they had no means to store more than a partial season’s worth of crop, and enough to plant the next season.
AS SUCH, let’s say that the current rate of CO2 growth would hold proportionately to the “Native Americans”. Wow, they’d be responsible for 1/600 the growth rate, or 1/300 PPM per year. Dramatic influence there. Oh, I forget, it’s the knock down of the Mammoths that did it. I put that in the same realm as the wolves on Isle Royal in MN controlling the Moose population. Heck, that’s a great study right there in GROUP THINK and an ERRONEOUS CONCLUSION propagated for YEARS by people with “credentials”. (By the way, Moose population controlled by: 1. Hardness of the winters…winter kill, and 2. A plant, vital to moose fertility, with a 7 year peak and trough abundance cycle.)


Think about all the potential methane emissions our ancestors cut down by killing those huge walking stomachs.

Ian Mc Vindicated

Who writes this nonsense. I still can’t believe it even gets published even on the internet.. I am still shaking my head that some people actually believe man can alter or control the climate…it is utter nonsense. Ian


I don’t like cold weather. Which species should I hunt to extinction next to assure that it won’t ever return?

John H

Now, now…according to this article
mammoth farts kept the planet warm, so if they killed all the mammoths it should have caused global cooling. We also have a guy painting the Andes this week. Just when you think the “warmers” can’t possibly get any dumber or desperate, they prove you wrong. I’m waiting for the next one, which shouldn’t be soon.

D. King

What a mammoth waste of money.


I want to see evidence of how vegetation can affect climate. Anyone?


Just another imaginative story based on one truth – the mammoth is now extinct. There must be a cause (man) and an effect (AGW.) How cleaver?


Once again, correlation is causality – provided it causes “global warming.”
But the general public often buys it all based on horribly botched works like Al Gore’s.


Sounds even worse than some of the reasoning behind the homesteading act (mid to late 1800’s). The belief at the time regarding the lack of RAIN in the Great Plains was the lack of trees. Once trees were planted, the rain would surely come. After all, there is plenty of rain and trees east of the Mississippi!
Needless to say, this theory was eventually abandoned.

David L


But… but… but…
Just last month, USA Today told us that Felisa Smith of the University of New Mexico in Albuquerque discovered that…
Mammoth extinction triggered climate COOLING
Apparently we killed off those wonderful mobile methane manufacturers.
Which naturally prompted me to make the following comments:
“Okay, now that you’re done laughing at the patent absurdity that a tiny population of primitive hunter/gatherers armed with – at best – stone-tipped spears completely wiped out all the over-sized critters, that I’d avoid unless armed with a Barrett .50 cal, on the entire continent – including areas they hadn’t even reached yet – let’s pretend this is real. Now tell Gore to shut the eff up; we’re just fixing what we broke 12,000 years ago.” (May 23, 2010 5:45PM)
Now if only someone would hunt the giant sex-crazed poodles to extinction.


‘Normally, mammoths would have grazed down any birch that grew, so the area stayed a grassland.’
Oh, now I get it, so the fact that the “tiny” speck of ice that melted during the last couple of thousand years ending that ice age didn’t have anything to do with it. Neither, of course, did the fact that when the ground became bare it was still cold enough to freeze the ground to “six feet” down, and more, and only heating up one foot or so during summer leaving the rest frozen still, have anything to do with it.
The few mammoths that the humans hunted down far vastly had a more impact then all the natural change that the mammoths couldn’t adapt too. Or maybe Siberia had a large population back in the day, maybe russian ice boarders perhaps?


Isn’t the corollary of this theory that prior to mankind coming on the scene we had Woolly Mammoth induced cooling?

Nick Yates

But that can’t be right. According to this theory, when humans killed the mammoths the sudden drop on methane produced the Younger Dryas cold episode. Or perhaps they all just can’t see the mammoth in the room 😉

David L

BenS says:
June 30, 2010 at 3:20 pm
Just another imaginative story based on one truth – the mammoth is now extinct. There must be a cause (man) and an effect (AGW.) How cleaver?”
Yes, it’s very formulaic. Take a fact, link it to evil humans, and conclude AGW.
How about this: some unknown effect caused the retreat of the ice age, making the climate more hospitable for humans and birch trees and less hospitable for mammoths. If that effect reversed then the climate will become more hospitable for mammoths and less hospitable for humans and birch trees.

Peter Miller

The following is an equally stupid hypothesis:
There have been ~10 warm interglacial periods during the Pleistocene Ice Age.
That means man must have killed off the mammoths ten times over the past couple of million of years to create these warm periods, otherwise these warm periods would never have occurred.
The expression “climate scientist” is once again shown to be an oxymoron.


Let me see if I got this straight: If I make up stuff like this and write it down I can get lots of money??

Al Gore

See….I told you so….mammoths caused global warming….I mean global cooling….aww hell….where’s that masseuse that global warming in my pants is acting up again!


There was never any mammoths on Venus and look at it today… out of control global warming there!!!


When one looks at the ice records, this happened around 100,000 years ago. Is this an indication that we are repeating history? No point in doing anything about it because it all worked out all right in the past.

Gary Pearse

How many of those pesky beasts were there? There were only a few million people in the world at the end of the ice age and most of them lived in warmer climates than the regions where the mamoth roamed – heck this is true today. So some thousands of hardy hunters killed off some hundreds of mamoths a year – many, but apparently not all, were replaced by mamoth offspring. And the birch trees encroached. I would say 15,000 years ago they were pretty spindly birch – like the dwarf birch of about a meter high or so that one can still find in the Yukon (the roots are great for smoking artic grayling, dahl sheep and the like which I enjoyed greatly some 40 years ago – so I guess mea culpa on a global warming contribution, although ripping out some of the birch for smoke may have held them off and I might have been GW neutral).
In earlier posts after the Climategate affair, I predicted that the desperation and hysteria would redouble and a fury of crazy articles would fill up the usual journals until, at last, it would all reduce to a small nutty end-of-the-world fringe that is always with us. Note that several of the nuttiest AGW types, like Ehrlich the biologist, were screaming back in the 1970s about the coming ice age and deaths of billions by 2000. He’ll be back to tell us “I told you so” on the ice age in the next few years.


Men and Mammoths could not live on the same territory… one of them had to go. Good for us it turned that way.


At least they admitted the planet has only warmed .6 (6/10th) of a degree in the past 150 years……..
that’s a start


What are they waiting for, then? Get out the cloning kit and get busy.
As soon as they can bring back the Woolly Mammoth, the better.

North of 43 and south of 44

Study forthcoming on the true cause of climate change, crazed poodle sex, er, help me here which NGO or government organization gives out grants for studying the climatic impact of poodle sex?
CRU must have some money still in the till, the fine media mouthpieces that run Realclimate should also have a few dollars.


What nonsense. World population back then was less than 1 million. Less than the population of Rhode Island, spread out all over the planet. Idiots.


So let me get this right. It was the extinctions in North America that triggered global cooling. The extinctions in other parts of the world at other periods did not have this effect?
So if the loss of some of the large mammal species in one continent was enough to cool the planet what would be the effect if every single species died out at the same time? I’m not thinking about those piddling little mammoths. I’m thinking DINOSAURS. The fart shortage must have been immense for millions of years. So that is why there was a massive ice-age for millions of years at the beginning of the Tertiary – NOT.
Hey, could this be a new theory about the extinction of the dinosaurs? It wasn’t an asteroid impact nor the Deccan Traps, it was those public spirited dinosaurs holding it in for the sake fo the planet that caused them all to die.

This is utter, utter hogwash. They have it COMPLETELY BACKWARD.
The Younger-Dryas stadial (12,800 to 11,500 years ago), otherwise known as “The Big Freeze” coincides with the extinction of large fauna in North America and most of them in Siberia (one small species of mammoth survived a few more thousand years).
The onset of the Younger-Dryas stadial is accompanied in the geological record by a black mat:

…[A] charred carbon-rich layer of soil that has been found at some 50 Clovis-age sites across the [North American] continent. The layer contains unusual materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, charcoal, soot, and fullerenes enriched in helium-3)… at the very bottom of the “black mat” of organic material that marks the beginning of the Younger Dryas.

Remains of large fauna in NA is found up to and slightly into the black mat, but not above it. Remains of Clovis man is also found up to the black mat and no further. This has led – along with the nanodiamonds, fullerenes, Iridium, Helium-3 and spherules – to the new (dating only from 2007) hypothesis of what is called the Younger-Dryas Impact Event, which is currently being researched widely.
While it may be too early to say definitively that The Big Freeze was not caused by an impact (the jury is still out – even though Iridium, nanodiamonds, Helium-3 and magnetic spherules are almost always considered 100% evidence of an impact), evidence is being accumulated at a rapid rate because of serious interest in the hypothesis, and the black mat and extinctions are solid fact, regardless of the final conclusions.
What are these people smoking?

P Wilson

Maybe this newly discovered mammoth correlation supplant’s all others The cooler the temperature, the more mammoths.
to quote:
“(AGU), argues that this die-off had the side effect of heating up the planet.”
There must have been another extinction of mammoths since the late 1920’s, a renaissance since the 1940’s, and another mammoth extinction since the late 1970’s.
During the holocence optimum there were none. They staged a revival during the little ice age, soon to see their numbers decline during the1870’s (again)
remarkable creatures

The mammoth die off did NOT happen at 15,000 years ago. They don’t know what they are talking about. It happened at the onset of the Younger-Dryas, at 12,800 years ago.
What utter trash.

The odd thing about this is that it is the AGU who hosted the conference in Acapulco in 2007 about the Younger-Dryas Impact Event. It appears the AGU is speaking out of both sides of its mouth.
The best that can be said for the AGU is that they are open to competing hypotheses.
But this idea is as unsound as the ships slinging mist up into the stratosphere.
DAMMIT, PEOPLE! Speculation is not science.

P Wilson

North of 43 and south of 44 says:
June 30, 2010 at 3:54 pm
“Study forthcoming on the true cause of climate change, crazed poodle sex, er, help me here which NGO or government organization gives out grants for studying the climatic impact of poodle sex?”
I think the real cause of climate cooling/warming is Maine Coon breeding. The more red coloured, the cooler the planet. Ther darker the breed, the greater the absorbtion of life-giving heat.
The poodle notion would only support global cooling, as poodles have a high albedo (and sex drive) , and reflect solar energy (assuming they’re white). Therefore, the more poodles, the greater the threat of an ice age.
I’m sure they would give a whopping big grant to poodle breeders, if it gets too darned hot….

Chuck L

Well, if NASA is funding the study, they must be on to something! . The word that comes to mind is “shameless.”


At some point the CAGW movement must publish the complex book upon which their belief is founded. I am sure it will sell well. Those interested can then debate the difference between climate truth and climate fact – endlessly.
Everyone else will try to avoid them in airports.


And don’t forget, children, every paper these authors get published increases their “expertise”, and makes each of you more of a “denier”.


Therefore… killing trees will save the planet? o_O

k winterkorn

So the mammoths were committing the eco-sin of deforesting large parts of North America, and the eco-guys are upset that we whacked them till they were gone. Yet Man cuts down a few trees in the Amazon to make some living space, and the same ecoguys are upset at us. What’s that all about?

Gail Combs

So how does this explain the famous Beresovka mammoth carcass
“..The remains of its stomach were intact and there were grasses and buttercups lodged between its teeth. The flesh was still edible…”