Ancient farmers spared us from glaciers but profoundly changed Earth’s climate
MADISON – Millenia ago, ancient farmers cleared land to plant wheat and maize, potatoes and squash. They flooded fields to grow rice. They began to raise livestock. And unknowingly, they may have been fundamentally altering the climate of the Earth.
A study published in the journal Scientific Reports provides new evidence that ancient farming practices led to a rise in the atmospheric emission of the heat-trapping gases carbon dioxide and methane – a rise that has continued since, unlike the trend at any other time in Earth’s geologic history.
It also shows that without this human influence, by the start of the Industrial Revolution, the planet would have likely been headed for another ice age.
“Had it not been for early agriculture, Earth’s climate would be significantly cooler today,” says lead author, Stephen Vavrus, a senior scientist in the University of Wisconsin-Madison Center for Climatic Research in the Nelson Institute for Environmental Studies. “The ancient roots of farming produced enough carbon dioxide and methane to influence the environment.”
The findings are based on a sophisticated climate model that compared our current geologic time period, called the Holocene, to a similar period 800,000 years ago. They show the earlier period, called MIS19, was already 2.3 degrees Fahrenheit (1.3 C) cooler globally than the equivalent time in the Holocene, around the year 1850. This effect would have been more pronounced in the Arctic, where the model shows temperatures were 9-to-11 degrees Fahrenheit colder.
Using climate reconstructions based on ice core data, the model also showed that while MIS19 and the Holocene began with similar carbon dioxide and methane concentrations, MIS19 saw an overall steady drop in both greenhouse gases while the Holocene reversed direction 5,000 years ago, hitting peak concentrations of both gases by 1850. The researchers deliberately cut the model off at the start of the Industrial Revolution, when sources of greenhouse gas emissions became much more numerous.
For most of Earth’s 4.5-billion-year history, its climate has largely been determined by a natural phenomenon known as Milankovitch cycles, periodic changes in the shape of Earth’s orbit around the sun – which fluctuates from more circular to more elliptical – and the way Earth wobbles and tilts on its axis.
Astronomers can calculate these cycles with precision and they can also be observed in the geological and paleoecological records. The cycles influence where sunlight is distributed on the planet, leading to cold glacial periods or ice ages as well as warmer interglacial periods. The last glacial period ended roughly 12,000 years ago and Earth has since been in the Holocene, an interglacial period. The Holocene and MIS19 share similar Milankovitch cycle characteristics.
All other interglacial periods scientists have studied, including MIS19, begin with higher levels of carbon dioxide and methane, which gradually decline over thousands of years, leading to cooler conditions on Earth. Ultimately, conditions cool to a point where glaciation begins.
Fifteen years ago, study co-author William Ruddiman, emeritus paleoclimatologist at the University of Virginia, was studying methane and carbon dioxide trapped in Antarctic ice going back tens of thousands of years when he observed something unusual.
“I noticed that methane concentrations started decreasing about 10,000 years ago and then reversed direction 5,000 years ago and I also noted that carbon dioxide also started decreasing around 10,000 years ago and then reversed direction about 7,000 years ago,” says Ruddiman. “It alerted me that there was something strange about this interglaciation … the only explanation I could come up with is early agriculture, which put greenhouse gases into the atmosphere and that was the start of it all.”
Ruddiman named this the Early Anthropogenic Hypothesis and a number of studies have recently emerged suggesting its plausibility. They document widespread deforestation in Europe beginning around 6,000 years ago, the emergence of large farming settlements in China 7,000 years ago, plus the spread of rice paddies – robust sources of methane – throughout northeast Asia by 5,000 years ago.
Ruddiman and others have also been working to test the hypothesis. He has collaborated with Vavrus, an expert in climate modeling, for many years and their newest study used the Community Climate System Model 4 to simulate what would have happened in the Holocene if not for human agriculture. It offers higher resolution than climate models the team has used previously and provides new insights into the physical processes underlying glaciation.
For instance, in a simulation of MIS19, glaciation began with strong cooling in the Arctic and subsequent expansion of sea ice and year-round snow cover. The model showed this beginning in an area known as the Canadian archipelago, which includes Baffin Island, where summer temperatures dropped by more than 5 degrees Fahrenheit.
“This is consistent with geologic evidence,” says Vavrus.
Today, the Arctic is warming. But before we laud ancient farmers for staving off a global chill, Vavrus and Ruddiman caution that this fundamental alteration to our global climate cycle is uncharted territory.
“People say (our work) sends the wrong message, but science takes you where it takes you,” says Vavrus. “Things are so far out of whack now, the last 2,000 years have been so outside the natural bounds, we are so far beyond what is natural.”
The reality is, we don’t know what happens next. And glaciers have long served as Earth’s predominant source of freshwater.
“There is pretty good agreement in the community of climate scientists that we have stopped the next glaciation for the long, foreseeable future, because even if we stopped putting carbon dioxide into the atmosphere, what we have now would linger,” says Ruddiman. “The phenomenal fact is, we have maybe stopped the major cycle of Earth’s climate and we are stuck in a warmer and warmer and warmer interglacial.”
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h/t to WUWT reader Chris C.
The paper: https://www.nature.com/articles/s41598-018-28419-5
Glacial Inception in Marine Isotope Stage 19: An Orbital Analog for a Natural Holocene Climate
Abstract
The Marine Isotope Stage 19c (MIS19c) interglaciation is regarded as the best orbital analog to the Holocene. The close of MIS19c (~777,000 years ago) thus serves as a proxy for a contemporary climate system unaffected by humans. Our global climate model simulation driven by orbital parameters and observed greenhouse gas concentrations at the end of MIS19c is 1.3 K colder than the reference pre-industrial climate of the late Holocene (year 1850). Much stronger cooling occurs in the Arctic, where sea ice and year-round snow cover expand considerably. Inferred regions of glaciation develop across northeastern Siberia, northwestern North America, and the Canadian Archipelago. These locations are consistent with evidence from past glacial inceptions and are favored by atmospheric circulation changes that reduce ablation of snow cover and increase accumulation of snowfall. Particularly large buildups of snow depth coincide with presumed glacial nucleation sites, including Baffin Island and the northeast Canadian Archipelago. These findings suggest that present-day climate would be susceptible to glacial inception if greenhouse gas concentrations were as low as they were at the end of MIS 19c.
“These opposing trends are consistent with the prediction from the Early Anthropogenic Hypothesis (EAH) that MIS1 values would have continued falling if not for early agriculture, as they did in other recent interglacials14”
CO2 always was and always is a well mixed gas. How could humans spread out over Africa produce enough of anything especially CO2 to affect anything considering they were all hunter gatherers before 8500 BC?. It is well documented that agriculture as practiced by humans started around 8500 BC. (Neolithic period) in the Mediteranean Fertile Crescent area. There were less than 5 million in population of the world at that time.
One of the studies referenced in this study was a study by one of the coauthors Ruddiman. I quote him in his previous study.
“In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of ∼ 0.8 °C and roughly 2 °C at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models. ”
This climate scientist should have all his funding taken away and he should be enlisted in a special deprogramming regime whereby scientists who stop believing in reality in favour of their models; get help.
Not well mixed on a global scale as the new satelitte measurements have show …
Well mixed, not perfectly mixed.
I think it is well-mixed. Only a difference of a few PPM overall.
The researchers deliberately cut the model off at the start of the Industrial Revolution, when sources of greenhouse gas emissions became much more numerous.
Well of course they did. For a few million humans with no industrial capacity at all, and no use of fossil fuels to materially affect the temperature of the earth, sensitivity to GHG’s would have to be enormous. If they’d allowed the model to continue to run through to the present with sensitivity modeled that high, the modeled temperatures for the present would be high by (WAG) dozens of degrees. They’d have looked like total idiots.
So they cut them off at 1850 to hide, dare I say it, “the rise”?
But, we’re told that CO2 was stable before the industrial revolution.
I got the following from a google search:
“In the Devils Hole, Nevada, paleoclimate record, the last four interglacials lasted over ~20,000 years with the warmest portion being a relatively stable period of 10,000 to 15,000 years duration. This is consistent with what is seen in the Vostok ice core from Antarctica and several records of sea level high stands.”
If the current interglacial has lasted less than 12,000 years, why would anyone conclude that farming has had anything to do with prolonging it? What was it that made the previous interglacials last over 20,000 years, alien visitors stopping by to grow more supplies before continuing on with their long-distance travels?
I’m tired of climate scientists loading the dice when programming computer models, knowing there are too many unknowns to simulate the earth’s climate in any kind of precision. Then they claim the models have verified their understanding of the climate when they spit out exactly what they programmed them to do.
Notice they said “research” and then said “more models”. Models are NOT research.
Models are used in research all the time. Whether the models are useful is another issue.
Models can be useful in helping you figure out what it is you don’t know yet.
Ban the past!
In the early days of the climate hysteria, paleoclimate data quoted by skeptics, was perhaps the biggest threat to the anthropogenic global warming theory – well established facts that they couldn’t explain. At first they ignored the paleo data (probably because they’d never seen it before). Now the climate establishment is all over paleoclimatology, trying to shoehorn it into the “CO2 rules them all” hypothesis. They are learning stuff, and getting more sophisticated as they go, and we see references to insolation and Milankovich cycles. But in terms of producing any evidence that the climate has been dramatically affected by human activity, they aren’t doing very well. This study certainly doesn’t help them; it just makes the idea of anthropogenic forcing look silly.
Agreed. Every field will eventually fall to the climate cult.
It’s not possible to ban the past, Mike. The past will continue to change whether we like it or not. Only the future is certain. /sarc
There ya go…..
The potatoes, rice and squash are what done it. They caused prehistoric global warming.
Currently, it is the CO2 feted arugula, soy beans, and estrogen driven soy boy gynecomastia that’s forcing global warming.
Next time it will be due to planetary gender reassignment: Men are from Mars, or Venus, or Neptune, by Jove! /s
I like to make fun of it but this climate change scam is getting bat shit crazy. Says Vavrus “Things are so far out of whack now, the last 2,000 years have been so outside the natural bounds, we are so far beyond what is natural.” Boy, and Howdy! The ironic truth of Varvus’ so-far-out-of-whack declarations illustrate just how far disconnected from reality the climate change ‘sophisticated model’ based schizophrenia has progressed in the minds of the afflicted. The exhaled breath of every animal on the planet is now classified as ‘pollution’, as is the essential food of all plant life. I fear the dark ages of unreasoning are upon us once more.
“I like to make fun of it but this climate change scam is getting bat shit crazy.” Well said. I really think all of this should be transferred to the science fiction arena, under models run amok and the crazies that follow them. There’s virtually only fiction in any of this at this point. No science at all.
anywhere there is water and a mild temperature then things will grow. It does not need human farmers. Where did all the coal beds come from, busy busy humans of course.
MJE
Sediment on lake bottoms.
“The reality is, we don’t know what happens next. And glaciers have long served as Earth’s predominant source of freshwater.”
This seems a bit off. It’s true that a majority of freshwater volume is currently trapped in glaciers and ice caps, and during glaciations the percentage would be much higher. But as a *source* of freshwater for human use the vast stocks frozen in Greenland and Antartica might as well not exist at all, their contribution to the water cycle is just to calve into the ocean. Most countries have essentially no glacial melt at all, the freshwater coming from some combination of groundwater, rain, and melted *seasonal* snow/ice. Even in places like India glacial melt is not a “predominant” source of freshwater. For example, I found an analysis of the Baspa River basin (originates in Himalyas) showing 81.2% of flow from snowmelt, 11.4% from rainfall, and just 7.4% from icemelt.
Further, in order for the stored freshwater in glaciers to provide *any* net contribution to liquid freshwater, they must be melting! A glacier that releases no more fresh water in the summer than it captures in winter isn’t providing anything at all, just processing snow in a different fashion. A glacier that is growing is actually *removing* fresh water that would otherwise have been available.
Well it does usually even out river flow over the year by releasing meltwater during the often dry summer. Not in India/China though, where most rain comes with the summer monsoon and winter is the dry season. There the glaciers are indeed completely irrelevant as water sources.
Unfortunately, I believe I’ve been infected by the latest mutation of the Feynman virus. He said (in essence): “if the data disagree with your theory, then the theory is wrong.”
So the theory is this: CO2 goes up, temperature goes up. So far, so good?
Okay. Therefore, if there were ever a time when CO2 levels were significantly higher than they are now, and the temperatures were significantly LOWER than they are now, then that would prove the CO2 cannot be a primary driver of temperature, right?
To my knowledge this has happened at least twice . . . wait for it . . . during ice ages. So game, set, and match.
Further, data also show that CO2 trails temperature. So unless those CO2 molecules have little tiny time machines . . .
Oh, I know: the real explanation is that those early farmers had diesel-powered oxen.
Richard, Let me intervene here before you have to hear from RyanS or one of the other trollBots. Haven’t you heard that the sun was a dim bulb back in the Ordovician? It was barely brighter than our dusk at their high noon. And oh, by the way, the CO2 levels were not that high anyway. Look pal, the past will be conformed to our theories. Resistance is futile!
Funny!
It will probably get reported that as the snow gets compressed into Firn, before becoming the next layer of Glacial Ice, a percentage of the CO2 gets compressed out and what remains is what is measured. CO2 levels of the past were likely higher than what CO2 trapped in ice would indicate.
CO2 really needs a more likeable Facebook account so it can get better Firnded. UnFirnding it is a detriment to measurements.
If temperature goes up first, then CO2 follows, and then temp drops again as CO2 is still going up, that also disproves the hypothesis.
Not necessarily. Ocean outgassing/absorption is not the only source/sink. Volcanic action could also drive higher CO2 even in a cooling environment. Human activity has driven CO2 above equilibrium levels. Ocean currents, upwelling, etc. can be a factor. It’s a complex system. But in general, CO2 is mostly going to rise after ocean temperatures rise and drop after ocean temperatures drop.
These “scientists” will soon go the whole hog and “find” evidence that actually the world got out of the ice age because of neolithic farmers interfering with nature. Move over, Milankovitch.
“Things are so far out of whack now, the last 2,000 years have been so outside the natural bounds, we are so far beyond what is natural.” Translation: Human beings on earth are not natural. That leaves us being aliens dropped here from somewhere afar. Funny, I don’t remember learning that in any classes I ever took, but it must be true because these climate scientists said it was and so did their models.
This guy says you’re right. He didn’t hear your question, but the answer has to be…ALIENS
Well, Climate Scientists did evolve from some lesser primate, possibly even Mann
LOL
snicker, giggle, guffaw, ROFLMAO
I was actually looking forward to something discussing the actual advent of agriculture, how humans harnessed specific plant species, the evolution of growing and harvesting techniques, so on and so forth. And yet again it is just a jumble of crap based on crap computer models and pre-concieved political bias. Oh well, guess we could go to a movie, it raining and whatnot.
“Inferred regions of glaciation develop across northeastern Siberia, northwestern North America, and the Canadian Archipelago. ”
This study can thus safely be disregarded, like essentially all such studies of glacial inception based on GCM:s. They always model a huge icecap in Northeastern Siberia, where there never was one. Probably because they are unable to model precipitation realistically.
My problem with all of this is these people are counting how many angels can fit on the head of a pin. They are talking in tenths of a degree with wide error bands; who does that? It’s not real, it’s fake, as in fake science. They are worrying ‘no change’ to take a direction and cry uncle.
Ancient farmers spared us from glaciers but profoundly changed Earth’s climate
Ridiculous, laughable, useless and misleading “research”. Now, maybe, we are having a small effect on temperatures in cities.
Seems to be more “assuming” here than science.
I’ve noticed that once some folks get advanced education in a particular field, they assume they are experts in whatever subject is being discussed. It’s fun to look up what they say and show them when the actual facts disagree.
Wow! What a load of academigog double-spewed garbage!
If you can’t dazzle ’em with brilliance, baffle ’em with bullsh1t.
Irrigation added lots of Water Vapour into the air over a very large area. Of course it’s going to affect the climate. I believe irrigation for agriculture is more important than just agriculture when talking about these things. Agriculture by itself doesn’t change all that much, putting rivers worth of water into the air does.
Worth reading: “Noah’s Flood” by William Ryan & Walter Pitman
What a load of baloney
The farmers dunnit. Yeah, that’s the ticket. Actually, I believe ol’ Flim Flam Flannery proposed the idea in his book, The Weather Makers.
No, boys and girls. Total poppycock. The entire human population was only ~5 million 8000yrs ago and the Anatolia farmers would make up some fraction of that. If they have warmed the planet a couple of degrees to stave off an ice age, Iowa all by itself could do the same.
Am I right in saying that a huge problem with climate science is the gradeschool understanding of effective proportions, scales, magnitudes? I’ve judged highschool science fairs and found these weaknesses, but perhaps not as frequently as I have in climate science. An engineering estimate of the effect of the farmers of Anatolia is that it would be undetctable.
The only difference between now and 800K years ago was a very small increase in CO2 and methane?
If that tiny rise was sufficient to raise the temperature 2.3C, the modern rise should have increased temperatures by 10 times as much. At the very least.
What about the period 400K ago? Similar Milankovitch criteria with low eccentricity causing that interglacial to be a longer one also. Did that period not match their narrative so they left it out?
They need to have this established as its more proof that CO2, the emissions of white male capitalists, need to be banned and their political and economic system ended and changed over to socialism.
Surprised they haven’t spent more time, money, and created more studies on showing how sensitive the climate is to
planet killing maggots</strike. humans. They know they need this 'scientific' link, wouldn't be surprised to see more similar studies in the next 5 years coming out.Why do we pay for this garbage…?
Really?!?
https://youtu.be/5AYIcTVizM4