Why did agriculture start 13,000 years ago?

WUWT reader Susan Corwin writes:

Because it would work as CO2 became plentiful!

All the academic articles say: “and then agriculture happened”.

The “accepted wisdom”/consensus is:

….here was no single factor, or combination of factors, that led people to take up farming in different parts of the world.

But It is simple: it occurred because it Started Working.. 13,000 years ago.

People are clever, resourceful, adaptive, looking out for the best for their kids.

If it doesn’t work, it won’t happen.

If it will work, someone will figure it out and their kids/tribe will be successful

The Greenland Ice Chart for 9000 to 21000 years before present shows why agriculture arose:

(as presented on WUWT by Andy May)

GreenlandIceCore

So, my conclusion is that over 4,000 years or 160 generations, things improved and they tried, and tried, and tried again until it worked: people are smart.

…and animals actually could be pastured.

Starting 14,000 yag, the sparse, scraggly growth started getting thicker and slightly more abundant.  It wasn’t very good, but is was much better than 16000 yag.

=> and clever people could keep various animals alive in a herding lifestyle.

Source: http://www.mochaexpress.com/Commentary/Elucidate/AgricultureBecamePossible/

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Bear

Wow.

John Silver

Wow indeed.
I’m totally gobsmacked with awe.
Someone understand something.

Leo G

Don’t be too go smacked- the basic premise of this story is false. While it is true that many plants need an atmospheric concentration of at least 150 ppm during the growing season, not all plants have that requirement. In particular, most of the grasses on which agriculture depend can survive at atmospheric CO2 levels as low as 10 ppm.
The 1992 article in Nature by Ken Caldeira and James Kasting “The lifespan of the biosphere revisited” corrected the same misconception in a 1970s article by James Lovelock and Mike Whitfield in the same journal.

Gabro

Higher CO2 and genetic engineering can help solve the problem of feeding nine to ten billion people:
http://www.climatechangenews.com/2016/04/05/super-co2-sucking-crops-could-save-the-world-from-starving/
Leo,
Which C3 crops do you suppose can survive at 10 ppm?

gnome

You really need to re-read what you wrote, Leo G, and when you realise how stupid it is, come back and apologise all-round. Grass may be able to survive at 10ppm CO2 (I can’t imagine it but it might be true) but grass can also survive in deserts and at polar latitudes.
There’s a big difference between keeping stock where stocking rates of one animal to two square miles is possible and where stocking rates are one to the acre or less.

Gabro

Optimum CO2 level for winter wheat is 890 to 970 ppm, depending upon which metric you use:
http://www.ncbi.nlm.nih.gov/pubmed/26253981

Leo G

gnome, Grasses such as rice, wheat and maize do not die at CO2 levels below 160ppm as the article claims, and they are relatively insensitive to CO2 levels.

Duster

I doubt that agriculture started because CO2 became adequate in concentration. In fact agriculture appears to start because the human predator has inadequate prey and excess numbers, but, being adaptable, we can shift to lower grade diets – I know every vegetarian reading has spiking blood pressure but the facts are the facts. We are not obligate predators but we can survive as pure predators. Except in ideal environments – which excludes most of the planet – we cannot survive as pure vegetarians. We don’t have the teeth, nor do we have the digestive capability, or the patience (there’s a reason we have civilizations and our nearest relatives spend most of the day chewing). Cooking plants – and meat for that matter makes a huge difference to its digestibility – but to be a vegetarian we absolutely need all the dietary basics in the plant environment and – unlike most animal species – much of the plants we survive on lack on or more essentials (Vitamin D is the big one) and are often toxic without treatment or specialized breeding (acorns, maize, nightshades, cassava, etc.).

Gabro

Leo,
You’ve offered not the least shred of evidence that C3 crops and trees can survive at 10 ppm. Your assertion, I’m sorry, is laughable.
Higher CO2 has led to record crop yields and tree growth. More would be better. Much more. At least another doubling from 400 to 800 ppm. But 800 to 1000 ppm would be even better. Beyond that, there are diminishing returns.

Gabro

Duster,
Agriculture allowed there to be more, but inferior, humans. From stunted size to tooth decay, early agriculturalists were inferior to their hunter-gatherer ancestors. But there were more of them.
Agriculture allowed people to settle down more. Hunter-gatherers need to be on the move. So do slash and burn cultivators, but less often.

mandrake9

Why so shrill, gnome? Leo G did leave more than a shred of evidence, he left the title of an article easily googled that has an additional two references for the contention in question. Link: http://www.nature.com/nature/journal/v360/n6406/abs/360721a0.html
Sure, it may be completely mistaken, but screaming “stupid” and “laughable” while ignoring it is not in the highest tradition of WUWT.

Gabro

Mandrake.
Leo’s link doesn’t say what he imagined it did. He still can’t or won’t answer the question about C3, C4 and CAM plants.
His link talks about the biosphere, not the ability of plants to support agriculture and human population.
Yes, a biosphere could exist with only C4 and CAM plants, but humanity could not. Nor much of the rest of the plant, animal and fungus kingdoms, ie multicellular life.
He clearly doesn’t get the distinctions among CAM, C4 and C3 plants. Agriculture supportive of human life cannot exist without C3 plants. In fact, hunting and gathering wouldn’t work, either. Leo fails to grasp the importance of C3 plants.

mandrake9

As I indicated, I’m not surprised Leo G’s reference didn’t pan out, but I was waiting for a substantive reply, such as you have provided (thanks!), rather than screamed insults.

Gabro

PS:
On Planet Leo there would also be no trees, along with most of crops that sustain humans and many other animals.
Indeed, there might not be enough oxygen for any animals.

JohnKnight

Oh . . an article in Nature . . shiver me freakin’ timbers . .
How ’bout a link to some actual experiments of some kind, that we can examine and consider for ourselves, O Siants worshipers?

Chuck Dolci

I think the problem with Leo G’s position is his insistence that grasses can “survive” at very low CO2 levels. That may be true, but that is not the question. There is a difference between surviving and thriving. Grasses may survive but to support herds of grazing animals and growing populations of humans, grasses and other plants (man does not live by grass alone) have to grow like weeds (pardon the pun). Early agriculture booms when the conditions are such that in the morning you spit out a watermelon seed and by nightfall you have a fully mature plant with nice big fat fruit.

Leo G

“You’ve offered not the least shred of evidence that C3 crops and trees can survive at 10 ppm. Your assertion, I’m sorry, is laughable.”
You are offering a straw man as rebuttal. The premise under test was one that NO plants could survive atmospheric CO2 levels below the “red line” on the chart, which seemed to be just below 160 ppm. The premise is FALSE.

Crispin in Waterloo

My reply mostly addresses contributions by Duster, partly it’s to others
Human teeth are evolved to live on a diet of fruits and nuts, full stop. We can survive as pointed out, eating meat only under certain conditions but this is rare and requires a complete change in the gut bacteria. We are poorly constructed as carnivores. As pointed out in the book on our water-based evolution ‘The Aquatic Ape’, we are also not evolved to live on savanna as is frequently asserted. We require far to much water.
All that considered, once humans roamed out of the tropics and survived as largely hunters of meat in the temperate regions, a health catastrophe began when farming began. Farmers, based on skeletal remains, were in much poorer general health than temperate zone hunters. The farming societies were not eating a healthy balanced diet as did their tropical cousins. Health and longevity are associated with an almost totally vegetarian diet with very little meat. But almost monocropping a few plants is a poor substitute for a proper diet, especially with a lack of nuts and a surfeit of beer. A lot of agricultural produce is and was devoted to getting drunk or stoned.
All things considered, hunter-gatherers did very well with little effort, a couple of hours a day, in the places favourable to it. Those who had to herd and plant worked a lot harder and had to learn to cooperate a lot more. That led to the social advances described. Societies that learned to herd but never engaged in agriculture were socially stunted. Agriculture is artificial gathering but requires large scale collaboration, greater as one leaves the equator. Once we have developed enough socially, we will all be able to re-engage our healthier vegetarian roots. At the moment it is too soon. That said, every little bit of additional CO2 helps.

ralfellis

The trouble with C4 grass agriculture, is that C4 grasses are thick-walled and indigestable to most ruminents. Pastoral agriculture without C3 plants would be very poor, and perhaps not viable. However, C4 maize does produce a viable seed product.

RoHa

“A lot of agricultural produce is and was devoted to getting drunk or stoned.”
You write that as though it were a bad thing.

LeoG said:
“Grasses such as rice, wheat and maize do not die at CO2 levels below 160ppm as the article claims, and they are relatively insensitive to CO2 levels.”
Leo, rice and wheat are C3 plants, not C4. They require CO2 levels above ~160 ppm to survive, and more to thrive. These are the two leading food crops in the world. The current population of Earth could not survive without rice and wheat.
C4 plants can allegedly survive at lower CO2 levels, although one does wonder about their growth rates, which likely suffer at low CO2. Corn and maize are C4, as is sugarcane – are you suggesting that the current world population could survive on Corn Flakes? Much of current corn production goes to manufacture fuel ethanol, as does much of sugarcane production.
I suggest that your above posts are generally false and/or misleading.
http://www.cropsreview.com/c3-plants.html
Examples of C3 plants:
– most small seeded cereal crops such as rice (Oryza sativa), wheat (Triticum spp.), barley (Hordeum vulgare), rye (Secale cereale), and oat (Avena sativa); soybean (Gycine max), peanut (Arachis hypogaea), cotton (Gossypium spp.), sugar beets (Beta vulgaris), tobacco (Nicotiana tabacum), spinach (Spinacea oleracea), potato (Solanum tuberosum); most trees and lawn grasses such as rye, fescue, and Kentucky bluegrass.

Further LeoG:
Corn (aka maize, a C4 crop) is a New World crop, first cultivated in the Americas about 10,000 years ago.
In the Old World, writer Susan Corwin’s hypothesis could indeed be correct, since Old World grains such as wheat and rice (C3 crops first cultivated in Asia) require at least 160ppm to survive and more to thrive and produce good crop yields.
Readers may be interested to know about the C4 Rice Project:
http://c4rice.irri.org/index.php/component/content/article/19-about/55-why-c4-rice
“Converting the photosynthetic system in rice to the more efficient, supercharged C4 one used by maize would increase rice yields while using scarce resources (land, water, fertilizer) more effectively. However a technological innovation of this magnitude requires the skills and technologies of a global alliance of multidisciplinary partners from advanced institutions. In 2008, IRRI formed the International C4 Rice Consortium.”
I wrote about CO2 starvation in 2009 or earlier, and I suggest this 2009 post still has validity:
https://wattsupwiththat.com/2009/01/30/co2-temperatures-and-ice-ages/#comment-79524
(Plant) Food for Thought (apologies – written too late at night)
Background:
http://www.planetnatural.com/site/xdpy/kb/implementing-co2.html
1. “As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels – below ~200 ppm – will cease to grow or produce.”
http://en.wikipedia.org/wiki/Carbon_dioxide_in_the_Earth's_atmosphere
2. “The longest ice core record comes from East Antarctica, where ice has been sampled to an age of 800 kyr BP (Before Present). During this time, the atmospheric carbon dioxide concentration has varied by volume between 180 – 210 ppm during ice ages, increasing to 280 – 300 ppm during warmer interglacials…
… On longer timescales, various proxy measurements have been used to attempt to determine atmospheric carbon dioxide levels millions of years in the past. These include boron and carbon isotope ratios in certain types of marine sediments, and the number of stomata observed on fossil plant leaves. While these measurements give much less precise estimates of carbon dioxide concentration than ice cores, there is evidence for very high CO2 volume concentrations between 200 and 150 myr BP of over 3,000 ppm and between 600 and 400 myr BP of over 6,000 ppm.”
Questions and meanderings:
According to para.1 above:
During Ice ages, does almost all plant life die out as a result of some combination of lower temperatures and CO2 levels that fell below ~200ppm (para. 2 above)? If not, why not?
Does this (possible) loss of plant life have anything to do with rebounding of atmospheric CO2 levels as the world exits the Ice Age (in combination with other factors such as ocean exsolution)? Could this contribute to the observed asymmetry?
When all life on Earth comes to an end, will it be because CO2 permanently falls below 200ppm as it is permanently sequestered in carbonate rocks, hydrocarbons, coals, etc.?
Since life on Earth is likely to end due to a lack of CO2, should we be paying energy companies to burn fossil
fuels to increase atmospheric CO2, instead of fining them due to the false belief that CO2 causes dangerous global warming?
Could T.S. Eliot have been thinking about CO2 starvation when he wrote:
“This is the way the world ends
Not with a bang but a whimper.”
Regards, Allan 🙂

Campesino

Agriculture allowed people to settle down more. Hunter-gatherers need to be on the move.
=======================
No, agriculture *forces* people to settle down. They may not necessarily want to.
Hunter-gatherers don’t necessarily need to be on the move. It totally depends on the environment where they live.
For example, Indians on the California coast or in the Pacific Northwest, were always hunter-gatherers but were able to live in large permanent villages they had plentiful resources year-round

Campesino:
“No, agriculture *forces* people to settle down. They may not necessarily want to.
“Hunter-gatherers don’t necessarily need to be on the move. It totally depends on the environment where they live.
“For example, Indians on the California coast or in the Pacific Northwest, were always hunter-gatherers but were able to live in large permanent villages they had plentiful resources year-round”
When I studied prehistory (too long ago now!), the (new but accepted) theory was that the development of agriculture was all a bit of an accident. (I pass no comment on the importance of atmospheric CO2 concentrations, other than to say these things are rarely attributable to single causes – except, of course, for CAGW (sarc off)).
As others have pointed out, it takes a labour input of only about 4 hours a day for a hunter-gatherer to subsist – even in the Kalahari Desert (as Sahlins and Sahlins found – if memory serves). Why would people engage in settled agriculture, which required around 12 hours a day? Not because they knew that this would eventually lead to cities, writing, and civilisation! (That took many years).
It was found that a family could gather enough wild emmer wheat for a year in about three weeks. That meant they could become sedentary and cease practices to limit population – that often included infanticide and the infirm elderly ‘doing the decent thing’ when they heard the owl call their name, as it were. So the ease of harvesting wild grain led to a population boom, which eventually required some actions to ensure the next year’s harvest – and eventually agriculture had to intensify. Grain had to be stored, seed had to be retained, etc. (None of this was necessary on the Pacific Northwest – but they did not develop agriculture, because they did not need to because of the abundance of resources, but I seem to remember the Kwakiutl had some practices that limited population).
There was a similar story with the domestication of animals, which was thought to be a difficult achievement – until someone found that you could domesticate a wild musk ox in about three weeks.
In the case of both, it is the context that evolves and develops. There is no great strategic, ‘lightbulb’ moment, but rather a series of micro decisions that each make sense and lead eventually to fundamental change.

I googled “CO2 starvation” and found 483,000 hits including numerous papers – below is one from the Royal Society published in 1998 and entitled “Carbon dioxide starvation, the development of C4 ecosystems, and mammalian evolution”.
The very real threat to humanity and the environment of CO2 starvation has been carefully ignored by warmist fanatics. As I stated in my 2015 paper (below):
“4. CO2 is the feedstock for carbon-based life on Earth, and Earth’s atmosphere and oceans are clearly CO2-deficient. CO2 abatement and sequestration schemes are nonsense.”
https://wattsupwiththat.com/2016/05/28/greens-blame-donald-trump-for-crumbling-paris-climate-accord/comment-page-1/#comment-2225245
[excerpt]
We have known since about 1985 that global warming alarmism was scientifically wrong – a false crisis.
We have known with greater certainty since about 2002 that it was a deliberate fraud.
Regards to all, Allan
*************************
Carbon dioxide starvation, the development of C4 ecosystems, and mammalian evolution
T. E. Cerling, J. R. Ehleringer, J. M. Harris
Published 29 January 1998. DOI: 10.1098/rstb.1998.0198
http://rstb.royalsocietypublishing.org/content/353/1365/159
Abstract
The decline of atmospheric carbon dioxide over the last 65 million years (Ma) resulted in the ‘carbon dioxide–starvation’ of terrestrial ecosystems and led to the widespread distribution of C4 plants, which are less sensitive to carbon dioxide levels than are C3 plants. Global expansion of C4 biomass is recorded in the diets of mammals from Asia, Africa, North America, and South America during the interval from about 8 to 5 Ma. This was accompanied by the most significant Cenozoic faunal turnover on each of these continents, indicating that ecological changes at this time were an important factor in mammalian extinction. Further expansion of tropical C4 biomass in Africa also occurred during the last glacial interval confirming the link between atmospheric carbon dioxide levels and C4 biomass response. Changes in fauna and flora at the end of the Miocene, and between the last glacial and interglacial, have previously been attributed to changes in aridity; however, an alternative explanation for a global expansion of C4 biomass is carbon dioxide starvation of C3 plants when atmospheric carbon dioxide levels dropped below a threshold significant to C3 plants. Aridity may also have been a factor in the expansion of C4 ecosystems but one that was secondary to, and perhaps because of, gradually decreasing carbon dioxide concentrations in the atmosphere. Mammalian evolution in the late Neogene, then, may be related to the carbon dioxide starvation of C3 ecosystems.
*************************
EVIDENCE SUGGESTING TEMPERATURE DRIVES ATMOSPHERIC CO2 MORE THAN CO2 DRIVES TEMPERATURE
September 4, 2015
By Allan MacRae
https://wattsupwiththat.com/2015/06/13/presentation-of-evidence-suggesting-temperature-drives-atmospheric-co2-more-than-co2-drives-temperature/
Observations and Conclusions:
1. Temperature, among other factors, drives atmospheric CO2 much more than CO2 drives temperature. The rate of change dCO2/dt is closely correlated with temperature and thus atmospheric CO2 LAGS temperature by ~9 months in the modern data record
2. CO2 also lags temperature by ~~800 years in the ice core record, on a longer time scale.
3. Atmospheric CO2 lags temperature at all measured time scales.
4. CO2 is the feedstock for carbon-based life on Earth, and Earth’s atmosphere and oceans are clearly CO2-deficient. CO2 abatement and sequestration schemes are nonsense.
5. Based on the evidence, Earth’s climate is insensitive to increased atmospheric CO2 – there is no global warming crisis.
6. Recent global warming was natural and irregularly cyclical – the next climate phase following the ~20 year pause will probably be global cooling, starting by ~2020 or sooner.
7. Adaptation is clearly the best approach to deal with the moderate global warming and cooling experienced in recent centuries.
8. Cool and cold weather kills many more people than warm or hot weather, even in warm climates. There are about 100,000 Excess Winter Deaths every year in the USA and about 10,000 in Canada.
9. Green energy schemes have needlessly driven up energy costs, reduced electrical grid reliability and contributed to increased winter mortality, which especially targets the elderly and the poor.
10. Cheap, abundant, reliable energy is the lifeblood of modern society. When politicians fool with energy systems, real people suffer and die. That is the tragic legacy of false global warming alarmism.
Allan MacRae, Calgary

+1!

PaleoSapiens

For another ‘wow’ see Gobekli Tepe (lots of chaff to sift through on YouTube but, some useful introduction is there). Archeological dates of 14,000 years have been put to parts of the site(s).
Long story shortened: Agriculture may have started much earlier due to man’s desire of building stone ‘temples.’ In other words, building temples, at Gobekli Tepe, influenced the development of agriculture. It became logistically necessary to farm the area for the number of people needed to build and worship.
As a tie-in to the posted topic, C02 levels, in what is now Turkey, were high enough to allow for wheat cultivation 11,500 – 14,000 years ago. Those with specialized knowledge may know what minimal CO2 concentration levels (ppm) are required for growing semi-wild wheat found in Turkey/Mesopotamia.
In two parting tangents, CO2 concentration is measured in DRY air, i.e. NO water vapor present. This is supposedly done for accuracy as water vapor tends to skew results. However, wouldn’t it be more accurate to factor the water vapor volume, taken out, back in? Then, a more accurate ‘global average’ concentration could be established in a similar manner to temperatures (note the temperature sarcasm).
Last, is the use of Neanderthal. It is and has always been pronounced: NeanderTal. The modern spelling is ‘Neander’ – place name in Germany; ‘tal’ – German for “valley” thus, Neandertal. “Thal” was the old German spelling for valley but, the “h” was silent. ‘Neanderthal’ represents outdated, misconceived, and just plain wrong ideas. ‘Neandertal’ arguably represents a more enlightened view. “….and now you know the rest of the story…”

Show me the evidence for religious ceremony. It isn’t there.
They always go for the religion angle when there is nothing to support it. Just rampant speculation.
Per Neanderthal: I like old forms, and there is nothing wrong with a sense of history.

a rose by any other name would smell as sweet !

wws

“Show me the evidence for religious ceremony. It isn’t there.”
Do a short bit of research on Gobekli Tepe – if you go into it with an open mind, you will be gobsmacked.
The excavations and research at Gobekli Tepe (still 90% uncomplete) are revealing that everything previously assumed about beginnings of large scale social organization and the ensuing agricultural revolution has been wrong. From age alone, Gobekli Tepe is by far the earliest site of large scale ceremonial construction, indicating sophisticated social organization, ever discovered. It began not after the ice age ended, but while the glaciers were still ruling the north – that is how old it is.
Other evidence of its importance from genetic studies – Einkorn wheat, the first variety of wheat cultivated, began within 100 miles of Gobekli Tepe. Vitus Vinifera, the Eurasian grape from which most modern wines were made, was first cultivated within 100 miles of Gobkli Tepe. There’s an amazing list of early necessities of civilization that can all be sourced to western Anatolia, and Gobleki Tepe predates any other major ruins ever found by an astounding 4,000 years. It is even now proposed that rather than being from the Caucasus, the Indo-European language group had its beginnings in the area of Gobekli Tepe.
There is a very real possibility that this site represents the original flowering of what was to become “civilazation” and it spread out through the world from this starting point.
Ian Hodder of Stanford University has said, “Göbekli Tepe changes everything”.

TA

wws June 26, 2016 at 7:08 am:
“Do a short bit of research on Gobekli Tepe – if you go into it with an open mind, you will be gobsmacked.”
Thanks for that link, wws.

Lira

To introduce some real anthropology, ‘civilization’ is born of biological adaptations that permit division of labor. Both the “it’s just agriculture” and “it’s just ceremony” are simply inaccurate lay-reductions.
You can point out the evolutionary paths in ants, bonobos, gorillas, and so on. Once the biological mutation occurs to allow division of labor, you get more and more advanced cooperative structures. Looking at the history of leafcutter ants, which practice agriculture, may be illuminating.

Campesino

Long story shortened: Agriculture may have started much earlier due to man’s desire of building stone ‘temples.’ In other words, building temples, at Gobekli Tepe, influenced the development of agriculture. It became logistically necessary to farm the area for the number of people needed to build and worship.
=====================
Not necessarily.
Gobekli Tepe is amazing to European archaeologists, but not so much to those of us who work in North America.
Here there are many examples of monument building by hunter-gatherer peoples, the largest and best example of which is the Poverty Point mound complex in Louisiana
https://en.wikipedia.org/wiki/Poverty_Point
They didn’t have stone monuments like Gobekli Tepe, but they didn’t have any large stone nearby to use. Yes, it was later than in Turkey (3500 BP) but was done by people at the same stage of development and would have required a similar level of social organization to achieve.
The Adena Culture was a mound-building prehistoric culture in the midwestern US that was contemporary with Poverty Point and also consisted of hunter-gatherer peoples, who were able to come up with enough social organization to build substantial monuments.
http://www.britannica.com/topic/Adena-culture
Agriculture is not necessary for complex social organization if you live in the right environment. Indians living on the northwest coast of the US and Canada had substantial structures and monuments (though made of wood) and large complex societies and remained hunter-gatherers until European contact

PaleoSapiens,
No, “Neander” is not a place name in Germany, but Neanderthal (now Neandertal) is. The valley of the Düssel river, near Düsseldorf, was renamed in the early 19th century in honor of the beloved 17th-century German hymn writer Joachim Neander, who had found inspiration in that place for for his theology, poetry, and music.
He is best known for “Praise to the Lord, the Almighty, the King of Creation …” (“Lobe den Herren, den mächtigen König der Ehren …”).
“Neander”, by the way, was his grandfather’s rendering of the family name Neumann (“new man”) into Greek, as was sometimes done among educated people during the Renaissance. (Melanchthon, from Schwarzerd, “black earth”, is a better known example.)
By the way, there is nothing “just plain wrong” about the “h” in Neanderthal, as it does represent former German usage, and the designation homo neanderthalensis is still the proper one.
And now you know the rest of the story.

Philip Mulholland

PaleoSapiens
Thanks for the tip.
Deutsches Archäologisches Institut Gobekli Tepe website
Here are Google Translate links to the official Deutsches Archäologisches Institut Gobekli Tepe website.
How old is it? Dating Gobekli Tepe.
Google Maps: Pictures of Gobekli Tepe.
Google Maps: Göbeklitepe, Turkey.

l. angier

Global warming…saving us with abundance of CO2 making plants flourish. Now the “Changing Climate Deniers” wish to exterminate all life on earth by cutting back the essential to life gas, CO2…

Robert Clark

Do you understand the real true in what you just said?

Greg

Maybe temperature had something to do with it too?
Ice is not too conducive to plant growth either.

Henry Bowman

First, the temps rise, then CO_2 rises as a result of the temp increase. The events are coupled.

Henry Bowman & Greg – “spot on”…

Mark from the Midwest

Is this a question for Mr. Obvious? It’s so we could have the proper grains and hops in order to make beer! The whole thing about food is a secondary benefit.

glen martin

They started harvesting grain 14,000 years ago, 13,000 years ago they learned to ferment it to make beer, hence the spike in CO2 starting then.

Gunga Din

So….instead of CAGW it should CBGW?
Instead of the “War on Coal” we should be engaged in the “War on Beer”? 😎

I’m already doing my part. I consume every pint I find!
😉

@ Gunga Din 🙂
Please don´t give the watermelons any new idea´s! 🙂

Gabro

And the growth in CO2 after the invention of champagne?
Coincidence? I think not!

Duster

Actually, it was 13,999 years ago that they discovered how to make beer.

Gamecock

And the Romans figured out how to chill it. Hence, Pax Romana.

Ross King

If one created a hermetically sealed, translucent biosphere, with a ‘starter-load’ of moisture, decent soil, normal air but ‘tweaked’ as to initial CO2 content, located at a reasonable latitude, planted it as per a local natural wilderness area, and let it look after itself, I wonder what the results would be.
It’d have to be big enough to be self-sustaining and allow convection currents. Irrigation & humidity would be a problem … I guess one could replicate proximate external conditions (wind, temp., moisture-content) by means of sprinkler, a/c. and fans.
What’d be most interesting is the natural variation of CO2 over months/years, and the graph of bio-mass (and how do you measure that?)
Running some concurrent experiments with local fauna as residents might be interesting, if not essential to properly reproduce the ecology of the area.
Better still might be a long 1/2 cylindrical bio-sphere, partitioned with different starter-loads of CO2, everything else equal, and contrast results.
As a final point, surely such an experiment — if not already extant in labs/greenhouses — could be miniaturized, employing colonies of co-habiting micro-plants as proxies.
As to big biospheres, talk to Singapore … they have huge greenhouses already!

Ross King – Read about Biosphere 2. The building was huge and still exists as an education centre for the University of Arizona. It still needed external power to regulate the temperature of the glass structure. Perhaps with today’s PV technology, it might be able to provide at least some of its power internally. Note that due to a period of “Cloudiness”, the biosphere ran into a lack of oxygen problem due to low photosynthesis and CO2 rose to 18 % (not a typo – 18 percent). The inhabitants were able to function but reportedly had a lethargy problem.
See http://www.armaghplanet.com/blog/whatever-happened-to-biosphere-2.html
[The CO2 problem (too high!) was due to plant deaths (of the wrong kind; not enough survived to consume the excess CO2 and release O2) and too much “decomposition” (plant and vegetation and biologics (microbe) death that increased CO2 as they decayed). .mod]

Adam Gallon

Definitely a typo.
15% Lethal concentration, exposure to levels above this are intolerable .
http://www.ivhhn.org/index.php?option=com_content&view=article&id=84
The issue with Biosphere 2, was Oxygen levels declining, from 20.9% down to 14.5%.
CO2 reached 1,000ppm, 1%.

joel

Adam, 1000 ppm is 0.1%

John Harmsworth

My understanding was that the O2 reduction issue was a result of an unforeseen reaction with the structure’s concrete.

Ross King

Tks Wayne

David Ball

Just for readers of this blog’s edification (unsolicited, I know,…..):
Atmospheric Co2 is ~400 ppm ( parts per million ) This equates to 0.04%, a trace gas.
Man’s contribution is ~0.038 of that 0.04ppm atmospheric Co2 content. An astonishingly small amount no matter how you dress it up.

Little things like that don’t matter to the gospel of CAGW. Somewhere there is a true believer carrying on the work of AGW supported by peer reviewed papers that’s totally founded on the scientific principle of making it up as you go along. It could be or it might happen!

Someone decided to add more mulch / compost at startup without thinking it through. Decay consume more than budget O2, so more O2 had to be delivered.
It’s always best to ask the Engineer before fiddling the spec…
They also ended up with a huge ant problem…. but that’s a different problem…

You are correct – poor reading comprehension on my part and a fixation on CO2 – seeing what I expect rather than what was really there:

During the period the oxygen dropped, the Biosphere 2 experiment demonstrated that a human crew could operate well between an oxygen level of 16%-19%.

Sorry.

Geoff Sherrington

Please get it right.
One percent is ten thousand ppm.
It is hard to believe what you write when you make fundamental mistakes like this and confuse others.
Geoff.

Duster

mod. the problem was not excess CO2. The low photosynthesis resulted in a shift from oxygen output to oxygen uptake by the plants. This is seen by satellite very 24 hours in the diurnal O2 output and uptake in the Amazon. At night photosynthesis drops and respiration increases.

1saveenergy

Wane,
thanks for admitting a mistake (we all make them), I wish more people would has the ball to acknowledge that their belief or interpretation is not necessarily fact.

1saveenergy

I was wrong …again :))
Should read ‘ have the balls’

Steve Fraser

Modern greenhouse technique ( as practiced in the Netherlands, Ontario and elsewhere) steps this concept up to industrial scale, but controls the inputs for optimum productivity, rather than being a science experiment. When I visited one in Florence, Ontario a number of years ago, the owner explained the entire process, While I was there, the CO2 delivery tanker arrived 🙂

Ross King

Many tks this, Stev

peter

They are growing tropical fruit commercially in Ontario in Hoop Greenhouses.
https://www.facebook.com/canadabanana.ca/

upcountrywater

Well that changes my view of planet earth, with all the green forests and critters running around, into a giant desert… Science marches on…

Ross King

Eh??????

Pete Smith

I think he meant that the green and pleasant land with bountiful game that is portrayed, it wasn’t. It was all scrubby grass, stunted trees etc

gnomish

i got it.
you’re right, of course.
it was impossible to pasture animals because there were no animals – makes sense to the pathologically co2 obsessed magic gasifists

This might help put the current fixation on CO2 level in context. Bar chart displays graphic emphasis in Figure 5 at http://globalclimatedrivers.blogspot.com
Carbon dioxide levels, ppmv
40,000 Exhaled breath
20,000 No symptoms in healthy young people below this level
8,000 OSHA limit for 8 hr exposure
5,000 OSHA limit for continuous exposure
5,000 Approximate level 500 million years ago
1,500 Artificial increase in some greenhouses to enhance plant growth
1,000 Approximate level 100 million years ago
1,000 Common target maximum for ventilation design for buildings
404 Current atmospheric level
275 Atmospheric level before industrial revolution
190 Atmospheric level at end of last glaciation
150 All plants and animals become extinct below this level.

Geoff Sherrington

All plants and animals?
Including biota around smokers in deep ocean trenches?
Geoff

Duster

No. Things just get really dicey for land based ecologies below that level. The communities that aren’t based on photosynthesis and oxygen should survive nicely.

Jtom

I don’t think I’ve ever read of any carbon dioxide induced negative symptoms in UNhealthy recipients of mouth-to-mouth resuscitation, where they were subjected to 40,000 ppm CO2.

Alan Watt, Climate Denialist Level 7

Jtom:
In circumstances where mouth-to-mouth is appropriate, healthy is a relative thing. If a person is not breathing, the ambient CO2 is irrelevant. Any mixture which has oxygen is better than nothing.

Stephen Skinner

Or perhaps more land became habitable as the great ice sheets retreated and the warmer atmosphere held more moisture which meant more rain.

Gentle Tramp

Temperature and water supply cannot have been the main limiting reason against an earlier start of systematic agriculture. In the tropics it was always warm and wet enough. So the suggestion that the globally low CO2 content of the atmosphere during the last glacial was the crucial limiting factor sounds rather plausible to me.
See also:comment image
http://www.pnas.org/content/102/3/690.full.pdf

Thank you.
I’ve been looking for research articles like the one you identify.

ferd berple

the money quote:
“As a result, glacial trees were operating at ci values much closer to the CO2-compensation point for C3 photosynthesis than modern trees, indicating that
glacial trees were undergoing carbon starvation.”

Spot on again. Bit hard for “dawn of Agriculture” to dawn in the middle of an Ice Age…. Mankind (even perhaps in the African Tropics) was lucky to survive it and quite probably hominids other than Neanderthals from earlier exodus from Africa to Europe/Asia didn’t make it through the tough times at all, much less being in a position to settle down and become farmers…. No coincidence I think that all of our modern Ag’ history has been during the most recent Interglacial…. If the 11,000 year average for Interglacial periods over the last couple of million years is reasonably accurate, we are due any time to dip back into an ice age… The supposed successively lower warming peaks of recent millennia (Minoan WP –> Roman WP –> current WP….) based on Ice core results and other proxies may be early warnings of this…. The consequences of this give us more to worry about than a bit of extra warming that we may or may not be contributing. Look at some of the histories around the Little Ice Age…. Brrrr…..

Latitude

Starting 14,000 yag…..
You don’t want to chum your front yard until you can defend yourself

Bloke down the pub

I’m guessing that as the remnants of the last ice age became restricted to high latitudes, so humidity levels would have been rising at about the same time. The people of that time must have thought that they were doing something right for their gods to smile on them so much.

Bruce Cobb

According to Flim-Flam Flannigan, that was when our downfall started, since, in the process of cultivation, we were releasing tons of that nasty, evil, planet-destroying “carbon”. I guess we should have stayed hunter-gatherers.

Bill Partin

That is what the Greenies want, you know.

John Robertson

That can’t be right.
If I started hunter-gathering with a preference toward vegan eco-friendly food sources, these same people would call me a serial killer.
Yes Sarcasm.

H.R.

Cereal killer, John. Cereal killer.

ShrNfr

Some like E. Musk still hunt and gather subsidies.

ozspeaksup

bumper sticker on a car in my town
save the planet
plant a greenie

David L. Hagen

The consequence of moving from near CO2 starvation to modest supply!

I made this exact comment many years ago on one realclimate.org 10 years ago in 2006.
http://www.realclimate.org/index.php/archives/2006/11/how-much-co2-emission-is-too-much
“Onar wrote:
“Agriculture som 12.000 years ago when CO2 levels got high enough.”
You believe that agriculture wasn’t invented earlier due to a lack of carbon dioxide?
Are you getting this information from a book or website?
Who do you trust, and why, as sources for what you believe?”
Onar:
“Well, duh! As I’m sure a lot of good climatologists here on RealClimate can tell you, summer temperatures, precipitation and stability in the sub-tropics were suitable for agriculture during the previous ice age. (This is where agriculture first emerged) Human intelligence reached its current levels in Eurasia some 30-40.000 years ago. Thus, the only limiting factor was CO2. You have to remember that during the previous ice age, CO2 was from a plant point of view at an all time low. Plants were literally starving and there’s just no way that plants below 200 ppm are remotely close to supporting agriculture. Thus, modern civilization owes its existence to this dreaded gas of horror and destruction, CO2.”

So, is that when they banned you?

Pat Frank

It seems likely that extinction of the megafauna left paleo-humans with nothing to eat. One guesses that agriculture was plan B.

Pete Ross

Makes sense. We humans always have a plan B, and C if B fails, &c &c . It’s what makes us survive during ice ages and prosper during warm ones.

Curious George

Megafauna thrives when there are no plants to eat.

jorgekafkazar

Megafauna thrive when the O2 is 30%.

Javier

This is very well known in scientific literature since 1995. For example:

The emergence of agriculture among early human societies appeared throughout the world between 5000 and 10 000 yr ago, and this represents a rather short time span with respect to evolutionary change, particularly for crop plants. Sage (1995) proposed that such synchronous origins may have been the result of a common global factor, more specifically the rise in [CO2] from 200 to 270 ppm that occurred between 15 000 and 10 000 yr ago (Fig. 9). In this section, we discuss the role that low [CO2] may have played in the emergence of agriculture.

Gerhart, L. M., & Ward, J. K. (2010). Plant responses to low [CO2] of the past. New Phytologist, 188(3), 674-695.
https://www.uni-hohenheim.de/fileadmin/einrichtungen/klimawandel/Literatur/Gerhart-Ward-NewPhyt2010.pdf

Yes, the plant response to “low CO2” is very well know.
The novel/new insight is applying that information to the Greenland historical record to see how the really tough ice age environment, started blooming into a much more habitable environment that allowed human creativity (over 160 generations 🙁

mark

‘160 generations’
It is probably more. It depends when one is counting from, and average period between reproduction etc.
But:
What humans have done in so few generations is a completely breathtaking achievement.

Javier

Sorry but I fail to see any new insight. Human creativity was already blooming well before the Holocene. Humans had spread over the entire world and learned to live in a great variety of environments, developed very sophisticated cultures, domesticated the dog, learned navigation and started building complex big structures like Göbekli Tepe, before conditions improved enough for agriculture to be discovered.
And I don’t know of any Greenland historical record before the arrival there of the Vikings. I guess you are referring to the Greenland paleoclimatic record from ice cores. When you talk about “a much more habitable environment” are you referring also to Greenland or to other high latitude lands? The world has had a very habitable environment for many millions of years in the Tropics. That’s why there have been so many hominin species.

Pete Ross

So apart from the fact that the planet was colder than today by some 6C (~11F), which is a lot, the extreme low levels of CO2 compounded the issue, resulting in low vegetation growth which must have driven many land creatures to extreme situations of famine, low fertility and survival, or even to extinction. Mammoths come to mind. Today, scientists try to blame Neanderthals and Homo sapiens for their extinction, but was it lack of food due to the cold and extremely low CO2 levels? Why are many mammoth carcasses found frozen whole, as if blast-frozen, and not as remains of Neanderthal barbeques?

Bohdan Burban

When you consider the carnivores during the last glaciation: lions, sabre-tooth tigers, short-faced bears, dire wolves, etc., man was very much at the bottom of the food chain. To test is theory, go into the wild armed with a sharp stick and get a grizzly bear for dinner.

Gabro

People did kill mammoths with sharpened rocks attached to sticks. The big carnivores they kept away with fire or drove off by ganging up on them. Humans coexisted with big carnivores in the Old World for hundreds of millennia.
It was thought that maybe short-faced bears kept people out of the New World, but the best dating so far suggests that they at least briefly coexisted.

Gabro

PS: Dogs helped warn our ancestors about nocturnal predators, like leopards.

Duster

Evidence indicates that humans in groups tackled nearly every animal on the planet. At the Vero site in Florida there is an example of a sabretooth skull with incised designs on on the sabre teeth. Vero was originally considered a debatable site, but isotope analyses indicate the human and non-human bones in the deposits are contemporaneous. We started planning to be top predator probably over a million years ago.

Gabro

There were saber-tooth cats in Eurasia as well. The Old World boasted cave bears, giant hyenas, lions, tigers and bears, oh my!
Humans from at least 2.5 Ma took everything red in tooth and claw that Mother Nature could throw at us and won.
Our ancestors before that time were indeed threatened by eagles and leopards, but we adapted and overcame.

GTR

“o into the wild armed with a sharp stick and get a grizzly bear” – the technique for hunting bears with a sharp stick is to mount a stick firmly into the groud and entice a bear to charge, attack with all its mass. The stronger the bear pushes the better…

Crispin in Waterloo

Mammoths lived as far south as Mexico and beyond. The purported two species were in fact one, as announced recently based on mitochondrial studies. Their extinction was complex.
Central Americans have been cultivating maize and pumpkins and potatoes for at least 10,000 years, maize I recall, for 13,000. (Long memory, eh?)
As for development in general, Western materialist philosophers have it backwards. Spiritual development, which is episodic, precedes social development which precedes agriculture and the building of villages and large structures. In other words the initial conditions which ultimately favour material advancement arise de novo and are not the result of things like how much CO2 there is in the air. Isolated from the spiritual advances that underlie modern social organisation, primitive societies remain in a pre-agricultural state whatever the CO2 level. The idea that rising CO2 gave rise to civilisation is, like many materialist assertions, a vain imagining crafted to support their world view which excludes Revelation as a source of social advancement. With the mind thus closed, insights are elusive.
Which came first: the ten commandments or the societies that benefited from applying them? Which came first: a willingness to cooperate or an agricultural system that requires cooperation? If one answers the latter, from where did knowledge of it arise? Ultimately it becomes clear that social development precedes material development. Even if both evolve into an ever-advancing civilisation this remains the case.

Steve Reddish

Crispin, Note this post above: wws June 26, 2016 at 7:08 am
Isn’t it interesting per WWS post that wine making (and civilization) began where Noah landed (Biblical first vintner)?
SR

Interesting post. It is fairly well established that agriculture emerged in ~11 different ‘cultures’ at around the same time beginning about 13000BP, with domestication of animals and founder crops well established by about 8000BC. Example crops include rice and wheat. Example domestications include auroch (cow), boar (pig), sheep, goat, guinea fowl (chicken). So there have to be commonalities because some of these ‘cultures’ were at that time geographically isolated, for example Mesopotamia (wheat) China (rice), and MesoAmerica (potato).
In addition to CO2 fertilization, other speculated commonalities include stabilizing seasonality and precipitation, (both because weather is likely more extreme when colder), and simple population growth as climate milded–making hunter gatherer more difficult and precarious (bigger areas needed, yet travel time same). My view is there was likely a confluence of several factors that allowed agriculture to arise similarly in different isolated places, equivalent to convergent evolution where different species or genera evolve a ‘common’ solution to some fitness problem. Waxy leaves, fish schooling, herding, C4 photosynthesis…

Bill Illis

From 113,000 years to 13,000 years ago, the vast majority of the planet looked like this:
http://www.livescience.com/images/i/000/003/626/original/060720_sand_sea_02.jpg
or,
http://il9.picdn.net/shutterstock/videos/12434732/thumb/1.jpg
or,
http://farm4.static.flickr.com/3100/3139418707_dd4d1ce5d3.jpg
But there were a few places that looked like this and that is where we lived. Why? Because that is where the food was. There was no trees, or vegetables or nuts or berries and no agriculture but there was a lot of C4 grass grazing herbivores, especially the wild cattle and bison.
http://www.ducksters.com/science/ecosystems/prairie.jpg

ralfellis

Actually, there were still lots of (C3) trees at low levels in the tropics. Although they may have been stunted by low CO2 conditions, Chinese scientists have demonstrated that the northern China treeline was forced south by 1,000 km during the LGM. But it was still there. And C3 and C4 grasses still grew at low altitude, even though the C3 grasses would have been much less productive. The real problems were at higher altitude, where C3 trees and grasses would have really struggled, and their demise would have created CO2 deserts much like you show in those pics.

Menicholas

I agree that there were still trees around.
How do I know?
Because we have them today.
Many trees and plants cannot grow from old seeds, or seeds which have been desiccated or frozen.
If such a time ever existed that there were no trees, we would not have any of these sorts on the planet today.

Menicholas
Menicholas

And even orthodox seeds quickly begin to lose viability within a short time, often as quickly as two years.
I think being skeptical requires that people do not state questionable ideas or speculations as if they are factual information.
The idea that there was ever any significant amount of time without plant and tree species that now exist would require some very strong evidence to even be considered credible, unless it was so long ago that these species had time to evolve since then.
In addition to the trees and plants themselves, many species rely on very specific insects in order to produce viable seeds. In some cases, that tree or plant is the only thing that a particular insect eats or uses to reproduce itself.
The belief that any of the trees and plants that are now common, and there are many thousands of such species, underwent a period of time in which they all died out for centuries or millennia, as recently as 13,000 years ago, is frankly idiotic.
It is very doubtful that any seeds laying around in the environment could germinate after hundreds or thousands of years of dormancy is doubtful if not ludicrous.
Warmistas have, and have long had, the galling habit of repeating and disseminating speculative ideas as if they are or were facts. As such they demonstrate that they are a credulous lot, or else completing willing to spread disinformation if it helps to convince people that they are correct about their ideas.
No one who considers themselves to be a skeptic, or a scientist, or a credible source of factual information, should engage in this same sort of behavior.
JMO.

Ice age Antarctic and Greenland ice cores are loaded with dust from deserts. Not only because deserts were much more wingspread but it was damn windy. Storms were more violent.

ralfellis

>>Tab
>>Not only because deserts were much more wingspread but it
>>was damn windy. Storms were more violent.
The data does not support that. There were stronger winds in the Gobi, because the Loess Plateau shows an increase in aeolian grain size. But that is not true of either Greenland or Antarctica, so there were not greater winds here.
This makes sense, because the stronger winds will be around the ice sheet termini, where the temperature difference is greatest. But way up on the Greenland ice dome, winds were steady and moderate. So the majority of dust deposition was due to the (CO2) deserts being larger, and not due to stronger winds.
R

Javier

Not really. Tropical areas were pretty much like today. There were extensive rain forests, Tropical animal and plant species are much older than the last glacial period. Homo sapiens was a tropical species up to 75 kyr ago. Homo neanderthalensis lived in Northern forests up to the edge of the tundra, very much like the Sami of Laponia.

Yes,
While the plants we current have were around 15,000 YAG, the environment was really, really tough.
Anyone who had an area of their farm where the fertilizer was thin or the water not abundant knows what happens to a plant in a less than good environment.
The entire planet was grim for plants and herbivores (and humans) has to scramble to find enough food.

Javier

Are you imagining all that? Of course conditions were very difficult at high latitudes, and of course the land areas of the planet were less productive due to lower CO2, but overall conditions in the tropical areas of the planet were not that different from today. 99% of the species on the planet today were alive before the last glacial period. Except for the megafaunal extinction that Homo sapiens caused, almost all species of plants and animals did fine during the last glacial period. The evidence does not fit what you say. Perhaps you can point to scientific literature where your point of view is supported.

Menicholas

And somewhere between the tropical zone and the frozen high latitudes, there had to have been temperate zones where all the temperate plants and animals survived to recolonize the areas where they are now widespread.
The temperate zones were no doubt smaller, but they had to have been present. One look around proves it.

Bill Illis

This is a simplified map of the vegetation at the last glacial maximum. There are more complicated ones (that are just too hard to read) but generally you can think of it
–> forest in green (Amazon shrinks by two-thirds);
–> extreme desert in yellow (humans would have a hard time crossing these);
–> white is either grassland, tundra, or glaciated.
http://www.esd.ornl.gov/projects/qen/lastgla.gif

Steve Reddish

Except, the northern coastal plains of Siberia, Alaska and Canada are where woolly mammoths flourished.
These areas could not have been either extreme deserts or glaciated.
SR

Sleepalot

I don’t believe the North Sea was an “extreme desert” – not for one second.

ralfellis

Yes, plants suffer severe distress at low CO2 concentrations, and they were in distress during the Last Glacial Maximum (LGM). We know this from wood fragments discoverd in the La Brea tar pits in California. See Ward et al 2004.
This was even more so at high altitude, where vast CO2 deserts were formed. And it was these high altitude deserts that caused interglacial warming. A peer-review paper will be published on July 1st.
However, agriculture could have arisen in tropical regions before 13,000 years ago, where C4 maize and sugar cane could have been grown. Tropical C4 plants were not greatly effected by the low CO2 conditions during the LGM. Although ancient maize and canes were les than 10% as productive as modern varieties.
.
Another possible reason for the sudden rise of agriculture about 13,000 years ago might be the sudden demise of megafauna at the beginning of the Younger Dryas, which began about 13,000 years ago. Suddenly deprived of large fauna to hunt, agriculture became a viable alternative.
I am a firm believer that the Younger Dryas cooling (and the megafauna extinctions) were caused by a large meteorite impact on the Laurentide ice sheet, which splashed large slush-balls that impacted all over north America. These imacts created the hundreds of thousands of Carolina Bays, which otherwise have no logical explanation for their existence. And these Bay formations all point to the Great Lakes.
http://cintos.org/SaginawManifold/introduction/index.html
The Cintos explanation has moved away from a Younger Dryas explanation, as geologists were adamant that the Bays could not have been formed 13,000 years ago. However, I think they are mistaken. I think the dating techniques used are dating the original sand strata, and not the age of when these strata were heaped into oval Bay formations by slush-ice impactors.
Perhaps the best evidence for the Bays being linked with meterorite impacts, was a piece of flash-vitrified wood in a Carolina Bay. (Flash melted only on one side.) Wood can only vitrify or melt at 4,000 oc, and that can only be caused by a meterorite reentry, and not a fire.
Carolina Bays and the Destruction of America.
https://www.academia.edu/20051868/The_Carolina_Bays_and_the_destruction_of_North_America
R

Gabro

There is no valid evidence to support the YD impact hypothesis, and all the evidence in the world against it.
The YD was no different from other such cold snaps before and after it during the last deglaciation and those preceding.
Nor did the megafauna all die out because of such a nonexistent impact. What was different during the YD from other cold snaps was human hunters entering the New World and in the Old World developing improved predation tools and techniques. How else to explain why the megafauna of Caribbean islands survived until humans reached their habitats, while continental megafauna much farther away from the alleged impact site died out when people reached their territories?
More megafauna survived in Africa because the animals there weren’t naive, but had evolved alongside originally less effective hunters for 200,000 years.

Javier

I agree that all the evidence indicates that YD was simply a cold relapse, part of the 2500 years solar cycle, very much like the Little Ice Age, that came to an abrupt end due to the last Dansgaard-Oeschger event.
I also agree that all the evidence points that the megafaunal extinction had little to do with climate change and for most animals the extinction is linked to the arrival of Homo sapiens.
Neanderthal could not have caused the extinction of their prey because they were very dependent on them and followed the typical predator-prey relationship. Sapiens was a very resourceful hunter-gatherer, and thus could cause the extinction of their favorite prey as they could support themselves on alternative food sources.
By the time agriculture is invented, the megafaunal extinction is pretty much over everywhere except Australia. It had nothing to do with substituting megafaunal hunting with agriculture. A warmer more productive planet had supported a great increase in human population, and there was a lot of pressure to find alternative food sources to support such population on lean years. Proto-agricultural Göbekli Tepe, right at a site where agriculture was later developed, seems to have supported a big enough hunter gatherer population to sustain megalithic construction.

Gabro

The first Australians wiped out the megafauna of that continent, too, long before the Holocene extinctions.
Same happened when the first Maori arrived in New Zealand.

ralfellis

>>Gabro
>>The YD was no different from other such cold snaps
>>before and after it during the last deglaciation and those preceding.
The Younger Dryas (YD) was very different to the previous D-O temperature iscillations.
The YD was much longer.
The YD was coincident with a megafauna extinction.
The YD has evidence of extraterrestrial impact debris.
The YD appears to be coincident with hundreds of thousands if impact craters – the Carolina Bays.
Studies by Prof Vance Haynes have demonstrated that the megafauna demise was instantaneous – less than a century. There is no way that man could have extinguished megafauna within a century, while an impact certainly could.
In addition, the megafauna extinctions were pan-continental. Are you really suggesting that man rose up on three or four continents, and extingushed the megafauna simultaneously? That makes no sense. But an impact would do this.
And we have the evidence for this impact, if only people would open their eyes – 500,000 secondary impact craters, spread over most of North America, and all pointing to a primary impact in the Great Lakes.
R
P.S. The D-O warming events were probably caused by soot from forest fires.

Javier

Ralfellis, Vance Haynes is wrong, as you are. Megafaunal extinctions are spread over the second half of the last glacial period.comment image

ralfellis

Haynes is not wrong as far as I can see.
Replacement of megafauna with related species is NOT an extinction event. There were many species replacements over the last glacial period. But as Haynes says: “there are megafauna fossils below the black mat layers, and none above. And this represents an instantaneous extinction on geological timescales.”.
Do you disagree with that? Can you show me megafauna fossils above the black mat layer?
R

Javier

Of course I disagree with that. He is twisting the concept of extinction to his convenience. If a species goes extinct it goes extinct, and that is an extinction however you look at it.
The bolid impact is marked with a red star in the figure, and there are lots of extinctions before, and quite a few after. In fact by looking just at extinctions it would be impossible to determine the time of the bolid impact.
Your theory doesn’t hold water.

ralfellis

You seem unable to understand the concept of a mass extinction.
An extinction of a species is simply evolution in progress, it happens all the time. A mass extinction is when many species are all terminated at the same time, which is what happened at the Younger Dryas.
So I ask you again, please give us evidence of the megafauna species that existed after the black mat layer. They don’t exist, do they? In which case, Prof Vance Haynes is correct. The YD marks a mass extinction event that was most probably linked to an event.
And you have still not explained how the Carolina Bays were formed, if not from secondary slush-ball impacts.
R

Samuel C Cogar

Quoting article:

Starting 14,000 yag, the sparse, scraggly growth started getting thicker and slightly more abundant. It wasn’t very good, but is was much better than 16000 yag.

Now the growing biomass of pre-14,000 BP ….. maybe wasn’t very good or nutritious for the hunter gatherer Homo sapiens that were roaming there n’ about …… but I’m pretty sure is was plentiful, tasted good and was nutritious for all of the herbivores that were ingesting it.
Don’t be forgetting now, there was a lot more real estate available to the grazing herbivores prior to the pre-12,000 BP “time” of the Post Glacial Sea Level Rise.comment image
If you drop the sea level by 60 meters (180+ feet) …. edible growing acreage increases significantly.
Doggerland, for instance, was probably a rich habitat with human habitation in the Mesolithic period. To wit: https://en.wikipedia.org/wiki/Doggerland

A bit off-topic, but….How accurate is the following comment?
“Meat consumption is projected to double from 2014 to 2040. More meat means more greenhouse gas emissions from agriculture, which could triple by 2055, if current dietary trends and population growth continue. Crop yields are already reduced in some parts of the world due to climate change. Elevated ozone levels have caused losses of about 10 percent for wheat and soybeans. Global warming of more than 3 degrees will exceed the agriculture’s adaptive capacity.”
The Global Opportunity Network at EAT Food Forum, Published on June 20, 2016
I have no idea how to rebut…

Gabro

What a load of complete and total garbage.
More CO2 means more agricultural production, not less, thanks to more plant food in the air. Plants can conserve moisture by keeping their stomata open for less time. Also warmer means wetter, so again more plant drink in the ground.
Where are these crop losses? Wheat and soybean production are up, way up, since 1945, 1975 or 2005, all during the postwar increase in CO2.
Are they afraid of methane from meat production? The trees cut down to make pasture land for livestock also produce methane.
Scientific illiterates. Or liars.

Marcus

Meat is about right per FAO. China alone is a big factor. See my book Gaia’s Limits, Chapter 3.
Ag does not result in more GHG except for beef (digestive methanogens) and rice (paddy methanogens). Most meat increase will be farmed fish, pork, and chicken. Crops are a net GHG sink. So the GHG statement is flat wrong.
There are no yield reductions anywhere from GHG. There are places where yields have stopped increasing due to full adoption of best practices and plant physiology. China and India potatos are an example. Japanese and Chinese rice another example. See Chapter 3 for specifics.
Ozone has diddly to do with wheat and soy yields. Check their source; it will for sure be funky.
3C degrees will not exceed ag adaptation. Pure BS. For example, rice and corn cultivars are used extensively around the world in growing zones where the average growing temperatures differ by much more than that. Corn in Minnesota versus corn in Georgia versus corn in Kenya. Upland rice versus lowland rice in Laos and Thailand. Wheat in Egypt versus wheat in Russia versus wheat in Montana. See chapter 3 for an expose of the NRDC fr**d perpetrated on US Congress concerning US corn, which is likely where this last falsehood originated. A version was also posted here IIRC back in 2011. My first guest post at WUWT.

Richard G.

From U. of Illinois Urbana-Champaign SOYFACE experiments
http://www.life.illinois.edu/delucia/PUBLICATIONS/GCB_1502.PDF
“How do elevated CO2 and O3 affect the interception and utilization of radiation by a soybean canopy?”
Briefly: CO2 elevated to levels expected in 2050, result 15% increased yield.
Increased O3 resulted in 3% reduction of yield.
When both CO2 and O3 were elevated the effect of CO2 overcame the negative effect of O3.

gabro has it right – more alarmism than the mind can take in ! more CO2 and heat will make this planet a paradise !

joelobryan

One can easily recognize a Church of CAGW true believer if they use the term “carbon pollution” as part of their environmental lexicon to describe anthropogenic CO2 emissions.

Doesn’t everybody know the only decent food is meat. All those people who eat nuts and twigs… same as the animals I eat …. grazers. I never considered spinach as something you actually. .. gag …. eat. And the worst thing I ever ate was grass jelly. The black version is like semi solid motor oil.
Ever heard your mother say ” eat your vegatables”… yep kids know. Nobody had to tell me tomatoes were bad for you. … contrary to the health professionals, all the foods they push are bad for me and my family.

Ten

I wonder if your mother wonders how you never grew up…

Tomatoes are fruits, and like most fruits, yummy.
/Mr Lynn

Tomatoes are a fruit that is poisonous to me. Taste is one thing, the desired effect on the body another.

Amber

At the core of the global warming con game was the sales pitch that warming is scary and bad , WRONG .
IT is cause for celebration and hope because plants trees and animals do better when not under a mile of ice . If humans make some small contribution to warming well YIPPY !
We should enjoy it while it lasts .

Thanks to all for your comments.

This website says the beginnings can be traced to pre-Holocene.
https://6000generations.wordpress.com/2013/05/04/agricultural-beginnings-were-during-the-pre-holocene-glacial-period/
I had a rather lengthy discussion on Climate Etc about why didn’t agriculture begin during the Eemian.
Related to question I posed to John Hawkes who wrote: “I will note that there is now some evidence of intensive collection of cereals in tropical Africa before the Eemian
http://johnhawks.net/weblog/mailbag/eemian-agriculture-2012.html

Gabro

I’d say that because Anatomically Modern Humans were restricted to Africa in the Eemian.
Intensive collection isn’t quite the same as agriculture or even simple cultivation, but population densities in Africa before 114 Ka might have sufficed to warrant greater manipulation of the environment.
Even under glacial conditions in Europe and Asia, the dog was domesticated (or domesticated itself), and there is evidence of herd management of wild reindeer and horses, if not of true domestication. Maybe along the lines of Laplander reindeer herders.

Quite possibly domesticated twice. once in Siberia and once in Europe. Fascinating paper on that looking at genetic differences. Came out just a few weeks ago. Another evidence for ‘convergent evolution’ of domestication and agriculture.

Gabro

The article in the Atlantic on the Oxford and US team’s work said dogs were domesticated once in China and once in Europe, but that the Ancient Western dogs were genetically swamped by inc-coming Ancient Eastern dogs.
Previous work on wolves and dogs had suggested NE Asia, ie Siberia, as the where domestication first occurred.
Modern dog DNA is so homogenized that the team looked at archaeological dog remains to try to unravel the history of canine domestication.

Opportunistic collection of wild cereals is still hunter gatherer culture. Think bears and berries. Still practiced in parts of Africa. Agriculture is when permanent/semipermanent (seasonal) settlements plant, grow, and store foodstuffs seasonally, but do not roam about. The natural selection of better grains/ more productive plants is how MesoAmericans created maise from teosinte. The Plains Indians were hunter gatherers at a time when the Anastazi had been in agricultural settlements for centuries.

Duster

If you dig into the more technical archaeological literature, the concept of agriculture will gradually become rather fuzzy around the edges. Most “hunter-gatherers” surviving live in marginal environments, mostly desert, practice a “forager” economy. Deserts (e.g the upper Sonoran desert in the Great Basin) and savanah environments often have abundant grass, and other small, hard seed sources. The Great Basin has abundant Pinyon Pine was well as grass. Deserts also often have abundant bugs and animals that prey on grass (grasshoppers, jack rabbits, antelopes). Hunter gatherers in these environments prey on all of these, but preferentially weight their subsistence toward the more easily acquired and stored foods (seeds, pinyon nuts), followed by jack rabbits, which carry inadequate fat to use as a dietary mainstay (leads to a condition called rabbit starvation), and lastly by antelope, which are by far the most rewarding, but far and away the most difficult to take and thus the most costly in energy – directly, and in terms of energy needed to collect the materials needed to make and employ gear required for the hunt. In the Owens Valley in eastern California the Paiute dug ditches that directed water to “natural” stands of grass. That is, they essentially cultivated stands grass, but did not plant them. These prehistoric ditches were later improved and employed by ranchers to supply water to actual agriculture until Los Angeles stole the water judicially. The point here is that long before agriculture is recognized archaeologically, the elements were in place and very likely being practiced.

Agree, Duster. I thought the same.
Traditional subsistence patterns can’t be broken down into a simple hunter/gatherer or agriculture dichotomy.
Of course, only agriculture can support the large populations of early civilizations.
My argument regarding the Eemian has been that the anatomically modern humans were not totally human. We had to evolve more complex communication mechanisms, reduce aggression, and learn better cooperation.
https://broadspeculations.com/2012/12/22/lost-history-revenge-of-the-nerds/

There is an archaeological, historical question of when agriculture began. My guess is it began well before we had the large scale agriculture of the Holocene but evidence for this is sparse I admit.
Certainly increased CO2 in the Holocene enhanced the ability of early civilizations to support larger populations but so did warming and a reduction in climate extremes. So CO2 was one factor.
However, my question was regarding the Eemian when I believe CO2 reached levels similar to the early Holocene. Regarding whether humans were not out of Africa. I’ll quote John Hawkes in his reply:
“Demographic intensification in Africa and resulting mass migration DID happen in the Eemian, and we call this the out-of-Africa event.”

Gabro

CO2 was higher in the Eemian even than the Holocene Climatic Optimum.

“There was no single factor, or combination of factors, that led people to take up farming in different parts of the world. In the Near East, for example, it’s thought that climatic changes at the end of the last ice age brought seasonal conditions that favored annual plants like wild cereals.”
http://www.nature.com/news/2011/110325/full/news.2011.184.html
http://www.des.ucdavis.edu/faculty/Richerson/AgOrigins_2_12_01.pdf
Nonetheless, we propose that much about the origin
of agriculture can be understood in terms of two
propositions:
Agriculture Wcas Impossible During The Last
Glacial. During the last glacial, climates were variable
and very dry over large areas. Atmospheric levels
of CO2 were low. Probably most important,
last-glacial climates were characterized by highamplitude
fluctuations on time scales of a decade or
less to a millennium. Because agricultural subsistence
systems are vulnerable to weather extremes,
and because the cultural evolution of subsistence
systems making heavy, specialized, use of plant
resources occurs relatively slowly, agriculture could
not evolve.
http://tuvalu.santafe.edu/~bowles/Holocene.pdf
Summary: The evolution of complex societies began when agricultural subsistence
systems raised human population densities to levels that would support large scale
cooperation, and division of labor. All agricultural origins sequences postdate 11,500
years ago probably because late Pleistocene climates we extremely variable, dry, and the
atmosphere was low in carbon dioxide. Under such conditions, agriculture was likely
impossible. However, the tribal scale societies of the Pleistocene did acquire, by geneculture
coevolution, tribal social instincts that simultaneously enable and constrain the
evolution of complex societies. Once agriculture became possible, a competitive ratchet
drove further improvements in subsistence and in scale of social organization . Those
societies that grew and became better organized were advantaged in individual wealth
and economic and military power, and tended to conquer, absorb, or be imitated by
smaller and less well organized societies. Internal competitors for power espousing useful
social innovations could deliver improved returns when their quest was successful.
Notwithstanding the ratchet, social complexity increased only slowly in the first half of
the Holocene and even afterwards few periods except the past two centuries saw changes
that were dramatic on the scale of individual lifetimes. We attempt a taxonomy of the
processes that regulate rates of institutional evolution, cause reversals of complexity
against the ratchet, and impose historical contingency on institutional evolution.i

SM, said pretty much the same thing using less words upthread. But we fundamentally agree.
Ag developed as a confluence of rising CO2, lowering weather variability (extremes) as the world approached the Holocene optimum, and resulting rising human populations.
Human ‘inventions’ of that time include: keeping the best for next year (teosinte to maize), preservation (beer/kimchi fermentation being a lesser example, salted/dried/smoked meats being major), plowing, paddying, copping (cutting tree tops to let many new ‘straight’ shoots grow from the trunk/rootstock for straight spears and arrows and construction ‘lumber’), fertilizer (Amerindians teaching Pilgrims to bury an alewive fish with each corn seed), sewage planning (Japanese honey buckets), and with the resulting food wealth then even primitive division of labor as evidenced in Mesopotamia, Egypt, and China over 6000ya.

weirdly who ever wrote this
A) clipped a quote
B) failed to spend more than 5 minutes seeing what the “consensus” was.

SM, I did. Moniker is quite clear. Sorry that you rejected a factual peace offering. Par for course?

General P. Malaise

did I read that correctly? what there were no or insufficient green plants before 13000 years ago?
this is hogwash

Gabro

There was certainly vegetation to support the megafauna, but most of it was not susceptible to cultivation. Mammoths and rhinos could process steppe tundra flora, but not very well people.
Sea level rise also inundated such fertile areas as the broad valley where the English Channel now exists, and the Baltic and Adriatic Seas, Persian Gulf, South and East China Seas, etc. Later, the area around the previously much lower Black Sea was sunk by the rising Med pouring down into its depression.

Gabro,
One of the posts I linked to above pointed to evidence of intensive use of wild grains 23,000 years ago. They could not have been using these grains intensively if the plants did not grow perfectly fine.
For that matter, what did humans live on for two million years before the Holocene? It wasn’t just meat The human diet has probably included cooked plants and roots along with meat for several hundred thousand years at least.

Gabro

Yes, in most environments, human diets did include plants. But they were gathered, not cultivated, let alone domesticated, as in agriculture.
The hand ax, a multipurpose tool which remained unchanged for about a million years, could be used to dig up roots and process vegetable fiber as well as to smash bone to get at the fatty marrow.
In any case, 25,000 years ago is long after the Eemian. And intensively using seed plants doesn’t necessarily mean even planting their seeds in optimum environments close to home, let alone selective breeding and field or seed bed cultivation.

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03441.x/pdf says that plants stop growing at 10-145 ppm depending on the kind of plant.

Gabro

There are three different kinds of photosynthesis, two of which evolved to deal with an increasingly drier, cooler and CO2-starved world in the late Miocene. Most plants, including the majority of important crops, still use the old-fashioned, CO2-hungry C3 pathway. CAM and C4 plants can survive on much lower levels of carbon dioxide.
For some C4 plants, malnutrition actually sets in above 145 ppm, in the sense that they can’t flourish or in some cases reproduce before they actually starve to death.

CAM is just intermediate evolution between C3 and C4. All C4 plants retain and also use the C3 pathway. That is why maize (corn) still benefits from rising CO2. But as a C4, only about 1/3 of rice, a pure C3.

The lower limit for C3 plants ranges from 60 to 145 ppm according to the PDF I linked above.

Jim G1

13000 ybp, more CO2, more rain, warmer temperature, finding some edible plants, figuring it might be wise to grow them=agriculture begins. Not real complicated.

Simon

There is the argument that as a result of CO2 being steady for a few thousand years, the climate has been stable. This has allowed civilisations to determine what crops grow best where and to make the most of this. If temperature and rainfall patterns change quickly as predicted, then that also changes how efficiently we can grow things. Add to the mix an increasing global population and sea level rise reducing the amount of land available to sustain the population, then we could well be in serious trouble. Or I guess we can just hope the science is wrong.

Gabro

So-called “climate science” is not science but politics. It’s agenda-driven computer modeling, not climatology.
Sea level rise is no different now than 200 years ago. Maybe less. Far more land has been opened up to farming thanks to more plant food in the air than could possibly be lost under any likely scenario of sea level rise.
More CO2 increase the efficiency of growing things. It has been a boon to the planet and humans in particular. Some part of the huge increase in food production since WWII is thanks to more CO2.

Simon

Gabro
No sea level rise ? Really? And you read that where?

Menicholas

Simon, do you have a reading comprehension problem?
Gabro said “sea level rise is no different now than 200 years ago”>
How does that translate into “no sea level rise?

Simon. Gabro did not say no SLR. He said no different than (no delta SLR). I disgree only because we do not have enough geostationary long record tide gauges to be sure that far back. But for sure, for the last century the statement is factually correct. Essay PseudoPrecision gives many amusing details.

Gabro

Simon,
I said no change in the rate of sea level rise, or at least that’s what I tried to say.
In fact, sea level has been rising since the depths of the LIA 300 years ago, but we can’t get a good read on the rate until the 19th century. And of course the rate will vary. It would have slowed down during and after the Dalton Minimum, for instance.
There are proxies going back at least 300 years, and even actual data from the 18th century, but not AFAIK to form a global picture.
Salt marsh observations back 300 years:
http://www.sciencedirect.com/science/article/pii/S0012821X13006468
Liverpool since 1768:
http://onlinelibrary.wiley.com/doi/10.1029/1999GL900323/full

Simon, the real delta SLR to 2100 is maybe 30 cm. No agriculture takes place that close to sea level due to salt poisoning, (OK, maybe in Bangladesh, where less productive but much more salt tolerant rice cultivars are being reintroduced in the Sundarbans.)
Temperature and rainfall are not changing quickly. Even if they did, the many main crop cultivars adapted over the centuries to diverse agricultural climate backgrounds simply change geolocation. What, you think all wheat is the same? All maize is the same? All chickens are the same? Then you must also believe all of the subspecies of Canis lupus sp. familiarensis (dogs) are the same. Dachshunds bear no resemblance to German Shepards.
The same principle applies to crop cultivars. Regards from a Wisconsin farmer who plants Wisconsin climate adapted cultivars in order to survive. And if Wisconsin climate changes, so will the planted cultivars.

Simon

“The same principle applies to crop cultivars. Regards from a Wisconsin farmer who plants Wisconsin climate adapted cultivars in order to survive. And if Wisconsin climate changes, so will the planted cultivars.”
You re a lucky man. Some who share this planet with you may not be. And when people are starving they may come looking for a country like yours. Just saying this stable climate we have enjoyed for the last few thousand years has allowed people to remain where they are. There are 156 million in Bangladesh who are going to have to find somewhere to live, probably within a century, two at most.

Jeff Alberts

There are 156 million in Bangladesh who are going to have to find somewhere to live, probably within a century, two at most.

They have plenty of time, then. Does anyone expect nothing to ever change?

Crispin in Waterloo

Bangladesh in its oceanside deltas, is rising. The mechanism is the same as in the Okavango delta.

Simon

Crispin in Waterloo June 26, 2016 at 12:20 am
“Bangladesh in its oceanside deltas, is rising. The mechanism is the same as in the Okavango delta.”
Are you saying they have nothing to worry about from this…..comment image
Phew they will be so relieved. Quick get over there and tell them.

Menicholas

Also Simon, I think you can ease your worried mind on the impact of rising sea level on agricultural production.
Far more land will open up to production than would ever be flooded by rising seas.

Simon

“Far more land will open up to production than would ever be flooded by rising seas.”
Really? Where? Do you have another planet tin your pocket?

Gabro

Simon,
Did you miss the part about higher CO2 making more land arable? Consider the Sahel. In the ’70s, there was much hand-wringing over desertification. But now, thanks to higher CO2, not only can livestock graze and browse there, but crop cultivation has expanded.
Besides of course, in a warmer world, growing seasons expand farther toward the poles.
Please do try and keep up with the science. It’s elementary.

Jeff Alberts

Really? Where? Do you have another planet tin your pocket?

If it gets warmer, more arable land will be available. It’s really not that difficult a concept.

Simon

Gabro
“Besides of course, in a warmer world, growing seasons expand farther toward the poles.”
Well we will have to wait and see if your growing season expansion is as good as you hope. In the meantime, I think it is you who needs to keep up with the science. There are already a number of traditionally harvested species that are suffering from the speed of change. And while farmers may be able to grown plants that adapt to the temp change, you can’t grow things if you have no water. Predictions are rainfall patterns are going to change. We are already seeing the rivers fed by the Himalayas are not providing the water to the farmers they used to. China is also reporting the same problem. However I am buoyed by your blind optimism. I mean I suppose there is a slight chance despite your opinion being contrary to the science, that you could be right. Let’s hope.

Gabro

Your blind pessimism is totally fact-free.
The expansion of arable land is a fact, ie an observation. Much more land is now arable than during the LIA.
If you’ve got any actual science, please trot it out.

Gabro

And earth has greened even more so in the past 35 years:
http://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth
If humanity hadn’t increased CO2 by accident, we would have had to do so on purpose.

Simon

“If humanity hadn’t increased CO2 by accident, we would have had to do so on purpose.”
Wrong again. It was no accident.

Christopher Hanley

The hunter-gatherer native people in the dry centre encountered by early Australian explorers, genuine ‘ice age’ survivors (whose ancestors thousands of years earlier had wiped out the megafauna), baked cakes made from a rough flour from the seeds of a particular plant they called ‘nardoo’.

leon0112

And then there is biology.
This idea would fit nicely into Patrick Moore’s speeches on CO2.

I have this opinion that there were advanced civilisations like us before the last Ice-age, maybe they didn’t get the chance that we are collectivity squandering now in this interglacial period, but it has attributed an accumulation of human knowledge to further our existence.
I have this realistic view of the past several hundred thousand years, that humans exactly like us existed, it is obnoxious for archaeologists to suggest that after the last Ice-age when a resettlement of humans where great Ice fields and glaciers a mile thick receded was the beginning of human civilization on earth, human evolution happened over millions of years and we have reached this stage of development before, what remains we dig up of the past tells a story, for example, have you ever seen a movie set in a period in the past? have you ever noticed that these period films use old run down castles and buildings as their back drop? these castles and buildings didn’t look like that, people didn’t scurry around in mud and foraging lettuce leaves for survival, they built and farmed for a calculated reason before and after the last Iceage, it is arrogant to believe human development has taken a leap forward and has achieved what no other human civilization has done in the past based on a few rusty swords, engravings and pots from a nomadic settlements after the last glacial period.

To increase Co2 levels in the atmosphere might very well be the smartest mankind ever did to Earth!

Mankind didn’t increase CO2 levels moron!!

Are you sure?
If we take up hydrocarbons (CxHx) from the deep ground and burn it – I´m quire sure the process will produce CO2. That should add CO2 to the atmosphere shouldn´t it?

No offence intended by calling you a Moron.
It is claimed that from the latter half of the 20th century CO2 levels from 350ppm to 400ppm is causing so called “global warming” right? in reality what this claim is saying is that a 50ppm increase in CO2 is going to change earths climate in a catastrophic way right? this is clearly untrue.
Of course humans use hydrocarbons from the deep ground. I want you to understand this scale, humans can not compete with earth when we compare human CO2 with that 50ppm globally, humans are responsible for at maximum 4% of that, the so called “catastrophe” is natural, which isn’t really a catastrophe if earth is greening at a cyclical peak and producing more Carbon Dioxide is it?

No problem – I simply ignore name calling – feel free to call me whatever the moderation filter will pass 🙂 . I will not have an opinion about the effect increased levels of CO2 in the atmosphere will have on temperature. I´m only claiming that mankind are adding CO2 to the atmosphere, I believe that will increase the level of CO2 in the atmosphere, and I believe plants would love us for doing that – if they had that ability – to love I mean. 🙂

Ross King

For every finger that’s pointed at oneself as a “moron”, there are 3 pointed right back at themselves!

I know, I meant it in jest not as an insult. so un-bunch your panties ffs

Ross King

Calling anyone a “moron” on public air-waves is way beyond any jest. Your sign-off flippancy suggests you just don’t get it.
Can we please maintain some dignity and personal courtesy, despite our differences of opinion.

In my defence It was a moronic thing to say “To increase Co2 levels in the atmosphere might very well be the smartest mankind ever did to Earth!”
Forgive my sense of humour, at least I have one.
And who by the way elected you as some sort of moral compass? f** away off and mind your own business…

Ross King

You completely prove my point, esp’lly yr final flourish about ‘un-bunch your panties ffs’ (whatever ‘ffs’ means). I invite you to consider where — on an “A–holes Scale” — readers of your contributions might consider you to be.
Civility goes far …. But over & out on this as I’m not investing time in improving *your* capacity to communicate yr message effectively on a respectable forum such as this.
Earn your right to be heard and listened-to or be ignored as — dare I say it — a moron (which — in yr case — the evidence to date is convincing. evidence to hand).

Okay ffs, I’ll not call anyone else a “moron” ever again, happy?
I promise if it shuts you up, and what is really going on, you’re just trying to but-in on what is otherwise a fun conversation.
Everything that you’re suggesting is incorrect, I don’t live by you’re moral compass nor should I respect what ever you have to say, but I do take the time as a respectable person to do so out of politeness.
But anyway stop changing the subject Moron!!
Yes! we have a successor lol
(Okay ffs, no more calling any one a “moron” after that last one) deal?

*your lol

To be honest don´t know if temperature is the horse and CO2 level is the cart or if it is the other way around. And I don´t know how much of the increased level of CO2 in the atmosphere is due to humans. But gather that we are adding CO2 to the atmosphere.

I understand that, look at it this way, If human production of CO2 was comparable to a volcano right? how do you think this hypothetical volcano would measure up to all other volcanoes on earth?
Maybe this idea will help you understand the scale that we’re dealing with 😉

I understand figures – what are the numbers? This makes me think that It would have been nice to know how many tonnes of carbon are already at the surface, and in the atmosphere, and how many tonnes we have added – however, the plants seems to be quite hungry for it – I guess it won´t take long before they have absorbed any excess.

How would any amount of carbon dioxide produced by humans even compete with an entire planet?
In context CO2 is a tiny factor on this planet anyway, plant life loves more of it, more CO2 -> More plant life -> more animal life. All of this is a natural cycle and an aspect of biological life, and when life is flourishing, it shouldn’t be seen as a catastrophe.

This figure gives an idea about the involved amounts of Carbon.
http://bclearningnetwork.com/LOR/media/sc10/Science10/chapter_2/images/carbon_cycle.jpg

I realize that the figure does not contain units. The unit for stored carbon seems to be Giga tonnes. The carbon flow rates seems to be Giga tonnes of carbon per year.

@ Ross King
I believe that “oneself” should have been “someone”?

“No offence intended by calling you a Moron.
It is claimed that from the latter half of the 20th century CO2 levels from 350ppm to 400ppm is causing so called “global warming” right?
No wrong.

@ Mosher – ??? Isn´t that pretty much the claim by IPCC ?

@ Sparks
I agree with Ross King – you should try to be more civilized. I appreciated the comment from Ross – and I did not like your reply to him. I think you should refrain from being rude.

Alan McIntire

Termites beat us by 25 million years.
http://www.theverge.com/2016/6/25/12024324/termite-farming-25-million-years-ago-before-humans?yptr=yahoo
“When it comes to farming, termites are OG. By searching through cliffs in southwestern Tanzania, researchers have discovered fossilized “fungus gardens” created by termites 25 million years ago, reports The Washington Post. And the scientists are not kidding about this — the gardens revealed that these ancient termites cultivated fungus by arranging them along a complex plan and feeding them pellets of plant material. Because of this, the researchers say this is the oldest physical evidence of agriculture on Earth.”

Gabro

When did ants start herding aphids?

General P. Malaise

if it was stated last week in an article here Garbo would believe it.

Menicholas

You mean plant lice?

Gabro

Only if there were evidence to support “it”.
What does it take for you to believe? Blind, unquestioning, childlike faith?

Gabro

Me,
https://www.sciencedaily.com/releases/2007/10/071009212548.htm
You may call them plant lice if you wish. The ants just call them.

Duster

Look up ant-aphid farming or mutualism. Using “ant aphid farming” will yield 110,000 hits and the top one has this for a headline: “Herding Aphids: How ‘Farmer’ Ants Keep Control Of Their Food”

Loren Wilson

As I read this, I am breathing air in Ogden Utah that is equivalent to 18% O2 at sea level, just due to the elevation. What our bodies respond to is absolute concentration, i.e. the number of molecules hitting your lungs per second. I could have a pure oxygen atmosphere at low pressure and still suffocate. Hence, we developed partial pressure to express the absolute concentration in easily used terms. Interestingly, my old company would not allow us into an oxygen deficient atmosphere at work, but flying in an airplane (cabin pressure typically equivalent to 7000 feet elevation) violated that rule.

rtj1211

Agriculture started when man learned how to cultivate the great staple crops like wheat. It wasn’t to do with carbon dioxide, but the acquisition of human knowledge.

tony mcleod

+1
This obvious point seems to getting ignored.
The conditions for agriculture to develop may have been in place for millennia, but so were the conditions for the invention of the wheel.
It’s a quantum leap but once it’s made and only once its made can the idea spread.
Absolutely zero evidence CO2 level had anything to do with it.
This is yet another faux reason to deny rapidly rising anthropocentric CO2 is a problem today.

emsnews

Yes, the Amazon, Congo, Indonesia, etc. jungles were nearly utterly unchanged by all the Ice Ages. It had very little effect on these equatorial places. All the places north and south went through amazing, terrible changes, very severe changes.

tony mcleod

Why “terrible” emsnews?

If rising CO2 caused global warming, the recent increase in CO2 would have caused more evaporation, which would result in more water vapor in the atmosphere. But that’s not happening:
http://clivebest.com/blog/wp-content/uploads/2013/04/TPW-global.png
In fact, the rise in CO2 has had no measurable effect on global temperatures:comment image
But CO2 has caused a very noticable effect on agricultural productivity:comment image
And farmers know that CO2 enhances yields. Otherwise, they wouldn’t spend money to raise CO2 levels.
Here is a long term perspective. We see that current CO2 levels are still very low:
http://2.bp.blogspot.com/_cHhMa7ARDDg/SoxiDu0taDI/AAAAAAAABFI/Z2yuZCWtzvc/s1600/Geocarb%2BIII-Mine-03.jpg
Draw your own conclusions…

tony mcleod

Hogwash to link grain production to the cause of rising CO2. Absolute garbage.
Oh look, the number of washing machines produces has followed the same curve, So has the incidence of colon cancer.

David A

Well Tony, literally hundreds of peer review studies and thousands of experiments prove your statement to be “hogwash”

tony mcleod

David I could have superimposed washing machine sales over the rising curve of atmospheric CO2 concentration and claimed there was causation. But obviously that would also be hogwash.

Simon

DB
Moshers graph kinda says your “CO2 has no part in warming” opinion is rather wrong wouldn’t you say?

DaveR

Agriculture started working 13,000 years ago, or 11,000 BC.
And the missing words are….”end of the last ice age”

tony mcleod

No Dave, lets just ignore that and attribute all those advances to our good friend CO2.

The tropics were always warm enough to farm.
As anyone who actually has farmed knows, having seed, fertilizer, water, and photosynthesis is all that is really needed….
Unfortunately, the “photosynthesis” requires CO2

Gabro

And yet farming arose in the subtropical and temperate zones.
The Pearl River Valley of south China is admittedly on the cusp of tropical.

Dr. S. Jeevananda Reddy

History says that man has been on the Earth for approximately two million years. During 99% of the time he has lived as a hunter-gatherer. Only ten thousand years ago he started domesticating plants and animals and is living fewer than 300 years in an industrial society. Until today, life as hunter-gatherer has been the most successful and persistent adaptation to the environment that the human being has achieved. The capacity to differentiate between the dangerous plants and nourishing plants exists in animals than in humans.
Animals eat plants that surround them in a selective way. This enlightened humans and thus, before the consolidation of agriculture, the hunter gathered and used a wide range of species of plants for food and medicine. If one adds up the food value of these plants in typical gatherers diet, this diet is more balanced in proteins and carbohydrates than the diet of most of the modern population in modern societies. Thus, the origin of agriculture was a gradual transition starting with the planting of few seeds of the most useful plants in the areas surrounding the gatherers’ camp. As agriculture establishes, the struggle of humans against certain plants, the specialization and selection of plants, started within the framework of his environment in terms of soil and climate. Later he started conserving some good seed for the planting in the next season. Here he not only included food crops but also fruit crops and also domesticated animal for meat and milk as well as draught animal in agricultural operations and established agriculture technologies for different regions based on soil and climate. Here humans have established system of farming under variable climate conditions that minimizes the weather based risk. For this purpose collected and stored seeds for all seasons and variable climate conditions.
That is, prior to 1960, the farmers used indigenous technologies evolved over hundreds and thousands of years experience and passed it on to generation after generation. These technologies were weather & soil driven farming systems that include crops & cropping patterns – intercropping, mixed cropping, agricultural practices – crop rotation, land & water management practices, traditional seed, farmyard manure, and draught animal based implements, etc. This technology was highly successful and sustainable as they included animal husbandry – horticulture fruit crops and thereby the farmyard manure as fertilizer, bulls as draught animal, etc into agriculture system with which the cost of production was low and thus the risk in agriculture was low. Therefore it is called “no suicides” technology. These are said to be “Golden Days” in the history of farming. No pollution, no worry about seed adulteration, fertilizer adulteration as they used the good grain as seed and compost of farmyard manure as well green manure as fertilizer. However, the yields were low but the quality of food was excellent & and thus provide healthy – nutritious diet to people as well the fodder to animal. Timely crop management is the mantra for the success in this system of agriculture.
Dr. S. Jeevananda Reddy

Foxhuntingman

Bulls as draught animals? I don’t think so.

Dr. S. Jeevananda Reddy

foxhuntingman — Bulls were used and are in use as drought animals. Drought animal is not drought related animal. Bulls are used to till the land, known as drought animal.
Dr. S. Jeevananda Reddy

Gabro

Bulls can be used, but draft oxen are often steers.

Dr. S. Jeevananda Reddy

After around 1960 with green revolution technology [GRT-1], the Indian agriculture has grown leaps and bounds though in quantity but failed to achieve the quality of traditional food for humans and as well to animal through fodder. Unfortunately international agencies including UN agencies are giving importance to quantity over quality of food. The technology refers to high yielding seeds clubbed with chemical inputs [fertilizers & pesticides, insecticides, herbicides, etc] & irrigation. This was successful as after Independence the government invested major part of budgetary share towards increasing irrigation sources like big dams. Now this reached around 40% of the cultivated area. High yielding seeds technology was based on few years experience of few scientists interwoven with vested interests of multinational companies that created new problems hither to unknown to farmers that lead use of chemicals in the crop management by which cost of production jumped several fold. Entered government’s input subsidy, a huge component. However, government failed to support the traditional inputs systems.
The use of chemical inputs reduced the quality in food and created bad impact on environment, this lead modern environmental movements world over. That is, this technology was found to be more dangerous on long-term, over the short-term gains; that destroyed the environment drastically like degradation & salinization of the soil, health hazards to humans, animal & plant life along with water, air, soil & food pollution. They in turn increased the drug manufacturing industries – through which pollution –, through which hospitals – through which pollution – through which more health hazards, turning in to a vicious circle. When this technology was introduced nobody knew that this technology is going to create such environmental catastrophe, but scientists involved in this research received Noble Prizes and Awards and Rewards. All these factors are not accounted under food production costs. To counter this multinational companies with the tacit support from the Western Governments compelled UN to divert the attention from environment to global warming through IPCC, a political body created in 1988/89.
Even with all these ill effects, the yield growth curve has flattened after 1980-85 as there was no improvement in seed technology for increasing the yield or bringing the farm yields to the research station yield levels. The yield of Genetically Modified Seed is limited to the traditional high yielding seed only. The technology has no yield increasing potential. They also work under the same GRT-1 scenario only. Thus, science & technology, though indicates a media for sustainable development on short-term basis with disastrous consequences on environment became unsustainable proposition on long term basis and on the contrary the traditional technologies were found to be sustainable on long-term basis. Around 30-50% of production is going as waste as there are no sufficient storage facilities and timely transport facilities. That means, we are producing too much and wasting it at the cost of natural resources and energy. That means government talk on food security and thus showed more interest in pushing production but not storage and distribution to needy in time. This encouraged the politicians-bureaucrats-businessmen nexus to look at ways and means of hording and illegal export and thus raise the prices in the market with huge profits and thus create artificial inflation. Even in USA, the excess production is dumped in to sea to protect the farmers’ interests. Thus, resources are wasted to that extent.
The mono crop culture of GRT-1 with new high yielding varieties grown under chemical inputs reduced the animal husbandry hither to play a prominent role at household food & nutrition security as this fodder is not a good diet. While calculating the food production gains we rarely account this loss.
In Andhra Pradesh a state in India, the traditional paddy under irrigation yielded 1300 kg/ha with the high yielding seed the yield has increased by 500 kg/ha [that is, total of 1800 kg/ha] and by adding chemical inputs the yield level has increased by 2000 kg/ha [that is, total of 3800 kg/ha] under the farmers fields. The research yield is 5000 to 6000 kg/ha but the present average yields of farmers field are 2600 – 2800 kg/ha. This shows there is a large yield gap between research station and farmers fields. Till to date scientists haven’t tried to fix this gap. The main beneficiaries here are the chemical inputs manufacturers with huge government subsidies; illegal exporters. To monopolize seed industry under patent laws, MNCs introduced Genetically Modified [GM] Technology in to improved local crop varieties [Reddy, 2003]. To make it effective, the vast germplasm of native genetic resources of different crops were put in to their Gene Banks [Reddy 2000]. Now they are systematically dumping GM seeds on farmers with the tacit support from their PR groups. This has disastrous effect on farmers in developing countries, more particularly in India. This lead increased cost of production and thus, this created boom in the sale of adulterated seed-fertilizers; and thus leading to farmers’ suicides. After seeing the phenomenal success, now, they are planning to monopolize even the paddy & maize seed business under the disguise of hybridization and genetically modification hither too was not in the MNCs clutches.
The success of GRT-1 was possible with irrigation [Reddy, 2016b], as the diffusion of technology was possible only through irrigation. The irrigation potential was created with huge government subsidy. Because of this the rain-fed agriculture has not recorded the success as that was recorded in irrigated agriculture. That means most of the subsidies have gone to irrigated agriculture. Thus, the gulf between the irrigated agriculture and rain-fed agriculture is increasing with the passing of time with cost of production going up and up. Thus, with the GRT-1 the major sufferers are the small and marginal rain-fed agriculture farmers as the cost of cultivation increasing day by day with income coming down. Farmers’ suicides are growing with cash crop farming – GRT-1 is mono crop technology and could not withstand vagaries of monsoon unlike traditional intercropping or mixed cropping systems along with crop rotation practice. In India around 60% of the cultivated land is still at the mercy of “Rain God“. With the high costs, the rain-fed agriculture became an uneconomical venture. Farmers started migrating to urban centres for greener pastures. This created another problem to governments in creating infrastructure facilities at huge cost in urban centers. However, Yesterday Indian Prime Minister as part of launching of Smart City projects stated that “Planned urbanization can mitigate poverty”. The whole objective is to put agriculture in the hands of corporate and encourage GMOs. The present Indian government is pro-businessmen and anti-environment.
Dr. S. Jeevananda Reddy

Geoff Sherrington

Ten thousand years ago +/- 10,000 years, a few discontented females got together and decided to go Vegan. They withheld sex supply to males enforce their ideas and so vegetable agriculture flourished by dictate.
Nicknamed “United Naggers” they continued group pressure for centuries. Their demonstrations of discontent were strident as they herded dinosaurs over high cliffs as well as causing widespread dinosaur suicide.
There is ample contemporaneous evidence of the strength and durability both the Naggers activity and its Vegan derivative. Historic restoration of large scale events is more credible when strong drivers such as sex and reproduction are involved
……
This of course is speculative nonsense, so it is appropriate for it to be here, comfortably amid other speculation with little empirical support.
Does it matter?
Geoff

ferd berple

United Naggers
===========
the “N” word men truly fear!

And then there's biology

On a related subject, if a climate model predicts that increasing CO2 levels in the atmosphere from 270 to 1000 will reduce biomass rather than increase biomass, this seems to be evidence that the model is flawed and should not be considered for use in determining policy towards CO2 emissions.

Willis Eschenbach

Let me point to a 2006 book that makes the same claim that the author is making, albeit with much more detail.
Well spotted, Ms. Corwin.
w.

Plus many.

Willis,
Your posts are great! Keep doing them!
The book you point out, like most “ivory tower”, CYA ones has “could”, “whenever it occurred”, etc. It absolutely seems close to “correct” but the error margin is huge: “about 9000 years” is a cop-out.
My thesis is simple:
direct map from the Greenland CO2 estimates to the impact on the clever, wily humans.
It has an interesting management topic of the scenario of how the tribes stumbled on growing things, once they actually would grow with any sort of vigor.
It was a very, very hard life and every little bit let the kids live.
Having grown up on a farm, I am very amused by the naivety of the city folk.
When I created the research lab for Intel, my biggest problem was “guys” sure of themselves as they wandered in the dark and CYA’ed with wishy washy statements…
and then expected me to “look up” to their “superior” silliness.

Willis Eschenbach

Thanks for the reply and for your kind words, Susan. As someone who grew up on a 280-acre cattle ranch in the middle of nowhere, I share your amusement with city folk. In particular the “if it gets warmer we’ll starve” mantra drives me nuts, because it assumes that farmers worldwide are too stupid to change with changing weather … grrr. I describe people who think farmers are stupid as folks that might have used a shovel but never sharpened a shovel …
What I liked about the book that I referenced was that it confirmed what I suspected, that the C3 plants were the first to be domesticated. This, of course, supports your hypothesis.
I was entranced by your throwaway line of “when I created the research lab for Intel” … one hesitates to ask for the back story, but nothing ventured nothing gained, I’ll ask …
w.

Good discussion on a rather weak study. 12K years ago was the end of the last Ice Age, and temperature/growing seasons had a great deal to do with farming becoming practical, as I don’t think people have changed all that much in that short a period. The other problem is trusting archaeology too much, as decent dates derive only from work done since ~1950, a relatively short time. The other problem is that archaeology tends to be done in select areas, either close to the scientists home or in deserts exposing the appropriate eras.

Too many problems to itemize but a few:
1) CO2 increases are supposed here to have been simultaneously advantageous for all cultigens but not for weeds. (Weeds would include encroaching rain forest.)
2) There is no general botanical evidence for plant population variability due to CO2 variability in the Holocene (or whenever). (Do tree rings suddenly become thicker or more dense?)
3) There was no cross cultural simultaneity in the evolution of agriculture.
4) Too many more important factors, like:
a) Changing climate
b) Extinction of human predators
c) Better weaponry (bow and arrow), for improved hunting
The Sahara was grassland 11ky as well as much of the Middle East. Odds are agriculture evolved only once and by accident. In any case it would have required a relatively sedentary culture, but one not yet civilized, as agriculture is a prerequisite for cities. And of course no irrigation would have been involved initially. Agriculture must have been discovered where rain was sufficient for the cultigen involved. Dropped seeds–return later–grain growing. Some smart woman had to put two and two together. And if the Tiwi islanders are any indication, the first planters still didn’t know where babies came from, especially if animals had not yet been domesticated.
But they may have been–something allowed the first farmers to be sedentary. And modern pastoral nomads hold a symbiotic relationship with city folk, not enjoyed by the first herders.
Humans didn’t start planting seeds when mammoths went extinct–rather the Clovis hunters went extinct together with their prey. Crediting CO2 for the evolution of agriculture is like blaming modern species disruption on global warming.
So should this thesis be dismissed out of hand? Of course, until some evidence is produced to back it up. –AGF

Well, that is an interesting set of conjectures that don’t seem to have any point.
You might start by relating them to your personal farming experience and to your personal management experience. 160 generations is a long time for a tribe to struggle to survive when food is scarce.

gringojay

More reliable moisture for plant survival & generally warmer for plant growth happened; setting a “special” CO 2 threshold as the measure for when plant growth is worthwhile is simplistic. Rainfall patterns changed as cold/dry epoch relented; getting humans to cultivate beyond plant husbandry (transplanting close to water &/or protecting wild pocket from hooves) needed reliable seasonal moisture.

Darn. They promised me it was for the alcohol. Another great theory shot to h3ll.

General P. Malaise

CO2 and the advent of farming are not connected. primitive peoples ate what they later grew before they farmed and the plants existed before they farmed them. the entire CO2 as a destroyer of the earth is fictitious and articles that try to make inferences of correlation between man and CO2 are equally fictitious.
I am disappointed in some of the articles have of late. like all things conservative the left tries to infiltrate and convert. they have been very successful on other blogs. I hope this one does not allow the parasites to metastasize.

Interesting thesis with a lot of good ideas. But overall, mistaken, probably because water was a more powerful plant control than CO2 during glacial times and the early Holocene.
Precipitation was the main control on vegetation both in peri-glacial and tropical environments, while the limited availability of CO2 probably acted as a secondary control. The effect of aridity was amplified by the impact the lower partial pressure of CO2 upon stomata.
I suggest you add to your hypothesis the effect of evapo-transpiration on plant physiology, mainly stomata. Also, you should consider the differing responses of C3 and C4 plants.
While the hypothesis would be slightly more complex, it would explain much more.
Aridity continued to limit plant productivity long after CO2 had risen substantially from its glacial-period lows. In temperate latitudes, the return of the forests occurred both as a result of temperature increase and decline in aridity.
Agriculture is too complex for a single factor theory. The first attempt at domestication of wheat in southern Turky was not sustained because interrupted by the Younger Dryas which was both colder and drier.
I think the Jomon culture might be more relevant in support of your hypothesis than the middle eastern cultures.. As I understand in the Jomon areas of Japan there was no field agriculture.
A good general text for your purpose would be The Holocene, by Neil Roberts. I consulted my copy before writing this, which is why I have not dismissed your attempt to claim increased CO2 as a factor in plant recovery during the Holocene, a recovery that is continuing as CO2 partial pressure continues to rise.
For tropical Africa, L.C. Beadle’s Inland Waters of Tropical Africa has a few interesting passages, including a reference to sand dunes invading the Congo Basin.

Willis Eschenbach

Thanks for those insights, Frederick. I had not thought about the interplay between ice age drought and stomata. The problem for plants is that when they breathe they lose water. When CO2 levels are low, they have to open their stomata wider to bring in more CO2 … which leads to greater water loss.
In other words, low CO2 levels exacerbate the damaging effects of aridity. I knew that, but I hadn’t considered what it meant regarding ice ages. Very interesting.
Best regards,
w.

gringojay

Hi Willis Eschenbach, – The elevated (relatively speaking) CO2 effect on leaf stomata is a frequently mentioned detail; yet usually considered only in a linear sense (less open = more better). If look at the stomata there is something else important to consider than just how open they are.
In epochs when ambient CO2 was “low” the plants changed the physical size of their stomata so that each stomata was smaller than under “high” C02 epochs. This gave plants 2 things we overlook when interpret experimental high (~ 700 ppm) CO2 results.
By having smaller stomata more of the total # of stomata can arrayed in a leaf & also the smaller the stomata the more efficient diffusion of CO2 becomes; it is another plant adaptation to low CO2. On the other hand, our experiments with high CO2 are using plants whose stomata have been transitioning to larger stomata since CO2 has been rising; the physical attributes of our experimental stomata are simply not the same.
Smaller stomata, by being more numerous, also occasion relatively high water transpiration up & out; but the plant trade off was more photo-synthesis at low CO2. Meaning at low CO2 + small stomata the greenery could have been quite as impressive as the greenery we see in enrichment experiments.
By virtue of this stomata adaptation (smaller/numerous) the plant was more responsive (via hormone abscisic acid) in real time to fluctuating growing conditions (moisture/temperature/light) & thus small stomata in low CO2 improved ability to juggle available water in ways that let it optimize carbon fixation over it’s growth period (not just a linear relation to days’ water transpiration). The size of stomata & their density changed from over ~1,200 sq. micrometer size 400- 350 million years ago (high CO2) & low density/mm2, then dropping to smaller of ~ 500 sq. micrometer size 350 – 300 million years ago (low CO2) with a concurrent increase in density/mm2 (~ double than before), then rose to ~1,000 sq.micrometer in size with rising CO2 300-200 million years ago & more density/mm2 again, then when again high CO2 kept rising in size 200- 100 million years ago to ~4,000 micrometer size & density stayed low/mm2, then 100 million years ago as CO2 fell again the size of the stomata fell back to ~ 500 sq. micrometer size & stomata density/mm2 started to increase (but not as high density nor small as 350- 300 million years ago during earlier low CO2 epoch).
The preceding numbers are my general interpolated comparisons & there is of course variable ranges for different plants. The different stomatal densities in the same epoch (i.e: when CO2 either high or low) also create a spectrum of different plants, with what stomatal size & density constellation, are capable of accessing how much CO2 (in mol/mt. 2/sec.). Source for those wanting better data resolution see free full text online Fig. 5: “Maximum leaf conductance driven by CO2 effects stomatal size and density over geologic time”, by P. Franks