Effect of Atmospheric CO2 Concentrations on Early Human Societies

Guest essay by Don Healy

Agriculture in ancient Egypt. Their main crops were wheat, barley and ’emmer’ wheat. Source: wall mural

During the past 100,000 years, human societies have witnessed the vast change in climate that has occurred as we have transitioned from a glacial period that ended about 20,000 years ago, into the current interglacial period. During the early stages of this period, human lived as hunter/gatherers, relying on a diet that was very heavily weighted towards meat from a wide variety of wild animals, but also included eggs, nuts, fruits and grasses, to the past 10,000 years or less, when agriculture became a much more dominate feature in society and allowed human populations to remain in the one area and create towns and small hamlets. With agriculture came the domestication of many of the wild meat sources.

As the agricultural model was perfected, much larger town and cities were created, society became more complex and the overall standard of living increased. In the past, it was assumed that societal changes were the prime driver in the change from the hunter/gatherer life style to the agricultural based society, but with the recent research into the change in the composition of the atmosphere over time from the various ice core research programs, another possibility emerges. From the ice core data we can now track the quantity of CO2 present in the atmosphere at various points in history, back to about 500,000 years ago. CO2 is one of the key ingredients in the photosynthetic process.


From : http://www.atmos.washington.edu/~dennis/Our_Changing_Climate.html

Numerous studies have shown the benefits from increasing CO2 levels on plant growth, but until recently, few studies have been conducted to understand how plants respond to the lower CO2 concentrations that were the norm during the glacial periods. Currently, CO2 levels are slightly above 400 ppm. However, during the last glacial period, ending about 20,000 years ago, CO2 levels were as low as 170 to 180 ppm. Below 200 ppm marks the very lowest level for CO2 since plants evolved and at these levels most plants are essentially starved for CO2.

The purpose of this paper will be to show that it is very likely that it was the increase in the CO2 content of the atmosphere, to levels above 250 ppm, that created the conditions for the plants that served as food sources to humans to thrive, and that made it worthwhile for humans to spend the time and energy in cultivating crops, which then allowed for the creation of cities and much more complex social orders. Prior to reaching this turning point, it was more efficient for humans to let wild animal species forage for the more limited vegetative offerings available, convert the plant material to protein and fat, and harvest the animals. Until about 8000 years ago, the human diet was composed primarily of meat from wild animals, supplemented with nuts, berries, mushrooms, and fungi in the local area. The transition from hunter/gatherer to agriculturalist was not necessarily a one-way process. Climatic changes could have necessitated a return to past methods when necessary for survival, such as occurred during the Younger Dryas.

However, as the following graphs will show, the viability of numerous plants drops considerably as CO2 concentrations diminish. Biomass and seed yield were only about 40% of current plant production rates during the glacial periods; levels that would make agriculture an inefficient use of time and energy in those early cultures.


From: http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03441.x/pdf Pg. 682

To clarify, there are three different photosynthetic pathways: C3, C4 and CAM. For the purposes of this discussion, only the C3 and C4 pathways are of concerned. CAM is utilized by cacti and similar plants that are not a large component of the human diet. The C3 process evolved first, over 400 million years ago when CO2 levels where many times current levels and are utilized by about 85% of the existing plant species today. The C4 process evolved much more recently, about 30 to 40 million years ago, when CO2 levels had dropped to levels still above todays levels, but much lower than when C3 plants evolved.

It is believed that the C4 process was a natural adaptation to lower atmospheric CO2. With CO2 levels rising from levels of 180 ppm during the last glaciation to about 400 ppm currently, the C3 plants show a larger response, but the C4 plants also benefitted to a considerable degree, due to increased drought resistance and mycorrhizal colonization of plant roots. Examples of C3 plants are beans, rice, wheat, barley, rye, oats, soybean, peanut, cotton, sugar beets, spinach, potatoes, all woody trees and most lawn grasses. The C4 plants include corn, sugarcane, sorghum, millet, Bermuda grass and poa.

From: http://www.co2science.org/subject/b/summaries/biodivc3vsc4.php

A more graphic display of the effect of various CO2 levels on plant growth follows:


From: http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2010.03441.x/pdf Pg. 677

Higher concentrations of CO2 also have another beneficial effect upon plant growth. As CO2 levels increase up to certain limits, plants are able to use water more efficiently. The reason for this is that the stomata, the pores on the leaves of plants, must remain open longer at low CO2 concentrations to allow sufficient CO2 to enter the plant. CO2 is one of crucial ingredients in the photosynthetic process. While the stomata are open, water vapor escapes as transpiration. The longer the stomata remain open to allow sufficient CO2 to enter the leaf for photosynthesis to occur, the more water escapes. Thus, plants are more drought resistant at higher CO2 concentrations.

Many plants species evolved at much higher CO2 concentrations than we are experiencing currently. The predecessors to Gymnosperms, or evergreens, evolved about 360 million years ago when CO2 levels were about 4000 ppm, 10 times today’s levels. The Angiosperms, or flowering and deciduous trees, evolved about 160 million years when CO2 levels were about 2200 ppm, over five times current levels. So at the levels experienced during the last glacial period of 180 ppm, the plant kingdom was clearly under great stress. We are all quite aware that the survival of the more advanced members of the animal kingdom which includes humans, are clearly dependent upon the well-being of the plant kingdom. So it would appear that during recent glacial periods, much of the life on earth was in jeopardy.

Will rising CO2 levels enhance the growth of many plant species existing today? The answer is clearly yes. A note of caution is warranted here in that the burning of coal, oil and wood have been responsible for most of the increase in CO2 concentration in the modern era, and the burning of these fuels also releases many other toxic substances and pollution into the atmosphere, such as soot, nitric oxides, sulfur dioxides, and trace amounts of radioactive material. However, it would appear that within certain limits the increase in atmospheric CO2 has been beneficial to date, and very likely will continue to be for some time into the future. Please examine the graphs on the next page.


From: http://ibrarian.net/navon/paper/11__Evolution_and_Growth_of_Plants_in_a_Low_CO2_W.pdf?paperid=19948732 Page 236

Greening of the Globe: If the studies cited above are correct, then it would stand to reason that we should be able to detect a growth response in the vegetated portions earth and possibly see an expansion in the overall area occupied by vegetation. The abstract below indicates that this is occurring.

From: http://www.nature.com/nclimate/journal/v6/n8/full/nclimate3004.html

“Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services1, 2. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982–2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that CO2 fertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). CO2 fertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability.”

During the 400 million or so years that plants have existed on earth, the average CO2 level has been about 1100 ppm, with a high near 4000 ppm when gymnosperms first evolved about 360 million years ago,, to a low of 180 ppm during the last glacial period. Agriculture did not become a practical enterprise for humans until 8,000 to 10,000 years ago when CO2 levels finally moved above 250 ppm during the current interglacial period. At today’s levels, just over 400 ppm we are seeing a significant increase in both the growth of individual plants and in their global distribution. The last 2.5 to 3 million years comprise an ice age in which the pattern has been 100,000 years of glacial advance, interspersed with interglacial periods of 10,000 to 20,000 years, give or take.

During the recent glacial advance, when CO2 levels dropped to 180 ppm, mark the very lowest levels of CO2 during the past 500 million years, and probably much longer. It should be noted, that below levels of 180 ppm, things become extremely dire. Were we to return to levels much below 250 ppm we would probably lose 70 to 80 percent of the human population to starvation and the societal turmoil that would ensue as we have to forgo the benefits of agriculture and go back to being foragers.

The IPCC warns us that at CO2 levels above 300 ppm we face dire consequences. It appears that the quandary we are facing is this: Do we allow CO2 levels to rise, face a modestly warming earth, but one with abundant plant growth, or try to lower CO2 levels which could have much more disastrous consequences for mankind? Ironically, if past geologic history is any indication, we could be approaching the end of the current interglacial and will then have to deal with the glacial narrative.

So, the question I put to you is this: After reviewing the information above, and perhaps doing your own research, what would be the ideal concentration of CO2?


231 thoughts on “Effect of Atmospheric CO2 Concentrations on Early Human Societies

  1. An excellent article Don! I am not a climatologist, but to answer your question about CO2 concentration in the Earth’s atmosphere I would say right now (400ppm) it is at an absolute minimum. The irrelevant organisation, the IPCC, seems to think that 300ppm would be better. Am I right in saying that at levels of less than 175ppm CO2 photosynthesis cannot occur and all life would become extinct? If so I think 300ppm is too close for comfort and would not support the current and projected future, human population. The fact that CO2 levels were up to 20x higher in the past and we are still here and able to discuss it, makes the 300ppm figure look like typical IPCC scaremongering>

    • According to a long article in Pytology (the source of the color photo on the post) most C3 plants lose about 90 percent of biomass production at 150ppm.

      • Troe, according to the experimental paper, c3 plants have some typical net primary productivity per unit time (say the summer 3 months) at say preindustrial 280ppm, holding other factors (temps, water) constant. NPP is measured by dry weight biomass gain over the period. Now rerun the experiment using same selection of plants at 150ppm. They will only produce ~10 percent of the biomass at the lower concentration. (The papers actual average was a 92% reduction, but that is species mix dependent over-precision.)

    • https://wattsupwiththat.com/2015/03/14/matt-ridley-fossil-fuels-will-save-the-world-really/#comment-1883937

      I have no time to run the numbers, but I do not think we have millions of years left for carbon-based life on Earth.

      Over time, CO2 is ~permanently sequestered in carbonate rocks, so concentrations get lower and lower. During an Ice Age, atmospheric CO2 concentrations drop to very low levels due to solution in cold oceans, etc. Below a certain atmospheric CO2 concentration, terrestrial photosynthesis slows and shuts down. I suppose life in the oceans can carry on but terrestrial life is done.

      So when will this happen – in the next Ice Age a few thousand years hence, or the one after that ~100,000 years later, or the one after that?

      In geologic time, we are talking the blink of an eye before terrestrial life on Earth ceases due to CO2 starvation.

      I wrote the following on this subject on 18Dec2014, posted on Icecap.us:

      On Climate Science, Global Cooling, Ice Ages and Geo-Engineering:

      Furthermore, increased atmospheric CO2 from whatever cause is clearly beneficial to humanity and the environment. Earth’s atmosphere is clearly CO2 deficient and continues to decline over geological time. In fact, atmospheric CO2 at this time is too low, dangerously low for the longer term survival of carbon-based life on Earth.

      More Ice Ages, which are inevitable unless geo-engineering can prevent them, will cause atmospheric CO2 concentrations on Earth to decline to the point where photosynthesis slows and ultimately ceases. This would devastate the descendants of most current [terrestrial] life on Earth, which is carbon-based and to which, I suggest, we have a significant moral obligation.

      Atmospheric and dissolved oceanic CO2 is the feedstock for all carbon-based life on Earth. More CO2 is better. Within reasonable limits, a lot more CO2 is a lot better.

      As a devoted fan of carbon-based life on Earth, I feel it is my duty to advocate on our behalf. To be clear, I am not prejudiced against non-carbon-based life forms, but I really do not know any of them well enough to form an opinion. They could be very nice. :-)

      Best, Allan


      [excerpts from my post of 2009]

      Questions and meanderings:

      A. 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? [updated revision – perhaps 150ppm not 200ppm?]

      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 they cause 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 :-)

      • Dr. Patrick Moore, a co-founder of Greenpeace, has also written on this subject:

        Executive Summary

        This study looks at the positive environmental effects of carbon dioxide (CO2) emissions, a topic which has been well established in the scientific literature but which is far too often ignored in the current discussions about climate change policy. All life is carbon based and the primary source of this carbon is the CO2 in the global atmosphere. As recently as 18,000 years ago, at the height of the most recent major glaciation, CO2 dipped to its lowest level in recorded history at 180 ppm, low enough to stunt plant growth.

        This is only 30 ppm above a level that would result in the death of plants due to CO2 starvation. It is calculated that if the decline in CO2 levels were to continue at the same rate as it has over the past 140 million years, life on Earth would begin to die as soon as two million years from now and would slowly perish almost entirely as carbon continued to be lost to the deep ocean sediments. The combustion of fossil fuels for energy to power human civilization has reversed the downward trend in CO2 and promises to bring it back to levels that are likely to foster a considerable increase in the growth rate and biomass of plants, including food crops and trees. Human emissions of CO2 have restored a balance to the global carbon cycle, thereby ensuring the long-term continuation of life on Earth.


      • And then there was the possibility of human bottleneck, linked to the Toba eruption, but apparent back to 100,000 BP when the Eemian was beginning to decline, getting colder and CO2 levels falling. By 100,000 BP the CO2 levels had fallen to barely 225 ppmv from a peak of about 300 ppmv to at the Eemian hot spot. Then there was Toba about 75,000 years BP, and by 60,000 BP CO2 broke below 200 ppmv. And then 175 ppmv at 40,000 BP. So nasty volcanos can be a hinderance for human population stability with all that dark and dust, and then with the return of glaciation it was getting so cold with so little CO2 that nothing grows. Hard times back then for the poor folk and possibly a few hard times ahead if we can’t get the science focused and “settled”.

      • My past function messed up. I meant to post:

        However, it is a big mistake to treat ice core CO2 data as it it is absolute gas measurements. The leading authority on ice cores, whose name escapes me at the moment, has pointed out that brining ice cores to the surface is a seriously traumatizing event, causing 30–50% gas losses from the extensive micro fracturing of the ice cores as they decompress. Back calculate for 40% losses and you have CO2 concentrations pretty much the same as we have today, from the lowest of 250 up to 490 ppm.

        This correction factor is logical and honest. It makes sense of the 175 ppm low during the last glacial period (baby the way, glacial and interglacial periods collectively make up an ice age), which suggests that plants we at least not growing or even dying. the corrected readings would be 250–350 ppm, and indicate that plants grew the entire time.

    • andrewmharding
      “If so I think 300ppm is too close for comfort and would not support the current and projected future, human population.”
      Our watermelon ‘friends’ appear to seek a human population of no more (and possibly significantly less) than one tenth of our present population of about 7.5 billion.

      Not a desired conclusion, for me.


    • Yes, a good article, but I do have one (I think significant) criticism. In your graph of CO2 levels during the last 160,000 years, you paste on the current instrumental history. Must we remind readers once again that paleoclimate recreations have a very different time discrimination factor than instrumental data? Mike Mann pulled this kind of “Nature Trick” to generate his Hockey Stick, and he correctly was broiled for it.

      That said, I repeat, “Good article.”

      • I’d hate to see mine! Here in the tropics, if I leave my ‘garden’ for 3 months, or even 1 month in the wet season, cleared pathways are overgrown up to 2m!

        That must be because increased temperatures are really really bad for plants. Or something…

    • More than 1300 ppm isn’t necessary. Eight hundred ppm would be better than 400 ppm, but 1200 ppm would be best of all.

    • I’m already mowing my lawn once a week. It grows around 3cm per day at the moment. I’d have to apply dilute roundup at 1000ppm or I’d die from all the mowing.

  2. Descents into glacial conditions are slow and gradual for the first 10,000 yrs or so. So we have time to adapt and evolve technologies such as nuclear power, better (and more widespread) desalinization plants for fresh water.
    But high latitudes likely would become much more harsh more quickly due to polar amplification.

    The real crime against humanity though by the AGW climate alarmists’ propaganda is that governments won’t be prepared for another little ice age.

    • “Descents into glacial conditions are slow and gradual for the first 10,000 yrs or so.”

      Not that slow. 10,000 year was more than enough to go from full interglacial (MIS 5e) to full glacial conditions (MIS 5d) at the end of the last interglacial, and the onset was actually rater abrupt:


      “Here we present an annually resolved, layer-counted record of varve thickness, quartz grain size and pollen assemblages from a maar lake in the Eifel (Germany), which documents a late Eemian aridity pulse lasting 468 years with dust storms, aridity, bushfire and a decline of thermophilous trees at the time of glacial inception.”.

    • Global warming theory says that without CO2….our planet would be snowball earth.

      Yet people that believe in global warming agree that other forces we do not understand can overpower CO2….it just did it

      ….and they still want to reduce CO2

      That takes a special kind of stupid

      • Latitude, I agree with you on several points. 1) reduced CO2 concentration in the atmosphere would be an overall detriment to life on earth. 2) Those that want to “save the planet” by reducing CO2 concentration are indeed going in the wrong direction. And 3) other “forces” or drivers can exert considerable increases in Co2 concentration.
        From the bulk of the Antarctica ice core data I believe that the warmistas have the causative factors backwards. The ice core data show that temperature leads CO2 concentration, not the other way around. This appears to be supported by the first figure in this post where CO2 plunged during the ice age.
        The logic in this post, and many others, suggests the following sequence. Temperatures rise, CO2 rises, plants flourish, agriculture spreads, and humans thrive. If this causative sequence is true (and if the evidence shown here and in similar articles are true), then it takes a special kind of misunderstanding to want to reduce CO2.
        This is an excellent article but I do question the following statement.
        “A note of caution is warranted here in that the burning of coal, oil and wood have been responsible for most of the increase in CO2 concentration in the modern era, …”
        I doubt that most of the CO2 increases are anthropogenic. There are still too many suggestions that natural sources, such as a rise in temperature, cause rising CO2 and that the role of the oceans are not understood or emphasized.
        Finally, as the author requested, my guess is that CO2 concentrations in the 800 to 1000 range would be mighty fine.

      • well…climate science says CO2 is the driver

        We don’t know the feedbacks, etc. but we do know it follows temps….

        If CO2 is the driver you could just as easily say
        when CO2 gets too low…..it causes temps to go up
        ….when it gets too high……it causes temps to go down

        It’s not…

      • Hey Jim……exactly
        If CO2 is linear (ok I know) then it’s effect is higher at lower concentrations.
        In each peak, where you would have the least albedo and highest CO2…where everything is working in CO2’s favor…..temps still crash

        CO2 driving temps….whether it’s leading or following…does not explain what makes CO2 go up and down.

        But temps going up and down….irregardless of CO2 levels….does explain that CO2 levels has nothing to do with it

      • Thank you Jim. The article you referenced by Frank Lansner states:
        “But simple fact is: “No matter what rules temperature, CO2 is easily overruled by other effects, and this CO2-argument falls”. So we are left with graphs showing that CO2 follows temperatures, and no arguments that CO2 even so could be the main driver of temperatures.”

        I published q similar but broader conclusion in 2008 and good people are still trying to wrap their minds about this “climate heresy.” Please see points #1-3 below, from my 2015 summary paper. My key point is:
        “Temperature, among other factors, drives atmospheric CO2 much more than CO2 drives temperature.”
        MY statement does not say that temperature is the only or even the primary driver of CO2; in the short term, fossil fuel combustion, deforestation etc could be the primary drivers, but the CO2-lags-global-air-temperature (by ~9 months) signal still rings clear even in the short-term data.

        See also Humlum et al (2013)
        Highlights of Humlum:
        – Changes in global atmospheric CO2 are lagging 9.5–10 months behind changes in global air surface temperature.
        – Changes in global atmospheric CO2 are lagging about 9 months behind changes in global lower troposphere temperature.

        I suggest that this clear observation trumps the IPCC’s nonsense and disproves the CAGW (very-scary global warming) hypothesis. The problem is so many scientists , including even the skeptics, have been programmed into believing that “CO2 drives temperature”, aka “the cart drives the horse”, or “the future causes the past”, and only want to argue about the magnitude (ECS) of this impossibility.

        This is where I think the state of science of climate and energy will be in less than a decade:


        Here are my Observations and Conclusions on the subject of Energy and Environment, written in 2015.

        We knew most of these conclusions decades ago; even the newer bits are now almost a decade old.

        Almost everything the EPA has done in the past eight years had been dysfunctional and counterproductive – harmful to the economy AND the environment.

        One wonders how they could get it so completely wrong.

        Regards to all, Allan

        September 4, 2015
        By Allan MacRae

        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

      • Allen Mac R

        Spot on.

        Something I don’t see considered in this discussion is that within a forest, within any dense brush, in any deep crop, the CO2 concentration at night rises (a lot) in the absence of sunlight. In other words biomass emits CO2 at night – quite a lot.

        The point is that the CO2 level experienced by plants in lush jungle, for example, is well above the general ambient level. This leads to the conservation of CO2 around any place that already has a lot of growth.

        The OCO Satellite showed that the distribution of CO2 around the world is not at all what was presumed. In fact anyone measuring it locally would already have known that, but the scale of the difference was not well mapped.

        It has often been assumed that chemical based measurements of CO2 made over the past 200 years were somehow local deviations from some norm. Well, sort of yes and no. The fact is that the CO2 level in a town, or forest, or swamp, can be consistently higher than some putative global average. Plant growth and water efficiency is based on the local concentration, not the global average.

        I expect that if done carefully, plants that tend to grow in concentrated groups will show a higher stomata-based CO2 level, and plants that grow in sparsely populated regions will show less. One should be able to find the differences even now because we have such areas, and we have satellite data to confirm it. When push comes to shove, jungles with low wind at night would survive at ‘global average’ CO levels that would starve plants in lesser regions.

      • Good thoughts thank you Crispin. I have enjoyed your comments.

        Best personal regards, Allan

        Here is my post from 2009 re atmospheric CO2:


        We know a lot less about CO2 than we think.

        Please examine the 15fps AIRS data animation of global CO2 at
        [video src="http://svs.gsfc.nasa.gov/vis/a000000/a003500/a003562/carbonDioxideSequence2002_2008_at15fps.mp4" /]

        It is difficult to see the impact of humanity in this impressive display of nature’s power (unless you believe that most of our industrial capacity is located in the high Arctic).

        Still, annual CO2 concentration keeps increasing at ~1.5ppm/year – even as CO2 fluctuates by up to 16ppm/year in its natural seasonal sawtooth pattern.


        1. IF atmospheric CO2 declines in the coming years contemporaneous with global cooling (or soon thereafter), what does this demonstrate, if anything?

        2. IF atmospheric CO2 continues to increase in the coming years contemporaneous with global cooling, what does this demonstrate, if anything?

        3. IF CO2 drives temperature as the IPCC alleges, how is it that the only signal apparent in the data is that CO2 lags temperature by ~9 months? See

    • Let’s whine about the 5% of vegetation that is C4 plants and ignore the other 95% of C3s.
      New (Brainless) Scientist, what a marvelous reference…

    • The New Scientist article is full of possibilities and maybes. On the other hand, greenhouse producers have been using CO2 enrichment to enhance crop production for decades. NS talks about less effects on yields where water isn’t limiting. Watering is a cost in a huge amount of the worlds agricultural production so equal yields with less water, or higher yields with the same water is almost a universal benefit. I understand that there is good solid evidence that world’s deserts are greening. Balancing known benefits against speculative fears, I think I will go with the known benefits. The New Scientist article is just another in a long line of David Suzukiesque “be afraid, be very afraid” articles. Fear sells.

      • BCBill! You mentioned Suzuki doom and gloom.

        From WUWT Tips and Notes….

        Suzuki cites Desmog Blog, Pembina, and peer review from Skeptical Science, to prove CO2 emissions are going to destroy life as we know it.

        David Suzuki: Facts and evidence matter in confronting climate crisis

        We recently highlighted the faulty logic of a pseudoscientific argument against addressing climate change: the proposition that because CO2 is necessary for plants, increasing emissions is good for the planet and the life it supports.

        Those who read, write, or talk regularly about climate change and ecology are familiar with other antienvironmental arguments not coated with a scientific sheen.


      • You know what would be SO nice? If the damned hysteria and politics could be removed from all matters of “climate” and we could just do honest research and enjoy being dazzled by the magnificent complexity of Planet Earth! Articles like this one put to rest the idea that we can or should “do something” about the Weather. Why not just ENJOY it, enjoy studying it and increasing our knowledge base, and be awfully bloody glad we’re not living in the middle of a glaciation? Let’s keep exposing AGW alarmism for the discredited science fiction that it really is. More like this!

      • Cam_S- You mention David Suzuki, one of my favourite hypocrites! He mentions peer review once again as a great positive, in the face of massive evidence of incompetence , indifference and collusion in that area. Suzuki is himself a failed geneticist and it would be interesting for someone with a little knowledge in that area to examine his publication record and see how many of his findings were redundant, flat out copied or proved wrong afterwards. My money says he never discovered or described anything new or meaningful!

      • To Cam_S. I really appreciate you forwarding an article that I hoped would give a good counter to “pseudoscientific” arguments. Sadly it confirmed what years of reading about CAGW have led me to believe, which is that the people who are skeptical of the claims for the warming effects of CO2 are the ones sticking most closely to the science and the those promoting the CAGW scenario are the ones employing rhetorical devices and fear mongering. For example, the Suzuki article says it is easy to refute the “junk science” claims for CO2 as a plant food but then the article doesn’t actually refute anything. I happen to have read a great deal about CO2 effects on plant growth as this does fall into my area of scientific expertise and, if nothing else, I know it is a difficult question. Based on my reading and training I would say the balance of probabilities is currently at CO2 is a good thing for crop production. By brazenly lying in a article through suggesting that there is an easy resolution to the question of the CO2 fertilization effect, Suzuki is playing to the converted through the use of rhetorical device. On the other hand, he alienates reasonably well informed people who have read enough to understand something of the difficulties surrounding the problem. And that in a nutshell is the problem with Suzuki and his acolytes, long on rhetoric, short on science and logic.

    • The fact that it is already boosting plant growth and productivity doesn’t matter.
      Models say it’s going to stop.

    • PS: None of the bad things that you and others are predicting happened when CO2 levels were between 1000 and 2000ppm. However you want us to believe that 500ppm will bring the world to a halt.
      Nonsense on stilts.

      • A normal person would say that low CO2 causes temps to go up…
        …and high CO2 causes temps to go down

      • That’s a good point. “The IPCC warns us that at CO2 levels above 300 ppm we face dire consequences. ” so,why hasn’t the Earth gone into thermal runaway before now?

    • Please send me that learned journal if you’re done with it, Griff. I’m running low on toilet paper.

    • The New Scientist would have more credibility if they knew the difference between acids and bases. Ms. Fabry also apparently does not know the difference between microcosms and the oceans. “Victoria Fabry saw the future of the world’s oceans in a plastic jar.” Apparently they don’t understand the scale. There are references about this. Also there is nothing new about changes in limiting factors. Please quit posting “authorities” who would have failed my ancient oceanography exams. However, if the basic principles have changed, let me know. Hard to keep up to date.

      • I should add that our local Navigation District, which has had consistent failure planting seagrasses and marshes, has now discovered “Restoring our seagrass will provide (usual stuff)……and help take carbon dioxide out of the atmosphere.” They don’t know or care about limiting factors and they are also trying to ship nitrogen into the atmosphere. Maybe they think it is deficient. They claim to talk to experts.

    • First we get to read more woulda shoulda coulda what if BS from the New Scientist rag. Then someone else mentions “carbon in the glass” Suzuki, a world-class scam artist. How did the climate alarmist camp attract such clowns? Gore. Pachauri. Oreskes. Hansen. Mann. Griff. Too many to name. Truly a blight on science and humanity.

      • “How did the climate alarmist camp attract such clowns? Gore. Pachauri. Oreskes. Hansen. Mann. Griff. Too many to name. Truly a blight on science and humanity.”

        A high ‘Money to Ethics’ ratio?

      • Dang! I forgot the bow tie. The science guy. Nye. Rhymes with tie. Rhymes with guy. He never mentions what science. I think it is the science of separating the citizens from their hard-earned coin to pump into the, how do you say it? The One-World Mafia? The Warmanistas? The Climate Change Commies? The Gorephytes? The UN-ema’s? The Oreskemites?

        Any other ideas?

    • First, the assumption of nitrates is incorrect. We have reduced the inadvertent production of nitrates, but it is still ongoing. Second, the differences of C3 and C4 are lessened when nitrates are available. Third, the link about IPCC did not work. So, not sure what they wanted to link to, but biodiversity loss is not just about CO2 and temperature rise, but land use as well. Fourth, species have gone extinct and others have come into being during our glacial cycles. To assume otherwise is unsupportable.The ability to separate CO2 induced declines with habitat encroachment is contentious for good reason…nature has only conducted one experiment on this, with man’s help, or interference if you prefer. Lat point, the problems with glaciation make sea level rise and acidification look small. Considering the levels most ocean species evolved, it is about an order of magnitude smaller.

    • Griff, you linked to an article that’s a decade old…..
      Link to the recent one in Nature Climate Change that says the earth is greening at an unprecedented rate…

    • IPCC scare mongering is a complete and total crock.

      What species are threatened with extinction due to more plant food in the air? That’s akin with IPCC lies like the supposedly disappearing Himalayan glaciers.

      Doubling CO2 from 400 to 800 ppm would be entirely beneficial. Tripling to 1200 ppm would be even better.

      • The IPCC actually say that changes in technology and society will outweigh any potential increases in temperature. It’s tge political activists who are scare mongering.

      • The 30-odd so-called scientists who perpetrated the Summary for Policymakers wrote this:

        “Human influence has been detected in warming of the atmosphere and the ocean, in changes
        in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and
        in changes in some climate extremes (see Figure SPM.6 and Table SPM.1). This evidence for
        human influence has grown since AR4. It is extremely likely that human influence has been
        the dominant cause of the observed warming since the mid-20th century. {10.3–10.6, 10.9}”

        “Global surface temperature change for the end of the 21st century is likely to exceed
        1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likely to exceed 2°C
        for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will
        continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to
        exhibit interannual-to-decadal variability and will not be regionally uniform (see Figures
        SPM.7 and SPM.8). {11.3, 12.3, 12.4, 14.8}”

        “Changes in the global water cycle in response to the warming over the 21st century will not
        be uniform. The contrast in precipitation between wet and dry regions and between wet
        and dry seasons will increase, although there may be regional exceptions (see Figure SPM.8).
        {12.4, 14.3}”

        (IOW, no matter what happens, ie drought or deluge, it’s all bad and all the fault of those nasty capitalists.)

        “The global ocean will continue to warm during the 21st century. Heat will penetrate from
        the surface to the deep ocean and affect ocean circulation. {11.3, 12.4}”

        “It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern
        Hemisphere spring snow cover will decrease during the 21st century as global mean surface
        temperature rises. Global glacier volume will further decrease. {12.4, 13.4}”

        “Global mean sea level will continue to rise during the 21st century (see Figure SPM.9). Under
        all RCP scenarios, the rate of sea level rise will very likely exceed that observed during 1971
        to 2010 due to increased ocean warming and increased loss of mass from glaciers and ice
        sheets. {13.3–13.5}”

        “Climate change will affect carbon cycle processes in a way that will exacerbate the increase
        of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will
        increase ocean acidification. {6.4}”

        “Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st
        century and beyond (see Figure SPM.10). Most aspects of climate change will persist for many
        centuries even if emissions of CO2 are stopped. This represents a substantial multi-century
        climate change commitment created by past, present and future emissions of CO2. {12.5}”


    • The article speaks only of C4 type plants, which have a lesser response to increased atmospheric CO2 It never once mentions C3 type plants, nor the ratio of the two types of plants. Here’s a good web reference: http://www.majordifferences.com/2014/03/difference-between-c3-and-c4-plants.html

      All the players in this response by Griff, himself, the article authors, and the New Scientist magazine understand that once people realize CO2 is beneficial (it is) and ensconced in people’s minds, then the entire business of climate alarm, the need for wind and solar power, the political impetus for greenies to control our economies via NGO infiltration into non-responsive, unelected bureaucracies will completely collapse. As such, Griff grasps at every folly that maintains the illusion of CO2 “danger.” Shame on you, Griff. Stop being a putz.

  3. Given the effects on plants, and the fact that 2000 ppm CO2 did not cause runaway warming, what is all the concern about CO2 levels anyway?/s

    • Hey Tom, a primitive religious cult has to worry about something. And what better to worry about than CO2 levels. After all CO2 can make the world warmer, colder, wetter, drier, more prone to unusual weather and less prone to unusual weather.

      • Haven’t noticed the cultists giving up air travel, living in unheated yurts, or eschewing cable TV or I-phones.
        They still have children, who enjoy expensive “back to Nature adventure experience” summer camps. Only thing carbon-neutral about any of ’em is the weed they smoke to come up with their dotty pseudo-science.

  4. Look at the ice core records, Dome C, Vostok. They all show continuous cold and low CO2. An interglacial starts with a sudden warming, often apparently over no more than a few thousands of years, followed by a slow, erratic decline in temperatures until the next warm period starts. The CO2 levels peak at ~300 ppm. Allowing for the length of time for the ice to form and possible diffusion, those numbers must have significant differences from the actual atmosphere at the time. So the current 400+ppm for 40 or so years won’t even show up. And by all the previous ups and downs in temperature we are most likely starting the slow decline into another glaciation.


    • philohippous,

      The resolution of the ice cores depends of the snow accumulation rate, which also gives the maximum years one can look back in time.
      The best resolutions (~10 years) are for 2 cores at Law Dome, maximum 150 years back in time. The worst resolution (~560 years) is for Dome C, looking back over 800,000 years.

      The current increase of ~110 ppmv in 165 years would be detectable in all ice cores over the past 800,000 years, be it with a smaller peak.

  5. The content on CO2 effects on plant productivity seems reasonable enough but I could have done without the proselytizing on the joys of City life. Cities were until very recently cesspools (literally) of misery and disease . The only way the populations of those concentrations of despair could be maintained was by a continual influx of people from the country and nobody would voluntarily leave a bucolic country life to live as a slave or a wage slave in the city. Don’t give me any revisionist balony about how hard farm life was. I spent my childhood on a farm that still used horses as the main source of power and nobody in modern times has anywhere near the time that my grandparents had for doing crafts like needlework, preparing meals and living a good life.

    If you want to understand where cities came from, it is best to look at the process of citification that is going on around the world today. Cities essentially create a vulnerable population that is easily exploited for labour or war. If you tour around China today you will see nary a tractor in sight. China abandoned its peasants to create a pool of cheap labour for manufacturing- the same reason that the commons were closed and the same reason that the power hungry have always worked to drive people off the land and concentrate them in unsustainable disease centers.

    As a friend once remarked upon looking at the banks of condominiums housing worker/consumers in Vancouver, “they aren’t even human”, and so we came up with a new species- Homo urbanensis, the useless ape. Or Citiots as they are commonly known.

    • Nicely put BC Bill. Amongst their many faults, our urban intelligentsia believe that any and all manual work is degrading. It’s practitioners are unfortunate souls who will never know the joy of being utterly useless and commanding things to be done without regard for cost or utility. And they are legion!

    • Initially some cities were made by a few thugs who took transportation tolls on roads and rivers. Others grew on critical spots at junctions of transportation to aid commerce and profit from it. All required higher CO2 levels to be practical. Then came the industrial revolution, where the decrease in farm labor came from more technology development, which allowed more farming with fewer people. The unemployed farmers had to go find work where the new technical industries needed workers. There were many abuses, but do not simplify the actual process. In fact, the so called abuses related to the industrial workers were generally less extreme than experienced by poor farm work. Farmers were rounded up for wars as much as city people. The so called ideal farm life is mostly an unrealized fact that was only available to a few at a few time periods.

    • One well-known medieval country boy, like many before and after him, went to London because he would not inherit his dad’s land:


      During the Medieval Warm Period, rural population grew more rapidly than did the work available for country people. They had no choice but to seek work, let alone their fortunes, in the burgeoning cities. In the 14th century, these were truly awful with offal, but before the Black Death, population still increased despite the poor conditions for many.

      In many parts of Europe, serfs earned their freedom by staying in a city for a year and a day. Hence the German expression, “Stadtluft macht frei”.

      After the Black Death and the decline of serfdom, landowners wanted to keep paying agricultural laborers the low rates which obtained when the population was up to twice as high, before the plague wiped out so many in town and country alike. Hence, the Peasants’ Revolt, aka Wat Tyler’s Rebellion or the Great Rising, of 1381.

      The reverse situation occurred after the Napoleonic War, when rural rebellions broke out in England as the demand for agricultural products fell, but workers still wanted to be paid the previous higher wages.

  6. Don Healy,

    One small addition: as a bonus for C3 plants, levels of CO2 at the near surface over land are -today- average 40-50 ppmv higher than “background” as measured in ice cores. Below 180 ppmv, most C3 plants have little or no photosynthesis.
    If the extra CO2 over land was also the case during the long glacial periods remains to be seen, as less plant growth als means less plant decay, which is what gives the extra CO2 levels over land…

    • If the extra CO2 over land was also the case during the long glacial periods remains to be seen, as less plant growth als means less plant decay, which is what gives the extra CO2 levels over land

      YUP, that should make sense to most any Academically employed person.

      And on the contrary, …… more plant growth ….. also means more plant decay ….. which is what causes lower CO2 levels over land.

      YUP, shur nuff, …… when the microbial decomposition of dead biomass INCREASES ….. the outgassing of CO2 causes a DECREASE in the ppm quantity in the atmosphere.

      So, there ya have it, …… less equals more ……. and more equals less.

      It’s kinda like engaging in physical sex, ……. Right? The less you get the more ya want it, ….. and the more ya get the less ya want it.

      • Plants emit CO2 at night. Basic science. It is not rotting vegetation. That continues day and night.

      • Crispin in Waterloo, ….. you be sure to tell Ferdinand E about that AMAZING scientific fact regarding plant respiration.

        Of course you might have a problem trying to convince Ferdinand E that most all of the nighttime and winter emissions of CO2 really don’t originate “out” from underneath snowdecks of side porches in Alaska and other northern latitudes.

      • Crispin,

        Nightly respiration is part of the increase of CO2 near ground over land. Rotting vegetation goes on day and night and even -at a lower pace- mid winter under a snow deck. Something Samuel doesn’t want to believe, even if it was measured at -20°C in Alaska.

        The diurnal global change is – according to the IPCC (but backed by real world measurements) – some 60 GtC in and out, the seasonal changes are of the same order, but as respiration (~60 GtC/night) and photosynthesis (~60 GtC/day + 60 GtC/growth seasons) is only in warmer months for a lot of trees, in average photosynthesis would win the battle, thus lower levels over land than in the rest of the atmosphere in the growing season… In part that is compensated by vegetation decay, which is faster at higher temperatures, in part it is the distribution: increasing to (very) high levels at night (often less wind/mixing, especially under inversion), while during the day, the warming ground gives more turbulence and thus better mixing with the bulk of the atmosphere.

        The average is about 40 ppmv above background for places like (semi-rural) Giessen (mid-west Germany) where CO2 is continuously monitored:

        There is hardly a seasonal signal in the monthly CO2 data, just a lot of noise and a positive bias.

      • Ferdinand Engelbeen – March 27, 2017 at 8:14 am


        Have a look at the seasonal CO2 levels in Barrow, Alaska:

        Ferdie, ……. you intentionally neglected to mention the fact that the intake height of CO2 sampling at Barrow, AK, is only at 27 masl ….. and the bi-yearly CO2 cycle is an average of 18 ppm ….. with a “steady state max CO2 ppm” occurring from mid-November through to mid-May of each year.

        So, getta clue, Ferdie, ……and educate yourself to the fact that those 4 ½ months of 18+- ppm of “near-surface” measured CO2 quantities is a direct result of the residents of Barrow, AK, burning fossil fuels and firewood to prevent their arses from freezing solid …… and has nothing whatsoever to do with the biological decomposing of dead biomass.

        Barrow Alaska monthly mean CO2 ppm profile – annual bi-yearly cycle

        Give it up, Ferdinand, ….. you are neither smart or clever enough to be “blowing smoke” at learned scientists and getting by with it. You should be touting your “junk science” on YouTube or FaceBook because I’m you will find plenty of gullible believers thereon.

      • Samuel,

        Point Barrow station is at a peninsula where the CO2 monitoring is done, some 14 km from Barrow itself, carefully avoiding their own heating outlets, that is when the wind is blowing to the opposite side…

      • Ferdie, …… Point Barrow is east of Barrow and that is the way the wind is always blowing,

        And Ferdie, the CO2 data that is plotted on the Barrow “Keeling Curve Graph” …… is 100% supportive of what I have been telling you about the CO2 data that is plotted on the Mauna Loa “Keeling Curve Graph”, to wit:

        Atmospheric CO2 ppm quantities, as measured monthly, bi-yearly and/or annually, are determined by the action of the ocean water ingassing/outgassing of CO2, Henry’s Law

    • Samuel,

      Somewhat wrongly formulated I suppose…

      Plant decay is what gives extra CO2 in the atmosphere, less plant growth gives less plant decay and thus less extra CO2 near ground compared to “background” levels in the bulk of the atmosphere…

      • Ferdinand,

        Plant growth and decay can be near balanced or one may dominate. However the more decay adding more CO2, the more growth is stimulated which tend toward rebalance with more growth. In general your comment is wrong. Unless there is “temporary” large unbalance, the long term tend would not be greatly affected by plant decay.With other sources (volcanoes, farming and tree removal, making cement, burning older sequestered fuels) making much more CO2 than is sequestered, there can be a net increase, but all of these processes are finite, including the increase due to human activity, and will not go much higher that present, and thus also lead to rebalance ( I would guess we won’t reach much over 600 ppm CO2 unless there is super volcanic eruptions like the ones that formed the Siberian and Deccan traps, and possibly smaller events).

      • LEonard,

        I agree that plant growth and decay are more or less balanced, but that is not the case for CO2 levels near ground over land: more plant growth gives more decay and that increases the CO2 levels in and near ground.
        In the ground by bacterial growth on fallen leaves and near the roots (with plant sugars as food) and just above it. If you dig a hole, you can measure 1000 ppmv CO2 and more…
        That doesn’t affect the long term T-CO2 balance in the bulk of the atmosphere, but it may affect the local CO2 levels near ground over land where C3 plants struggle to survive in low CO2 during a glacial period.

        Indeed higher CO2 levels mean more growth, but that is not 100% for a CO2 doubling. In ideal circumstances (like in greenhouses) the growth in average is 50% more for a CO2 doubling. In nature that is much less as CO2 is not always the limiting factor: water, nutrients, sunlight, temperature,… all may be limiting factors…

      • Plant decay is what gives extra CO2 in the atmosphere, less plant growth gives less plant decay and thus less extra CO2 near ground compared to “background” levels in the bulk of the atmosphere…

        Shur nuff, Ferdinand,

        Dat t’was a somewhat “weazelworded” response I suppose ….

        So yup, to reply in kind, …… plant growth is what removes extra CO2 from the atmosphere, more plant growth gives more plant decay and thus more extra CO2 near ground compared to “background” levels in the bulk of the atmosphere …….. except during periods of high humidity, …… rain events ….. and/or extremely dry, chilly, cold or freezing surface conditions …… which directly causes a drastic decrease in the aforesaid “more extra CO2 near ground level”.

        Ferdinand, you really need to intensely study the following for the next 2 or 3 weeks in order to better your mindset of the subject matter, ….. to wit:

        A Scandinavian group accordingly set up a network of 15 measuring stations in their countries. Their only finding, however, was a high noise level. Their measurements apparently fluctuated from day to day as different air masses passed through, with differences between stations as high as a factor of two.

        Charles David (Dave) Keeling held a different view. As he pursued local measurements of the gas in California, he saw that it might be possible to hunt down and remove the sources of noise. Taking advantage of that, however, would require many costly and exceedingly meticulous measurements, carried out someplace far from disturbances.

        Keeling did much better than that with his new instruments. With painstaking series of measurements in the pristine air of Antarctica and high atop the Mauna Loa volcano in Hawaii, he nailed down precisely a stable baseline level of CO2 in the atmosphere.

        Read more @ http://www.aip.org/history/climate/co2.htm

  7. The first graph is a typical hockey stick production, with directly observed instrumental values spliced on to indirect (ice core) measurements. It doesn’t offer a real comparison between the Modern Warm Period and the previous interglacial.

    Other than that scary-looking graph, a good article that summarises a lot of what we should be talking about.

    Mr. Healy characterises early humans as hunter-gatherers. True as far as it goes. However, all of our nearest relatives among the apes are AFAIK not meat eaters; they all live in hot countries and feed on fruit and stuff that is readily available. It’s a reasonable conjecture that humans evolved into omnivores as a response to one of the early glacial periods where fruit became scarce and jungles turned into grasslands. And as a further reasonable conjecture, that human intelligence evolved as a consequence of the challenges of capturing and killing animals that are bigger and stronger and faster than many humans together. This involved the necessity of group action, perhaps helping language to develop. And then there are the intellectual challenges of staying warm in cold climates (fire, fur and shelter).

    It really is no coincidence that humans evolved during the ice age. Environmental stress will usually accelerate the process of natural selection to promote evolution of new phenotypes that are adapted to deal with the stress.

    Possessing intelligence is not always the same thing as using it though. As we see on a daily basis, and often highlighted by this most excellent blog..

    • >>
      However, all of our nearest relatives among the apes are AFAIK not meat eaters;

      I’ve seen videos of chimpanzees using small sticks to pull termites out of their mud homes and eat them. I believe that counts as animal protein. One of Jane Goodall’s shows showed a female chimpanzee dragging another female’s dead baby off to consume–so chimps are cannibals too.


      • There are videos on the web of Chimpanzees hunting and eating smaller monkeys. I remember a similar movie before there was a web.

    • Smart Rock,

      The CO2 (and CH4 and N2O) are real HS’s as what is measured in ice cores are direct measurements of ancient air, be it averaged over several (10-600) years. Even with a direct overlap between atmosphere and ice core CO2 (1960-1980) with the same GC:

      Ice cores with different accumulation rates (and thus different resolution) overlap each other for the same average gas age within 5 ppmv…

    • Agreed Smart Rock. Mike’s nature trick is an object lesson of the pitfalls of splicing instrumental data onto proxy based graphs.

      And I am not persuaded of the link between CO2 levels and human progress. That is a big stretch indeed. Your environmental stress explanation seems a much better fit.

      • Most sociologists link the development of civilization with the development of agriculture. If more CO2 made agriculture easier, then there could be a possible link.
        Would civilization developed had CO2 levels not started to rise? Possible, we will never know for certain.

    • Humans are far from the only omnivorous primate.

      Chimps consume a lot of animal protein, not just from insects, but from hunting bush babies and monkeys. Bonobos are less carnivorous, but still eat some meat.


      Besides these partially carnivorous apes, there are also meat-eating monkeys. With more traditional monkey fare as fruit, leaves, flowers, buds, nectar and seeds, capuchins also eat insects and other invertebrates, bird eggs, and small vertebrates such as birds, lizards, squirrels and bats.

      The nearest primate kin of apes and monkeys, tarsiers, are entirely carnivorous, primarily insectivorous.

      • Ape and monkey teeth are suited to an omnivorous diet. Human teeth are not. We are suited to eating fruits and nuts, vegetables and grains. No carnivore has teeth like humans. I don’t count ‘animal protein’ like grubs and worms as ‘meat’. If we are talking about predators, carnivores, we don’t have the right teeth for that. If evolution works as advertised, we did not evolve as meat eaters.

    • Smart Rock – March 24, 2017 at 10:24 am

      It’s a reasonable conjecture that humans evolved into omnivores as a response to one of the early glacial periods where fruit became scarce and jungles turned into grasslands. And as a further reasonable conjecture, that human intelligence evolved as a consequence of the challenges of capturing and killing animals that are bigger and stronger and faster than many humans together.

      Sorry bout that but me thinks you are confusing “reasonable conjecture” with “circular reasoning”.

      Here following is “reasonable conjecture” for your consideration, to wit:

      Nothing makes sense in the Evolution of Homo sapiens other than a close association with an aquatic environment (the shores of rivers, lakes, inland seas or tidal zones) which provided those early hominoids with an easily accessible, abundant supply of high protein foods which did not require the use of tools to gather or to eat.

      Bipedal locomotion, loss of protective body hair and the evolving of “sweat glands” over their entire epidermal skin area are just three (3) of the physical attributes that our early human ancestors, the only sub-species in the Family of Great Apes, evolved to best survive in the environment that they chose to live and reproduce in.

      So, the question is, what was their selected environment like that best suited a bipedal stance or movement, ….. did not require the protection of a heavy coating of body hair, ,,,,, but absolutely, positively required that their entire body surface (epidermis) contain sweat glands that secrete copious amounts of salt (NaCl) containing water (H2O).

      Surely that environment was not a hot, semi-arid African savannah simply because salt (NaCl) and water (H2O) are the two (2) most important, precious resources necessary for human survival ….. and thus it would be highly detrimental to one’s survival if they indiscriminately rid their body of said without an immediate means of replacing said losses. Too little, or too much salt (NaCl) is a cause of certain death to humans.

      As far as anyone knows, ….. the evolving of “sweat glands” in the epidermis covering of the human body may have specifically evolved for ridding the body of excess salt (that was/is ingested as a result of their primary food source) …… because the retention of too much salt will kill you “deader than a door nail”, There has been more than one (1) human that has died from drinking “salty” water.

      Be it “reasonable conjecture” or “logical reasoning”, the literal fact is, our early human ancestors evolved to be the “brainy” ones of the family of Great Apes simply because they resided on the shores of large bodies of saltwater which provided them an easily accessible, abundant supply of “iron rich” high protein food sources, ….. to wit:

      What seafood is rich in iron? If oysters, mussels, and clams aren’t on your regular menu, common fin fish, like haddock, salmon, and tuna, are also good sources, although not as high in iron as mollusks (shellfish).

      • >>
        Samuel C Cogar
        March 25, 2017 at 6:03 am

        That sounds like the Aquatic Ape Theory (AAT). I like the theory, and it explains much. However, the current consensus literally hates it–almost violently. After finding “Lucy” lived primarily in a forested region (which they are working on to change), I find it strange people still believe in the “Savannah Theory” of human origin. Baboons live on the Savannah and show no signs of bipedal-ism or of hair loss. Nor would they leave their unprotected females and offspring behind to gather food. They would return finding their females and offspring missing.


      • Jim Masterson – March 25, 2017 at 10:18 am

        That sounds like the Aquatic Ape Theory (AAT).

        Right you are, Jim, it is the basis of the AAT ….. and of course the current consensus literally hates it because any acceptance of the “literal truths” of the AAT will destroy just about everything their fame, credibility, job status, monetary income and/or career is based in/on.

        And like the Biblical Creation believers’ FALSE claims that “the evolution theory claims that humans evolved from monkeys”, …… the African Savannah Theory believers are touting FALSE claims that “the AAT theory claims humans evolved because their branch of the family of great apes migrated to and lived in/under the water” without ever setting a foot on dry ground.

        Ells bells, iffen our early evolving “water living” human ancestors never ever “set a foot on dry ground” then they sure as hell didn’t need to evolve a pair of “bipedal legs” for walking or running.

        And Jim, me thinks “Lucy” actually lived near the shore of a great “inland sea” which was located in what is now known as the Great Rift Valley of eastern Africa. http://www.hiddenjourneys.co.uk/London-Dar-Es-Salaam/Great%20Rift%20Valley/Lowest.aspx

        And the Great Rift Valley is not now and never was, what is now referred to as “African savannah” topography. To wit:

        The Great Rift Valley is part of an intra-continental ridge system that runs through Kenya from north to south. It is part of the Gregory Rift, the eastern branch of the East African Rift, …………..

        The valley contains the Cherangani Hills and a chain of volcanoes, some of which are still active. The climate is mild, with temperatures usually below 28 °C (82 °F). Most rain falls during the March–June and October–November periods.[3] The Tugen Hills to the west of Lake Baringo contain fossils preserved in lava flows from the period 14 to 4 million years ago. The relics of many hominids, ancestors of humans, were found here.
        Read more @ https://en.wikipedia.org/wiki/Great_Rift_Valley,_Kenya

  8. I have no personal knowledge of growing Cannabis plants. However, one site … : Link. … provides a graph that claims 1200 to 1400 ppm CO2 will double growth rate.

    Insofar as this, and may others, is an important crop in many places (out of doors, I mean), governments could increase the local economy by subsidizing the production and injection of this gas into the environment. More product, sales, wealth, taxes – a win – win situation.

  9. 1saveenergy:
    I don’t know a lot about climate, but I do know a bit about motorcycles and Suzuki did hit some home runs there. Had a supercharged GSXR 750, it posed one problem, nobody would ride with you!

  10. Like everything else on our extremely complex planetary system, it’s never only about atmospheric CO2 concentration alone, but as part of a much more diverse system. Other factors that affect green plant biomass growth are temperature – warmer = more growth; atmospheric oxygen concentration; and perhaps most importantly sunlight intensity and duration, which are also directly affected by atmospheric relative humidity, aerosols, and cloud formation, the operation of our magnetic field and cosmic rays, etc. etc. etc.

    Way too many variables to focus on only one – atmospheric CO2 concentration, as telling or controlling. Not to mention the relationship between causation and effects, and various feedbacks.

    One thing is very clear – the warming climate of the past 10,000 has been phenomenally beneficial to humans. The warmer, the better. Colder eras are always accompanied by crop failures and thus greater human mortality and lower social stability. And vice versa.

    Consequently, it has always been my opinion that the greatest social damage done by the warmers has always been their insistence that warmer climates are bad for humans, and colder climates are good for humans. They could not possibly be more wrong headed in that concept.

    • Duane: “it’s never only about atmospheric CO2 concentration alone”

      Perhaps, yet life cannot exist without atmospheric CO2.

      CO2 alone, is the singular throttle in the Carbon Cycle of Life.

  11. I always found it very unrealistic to believe that stone age humans had a meat intensive deit. I think it is a modern misconception, everywhere we portrait a cave man he caries a spear and os part of a hunting party.

    It was much easier for early humans to gather roots, seeds, beries, etc than to hunt with a stone spear. Not to say much, much, much safer. And life was hard already back then.

    Their diet was almost certainly based on gathered food, complemented by hunting and fishing. Gatherers/Hunters would be a better name. As inspiring as it may be to think of a brave caveman as our ancestor was likelly not the norm.
    The fact that we find archeological evidence of animal bones in caves means they did eat the ocasional meat, but bones are fosilissed much frecuantly than any gathered food leftovers.

    Apart fron that the article was interesting

    • I don’t think there is a general answer, some human diets consist of 100% animal and other 100% plant, and it was just like that in paleolithic time. It is our ability to eat most anything that has helped us rise to the top of the food chain. Lucky for us that bears didn’t evolve opposable thumbs first.

    • About hunting.

      One thing that is always remarked upon is how much more wildlife is around when there are no humans.

      Read some historical accounts. The plains buffalo, for example. The American Indians didn’t have the horse to hunt them efficiently.

      Remember the passenger pigeon? Or the dodo bird?

      Fish. The ocean, lakes, and rivers teem with fish without humans around. Again, historical accounts of Europeans coming to the new world.

      Think how much game there was for the early humans to catch and eat! All they needed was the right technology.

      With the right technology, meat could be a big part of the diet. Think of all the meat in a mammoth!

      • You are mixing timeframes. American indians of the 15th century have nothing in comon to paleolithic himans 20000 years ago. Not to mention dodo bird.
        For alternative interpretations of the plains of buffalo, read “1491: New Revelations of the Americas Before Columbus” a real eye opener

  12. It would be interesting to actually observe various crop yields with 200 ppm CO2. It’d probably be a sad sight.

    • Gerhard et. al. 2010 review paper in Tansley Review. Original review paper published in New Phytologist 188: 675-695 (2010). Covers all the experimenatal data of the past 15 years.

  13. Future generations in the long term future will look back at this point in humankind’s history as the turning point in ensuring that that the human race would survive into the long term future by introducing and releasing some of the CO2 that had been locked away geologically. Looking back through previous ice ages shows that each progressive interglacial peaks with a declining CO2 maximum, and the long term ice age having lower CO2 concentrations going lower per ice age cycle. At 180 ppmv, photosynthesis starts to really slow down and below 150 ppmv it basically stops on a global scale. That would most certainly be a game changer for all life on earth. The stakes are very high in this debate over CO2 in general, but especially important for anthropogenic CO2 releases from FF.

    The latest ice age peaked at 20,000 years BP with CO2 concentrations at 180 ppmv, which as stated is on the brink of photosynthesis failure. How much this contributed to the Mega Fauna extinctions at the time of the Younger Dryas event remains to be seen, although that appears to be coincidental with some form of massive external forcing. Some speculate that an asteroid, comet or bolide collision with the ice sheet perhaps sped up its hastier demise, and led to the mega fauna extinctions including end of Clovis habitation over all North America.

    With regards to present short term human evolution, it is clear that this modern expansion of rapid human growth was due to principally to the exploitation of FF. (and 1 man will do the work of 10) More like a 100 and made slavery obsolete as a sidebar. To demonize CO2 for the most recent warming in the last 177 years, is the height of folly. By far our largest threat to human kind now is a sort of rapid cooling that has the northern hemisphere not producing a crop for 1 or 2 seasons. With 7.3 billion people now on the planet and few of us familiar with hunting and gathering just to stay alive, is without precedent at any time on earth. What would would be the result if the same volcanic activity of the Tambora volcanic event initiated in 1815-16 on global agriculture, or the Icelandic Laki eruption of 1783-1784. In todays world where we just have a few months food supply available at any one given time, it would certainly be an instant global tragedy of epic proportions. Why does no one talk about this?

    The one thing we know for absolute certainly is that the earth changes fairly slow over time via Uniformitarianism punctuated with periods of short term random Catastrophism. It may be difficult to plan for such random chaos cooling to the climate other than honing our skills on perhaps diverting an asteroid or comet that has our name on it. The fact that CO2 has been declining with every successive ice age cycle however, should be a wake up call to start to understand the effects that CO2 has on life itself.

    • A know-nothing here. But, I have a question about ice cores.

      Could the progressively lower values of CO2 in ice cores with successive ice ages just be an artifact of diffusion of CO2 in the ice. Diffusion would blunt maxima and minima, with the effect increasing with the increased age of the ice. The newest cores would have the more accurate results.

      Any thoughts?

      • Joel I can’t shed any insights on the subject but I too am yet to be convinced that information produced by analysis of ice cores is anywhere near as reliable as advocates seem to believe. And then there is tree ring analysis.

      • Joel,

        If there was appreciable diffusion over 10,000’s of years, the peaks (~300 ppmv) as measured today would have been much higher originally and spread over the glacial periods. That means that the 180 ppmv measured in glacial periods would have been even lower, which is already at the edge of survival of C3 plants…

        Moreover, there is a nice correlation between the temperature proxies (dD and d18O) in the ice and the CO2 levels in the enclosed air bubbles (with long lags). If there was diffusion, the peaks further into the past would have faded out, and thus the ratio between CO2 and T. That is not the case: the CO2-T ratio remains the same over the full 800,000 years.

        As any diffusion is not directly measurable, one has calculated a theoretical migration from remelt layers in the relative “warm” (-23°C) coastal ice core of Siple Dome, where slightly higher CO2 levels were found:
        That gives an increase of the resolution from 20 to 22 years at middle depth (2.74 kyr) and from 20 to 40 years at full depth (~40 kyr). No big deal.

        For the much colder (-40°C) inland ice cores like Vostok and Dome C, the migration is unmeasurable small.

      • Forrest Gardener,

        The difference between ice cores air bubbles and proxies is that ice core air is really ancient air and any measurements are direct measurements, not proxies that need to be calibrated.
        The main drawback is that it is never the air of one year, but always a mix of several years of air. Depending of the local snow accumulation rate, that is an average of 10 to 600 years.
        Etheridge e.a. in 1996 has drilled several cores at Law Dome with different techniques (wet and dry), gas collection in air, firn and ice and found only 7 years average difference between the atmosphere and the CO2 levels at bubble closing depth (~72 meter). Also the same levels of CO2 in still open pores and aready closed bubbles in the ice, thus no last minute separation for CO2.

        More background info at:

  14. This would explain why there was a mass grass growth event over sand dunes in regions with marginal rainfall 15000 to 10000 years ago. And would explain the end of the dustiness at the same time.

  15. Had to read some sections several times being a non-expert. A good sign from my experience. Buy into the increased vegetation leads to civilization to an extent. To what extent would be the question. More than other factors influencing early human developments in Mesopotamia, the Nile and Indus Valleys? Requires more thought on my part. A very good read resulting in the appropriate “wait a minute” moment when it sinks in that increased CO2 may be a good thing. Completely counter-narrative which is exactly what everyone needs.

  16. Lots of things happen to CO2 gas trapped in ice for thousands of years and hence the absolute values deduced from the Vostok data should not be taken at face value and then compared with recent data.
    The relative values that reflect a doubling from glacial coolings to interglacial warmings are more accurate.
    That doubling occurs in the absence of any human emission and hence is not attributable to any human emission.

  17. Don Healy,
    A solid summary of known facts, leading to an interesting hypothesis: Increasing CO2 levels during the Holocene intraglacial period stimulated plant growth sufficiently to allow human evolution from ‘hunter/gatherer’ bands to agricultural supported communities of increasing size and complexity.


  18. This interesting post postulates that rising CO2 afyer the LGM enabled the Neolithic transition to sedentary agriculture. Been doing research on that idea, because is not among the several conventional archeological explanations for the transition.(Wiki has a list with explanations.)

    Within the limits of dating and definitions, seems a strongly supported hypothesis. Domestication of formerly gathered wild plants was not instantaneous, nor something that happened in a hunter/gatherer lifetime. The technology had to develop by trial and error. Archeological evidence for primarily sedentary agriculture (domesticated plants) includes sufficient plant improvements over ancestral wildtypes (e.g. Larger cereal grain seeds) and specialized agricultural implements (e.g. stone scythe blades, storage systems). Domestication of farm animals was apparently largely coterminus according to Jarod Diamond (Nature, 2002).

    At several places around the world, the evidence points to the initial transition to sedentary agriculture being ‘completed’ about 9000ya despite completely different ecosystems. In Mesopotamia, wheat and barley. In China, two types of millet plus rice. In the New Guinea Highlands, taro and bananas. In Mexico, the development of maize from wild teosinte (the most obvious selective breeding grain enhancement). The similar timing around the world despite very different ecosystems and domesticated crops cannot be a coincidence. Nor can it be from cultural diffusion of agricultural knowlege; at that time, these areas were geographically isolated. Increasing plant productivity enabled by rising CO2 levels provides a global explanatory timing signal.

    • Ristvan,

      Interesting points anyway… Maybe in addition the increasing population that made that hunting/gathering was not sufficient anymore to feed everybody and the overhunting of several species that were hunted with ever better tools…

      • FE, based on what little I know (I am a business/law math models guy by training) if hunter/gatherer was not sufficient, those populations would have declined. Neaderthals in Europe may be an example, albeit out of time sync for this post.
        It is pretty clear that the Neolithic transition to agriculture was a BIG deal. For wild aurochs, see my essay No Bodies in ebook Blowing Smoke.

      • Ristvan,

        Looking at what the Neanderthals did eat, they were eating as good plant food as meat. Humans have similar digestive track (according to the following article: https://askabiologist.asu.edu/plosable/proof-poop-what-neanderthals-ate ), thus the switch from hunter/gatherer to agriculture + domesticated animals was not that difficult for humanoids as seen from the food side.

        Remains why the switch was so fast worldwide in completely separated areas. Increasing temperature + CO2 and resulting boom in plant species and abundancy may be the main cause.

    • Agreed. These different areas were also largely culturally isolated from each other. In the case of North and South America vs. Asia and Europe- completely.It is a lot to believe that agriculture arose independently in all those places within such a narrow time frame without some over-arching factor.

      • Yup, had never though about it before, but several hours of on line research (google fu to peer reviewed papers) said wow! This has to be correct new science. Am now working on an anti-warminist neolithic sound bite. Better than CO2 is plant food. Heck, CO2 is OUR food. Or something. Feeble and uninspired so far.

      • The time frame wasn’t really all that narrow.

        Dogs were domesticated, or domesticated themselves from outcast wolves hanging around human camps, in the hunting and gathering Paleolithic, long before agriculture. Pigs were domesticated in Mesopotamia around 15,000 years ago (Ka), followed by sheep between 13 and 9 Ka. Goats were kept in Near Eastern mountains from 11 to 10 Ka. Cattle were domesticated from the wild aurochs in modern Turkey and Pakistan around 10.5 Ka. Camels were domesticated late, perhaps around 5 Ka. The dates of horse and donkey domestication remain controversial, but could be early.

        Rice was domesticated in China between 13.5 and 8.2 Ka, followed by mung, soy and azuki beans. From around 11.5 Ka in the Levant, cultivation commenced of the eight Neolithic founder crops: emmer and einkorn wheat, hulled barley, peas, lentils, bitter vetch, chick peas and flax. Sugarcane and some root vegetables were domesticated in New Guinea around 9 Ka, and bananas were cultivated and hybridized between 10 and 7 Ka. Sorghum was grown in the Sahel region of Africa by 7 Ka.

        In the New World, domestication generally occurred a bit later. In South America, the potato was domesticated between 10 and 7 Ka, along with beans, coca, llamas, alpacas and guinea pigs. In Mesoamerica, wild teosinte was selectively bred into maize (corn) by 6 Ka. Cotton was domesticated in Peru by 3.6 Ka. Don’t know when turkeys were domesticated, but at least two thousand years ago.

        So, even ignoring dogs on one end and turkeys on the other, the most common crops and livestock were domesticated over more than ten thousand years, between 15 and 3.6 Ka. But for most crops, domestication did indeed occur following a rise in CO2 from near starvation glacial levels to near the salubrious levels of the Holocene Optimum, c. 8 to 5 Ka.

      • Narrowing it down to the origination of agriculture in each region, from the earliest possible date for rice in Asia, ie 13.5 Ka, to the latest for corn in North America at 6 Ka, still leaves 7500 years, with a range of CO2 levels, from still fairly low toward the end of the Pleistocene to high during the Holocene Optimum.

      • Chimp, had read the Pig was domesticated in China. You said Mesopotamia. We were both Half right. Been doing more research, thinking about writing a longer paper/guest post with lots of references. Found a Fascinating dna paper by Giuffra et. al. , ‘Origins of the domestic pig:independent domestication and subsequent introgression’, Genetics154: 1785-1791 (2000). Not paywalled. The pig was domesticated from the Eurasian wild boar (Sus scrofa) of which there are several subspecies that can be distinguished by variation in mitochondrial (maternal only) DNA. Based on mitachondial DNA analysis of present day wild and domestic types, domestication happened independently from at least two different subspecies in the Near East and in China at about the same time ~9000ya based on mDNA mutation rates (a now standard ‘clock’ dating method). Darwin knew there were two basic domestic pig types, but not why. The Asian domestics were introduced into Europe for further cross breeding in the 18th and 19th centuries (the ‘subsequent introgression’ part of the paper title).
        Not only lends further very strong non-archeological scientific support for the main post hypothesis, and to its timing, also supports Diamond’s Nature paper that plant and animal domestication occurred simultaneously in a single larger agricultural technology development.
        Neat paper, very hard DNA science.

    • Ristvan, What if some group figured out that instead of chasing herds of animals all over they figured out a way to start keeping small groups of animals in one place by providing them with feed? And as a result of that they developed ” agriculture” for the animals first before realizing they could do the same thing for fruits and other “greens” for them selves? Just a thought.

      • Asy, plausible for one group, not plausible for several, all of whom at the same time started developing the same basic technologies. Like plant next year the best of this year.

      • How does more CO2 in the air make humans put two and two together and figure out how to grow plants themselves?

        It seems to me that humans didn’t need to have more CO2 to figure out how agriculture works. They could still plant their plants and the only difference would be a lower yield during lower CO2 times. Was the crop yield so low at these times that the effort would obviously be wasted and thus inhibited them from developing agriculture?

      • TA, spent all of today further researching this fascinating lead post hypothesis. Motivated by a possible paper/ further long but very sharp review guest post. I think you pose the wrong question framework in your comment.
        There were small bands of Neolithic hunter/ gatherers all over the world. We know they were all genetically similar, had similar Neolithic technology (fire, stone tools, spears, atalatl, bow and arrow), and faced similar food survival pressures albeit in very different ecosystems. If there is a general enabler like more CO2 means more plant productivity means you don’t have to keep wandering long distances in a risky search of food you might not find, the H/G survivors will all ‘figure’ that out at more or less the same time. Think a cultural Darwinian extension. BTW, Lamarkian evolution does exist in the cultural, not biological, sense.

        The key underlying idea is the requisite ‘territory’ size for a hunter/gatherer band to survive the seasonal year. As CO2 rose and plant productivity increased, that territory shrank both for food plants and dependent food animals– to the point where people could eventually afford to risk year round fixed (initially small) settlements with everything within a short (perhaps day or two) walking distance. From there, agriculture evolves as a simple matter of being smart (which I hereby pronouce to be the laziness (biological least food acquisition food energy expenditure) principle). Some Seeds produced more seed. Save those to plant next year and eat the lousy miserable rest. Some animals are easier to handle. Keep those around to breed, and kill and eat eat the cantankeries. Sort of an extra flavorful vengance for getting kicked, bit, whatever.
        And there is even a beautiful multiple example counterproof that just occurred as was composing this comment. Where true agriculture never emerged in the Neolithic (Eskimos and Plains Indians), these quite specific requisite preconditions never emerged either. Eskimos depend mainly on hunting, mainly of seals or transient wildlife migratory caribou wirh limited means of preservation (unlike the Plains Indians, who could at least smoke raw buffalo into pemmican, yet still did not develop sedentary agriculture). Nothing to keep around on land to domesticate. The Plains Indians depended on buffalo. The Plains buffalo had to keep wandering because the late summer theough winter grasses were otherwise too nutrient poor. 1/4 of a year does not equal a year, nurirition wise. Needed large areas because of the ecosystem so nothing to domesticate. My guess is this could be extended to portions of Africa and Australia (thinking the Masai and Kalahari and Bushmen) , just have not done any of that that research yet. This even helps explain why the various geographical areas where agriculture did emerge bear specific similarities in annual fruitfullness. Research TBD.
        Man this is a big and beautiful new Neolithic transition hypothesis. It flows together seamlessly, and explains so much. A major intellectual advance.
        WUWT advances true science.

      • Plains Indians came out of the ag zone, so were familiar with the concept, but gave it up to exploit the great resource of bison, once they had the horse and later firearms, thanks to Europeans.

        Similarly, the PNW coast Indians knew ag but lived in such an abundantly rich environment, they didn’t need to work that hard. Largely applies to CA Indians as well.

        Note that ag developed first outside of tropical Africa, where again the natural environment was abundant year-round. It did develop in the tropics of the Americas, but at high altitude in Mexico and even more so in the Andes.

    • The book ‘Guns, Germs, and Steel’ has some interesting theories about how crops were ‘domesticated’ by humans. Initially it was mostly accidental and kind of a human induced natural selection. It’s a very interesting book.

  19. I suppose if one clings to the outdated idea that human development and expansion of modern society is a good thing then, of course more CO2, some gentle warming and an allover more comfortable climate with a fuller larder may seem a good thing. The more progressive view that anything allowing humans to continue their perverse invasion of virgin mother Earth a minute longer is an affront to Gaia would say that we should make every effort to rid the atmosphere not just of CO2 but of oxygen as well. We need to ask ourselves just how fast we can turn Earth into another Mars and then get busy with a new round of international conferences and policy commitments to societal cleansing. As this is clearly a new field of endeavor, I would welcome any of the more ardent defenders of Mother Earth to lead by example so that we can all learn the proper way to enter the hereafter with the least disturbance to the cosmos.

  20. I do not believe there is an ideal CO2 concentration providing it is sufficient to create biomass (150ppm +??) and that any change from the status quo occurs over an appropriate time frame.

    With human intervention selective breeding of both animals and plants can change characteristics and performance within a decade or two. Genetic science may reduce this to a few years. Combined farm and power station units may become synergistic to improve yields.

    Similarly human populations can change rapidly. In the last 100 years world populations have trebled. But increasingly developed countries are no reproducing at below replacement rates.

    The change in CO2 levels (even in these carbon profligate times) has been approx +40% over the last 150 years since pre industrial levels. There may be some rapid external forcing (volcanic, meteor etc) which could change the balance, but adaptation may be preferable to costly over reaction.t time to adapt

  21. what would be the ideal concentration of CO2?

    Enough to cause panic attacks and cardiac arrest in Greens?

  22. We are the most successful of Gods many creations. The ideal CO2 is the one we have. Lets go from there as we have since the blessed Enlightenment. Off your knees and on your feet people.

  23. Based on all my reading at this blog, I would have said around 1000 ppm CO2 would be “ideal”, if there is such a thing as “ideal”.

    This way alamist whining would be amplified to greater proportions, giving more purpose to more alarmist lives, further inducing alarmist charities to fork over more dollars for more research revealing why 1000ppm CO2 is just this side of doomsday, thus, giving even more alarmist lives more meaning.

    More CO2, thus, gives more lives more meaning. Oh, and there’s the plant-growth thing.

    • Previous advocates of AGW, like Arrhenius and Callendar, were right that it would be beneficial, even if they overestimated the effect on temperature of rising CO2 in the real climate system.

  24. The first evidence of permanent settlements and agriculture started in the Levant with the Natufians. The start date was about 14,500 years ago and then the culture seems to have disappeared 12,400 years ago. It restarted later but that is much later.


    I have a database of all the CO2 estimates and the 14,500 years ago date also coincides with the first time that CO2 got over 250 ppm after the last ice age.

    It also then fell below 250 ppm again 12,400 years ago when the Natufian agriculture culture collapsed. This is also the Younger Dryas temperature decline period.

    The next re-start of agriculture after the Natufians was in southern Turkey where the Gobekli Tepe first stonework temple is sited. The very first stone work anywhere and a surprisingly complex temple at the same time, 11,800 years ago.


    Wheat and barley grows wild here.


    The date of this restart is 11,800 years ago. Not surprisingly, this is also the next time CO2 got to 250 ppm again after the Younger Dryas decline.

    The premise is that C3 pathway wheat and barley just does not grow well enough to support permanent settlement and farming until CO2 gets to 250 ppm. I think it holds.

    • Yup. Those plants can survive below 250 ppm, but they don’t thrive. They also need more water when CO2 is low, since they have to leave their stomata open longer.

      Earth has greened as CO2 has climbed thanks to the water-savings from higher plant food concentrations in the air.

    • Yep. 280ppm and the accompanying mild, steady temps have been rather a salubrious, prosperous period for our species. Be a pity to spoil it.

      Hey I know. Lets dump 30gt of co2 into the atmoshere and see what happens. What could possibly go wrong.

      • Sorry Tony,

        Wheat and barley will grow ever more abundantly until CO2 gets into the 1,200 ppm territory. They will also progressively become more drought tolerant. Even if temps go up with more CO2, the C3 plants are going to grow up to 100% more productively. Yes, that is right.

        The bad side is that C4 grasses (mostly tropical species) and CAMS pathway cactus will progressively get outcompeted by the C3 plants. But the C4 grasses will then move into the low vegetation desert regions like the Sahara and the US southwest and, well, that will probably be good anyway.

        The downside is only for cactus.

      • Tony,

        So far fertilizing the air with plant food has been a good thing, greening deserts and increasing food and fiber production.

        All trees and most crops are C3 plants, which have been famished until humanity improved the environment, if indeed we can congratulate ourselves for increasing the essential trace gas CO2 in the air.

      • Tony, it is not optimism. This is what real science actually says. And in this case, real science is backed up by real studies and real evidence. Unlike climate science which is only backed-up by pessimistic “musings”.

      • No scientific, rational basis for alarmism.

        The pioneers of the AGW hypothesis in the first half of the 20th century considered it beneficial, without even factoring in plant fertilization.

        In the late 20th century, Hansen, et al, decided all of a sudden that AGW (assuming without evidence that it exists) had to be a terrible threat instead of a boon, because it suited their needs.

      • “Tony mcleod March 24, 2017 at 5:29 pm”

        Daylight savings soon Tony, don’t let the milk turn sour or adjust your clocks, I know how you Queenslanders like to panic and worry over nothing.

    • Hello Bill:
      Thank you so much for your comments. If you are willing to share your CO2 data base that you mentioned, I would greatly appreciate it. My email is dr.liz@frontier.com. Posting this article has created many good comments with which to pursue this idea further.
      Thanks, Don Healy

    • Great and green again.

      One thousand ppm would be quite enough. Too bad that’s probably not possible given the Ice House in which our planet currently finds itself.

  25. There are interesting questions that are not the same. One is what would be an ideal level of CO2 for Humans? Another is what would be an ideal level of CO2 for us, given that we are distributed as we are?

    I am reasonably confident that humans would do very well with a CO2 level of 600 ppm, say. What I am not so sure about is whether we would do so well in the transition from 400 to 600ppm.

    Take sea level as an instance. There is no reason at all that humans could not do very well if sea levels were 100 ft higher than today. We would have a different coastline, but it would not be intrinsically inferior to the one we have today. (this is an example – I am not saying sea level would rise by 100ft with CO2 at 600ppm. Maybe it would but that is not the point I am making)

    However, if we ask the other question, how would we do if sea levels rose 100ft we get a very different answer. We would do very badly because most of our infrastructure would be under water. Our descendants would probably do fine, but there would be a huge cost in the transition.

    Similarly, humans would do fine if Siberia was like the African Savannah and the Savannah was uninhabitable. However, we would do badly because lots of people require the Savannah to be productive. In a few generations, after the Africans and coastal dwellers have died, Humans will have established themselves in the new coasts and productive areas. However, millions may have died prematurely and caused massive disruption through forced migrations.

    I think it is very important to recognize the distinction between these two questions. If you want to take the long view, then it does not matter too much. If you care about the welfare of people alive today and in the near future, then it does matter a lot.

    • However, if we ask the other question, how would we do if sea levels rose 100ft we get a very different answer. We would do very badly because most of our infrastructure would be under water.
      We don’t have any infrastructure that’s going to last 1000 years anyway….no point

    • In a few generations…..you act like these people are too stupid to evolve

      They can drive cars you know

    • 1) No way could MSL going to rise 100 feet so rapidly that people could not adapt.

      2) No way is MSL going to rise 100 feet.

      During the prior interglacial, the Eemian, which was much warmer and lasted longer than our present Holocene, sea levels were previously pegged at four to six meters higher than today. Recent investigation raises that estimate, reporting peak Eemian sea levels peaked between 6.6 and 9.4 meters higher than now (~20 to 30 feet).

      The long, hot Eemian caused the Southern Dome of the Greenland Ice Sheet to melt about 25% more than it has so far in the Holocene.

      A thousand ppm would be better than 600 ppm. Commercial greenhouses operate at 1000 to 1300 ppm.

    • There is absolutely no indication that this bad stuff would happen. Why would the savannah become uninhabitable when CO2 increases the ability of plants to use water? The Sahara is already greening! Why would you assume sea level will rise at some catastrphic rate? It has been going up at approximately 2mm/yr for 200 years or more, with no sign whatsoever that CO2 has or will effect that rate in any way. In reality, our coastlines would not look very different at all. Severe storms are the main reason for coastline damage and they have decreased. Think with your head-not your bad nerves!

    • Latitude and Chimp, putting aside the details for the moment, do you recognize the distinction between the two questions? Some outcomes might result in a world that is very conducive to human life, but would cause us great problems given our current distribution?

      I was quite clear that I was not saying that sea level would rise by 100 ft, but that I was using this as an example of a situation that would not be intrinsically harmful to human life on Earth, but would present us with huge problems.

      One could argue that an instantaneous rise of 100 ft would be fine because the new coastline is just as good as the old coastline as far as humans were concerned. However, it would leave a great many cities underwater, so there are good reasons why we might not want this sealevel rise.

      Do you see the point I am making?

      • no……

        These are West African Fulani nomads, nomads wander around to where the food and better conditions are….
        ….see the cell phone…they get the weather channel

      • Whether from manmade CO2 or natural causes, there is not going to be sea level rise too great and rapid for us to adapt.

        Sea level fluctuates naturally and locally from human activity all the time on different time scales. Venice and New Orleans might not be able to adapt to sea level changes, but no one is going to perish as a result. Many cities have been built in what proved bad locations, as has happened throughout history.

        Cutting fossil fuel use is far more dangerous than any possible continued sea level rise, which so far isn’t accelerating over the background rate from recovery from the LIA.

      • Certainly seaice — you are making the point that not only the absolute levels matter, but the velocity of change matters. Ocean levels rising 10 feet over a century can be easily coped with. Ocean levels rising 10 feet overnight could cause serious problems for many things, including humans at the coast.

        But it wouldn’t cause serious problems for those coastal critters who are adapted to live in air or water — the coasts has plenty of mobile tidal critters who cope with a 10 feet rise in sea level (local) *every single day*, and have no problem with it occurring in a slightly different location overnight. In the case of CO2 concentration, the entire biosphere is full of things that function *just fine* at higher CO2 concentrations, in fact that prefer it substantially higher than it is now. And while the growth in annual concentration from anthropogenic may look scary, at a local level organism cope with much larger swings in CO2 concentration due to seasonal or biological effects.

        CO2 isn’t sea level. Independent of climatic effects, there’s no reason to think that doubling CO2 from current levels over a period of decades would have a negative effect on humans or a net negative effect on the biosphere at large.

      • You are avoiding the question. Whether or not such things will or will not happen, do you recognize that that these are two very different questions? I am not saying here that these things will happen, but that the two questions are very different.

        Do you see the point I am making?

      • Seaice,

        Sea level rise is simply not going to be fast enough to leave cities underwater such that people can’t adapt. Some cities would survive with public works as the Netherlands has done for centuries. Others might have to be abandoned, as has so often happened in the past, when sea level was higher than now, as during the Holocene Optimum (when there already were coastal cities), Egyptian, Minoan, Roman and Medieval Warm Periods. MSL fluctuates all the time, dropping during cold phases and rising during warm ones.

        Buildings which were by the sea during the Roman and Medieval WPs are now high and dry. Maybe they’ll be coastal again if the Modern WP lasts long enough.

      • Which is why mentioning 100 feet doesn’t make for a useful analysis. If at most MSL might rise 30 feet over the next century (which it won’t), then people would have to adapt to only 3.6 inches per year rather than a foot.

        In fact, there is no reason to expect more than three mm per year, ie maybe a foot in a century, although probably less than that. Two mm a year is more likely.

        So, no worries.

      • You are avoiding the question. Whether or not such things will or will not happen, do you recognize that that these are two very different questions? I am not saying here that these things will happen, but that the two questions are very different.

        Do you see the point I am making?

      • Seaice,

        No, I don’t see your point.

        That climate change might happen quickly doesn’t matter if we can adapt to it. But it won’t in any case.

        Whether sea level rises a foot in a century or 30 feet, it’s not a catastrophe. Whole cities have been destroyed during wars, continents laid waste, tens of million of people killed in a matter of years, yet humanity has adapted and overcome. Up to half of all Europeans died in the Black Death, in just a few years.

        CACA is a myth, but even if alarmism were justified, it would be nothing we can’t handle. A “catastrophe” it wouldn’t be. Not even his fellow alarmists buy Hansen’s “Venus Express”.

      • Chimp.
        “That climate change might happen quickly doesn’t matter if we can adapt to it. But it won’t in any case.

        Whether sea level rises a foot in a century or 30 feet, it’s not a catastrophe. Whole cities have been destroyed during wars, continents laid waste, tens of million of people killed in a matter of years, yet humanity has adapted and overcome.”

        I argue that it does matter. Are you saying that if cities were destroyed and tens of millions of people killed it doesn’t matter because humans will survive?

        Dale S acknowledges that there could be problems in the short term, but then says that critters will survive OK. That is fine, but I am more concerned with the people.

    • “Take sea level as an instance.” Why? Other than the fact that it is a fave Alarmist talking point that is. There is no reason to believe (other than wishful thinking on your part) that SLR is going to speed up, and pure fantasy on your part that it might rise 100 feet.

  26. I’ll speculate that CO2 level of 600-800ppm would be s good range. The question then becomes what happens to CO2 during an 100Kyr glacial period then humanity might need it to be 1000-1200om entering the glacial period.

  27. Maybe the 400 million year old evolution of the C3 process refers specifically to vascular land plants, but green algae, the ancestors of plants, also employ C3 photosynthesis, so the process itself is much more ancient than 400 Ma. The main difference between C3 processes in algae and land plants is that unicellular green algae avoid photorespiration via a CO2-concentrating system. Biochemically, photosynthesis and photorespiration in the green algae are similar to C3 higher plants. There is a difference, however, in the mechanism of inorganic carbon uptake prior to the actual fixation of CO2.

    • Algae has two sources of CO2. It can extract it for the gas dissolved in water. It can also get it from carbonates such as calcium carbonate CaCO3 which is also dissolved in water. (I have seen PH and KH changes in my aquarium that indicate this does happen. Plants can also extract carbons from carbonates. However they generally have to be in very wet environment to have access to enough carbonate.. Wet territorial environments typically have a lot of rain which will wash away carbonates. So most terrestrial plants don’t have enough access to carbonates to compensate for CO2 depletion in the air.

  28. Why don’t we let it rise- correct that-make it rise until we have some indication that the pause is not a stop or that CO2 is actually affects temperature and is not some fevered environmentalist nightmare. Then we can decide whether we like that world better or not, whether we are in danger of slipping back into glaciation or not and what sort of technical options we have to deal with our CO2 issue at reasonable cost. The IPCC says that a global temperature rise of 1.8C is beneficial to the planet. Why is it “critical” that we limit it to 1.5C?

    • Earth suffered an ice age or glacial episode when CO2 was four to five thousand ppm during the Ordovician. Solar power was some four percent lower, but that’s not enough to explain ice sheets under CO2 more than ten times higher than now.

  29. That’s the problem right there! CO2 explains everything until you start to drill down. Then it explains nothing!

  30. Don, your essay is perfect timing. Two evenings ago on the 22nd, I attended a Vancouver lecture by Gwynne Dyer. Dyer, known to most older Canadians for his seminal 1980’s broadcasted NFB series “War,” has taken on Climate Change as author of “Climate Wars: The Fight For Survival as the World Overheats.”

    Dyer’s main thesis was that we are all doomed by feedback mechanisms if the temperature exceeds about 2 degrees, beginning with the death of “all non-native (ie: most)” food plants around the Earth’s tropic band resulting in massive numbers of nourishment refugees moving into the temperate areas in order to feed themselves.

    I asked the first post-lecture question: How do you reconcile 2 degrees to doom when we already know the Vikings enjoyed decent temperatures in Greenland as evidenced by discovery of crop seeds, subsurface burials, grapes in northern Britain on Vine Street… And how to reconcile tropic food crop destruction to the benefits of life-giving CO2 increases producing measurable greening of the Earth including forests and food plants.

    Without directly answering my questions, Dr. Dyer simply replied that there has always been climate fluctuations before the Little Ice Age; and that any benefit attributable to CO2 plant fertilization is currently, and will continue to be, negligible.

    But I think he may have jumped the shark with his serious promotion of a plan for global salvation in the form of seeding the upper atmosphere with sulphur compounds to stave off human destruction for a little while longer at least. (After proper testing, of course.)

  31. “So, the question I put to you is this: After reviewing the information above, and perhaps doing your own research, what would be the ideal concentration of CO2?”

    I think that is the wrong question. There is a threshold below which life becomes difficult, but above it many other factors become more influential, until a higher threshold above which life is again, impossible. In between the concept of an ideal concentration is not very useful, except in an environment in which all other factors are controlled, such as a nursery – or spacecraft, come that. I suspect also that the ideal is itself dependent on the other factors, too.

    Perhaps it is a tongue in cheek shot at the AGW alarmists, who have precisely this problem – impossible to define an ideal temperature.

  32. Since all plants benefit from CO2, your supposition needs to include an explanation of what the low CO2 animals were eating. The history of human advances can be attributed to a very small number of remarkable births. We know that a large number of important crops, viz., potatoes, tomatoes, and peppers were unknown in Europe and Asia before the Americas were “discovered”.

    My point, agricultural technology likely played a primary role in the shift from subsistence to agrarian societies.

    • C4 and CAM plants can survive on remarkably low levels of CO2. But the vast majority of plants achieve optimum growth at around 1200-1300 ppm. They can flourish however upwards from 800-900 ppm.

    • Don’t forget maize (corn), the leading grain crop, world production of which almost equals the mass of numbers two and three wheat and rice together. Much of that however is field corn for animal feed or ethanol rather than sweet corn for corn syrup or direct human consumption.

      • Chimp, the main reason maize (corn) is such a large global crop is its ‘harvest index’. That is the ratio of grain to everything else above ground (corn stover). The harvest index ignores roots, so exludes the more scientifically correct total biomass. But it is easy to measure in the field by harvesting thengrain, then harvesting the straw or soy stubble. Corn is incredibly ~55% food grain, 45% everything else above ground (dry biomass basis). US harvest index ~0.55. Borlaug’s dwarfing of wheat (that and rust resistance were his original green revolution and Nobel Prize basis) is a cultivar dependent ~0.5 HI. About the same for dwarfed rice, also cultivar dependent. Soybeans are only about 0.4 HI, but more highly cultivar dependent. So for a given amount of land, corn simply produces more food. Of course, wheat produces more protein and soy produces more oil. Corn produces more calories, which is why it is the principal poultry/pork feedgrain.

      • The production figures I cited were for tonnage of grain alone, not all harvested biomass.

        I grew up on a 1400-acre family wheat ranch near one of the ag experiment stations where modern varieties of soft white wheat were bred, and ran it until 2001. Nowadays even the short straw of modern varieties often gets harvested, too. As with corn, of course, the roots get tilled up.

  33. The enhanced biomass and increased diversity of the current age should be celebrated. Thanks to the climate obsessed fanatics we are instead destroying the environment with industrial wind farms, solar farms and idiocratic ideas they may succeed in wrecking it all.

  34. This excellent summary by André Bijkerk copied from http://www.climategate.nl
    In short, in order to survive we need to continue recovering carbon from its natural sinks to the atmosphere as we do through fossil fuel combustion:

    Recently I posted this somewhere and for the first time no alarmist came around attempting to trash it:
    Carbon dioxide, soda water, sugar, limestone, mice, roses, marble, all have one thing in common, the element carbon (C). It’s the most versatile element, because you can make a lot of very different things of it. Carbon goes around in a big carbon cycle. Green plants make sugars out of carbon dioxide, the very base of life. Eventually with the death of life, carbon returns to more simple forms like methane and carbon dioxide, completing the organic carbon cycle. But the bottom line is: carbon=life and CO2 is its major primary building block. Essentially this also means that the available amount of carbon in the biosphere determines the total amount of biomass
    There is another cycle, the inorganic cycle. Carbon has a nasty habit to bind with calcium to form calcium (bi-) carbonates in marbles and limestone and calcium shells. This is a very stable compound which hardly dissolves and just forms rocks, mountains etc. This carbon would be lost for the organic carbon cycle of life and hence for the total biomass on earth, if it wasn’t for volcanoes. The high temperatures >1000 degrees Celsius dissect the carbonates back into CO2 and calcium oxides, adding CO2 again to the atmosphere, and useable for plants to grow again.
    However in the late Cenozoic more and more carbon became trapped in the inorganic carbon cycle, leaving the atmosphere with less and less carbon. Maybe volcanic activity was decreasing gradually, suppressing the carbon return in the inorganic cycle. In the late Pleistocene a mere 180 ppm remained, hardly enough for many trees, causing steppes to dominate the landscape. But also 150 ppm is the limit of life. Below that, plants are unable to take in CO2 anymore and life on Earth was on the brink of disaster, if it wasn’t for a temporary carbon injections during stages which are known as interglacials. But how much longer would it last?
    This leads to three important conclusions:
    1: if there weren’t volcanoes, life would cease to exist on earth with all carbon being sequestered in limestones and shells eventually.
    2: humans are doing a great job, bringing fossil fuel carbon, lost in the earth, back into the organic carbon cycle and thus prolonging the era in which life is possible on Earth.
    3. Curbing CO2 is the single most largest stupidity of mankind ever and for ever to come.

    • I believe most scientist agree that volcanoes are a key part in recycling carbon back into the atmosphere. So yes there is an inorganic carbon cycle, There is also a second aspect to the carbon cycle you may have note realized. In order for carbonates to continuously increase you must add continuously calcium, or magnesium to the water. There is a theory out there that the creation of the himalayan mountains started the ice age cycles. As the mountains grew, erosion and carbonate production increased leading to the lower CO2 levels we have today.. Prior to the formation of the mountains CO2 levels were about 1000ppm. Eventually the uplift of the mountains will end and if the theory is right CO2 levels should start to increase buy that is at least 50 million years away.

      • The problem is that falling CO2 didn’t cause our present Cenozoic ice age or ice house. Eocene CO2 has been estimated at 700 to 2000 ppm, but those levels were because it was warm then. CO2 is more effect than cause of warmth.

        Neither did the Azolla Event cause the Cenozoic ice age.


        Ice sheets started to form on Antarctica in the Oligocene when that continent was separated from South America and Australia by deep oceanic channels. They retreated some in the Miocene when the paleo-Drake Passage between the South American and Australian plates temporarily grew shallower. In the Pleistocene, they grew again. (Not sure about the intervening, short Pliocene Epoch.)

      • Cold already returned late in the long Miocene, then earth enjoyed a brief last blast of warming in the Pliocene, against the long-term trend.

  35. As usual I am confused, it doesn’t take much. Anyone who has accidentally frozen a can of coke knows that when you freeze water it outgasses all dissolved CO2. If sea levels are down 20 meters because the water has frozen then you would think that all that outgassing would have put atmospheric CO2 up, not down.

    • I’m not sure about the outgassing part, does most of it remain trapped in ice as bubbles?

      However the other part is that the oceans across the globe cool and more CO2 taken from the atmosphere. Water and CO2 react chemically, to form Carbonic Acid, this is aided by lower temperatures. O2 and N2 do not react in the same way but just occupy the intermolecular spaces, In the case of O2 this is handy for fish who extract Oxygen with their gills.

      That’s how I remember it from school 50 years ago.

    • Robin,

      Sea ice indeed doesn’t retain CO2 and other gases in the ice, that doesn’t change the atmosphere that much as that is only a small part of the carbon cycle. Most CO2 is going down with the heavier waters at the edge of the sea ice fields. Heavier in part due to the cold temperatures and the fact that freezing waters also expels its salts which makes the surrounding waters saltier and thus heavier…

    • In 100 years we have discovered genetics and have developed tools that allow use to change DNA in plants and animals. We have also developed ways to make and break chemical bonds between atoms. It will take at least a 1000years for the next ice age to start. By then we may already have converted using genetic engineering C3 food plants into C4 plants which can tolerate very low CO2 levels. We can also today convert calcium carbonate to CO2 and calcium metal young only electricity. So I think our ancestors will handle the next ice age better than our ancestors.

      • Our descendants indeed should be able to survive the inevitable, coming cold, but our ancestors did alright, too. Their numbers exploded with agriculture, then the Industrial Revolution, during our current balmy interglacial, but our modern human, hunter-gatherer ancestors managed to live through one glaciation by staying in Africa (although H. erectus-grade people lived in Asia and even Europe then), and during the next spread everywhere (depending upon the date you assign to their entry into the Americas south of the ice sheets).

  36. Am I the only one who thinks that its strange that a few percent extra of emissions from fossil fuel use could increase levels by 100ppm but levels at the limit of sufficient for terrestrial plants to survive did not lead to large swings?

  37. How many laboratories would risk their reputation by reporting gas analysis results at <0.0005% precision, even for a hermetically sealed sample, under strictly controlled conditions in their own premises?

    Outside air concentrations at the same precision 158 000 BC requires paranormal talent. Good enough to claim the M$ offer from Randi et al.

    • jaakkokateenkorva,

      Still a challenge, but they even measure changes in O2 in outside air to a precision of better than 0.0001% (less than 1 ppmv on 210,000 ppmv)…

      The CO2 levels in ice cores are measured using either the grating technique: grating the ice just below freezing point under vacuum where water vapor is frozen out of the gas in a cold trap, or the sublimation technique: again just under the melting point with an IR lamp where everything is sublimated and cryogenic frozen out and later separately released. The latter is used to measure the isotopic composition on a mass spectrometer.

      Average repeatability of samples taken at the same ice depth for CO2: 1.2 ppmv (1 sigma). Maximum deviation for the same average gas age between cores with extreme differences in temperature and accumulation rate: 5 ppmv.

      See further:

  38. Any news from OCO-2? No? For this reason, the story is good otherwise, but the average global outside air composition from the homo neanderthalensis period at 0.0005% precision is excellent entertainment in Star Trek.

  39. This cannot be. Intelligent carbon based life cannot possible evolve on Earth. Elsewhere in the universe carbon scores the 4th most common chemical element. On Earth it’s only the 15th. Even chromium, sulphur, nickel and cobalt are more common. And, according to the settled models of the scared scientists, have already poisoned our ancestors./sarc

  40. It is reasonable to speculate on the effects of changing atmospheric CO2 concentration. However, as soon as an ‘ideal’ concentration is specified (by scientific consensus, of course), the pressure will be on to achieve it. The prostitutes and parasites who presently infect the more speculative branches of science will have another lucrative honeypot with which to SAVE THE PLANET. This should not be encouraged.

    Given a reasonably slow rate of change, it is likely that most forms of life will either adapt or mutate to cope. As there is presently no convincing method of distinguishing anthropogenic CO2 from the natural stuff, and given the fact that atmospheric CO2 concentration has varied widely over the aeons with no anthropogenic influence whatsoever, I don’t see much point in worrying about the matter.

  41. Please do not be too hard on Doctor Suzuki. He has done some world class, ground breaking research on why fruit fly genitalia are larger than his.

  42. “During the 400 million or so years that plants have existed on earth…”

    Not to burst your bubble or anything, Don Healy, but blue-green algae, aka cyanobacteria, began their existence 2.4 billion years ago. They are plants. They may be microscopic, and not have fronds or flowers or leaves, but algae belong in the PLANT Kingdom. Cyanobacteria cleared the toxins out of the atmosphere and released O2, the Great Oxidation Event. Before they existed, there was NO oxygen in the atmosphere at all. Blue-green algae are the OLDEST plants in existence. We owe everything to those little cyanobacteria.

    • Sara March 25, 2017 at 8:13 pm
      “During the 400 million or so years that plants have existed on earth…”

      Not to burst your bubble or anything, Don Healy, but blue-green algae, aka cyanobacteria, began their existence 2.4 billion years ago. They are plants. They may be microscopic, and not have fronds or flowers or leaves, but algae belong in the PLANT Kingdom.

      Not using the current definition of plants which are eukaryotes, therefore excluding cyanobacteria (the ancestor of the chloroplast in plants).

  43. This thesis was proposed 9 months ago:
    The problems have not gone away:
    1) If the invention of agriculture were simply waiting for edible grains to grow bigger, faster we might expect it to happen nearly simultaneously in various parts of the inhabited globe, in Eurasia, Africa,
    Australia, and the Americas. As far as we know it happened just once, in the Levant or thereabouts.
    2) No direct evidence is presented or mentioned here connecting the prevalence of any plant species to CO2 concentration, that is, in an environment where climate could otherwise be controlled for. Can a single plant extinction be attributed to CO2 starvation?
    3) Non-anthropologists are prone to project their world view into the mind of primitive man. Just as humans could never invent technological fundamentals like writing or the phonetic alphabet, but could only discover them through a series of accidents, so humans could only discover by accident how plants and animals reproduce. The most primitive people on earth in the first half of the 20th century, the Tiwi of Melville and Bathurst Islands north of Australia, had remained sufficiently isolated to allow their largely uncontaminated Paleolithic technology and culture to be studied independently by two
    anthropologists a quarter of a century apart. The two eventually collaborated in a book, “The Tiwi of North Australia.” One point that was abundantly clear through many aspects of their culture, from marriage practices to naming customs, was that the Tiwi did not know where babies came from. This anthropological discovery leads directly to the conclusion that just as Austrialian-Tiwi isolation
    prevented their introduction to the bow, animal domestication and agriculture, so it prevented their learning of biological reproduction: Paleolithic man did understand paternity.
    4) Accordingly seed function and incipient agriculture would only be discovered by accident, and the proper question becomes, what circumstances would most likely lead to the discovery in the apparently unique time and place it occurred, while at the same time explaining its uniqueness–not in Africa, America, China, or Australia. CO2 abundance does not seem a likely candidate. –AGF

  44. One obvious argument for the timing of the development of agriculture has been that the climate during a glacial maximum would not support agriculture. However if you look at the region around Laos, Viet Nam and the seafloor towards Indonesia which was exposed, this area had temperatures and rainfall that would support agriculture ( http://anthro.unige.ch/lgmvegetation/Ray_Adams_2001.pdf ). It has also been showed that modern humans have been in this area for over 60,000 years. The question was what these lazy bums were doing for 50,000 years when they could have been raising crops? This article supplies a compelling answer.
    These humans had access to the animal and crop species of the Eurasian continent as well as a good local climate which would imply they had the opportunity to develop agriculture. The 50,000 years which passed without the development of agriculture would seem to provide good support for the conclusions of this article.

  45. We should keep in mind that CO2 starvation is only the result of plant success and a long history of plant competition for CO2. While in the short run plants compete for sunshine, water, space and nutrients, in the long term they compete for CO2. They use it up until it is almost gone. If animals could make much of a dent on plant success (and they do) they would contribute to CO2 abundance by eating plants. To the extent that grasses evolved due to plant predation and CO2 scarcity, animals and humans could contribute to CO2 fluctuation.

    If after millennia of grain consumption gluten intolerance is still a problem, it is likely that it was more of a problem anciently. Humans must have evolved gluten tolerance just as Caucasians evolved lactose tolerance.

    Anthropologists have determined that intensive agriculture, while increasing the food supply, did so at the expence of food variety, causing vitamin deficiencies. Hunters and gatherers were healthier than farmers.

    Occasional sowing might have led to intensive agriculture through an increasing population of gluten tolerant people. –AGF

  46. I wish to thank everyone that read and commented on this post for their interest and input. Life got very busy about the time this was posted, but many of the comments lead to new and interesting avenues that deserve to be investigated further, so I have saved many of your comments and will pursue them in the future. Thank you.

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