Life on Earth was nearly doomed by too little CO2

During the last ice age, too little atmospheric carbon dioxide almost eradicated mankind

Guest Essay by Dennis T. Avery

Aside from protests by Al Gore, Leonardo Di Caprio and friends, the public didn’t seem to raise its CO2 anguish much above the Russians-election frenzy when Trump exited the Paris Climate Accords.

Statistician Bjorn Lomborg had already pointed out that the Paris CO2 emission promises would cost $100 trillion dollars that no one has, and make only a 0.05 degree difference in Earth’s 2100 AD temperature. Others say perhaps a 0.2 degree C (0.3 degrees F) difference, and even that would hold only in the highly unlikely event that all parties actually kept their voluntary pledges.

What few realize, however, is that during the last Ice Age too little CO2 in the air almost eradicated mankind. That’s when much-colder water in oceans (that were 400 feet shallower than today) sucked most of the carbon dioxide from the air; half of North America, Europe and Asia were buried under mile-high glaciers that obliterated everything in their paths; and bitterly cold temperatures further retarded plant growth.

In fact, Earth’s atmosphere had only about 180 parts per million CO2, compared to today’s 400 ppm: 0.018% then versus 0.040% today.

The Ice Age’s combined horrors – intense cold, permanent drought and CO2 starvation – killed most of the plants on Earth. Only a few trees survived, in the mildest climates. Much of the planet’s grass turned to tundra, which is much less nourishing to the herbivores prehistoric humans depended on for food and fur. Recent Cambridge University studies conclude that only about 100,000 humans were left alive worldwide when the current interglacial warming mercifully began.

The few surviving prey animals had to keep migrating to get enough food. That forced our ancestors to migrate with them, in temperatures that routinely fell to 40 degrees below zero (both Fahrenheit and Celsius). The Neanderthals had been living in relatively warm caves protected from predators by fires at the cave mouths. They had hunted their prey by sneaking through the trees – which no longer existed. They apparently couldn’t adapt, and starved. Cambridge found no evidence of genocidal warfare.

The most successful human survivors – who provided most of the DNA for modern Europeans – were nomads from the Black Sea region. The Gravettians had never had trees, so they invented mammoth-skin tents, held up by salvaged mammoth ribs. They also developed spear-throwers, to kill the huge beasts from a safe distance.

Equally important, Gravettians domesticated and bred wolves, to protect their tents from marauders, locate game animals on the broad tundra, and harry the prey into defensive clusters for easier killing. The scarcity of food in that Glacial Maximum intensified the dogs’ appreciation for the bones and bone marrow at the human camps.

When that Ice Age ended, moreover, CO2 changes didn’t lead the warming. The atmospheric CO2 only began to recover about 800 years after the warming started.

Carbon dioxide truly is “the gas of life.” The plants that feed us and wildlife can’t live without inhaling CO2, and then they exhale the oxygen that lets humans and animals keep breathing.

Our crop plants evolved about 400 million years ago, when CO2 in the atmosphere was about 5000 parts per million! Our evergreen trees and shrubs evolved about 360 million years ago, with CO2 levels at about 4,000 ppm. When our deciduous trees evolved about 160 million years ago, the CO2 level was about 2,200 ppm – still five times the current level.

There’s little danger to humans of too much CO2 in the air they breathe. Even the Environmental Protection Agency says 1000 ppm is the safe limit for lifetime human exposure. Space shuttle CO2 alarms are set at 5,000 ppm, and the alarm in nuclear submarines is set at 8,000 ppm!

If there’s little danger of humans having too much CO2 in their air, and a real danger to civilization from having too little, what’s the ideal level of atmospheric CO2? The answer? There’s a broad safe range – with far more risk of too little than too much. At low levels, with few or no plants, there’d be no people or animals, let alone civilization.

Human numbers, moreover, expanded strongly during the Holocene Optimum, with temperatures 4 degrees C higher than today! Even now, residents of the tropics keep demonstrating that humans can tolerate much higher temperatures than most of us experience. (As we utilize the new malaria vaccine, the tropics will prosper even more.) And far more people die from “too cold” than from “too warm.”

The crops continue to produce record yields in our “unprecedented” warming – and the extra CO2 in our air is credited with as much as 15% of that yield gain!

It’s not whether more CO2 in the air raises Earth’s temperatures. We know it does, by some small but still hotly debated amount. Both sides agree that a redoubling of CO2 in the air – by itself – would raise earth’s temperature by only about 1 degree C.

That’s hardly noticeable or measurable in the midst of all the local temperature variations, with the myriad of natural forces that govern planetary climate, with all the discrepancies among the various measuring systems, and amid all the errors, biases and missing or revised data that have crept in.

Moreover, 1 degree C of warming was obviously not enough to frighten the public.

So, the computerized models cited by the Intergovernmental Panel on Climate Change made another assumption: that a hotter world would hold more moisture in its atmosphere. Since water vapor is the most effective greenhouse gas, the climate modelers claimed Earth might heat by 5 or even 10 degrees C. One scientist (who supposedly advises Pope Francis) recently claimed 12 degrees C (21 degrees F) of overheating!

The awkward truth, however, is that NASA has monitored moisture in the atmosphere since 1980 – and water vapor has not increased despite the higher levels of CO2 in the air. Is that why the IPCC models have predicted more than twice as much warming as we’ve actually seen?

The year 1936 recorded the hottest thermometer readings of any year in the last 5,000. However, these days NOAA reports only its “adjusted” temperatures, which always seem to go only higher. In fact, the first surge of human-emitted carbon dioxide after World War II should have produced the biggest surge of warming – if CO2 is the control factor. Instead temperatures went down from 1940 to 1975.

Why did the computer models fail to predict (or even factor in) either the Pacific Oscillation’s current 20-year non-warming or the coming solar sunspot minimum?

The latest data from the CERN particle physics lab has produced a model based on cycling – and it foresees no runaway warming. Instead, it sees an impending cold solar minimum.

Is the long, wrong-headed war against carbon dioxide finally fading? Science certainly says it should. But perhaps there is still too much money, prestige and power in climate alarmism for that to happen.

Dennis T. Avery is an agricultural and environmental economist and a senior fellow for the Center for Global Food Issues in Virginia. He was formerly a senior analyst for the U.S. Department of State and is co-author, with S. Fred Singer, of Unstoppable Global Warming Every 1500 Years.

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June 30, 2017 2:49 pm

The last glacial maximum was definitely not a good time for C3 plant life.
In the following bar chart I grouped CO2 by geologic period. The Cambrian through Cretaceous are drawn from Berner and Kothavala, 2001 (GEOCARB), the Tertiary is from Pagani, et al. 2006 (deep sea sediment cores), the Pleistocene is from Lüthi, et al. 2008 (EPICA C Antarctic ice core), the “Anthropocene” is from NOAA-ESRL (Mauna Loa Observatory) and the CO2 starvation is from Ward et al., 2005.comment image
Ward, J.K., Harris, J.M., Cerling, T.E., Wiedenhoeft, A., Lott, M.J., Dearing, M.-D., Coltrain, J.B. and Ehleringer, J.R. 2005. Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California. Proceedings of the National Academy of Sciences, USA 102: 690-694.
And I highly recommend Dr. Avery’s and Dr. Singer’s book… Unstoppable Global Warming Every 1500 Years.

Reply to  David Middleton
June 30, 2017 3:18 pm

DM, great graphic find. Permabookmarked for much future use. See also my comment below for further reading.

Reply to  ristvan
June 30, 2017 4:03 pm

Find it? I wrote it!

Reply to  ristvan
June 30, 2017 4:27 pm

I surrender to your superiority! Great job. No wonder I could never google it before! Did not exist.

Reply to  ristvan
June 30, 2017 6:59 pm

Ah ristvan, please note he wrote it and it was published on WUWT in Dec 2012. Maybe google din’t want it to be found.

Reply to  ristvan
July 1, 2017 5:25 am

I think Google’s denialist filter is to blame… Sarc?

Reply to  ristvan
July 3, 2017 1:38 pm

Use duckduckgo instead. They don’t track you and are not iinfested with zealots like goigle…

Reply to  ristvan
July 3, 2017 1:42 pm

E. M.,
Thanks for mentioning duckduckgo here. I’ve recommended it to security-conscious friends and family.

Reply to  ristvan
July 3, 2017 2:18 pm

But of course the Web sites you visit still track you.

Reply to  David Middleton
June 30, 2017 4:29 pm

Good graph, Davy Middleton!
The high, low and average bar graphs are a good way to go. Better than the usual representation of the range estimates.

Jeff L
Reply to  David Middleton
June 30, 2017 8:20 pm

Note the general downtrend through geologic time – with time more & more CO2 is naturally sequestered in coal, shale source rocks & carbonates – project that forward in geologic time – those processes haven’t ceased. It is essential that we burn our fossil fuels now to enhance CO2 in the atmosphere for our long term survival. Burning fossil fuels & releasing CO2 back into the atmosphere, where it started before being sequestered into hydrocarbon deposits, is the ultimate in sustainability. And the sun & photosynthesis will continue this cycle as we put the CO2 back into the atmosphere
Ironic perhaps, but it is easy to argue that us Humans are saving the planet because we evolved sufficiently to harness this fossil energy. Or perhaps part of a greater plan.

Shawn Marshall
Reply to  Jeff L
July 1, 2017 4:54 am

…the greater plan… right… now we know why the demons rage.

Reply to  Jeff L
July 1, 2017 5:16 am

Without the burning of fossil fuels, Earth will become uninhabitable due to CO2 depletion in about 20 million years… Sarc?

Reply to  Jeff L
July 1, 2017 2:33 pm

I had a t shirt made up “burn the coal, save the trees. C3 photosynthesis.. ask a botanist’ and I wear it to the disgust and angry stares of True Believers. I also get called a moron a lot and told I’m not a climate scientist so my opinion doesn’t count. I keep forgetting to many, opinions are a valid logic.
I also wonder how the heck they got through school not knowing about the carbon cycle but maybe I was in the minority, trying to grasp concepts and understand them.
Please bang this drum loud and often – C3 plants ARE at risk of starvation and using the trapped carbon reserves to obtain energy and replenish the air is a sensible way to use the resource that’s there beneath our feet.
Another point I like to ask folk to comprehend is, Paulownia sp. trees grow rapidly, to produce an acre of harvestable trees takes 5 years – in that 5 years they’ll require *all* the CO2 from 20 cubic kilometers of air per year to grow .. to put that in perspective that’s a column of air above that acre rising 3x the distance to the moon, Obviously they obtain it through the air being replenished by various means including microbial decomposition of stuff elsewhere – but it gives you an idea how little CO2 there actually is, and how more CO2 can only be a good thing.

leopoldo Perdomo
Reply to  Jeff L
July 2, 2017 1:27 pm

Perhaps the ups and downs of the climate are not related or caused by CO2. What looks pretty clear is that the seas give off CO2 when increases its temperature. And and they cool start to recover the CO2 that shows a clear affinity to dissolve in water. Heat the water and it gives off their gases, like O2 and CO2 and methane, or other gases.
In some conditions our planet can heat with the increase of insolation (Milankovitch curves), but there is something that opposes the absorption this radiation, the ice and snow. Then, below some threshold, of insolation of insolation, the amount of snow and ice increases, increasing the albedo of the planet.
As the planet keeps cooling the seas also cool, and the amounts of rains are reduced. This increases the desertification and the storms or dust began. As the time with low temperatures last longer, the seas get colder, and the surface of the deserts increases. The storms of dust get denser, and this work as well as some sort of umbrella, reducing the amount of sunlight that arrives to the surface, Those storms can
last several thousands of years, as can be seen in the ice cores records of Greenland. This dust is falling over the snow and ice, and when the dust storms stop, the insolation heats the snow and ice, starting a fast process of melting, increasing very fast the lands liberated of snow. That is the reason why the temperature rises so fast.
The inverse process, the cooling occurs as the temperature get below some threshold and began to snow a lot. As the snow accumulates the dark surface are reduced, and the temperature lowers. It is slower process than when getting out of an interglacial period. That is the reason it rises fast and lowers slowly the temperature of the planet.

Reply to  David Middleton
July 1, 2017 12:36 am

In regards to water vapour, this is largely dependent on CO2 being released from the ocean. The more its released out of solution the more water vapour created. CO2 reduces water tension or polarity. However, this does not mean that the atmosphere can “hold” more water vapour. CO2 is not the driver, just a mechanism.

Dr Deanster
Reply to  Geoff
July 1, 2017 6:45 am

And water vapor rises, becomes clouds, produces rain, and cools everything back down. The nonsense of positive feedback from water vapor is a bunch of bs.

Eric Harpham
June 30, 2017 2:50 pm

This article should be sent to all political leaders in the western world.

Melbourne Resident
June 30, 2017 2:54 pm

I tried to point this out at an association debate about 4 yrs ago and was laughed at. So roll on the next glacial ion I say and then see who is laughing!

Melbourne Resident
June 30, 2017 2:54 pm

Glaciation !

June 30, 2017 2:56 pm
Reply to  Jones
June 30, 2017 3:58 pm

It’s normally ten years. They’re getting desperate for grant money.

john harmsworth
Reply to  AP
June 30, 2017 4:14 pm

the Guardian won’t be around more than three years!

Reply to  AP
June 30, 2017 8:02 pm

Hasn’t the tipping point already happened though?

Reply to  AP
July 1, 2017 7:32 am

>>Jones June 30, 2017 at 8:02 pm
Hasn’t the tipping point already happened though?<<
It has for CNN, hopefully the Guardian soon.

Reply to  Jones
June 30, 2017 4:27 pm

Three years is bold even for them, someone might actually Google that in 2020.

Reply to  Jeanparisot
July 1, 2017 12:35 am

I might indeed…..

Reply to  Jones
July 1, 2017 5:32 am

If we stop burning fossils fuels, we’ll be doomed anyway…comment image

Reply to  David Middleton
July 1, 2017 6:39 am

We are doomed, Doomed, DOOMED I tells ya!!! Doesn’t have quite the same impact without the sloppily lettered sandwich board sign, does it?!?! 😉

Reply to  Jones
July 1, 2017 7:38 am

I’m ready to bet on we have some time left in 2020 and The Guardian will tell so. I’m also ready to bet on emissions in 2020 are larger than now.

June 30, 2017 3:12 pm

The alarmists will ignore CO2 starvation while, at the same time, postulating that two degrees warming will be catastrophic.
I really can’t imagine how they will be able to write papers insisting that CO2 starvation isn’t a problem. I do have faith that they will be able to do so because of their superior imaginations.
The alarmists can take data from one tree or one sediment sample and spin it as representative of the entire globe. It’s like a scientist 50 million years from now inferring global conditions based on data from Death Valley. Conditions in Death Valley aren’t even representative of California let alone the planet as a whole.

Reply to  commieBob
June 30, 2017 3:21 pm

De-population is one of the liberals goals. CO2 starvation fits right into their plans.

Reply to  commieBob
June 30, 2017 3:48 pm

The scene from the Planet of the Apes just popped into my mind of the human dump excavation to the Statue of Liberty as Taylor yelled “Oh God. No. What did they do…” (Or something like that)

Reply to  johchi7
July 1, 2017 12:40 am

Johchi, jump to 1.00…

June 30, 2017 3:16 pm

Some here might also like to read my somewhat complementary but much more detailed about the emergence of agriculture guest post at Climate Etc., ‘A beneficial climate change.’ Arose from a previous thread comment here at WUWT, with full attribution. Was a fun couple of week’s research into primary sources (not primary research itself– that only done on other topics and patentable subject matter fields).

Lance Wallace
June 30, 2017 3:16 pm

“In fact, Earth’s atmosphere had only about 180 parts per million CO2, compared to today’s 400 ppm: 0.018% then versus 0.040% today.”
“The year 1936 recorded the hottest thermometer readings of any year in the last 5,000.”
References, please.
In fact, the entire column is nearly reference-free. Please put in the work to make your claims more believable.

Reply to  Lance Wallace
June 30, 2017 3:24 pm

LW, see my comment above. The post contains the references you seek. In short, ice cores. All peer reciewed literature.
A gentle suggestion. Rather than demand everything be spoon fed you, learn how to google peer reviewed literature. I teach a bunch of tricks in ebook The Arts of Truth.. That way you will in the future be able to sort news from fake news yourself. BTW, the last major wrap,chapter goes 88 pages on climate change and was critiqued in person for half a day by Prof. Lindzen of MIT three weeks before he retired. So it may not be correct, but contains no major ‘amateur’ errors.

Reply to  ristvan
July 1, 2017 2:16 am

riistvan – References please is a polite request. References are a standard requirement for any academic submission – have you not submitted theses or dissertations? 1936 the hottest year on record? It was the hottest July and it was in the US not world wide.

Reply to  Lance Wallace
June 30, 2017 4:27 pm

Lots of them. This from 2011 found ~190 ppm:
[1] During the Last Glacial Maximum (LGM, ∼21,000 years ago) the cold climate was strongly tied to low atmospheric CO2 concentration (∼190 ppm). Although it is generally assumed that this low CO2 was due to an expansion of the oceanic carbon reservoir, simulating the glacial level has remained a challenge especially with the additional δ13C constraint. Indeed the LGM carbon cycle was also characterized by a modern-like δ13C in the atmosphere and a higher surface to deep Atlantic δ13C gradient indicating probable changes in the thermohaline circulation. Here we show with a model of intermediate complexity, that adding three oceanic mechanisms: brine induced stratification, stratification-dependant diffusion and iron fertilization to the standard glacial simulation (which includes sea level drop, temperature change, carbonate compensation and terrestrial carbon release) decreases CO2 down to the glacial value of ∼190 ppm and simultaneously matches glacial atmospheric and oceanic δ13C inferred from proxy data. LGM CO2 and δ13C can at last be successfully reconciled.
I’ve seen estimates as low as ~150 ppm in some environments.
But C3 plants can handle levels far lower than that.

Reply to  Gabro
June 30, 2017 4:27 pm

Meant C4 and CAM, obviously. Typing too fast.

Reply to  Gabro
July 1, 2017 9:50 am

” Indeed the LGM carbon cycle was also characterized by a modern-like δ13C in the atmosphere and a higher surface to deep Atlantic δ13C gradient”
That would be because at the LGM, like today, the vast majority of atmospheric 12CO2 was produced (substantially anaerobically) by decay microorganisms. [Not by humans]
Presumably Iron fertilization would encourage phytoplankton to help Henry’s Law out in sucking CO2 from the air, but plankton fractionate like plants. They are going to leave 13C in the surface water (and air) and rain their 12C laden hard parts on the benthos.
This might be a better explanation for the “higher surface to deep Atlantic δ13C gradient” than brine stratification, for which I am unaware of any evidence.

Reply to  Lance Wallace
July 1, 2017 1:32 am

“References, please”
The acme of academic bullying.

Reply to  Lance Wallace
July 1, 2017 8:43 am

I’d like to see a cite for Dennis Avery’s claim that global temperature at the Holocene Thermal Optimum was 4 degrees C warmer than today. The graphs that I have seen in other WUWT articles say half that or less.
As for global temperature increasing less than half as much as predicted by models, it is falling short but over half of what was predicted. HadCRUT4 is tracking around the lower edge of the main bulk of the CMIP5 models. For example, – and that is when the latest global temperature plotted was when global temperature was still pulling out of a La Nina dip, using HadCRUT4 of an older version and a pre-Karl version of GISS.

Michael Cox
June 30, 2017 3:16 pm

“The latest data from the CERN particle physics lab has produced a model based on cycling – and it foresees no runaway warming. Instead, it sees an impending cold solar minimum.”
Can you supply a reference for this one? I’d very much like to read it.

Reply to  Michael Cox
June 30, 2017 4:23 pm

Basing a model on actual data was their first mistake. That is not how “climate science” is done, don’t you know, old boy?

Tom Halla
June 30, 2017 3:18 pm

Good argument. Of course, the alarmists will ignore of dismiss it.(What say you, Griff?)

Reply to  Tom Halla
June 30, 2017 3:46 pm

Be careful what you ask.
It has just been demonstrated beyond a reasonable doubt that the “pause” or “hiatus” or “slowdown” was due to a technical mistake. There was no “pause”. Just technical mistake. The mistake has been corrected:
Now back to work!

Reply to  rd50
June 30, 2017 3:55 pm

“It has just been demonstrated”
The article was written in March 2016. If that’s the level of fidelity of your comments, then I don’t need to read the linked article to know it is b/s.

Juan Slayton
Reply to  rd50
June 30, 2017 5:27 pm

rd: /sark is a useful notation to keep people from getting confused….

john harmsworth
Reply to  Tom Halla
June 30, 2017 4:17 pm

Griff is in bed with a warm.

June 30, 2017 3:34 pm

I would love to see President Trump and lots of other politicians talk about the levels of CO2 in Earth’s history and the fact that doubling the CO2 level would not cause any problems.

June 30, 2017 3:48 pm

In fact, the first surge of human-emitted carbon dioxide after World War II should have produced the biggest surge of warming – if CO2 is the control factor. Instead temperatures went down from 1940 to 1975.
that one has always bothered me……35 years…if CO2 was ever the “control knob” it should have been right then

Dennis Laughton
Reply to  Latitude
June 30, 2017 7:44 pm

Our greenhouse growers add CO2 and increase yields by up to 40%. Tomatoes are one of the best responders. As a hobby myself and another person grew giant pumpkins for competition. We added CO2 in one greenhouse and got an additional growth rate of 5 – 7 pounds per day.

Barry Cullen
Reply to  Dennis Laughton
July 1, 2017 6:58 am

OT. Wonder how methanol (USP 1992 Benson & Nonomura) would work? Works for me on other c3 plants.

Reply to  Latitude
July 1, 2017 12:37 am

Except they used a second control knob to balance the result to anything you want…
That is (human made) aerosols: SO2 as side effect of coal burning, which have a cooling effect (true), but hardly measured in the period 1945-1976, only estimated. The combination CO2 and SO2 has an interesting effect: if you give much cooling effect to SO2, then the warming effect of CO2 must be high too and reverse. In all cases, the combined effect fits the 1945-1975 period with slight cooling and the 1976-2000 effect with more warming.
The differentiation starts after 2000 with the “pause” when SO2 hardly changed, only shifted from the West to S.E. Asia, thus the “cooling knob” didn’t change, while the “warming knob” still did go up. That makes that the models with the highest influence of aerosols (and thus of CO2) are now way too high…
See some (older) calculations on that balance:

Reply to  Latitude
July 1, 2017 5:40 am

Atmospheric CO2 stabilized during that period of cooling, despite acceelerated emissions. MacFarling Meure et al., 2006 found possible evidence of a mid-20th Century CO2 decline in the DE08 ice core…
The stabilization of atmospheric CO2 concentration during the 1940s and 1950s is a notable feature in the ice core record. The new high density measurements confirm this result and show that CO2 concentrations stabilized at 310–312 ppm from ~1940–1955. The CH4 and N2O growth rates also decreased during this period, although the N2O variation is comparable to the measurement uncertainty. Smoothing due to enclosure of air in the ice (about 10 years at DE08) removes high frequency variations from the record, so the true atmospheric variation may have been larger than represented in the ice core air record. Even a decrease in the atmospheric CO2 concentration during the mid-1940s is consistent with the Law Dome record and the air enclosure smoothing, suggesting a large additional sink of ~3.0 PgC yr-1 [Trudinger et al., 2002a]. The d13CO2 record during this time suggests that this additional sink was mostly oceanic and not caused by lower fossil emissions or the terrestrial biosphere [Etheridge et al., 1996; Trudinger et al., 2002a]. The processes that could cause this response are still unknown.
[11] The CO2 stabilization occurred during a shift from persistent El Niño to La Niña conditions [Allan and D’Arrigo, 1999]. This coincided with a warm-cool phase change of the Pacific Decadal Oscillation [Mantua et al., 1997], cooling temperatures [Moberg et al., 2005] and progressively weakening North Atlantic thermohaline circulation [Latif et al., 2004]. The combined effect of these factors on the trace gas budgets is not presently well understood. They may be significant for the atmospheric CO2 concentration if fluxes in areas of carbon uptake, such as the North Pacific Ocean, are enhanced, or if efflux from the tropics is suppressed.
From about 1940 through 1955, approximately 24 billion tons of carbon went straight from the exhaust pipes into the oceans and/or biosphere.comment image
MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith, and J. Elkins (2006), Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP, Geophys. Res. Lett., 33, L14810, doi:10.1029/2006GL026152.

June 30, 2017 3:51 pm

Why isn’t the CERN model reported in the media? Aren’t these guys supposedly the worlds best and brightest physicists? Certainly an order of magnitude smarter than your average climastrologer anyhow.

Reply to  AP
June 30, 2017 8:29 pm

Please avoid using derogatory terms like ‘climastrologer’. That just demeans the debate. I prefer to use the more respectful term, ‘climate scientologist’.

June 30, 2017 4:08 pm

I, for one, have done a ton of research about this very topic which leads me to conclude that Dennis Avery is exactly right here.
Earth at -4.0C to -5.0C from today with CO2 at 180 ppm to 250 ppm is a vastly different planet than it is today. Very, very different.
But humans (and our ancestor species) survived through about 30 different ice ages before that where these conditions existed. It actually made us who we are.
But then the peak of the last ice age from 40,000 years ago to 20,000 years ago was just that little bit worse than the previous one so that many other species just didn’t make it through. But by that time, we were lucky enough in that the previous 29 ice ages had made us just that little bit more adaptable, intelligent and technological so that we were not one of those dead-ends.

Reply to  Bill Illis
June 30, 2017 7:09 pm

Bill, I fully grant that full glaciation conditions were quite extreme on the planet and life.
However, the concern today about significant future heating (IF it occurs, for whatever reason) is how it might damage a large, widespread, complex society, far from the meager human population of 20 kyr ago. What IF (again hypothetical) future warming destroys large portions of the modern human economy?
The issue is not how past cooling affected society then, but how much future warming (again IF it occurs) might affect modern, complex society. Very different issues.

Reply to  donb
June 30, 2017 7:13 pm

Any warming from GHG could only be good, as it has been so far.
The most warming that can be defended scientifically is about one degree C per doubling, ie all good.

Reply to  donb
July 1, 2017 1:38 am

The (possible) future warming of a degree or two is not a problem. The likely (within 5,000 years max) reduction of 10-20 degrees is a very severe danger. Manhattan will be buried under a mile of snow, and we won’t know how to keep warm because we will have lost the technology.
Read “Fallen Angel”, by Larry Niven, et al for a thorough reference in green thinking.

Steamboat McGoo
Reply to  donb
July 1, 2017 7:31 am

” What IF (again hypothetical) future warming destroys large portions of the modern human economy? ”
Probably won’t. That’s why the Alarmists insist that the only solution to the (non)problem is to pre-destroy the economy. Every little bit helps …

Reply to  donb
July 1, 2017 7:53 am

Greens are not afraid of economy collapsing. They are afraid of economy not collapsing. By collapsing the economy they think they can save polar bears. But, sadly, if economy collapses, mammals are just some meat waiting for lunch time to arrive.

Reply to  donb
July 1, 2017 7:42 pm

By what mechanism would this destruction occur, what likely adaptations would be available (given that we can’t predict how our technology will advance), what would be the cost to reduce CO2 in the atmosphere, what effects would that have on the environment, what are the alternatives, what do the alternatives cost and what are their effects on the environment, and what hard evidence do you have of these assertions?
I mean, that’s kind of the minimum set of answers I’d need before I sign up for massive and disruptive social or economic remodeling.

Reply to  donb
July 3, 2017 2:54 pm

I will believe heat is bad for the economy once Phoenix Arizona and Miami Florida are no longer among the fastest growing cities… Los Angeles in the Southern California desert and Doha, Qatar too…
There is zero evidence heat is bad for economies. Arizona even grows tomatoes and wheat… they have year round growing seasons, though mid-summer needs hot crops like tomatoes…
Frozen Detroit, however… /sarc;

Reply to  donb
July 3, 2017 2:59 pm

Humanity thrived during the Holocene Climatic Optimum, two degrees C toastier than now. Likewise the Minoan Warm Period, 1.5 degrees C balmier than present. Ditto the Roman WP, one degree cozier, and Medieval WP, some half degree warmer than AD 2017.
It was the intervening cold periods which so savaged the people.

June 30, 2017 4:08 pm

There is no evidence of a Gravettian atlatl. Doesn’t mean that they didn’t use them, but the oldest in the archaeological record is Solutrean.
The culture which came out of the Near East to invade Europe was the Aurignacian. Gravettian is an Eastern European development of the Aurignacian, just as Solutrean is the Last Glacial Maximum follow-on to the Aurignacian in Western Europe.
While the Pleistocene megafauna hunted by humans also ate mainly C3 forbs, the steppe-tundra was dominated by C4 grasses, which can survive on very low levels of CO2.
As noted, the Last Glacial Maximum however was not only cold, but dry and windy. It was indeed a challenging environment for most plants, especially trees, which are all C3 photosynthesizers.

Reply to  Gabro
June 30, 2017 4:16 pm

The trees might be a bit optimistic, but depends upon where the scene is.comment image
Eurasians before the LGM enjoyed the Pleistocene equivalent of the modern African savanna. At the LGM, climate deteriorated, tundra replaced steppe-tundra close to the ice sheets and human hunters sought refuge in the Balkans, Italy, southern France and Iberia.
Solutrean culture took hold in the SW French refugium,

Reply to  Gabro
June 30, 2017 4:35 pm

Yes the trees are optimistic. The only places they would have grown like this at the last glacial maximum was the US southeast, a much smaller Amazon (and these did not have people in them at the time) and a tiny ribbon in equatorial Africa and most of the Indonesia region.
Otherwise, maybe a few trees along river banks. What did we burn for fires? It’s a good question but it must have been something. North of the Black Sea region, as far north as humans were at the last glacial maximum, they actually burnt mammoth bones which apparently burn very well.

Reply to  Gabro
June 30, 2017 4:41 pm

Dried dung and grass, but also dwarf tree species, such as birch and willow. And yes, bones do burn well once you have a fire going.
There was a boreal spruce/pine zone, but like all the others, constricted south of the steppe-tundra.

Reply to  Gabro
June 30, 2017 4:42 pm

And their lamps burnt fat.

Reply to  Gabro
June 30, 2017 4:52 pm

Actually, it was not that cold at the LGM. While polar temperatures plunged 12 degreec c, tropical temps only dropped 4 degrees.
And it may not have even been that bad, in reality. The 4 degree temp drop was derived from the lowering of tropical treelines, which were depressed down to 1,500 m. This was interpreted as being caused by reducing temperatures. And this necessitated a huge lapse rate, to make sea temperatures equal the treeline depression.
But if the tropical treeeline was actually depressed by lowering CO2 concentrations, then tropical temperatures need not be so low, and the lapse rates need not be so bizare.**
However, the assumed large temperature drop has been included in all the paleoclimate models, which therefore show far too much tropical cooling at the LGM. The whole thing is a mess.
Please see my paper, posted below.
** One esteemed professor said my assertion that CO2 lowered treelines was incorrect, because the concentration of CO2 does not change with altitude. Hmm, yes, but the partial pressure does. I did invite the esteemed professor to climb up Everest, and see if he-she ran out of oxygen there…..

Reply to  Gabro
June 30, 2017 5:01 pm

The issue with the temperature drop is that it also comes with a reduction in precipitation. Theory says it something like a 30% decline versus today.
Low CO2 (equals more open stomata which means more loss of water through evapotranspiration combined with lower precipitation) means that only C4 and Cams plants survive except for places that have about 200 inches of rain per year. Tropical rainforest-like regions if we are thinking about those areas today.

Reply to  Gabro
June 30, 2017 5:12 pm

How much colder “temperate” zone latitudes got depends largely on where you look.
With a high degree of certainty, that at the LGM it got too cold, dry, windy and dusty in Western Europe for people to live year-round, if at all, in Britain south of the ice sheet, the Channel, northern France, the Low Countries and Germany between the Scandinavian and Alpine ice sheets.

M E Emberson
Reply to  Gabro
June 30, 2017 11:23 pm
Siberian Upper Palaeolithic for comparison. It shows how life styles can be inferred from stone flake tools.
and so on. .
They have not assessed the animal bones yet.
The obsidian volcanic glass flake tools similar to the Siberian assemblage were also found in Alaska because of the land bridge.
Here is a very useful place to find out about the uses of the stone tool assemblages. This may be of some use.
The thing is we can only infer haftings except when wooden artefacts are found in wet places with the bindings of leather on them.
For uses of tools some people, anthropologists and ethnologists. look at recent tribes found here and there across the globe.
I have drawn many of these flakes and appreciate the technical proficiency of those who made them.
M E Wood M A (hons) Prehistoric Archaeology Edinburgh 1965

Reply to  Gabro
July 1, 2017 8:00 am

One esteemed professor said my assertion that CO2 lowered treelines was incorrect, because the concentration of CO2 does not change with altitude.

Funny is that. Really funny. D-G effect in action.

Reply to  Gabro
July 1, 2017 9:55 am

Animal density might be a little optimistic too 🙂

Reply to  Gabro
June 30, 2017 4:23 pm

Humans survived on grass-eating herbivores during the ice age periods which covered about 75% of the homo evolutionary line.
In interglacials, yes we liked out fruit berries and roots but for 75% of our existence, there just wasn’t any of these things except for the stray patches here and there. Not enough for a family or tribe to survive on.
We ate the big Auroch wild cattle, deer, buffalo and other grass-eating herbivores in that 75% of the time. We became a two legged hairless sweaty big brained communicative weapon carrying and weapon throwing animal because it is an extremely effective method of being a carnivore of grass-eating herbivores. There wasn’t anything else to eat except grass and cactus and tundra.

Reply to  Bill Illis
June 30, 2017 4:31 pm

Solutreans were an Eskimo-like culture in the South of France. Their post-LGM Magdalenian successors reinvaded NW Europe with a Lapp-like reindeer-centered culture.

Reply to  Bill Illis
June 30, 2017 4:34 pm

Although Solutrean population density was higher. They formed at least seasonal communities in caves and tents near reindeer crossings.

Reply to  Bill Illis
June 30, 2017 4:53 pm

Like Eskimos, Solutreans made extensive use of maritime resources, which is one reason why some have concluded that they crossed the then Arctic Ocean-like North Atlantic to America. Another of course is the similarity in their blade culture.

Larry D
Reply to  Bill Illis
June 30, 2017 9:24 pm

🙂 You forgot to mention our ability to jog herbivores into the ground. The sprinter herbivore can out run us, for a while. Then they’re exhausted and we catch up to them.

June 30, 2017 4:20 pm

Why didn’t the alarmists embrace the ‘pause’ earlier and with greater vigor?
Warming without increased water vapor disproves their hypothesis, so they need there to be little to no warming – until either water vapor increases significantly or they figure out how to get their thumbs on the scales used to measure it.

john harmsworth
June 30, 2017 4:20 pm

Take away the mammoths and it looks like Northern Canada today. Maybe add a few government workers.

Reply to  john harmsworth
June 30, 2017 4:32 pm

The bureaucrats would have been the easiest and most desired prey of all, thanks to their big, fatty brains put to such little use.
Neanderthals ate each other, moderns ate both Neanderthals and each other. Fats are where you find them in a brutal environment where fat is all.

Reply to  Gabro
July 1, 2017 5:47 am

According to Douglas Adams, we evolved from alien bureaucrats… 😉
(Hitchikers Guide to the Galaxy)

Reply to  john harmsworth
June 30, 2017 4:38 pm

Too bad that northern Canada doesn’t still have horses and mammoths, to go with the caribou, musk oxen, bison, etc. Saiga antelope still exist, but not in North America. Our continent never did have woolly rhinos or Irish elk.
The grazing succession in glacial intervals was like Africa, with horses in place of zebra, bison for wildebeest and mammoth for elephants, etc. Megatons of protein, fat, hides, sinew, etc on the hoof and foot.

Jimmy Finley
Reply to  john harmsworth
June 30, 2017 9:52 pm

John: Hilarious – “add a few government workers”. I suppose they are the new sabretooths.

June 30, 2017 4:38 pm

The same scenario was explored in the following paper:
Modulation of ice ages via precession and dust-albedo feedbacks
But this paper went much further and suggested that this low CO2 not only kills off a great deal of flora, it also initiates interglacial warming.
We present here a simple and novel proposal for the modulation and rhythm of ice-ages and interglacials during the late Pleistocene. While the standard Milankovitch-precession theory fails to explain the long intervals between interglacials, these can be accounted for by a novel forcing and feedback system involving CO2, dust and albedo. During the glacial period, the high albedo of the northern ice sheets drives down global temperatures and CO2 concentrations, despite subsequent precessional forcing maxima. Over the following millennia more CO2 is sequestered in the oceans and atmospheric concentrations eventually reach a critical minima of about 200 ppm, which combined with arid conditions, causes a die-back of temperate and boreal forests and grasslands, especially at high altitude. The ensuing soil erosion generates dust storms, resulting in increased dust deposition and lower albedo on the northern ice sheets. As northern hemisphere insolation increases during the next Milankovitch cycle, the dust-laden ice-sheets absorb considerably more insolation and undergo rapid melting, which forces the climate into an interglacial period. The proposed mechanism is simple, robust, and comprehensive in its scope, and its key elements are well supported by empirical evidence.

June 30, 2017 4:46 pm

These Gravettians’ furs would be worth fortunes today:
Their mammoth bone structures were more like huts than tents. They used interlocked skulls and long bones as well as ribs.

Reply to  Gabro
June 30, 2017 4:49 pm

And notice, fur inside. Unlike today where the fur is outside.

Reply to  Gabro
June 30, 2017 4:51 pm

Mostly scavenged rather than hunted, of course.

June 30, 2017 4:56 pm

More proof that Bio-Mass and the Earth itself creates more Carbon Dioxide and exponentially more Bio-Mass and very little contributes to temperature/climate. Billions of years of Carbon Dioxide is trapped in Fossil Fuels, fossils, liquid to frozen water on land and sea’s, in the rock’s soils and magma and Bio-Mass. That Solar activities create the sequestration during glacials or release of the stored Carbon Dioxide from the H2O sources during Interglacials…as well as season’s and cyclical cooling and warming of El Nina and El Nino. That El Nino’s creates heated ocean’s and more evaporation that is carried to the Poles by the atmosphere to become Ice forms of water and colder ocean’s causing more cooling of the ocean’s as El Nina’s. We have equated that Solar Minimums cause Glacial Periods and Solar Maximums cause Interglacial Periods. So why is the Earth hotter causing El Nino’s during a Solar Minimum? If Sun Spots are the Cooling of the Sun during Solar Maximums? If droughts are caused by both Glacial and Interglacial Periods and yet more are caused by Glacial Periods by reduced atmospheric water than during Interglacial Periods that cause more Tropical weather patterns globally wil the exponentially increasing Bio-Mass.
Are the Climate Alarmist really that ignorant to want the Climate to not get warmer? No. They hate capitalism that creates inequality. And yet we see more inequality during socialism with the elites that are the Alarmist, whom by the majority do not produced tangible products for the masses that capitalism does, they get rich from the people that are capitalist through taxes and banking and investments off those that produce what they need to live on. Environmentalist are saying they are saving the Planet, while doing everything to kill it and make the poor poorer by increasing their burdens of less energy and higher costs on everything.

Chris Hanley
June 30, 2017 5:34 pm

It invites the question why Gaia didn’t wipe out the human species while She had a chance, maybe next time.
The greens are doing their utmost to assist.

Reply to  Chris Hanley
June 30, 2017 5:38 pm

Even had Mistress Gaia managed to wipe out all the humans in the affected temperate zones, we would have rebounded from less affected Africa, southern Asia and Australia, which we reached before the LGM.

June 30, 2017 5:54 pm

Satellite temperature readings just altered to show a pronounced warming trend since 1998. That is how Warmists deal with data. Alter it.

June 30, 2017 5:59 pm

during the last Ice Age too little CO2 in the air almost eradicated mankind
The Ice Age’s combined horrors – intense cold, permanent drought and CO2 starvation – killed most of the plants on Earth. Only a few trees survived, in the mildest climates.
Recent Cambridge University studies conclude that only about 100,000 humans were left alive worldwide when the current interglacial warming mercifully began.
The Neanderthals had been living in relatively warm caves protected from predators by fires at the cave mouths. They had hunted their prey by sneaking through the trees – which no longer existed. They apparently couldn’t adapt, and starved.

This article is a collection of baseless speculations. Most of the things it says about the last glacial period are either impossible to know or unsupported by evidence.
A cursorial look at vegetation zones reconstructions from evidence for the last glacial period shows that every type of vegetation habitat was represented in the planet, which is only logical as very few species of plants and animals became extinct. The meridional temperature gradient became steeper and vegetation zones contracted and displaced southward. The CO2 crisis is not evident, and thus might not have taken place. Plants and trees continued growing and reproducing and supporting animal populations. A less productive planet yes. A planet in danger of mass extinction no. No evidence for that, so you are inventing it.
For the past 50,000 years Homo sapiens expanded its range, so the evidence is against “almost eradication.” Again inventing that. Usually with an expansion of range comes an increase in numbers. If you want to propose the opposite you better get evidence. The human population 2000 years ago, when already there were census in some parts, is unknown, so you come telling us that there were fewer than 100,000 people 12,000 years ago? Whoever says that is inventing it.
In fact the evidence supports the opposite, that human populations were expanding considerably during your conjetured CO2 crisis:
Genetic study pushes back timeline for first significant human population expansion
And that due to its increase in population size it was adapting to smaller prey hunting when depleting the slower reproducing larger prey:
Paleolithic population growth pulses evidenced by small animal exploitation
Human population is estimated by some at 1-5 million at the time the Holocene started. Gobekli Tepe was started to be built around 11,500 years ago, at the start of the Holocene, and required an awful lot of people considering that agriculture had not been discovered yet. Not consistent with what you say.
Regarding the Neanderthals, lots of hypotheses about their demise. Don’t talk like yours is the correct one. I personally consider very unlikely that they went extinct because they starved. It goes against biological principles. As a predator population decreases its size, it has less problem finding prey.
So the article is a nice tale. Too bad most of it is not true. A little bit of research before writing is what differentiates science from fiction.

Reply to  Javier
June 30, 2017 6:07 pm

Yes, clearly remnant populations of all the plant species we see today had to have survived.

Reply to  Javier
June 30, 2017 6:10 pm

However, greater population at the onset of the Holocene is only to be expected some 8000 years after the end of the LGM. During the deglaciation interval, for instance, the Magdalenian population explosion spread across the previously empty plains of NW Europe, recolonizing Britain, northern France, the Low Countries and Germany.

Reply to  Gabro
June 30, 2017 6:49 pm

I am not discussing the population expansion. I am discussing the statement that “too little CO2 in the air almost eradicated mankind” and “that only about 100,000 humans were left alive worldwide when the current interglacial warming mercifully began.”
This article here:
Human population dynamics in Europe over the Last Glacial Maximum
Estimates the minimum population of Europe during the last glacial maximum 23 kyr BP at 130,000 people. And Europe had at the time only a small part of the human population, as Africa and Asia had much better conditions and habitable surface.
While this other:
New estimations of habitable land area and human population size at the Last Glacial Maximum
Estimates the world population during the Last Glacial Maximum at 2,117,000–2,955,000 based on carnivore densities and 3,046,000–8,307,000 for hunter–gatherer densities.
Even if these estimates were on the high side, it is clear that the affirmations by Dennis Avery are completely unsupported. This article has not been researched, and thus has no value.

Reply to  Javier
July 1, 2017 4:00 am

So, let me get this straight, your big beef with this is the difference between 100,000 and 130,000?

Reply to  2hotel9
July 1, 2017 11:38 pm

You are not getting this straigh, 2hotel9, David Avery’s 100,000 is for the entire world. The article’s 130,000 is just for Europe which was the least populated continent of the Old World. The difference is actually a factor of 10, and there is zero evidence for the near eradication of humankind by low CO2 that Avery proposes.

Reply to  Javier
July 3, 2017 4:03 am

So you are picking nits. Gabro has said repeatedly that this is all speculation. The fact is we, today, can not ascertain with any degree of accuracy what the exact population numbers were at this far remove in time and not written records to study. We can only guess.

Reply to  2hotel9
July 3, 2017 5:43 am

Thanks. Exactly my point. The article’s statements about human eradication and nearly doomed life on earth due to low CO2 are not supported by evidence. It is baseless especulation as is so common with climate issues.

Reply to  Javier
July 3, 2017 6:00 am

So, why not just say that?

Reply to  Gabro
June 30, 2017 7:08 pm

Do you really think that there were eight million Europeans 20,000 years ago, when so much of the continent was under ice, and so much unproductive tundra?
If our ancestors were restricted then, as seems apparent, to enclaves in SW France, Iberia and the Balkans, and perhaps in the cis-Caucasus region, that works out to a very high density for hunter-gatherers, mainly hunters.

Reply to  Gabro
June 30, 2017 7:48 pm

Do you really think that there were eight million Europeans 20,000 years ago

Read it again. First article about Europe proposes 130,000 Europeans 23 kyr ago. Second article about the world proposes 2,1-8,3 million humans in the entire world, including the areas that are now under water.
As I said previously most estimates are about 1 – 5 million people in the world during the late Last Glacial. That’s at least 10 times what Dennis Avery proposes. Doesn’t look like they were starving for lack of CO2.

Reply to  Gabro
June 30, 2017 7:53 pm

To me, a million people in the world during the LGM does seem a reasonable estimate.
Sorry for misreading. But even for the whole world 20 Ka, eight million seems optimistic.

Reply to  Javier
June 30, 2017 6:13 pm

And during that interval, not only the Magdalenians in Europe but already the more “advanced” Mesolithic in the Levant, before the Holocene.

Jimmy Finley
Reply to  Javier
June 30, 2017 7:11 pm

I think you should look closely at your very interesting map (source?). In Europe and the Middle East, virtually no treed areas exist at the LGM – sort of like the author postulated. Steppes, desert and ice. Today’s map is vastly different – and possibly represents what came before the LGM. The change from one state to the other, over mere tens of thousands of years, would have been huge for societies entirely lacking in scientific knowledge.

Reply to  Jimmy Finley
June 30, 2017 7:37 pm

That map is from a PNAS article. You can locate it because the article number is in the figure link.
You cannot look at that crude map and say that “In Europe and the Middle East, virtually no treed areas exist at the LGM.” There are literally hundreds of articles on pollen studies identifying the range extension of most tree genres in Europe during the Last Glacial Maximum. It is well known that most sensitive species of trees took refuge in Southern Europe. Where do you think the trees we have now in Europe come from? The problem was cold, and lack of precipitations, not lack of CO2. There is essentially no evidence available that lack of CO2 was a problem for trees in Europe.
I understand that you are not going to read those studies, but then why are you going to believe the first one that comes and tells you a story? You might as well believe in catastrophic anthropogenic global warming if you are not going to demand evidence for what you are told.
Skepticism is a guiding principle that should be used always against anything and anybody. This article does not resist a minimum of skepticism.

Reply to  Jimmy Finley
June 30, 2017 8:19 pm

The current understanding is that temperate trees took refuge South of 45º N in Europe while boreal trees could be found North of the Alps and in northern refuges in Eastern Europe. Their distribution was patched in areas where microclimatic conditions were more favorable and where higher humidity compensated the low CO2 levels. Those areas probably also concentrated a higher number of mammals and humans.
Cryptic or mystic? Glacial tree refugia in northern Europe
You can also see:
Glacial refugia of temperate trees in Europe: insights from species distribution modelling
It is from models, but reaches similar conclusions.

Jimmy Finley
Reply to  Jimmy Finley
June 30, 2017 8:58 pm

Javier: “…I understand that you are not going to read those studies, but then why are you going to believe the first one that comes and tells you a story?…” You have no idea whether I will read those articles, or not. I suggest you moderate your tone. You posted a map on which I commented. Said map – your selection – shows climate zones that today are scant of trees. The author of this post suggested Neanderthals found themselves in a treeless situation where they were severely handicapped. Whether it had to do with CO2 or rainfall, I made no opinion. I just noted his comment seemed, to me, to be reflected in your map. That’s why I suggested you look at your map and think about it.

Jimmy Finley
Reply to  Jimmy Finley
June 30, 2017 9:11 pm

Speaking of plant “refugia” the white trillium is an example, I am told by our local botanists. Apparently wiped out everywhere except in the unglaciated zone in MI-WI in the last glaciation, it now is found over large areas of the north country. This, despite its depending on ants to carry about, and disperse, the seed (a form of “corpse-carrying behavior” I have read). As opposed to all those trees that bear seeds that may be dispersed on a far greater scale than a given trillium. As a result, trees would have speedily repopulated suitable areas once the conditions were right.

Reply to  Javier
July 1, 2017 12:59 am

Nice posting, Javier.
The important thing to note is that the CO2 decimation of flora was only at high altitude and in dry regions (because C3 plants need more water in low C02 condiditions). Hence the huge increase in the Gobi desert.
But in support of this article, it was proven that C3 plants are under a great deal of stress at 180 ppm, and would not have been as large and as fast drowing as today.

Reply to  ralfellis
July 1, 2017 11:34 pm

Laboratory tests on C3 plants are equivocal. In natural environments CO2 levels change so much in a matter of hours that a great deal of care has to be taken to measure atmospheric CO2 concentrations. Even if average levels of CO2 were 180 ppm, higher peak levels on a daily basis could have been common in most places allowing plants to grow vigorously for several hours everyday.
Even today it has been demonstrated that on maize fields on calm days CO2 is effectively depleted within a few hours after sunrise reaching very low levels with no ill effect for the plants. They just wait for some wind to bring more CO2.
Chemical measurements of CO2 during the early 20th century gave very high levels of CO2, demonstrating that global average levels and local levels can be very different.
Greenhouse laboratory conditions with constant low CO2 levels cannot be extrapolated to the real world of the last glacial maximum.

Reply to  Javier
July 1, 2017 6:02 am


Gobekli Tepe was started to be built around 11,500 years ago, at the start of the Holocene, and required an awful lot of people considering that agriculture had not been discovered yet.

Then you would be very interested in this interview with economic historian Michael Hudson discussing his latest book written with a colloquium of experts at Harvard. From the interview, by way of introducing it (April 25, 2015):

Michael Hudson: It’s a symposium of a group put together at Harvard University of the leading Assyriologists and Egyptologists and Mycenaean Greek specialists as well as archaeologists on how early societies mobilised the labour force, especially for large public building projects such as temples, city walls and other infrastructure.
We founded this project over 20 years ago at the Peabody Museum, which is their archaeology and anthropology department. We wanted to do a series of books on how modern economies and practices began.
And then ten years ago we had our fifth colloquium on Labor in the Ancient World. There have been so many revolutions in archaeology and Assyriology and even Egyptology in the last ten years that we’re only publishing this volume now, to be completely up-to-date.
We begin the volume in 10,000 BC in Gobekli Tepe in Turkey where you have very large city-like ceremonial sites, larger than Stonehenge, huge sites that took hundreds of years to build with huge stone megaliths, even in the pre-pottery Neolithic.

He said the biggest problem in 10,000 BC was a labor shortage.
There’s also a transcript at the link if you prefer to read. But it’s fascinating to listen to.

Reply to  MRW
July 1, 2017 11:35 pm

Thank you, MRW.

Reply to  MRW
July 3, 2017 6:55 am

Pre-agricultural civilization? I don’t believe a word of it. –AGF

Richard G.
Reply to  Javier
July 1, 2017 10:28 am

Thanks for posting a nice graphic that beautifully illustrates that climate is not some mythical average temperature, but is really a rich tapestry of diverse biomes of plant and animal communities. I urge you to refer to them as climate zones instead of vegetation zones.
See Köppen climate classification:

Reply to  Richard G.
July 1, 2017 7:20 pm

Climate changes, constantly. Humans are not causing it and can not stop it. THIS is what has to be hammered into the public’s’ awareness.

Patrick MJD
Reply to  Richard G.
July 2, 2017 5:54 am

“Richard G. July 1, 2017 at 10:28 am”
Remember, an average is a made up number and thus meaningless.

Jimmy Finley
June 30, 2017 7:26 pm

People were pretty thin on the ground in Europe at 23kybp. Must have been pretty hard to find a date over about 98% of it.

f e davis
June 30, 2017 8:24 pm

I looked at It is a model simulation of what European population distribution may have been given inputs from climate circulation models, modern hunter-gather data, and other assumptions. I would like to know the error bars in this study. Was the population, e.g., 1,000,000 +/- 900,000 ??

July 1, 2017 12:01 am

This data is shown as a bar graph in Fig 7 of The paleo estimates are near the minimum of the range determined by Berner as shown in the graph at
Carbon dioxide levels, ppmv
40,000 Exhaled breath
20,000 No symptoms in healthy young people below this level
8,000 OSHA limit for 8 hr exposure
5,000 OSHA limit for continuous exposure
5,000 Approximate level 500 million years ago
1,500 Artificial increase in some greenhouses to enhance plant growth
1,000 Approximate level 100 million years ago
1,000 Common target maximum for ventilation design for buildings
405 Current atmospheric level
275 Atmospheric level before industrial revolution
190 Atmospheric level at end of last glaciation
150 All land plants and animals become extinct below this level.
Land plants become extinct because they are unable to reproduce. Land animals then starve.

July 1, 2017 12:03 am

CO2 levels below 150ppm is a global extinction event….
Just 12,000 years ago, some proxy estimates put CO2 levels at 170ppm– just 20ppm away from all life going extinct…
We should be absolutely ecstatic that life-giving CO2 levels have increase to 400ppm…. but, alas…
Some research suggests the increase of CO2 levels alone (from 280ppm in 1750 to present day 400ppm) have increased crop yields 25%, with another 25% increase, if they beneficially increase to 560ppm by 2100…
CAGW Is such a loony Leftist sc@m…

Reply to  SAMURAI
July 1, 2017 5:33 am

The CO2 count under a forest canopy today is 600 PPM. For all those who like to go camping and hiking in the Rockies.

Reply to  MRW
July 1, 2017 9:00 pm

Yes, the canopy prevents the CO2 produced by soil from dispersing.

July 1, 2017 2:24 am

Without CO2 there would be no Oxygen …

Willy Pete
Reply to  vuurklip
July 1, 2017 12:11 pm

The O2 in our air comes from water, but it wouldn’t have been released without both water and CO2 in photosynthesis.

Thomas Homer
Reply to  vuurklip
July 2, 2017 5:28 am

There’s 500 times more oxygen than Carbon Dioxide in Earth’s aytmosphere

Reply to  Thomas Homer
July 2, 2017 6:40 am

Exactly. Without plants, water and CO2 there would not be oxygen in the atmosphere. So, more CO2 = more plant matter = more oxygen.

July 1, 2017 3:56 am

Just a thought from a non-expert: I frequently hear about ocean outgassing when it warms, but wouldn’t the huge amount of ice melt from glacial maximum to/through the HCO also release a lot of sequestered CO2? Would that also contribute to the 800ish year time lag?

Reply to  ChrisDinBristol
July 1, 2017 3:59 am

(oh, and aren’t the ice cores an unreliable measure of historic CO2, becoming more so the further you go back in time?)

Reply to  ChrisDinBristol
July 1, 2017 5:59 am

They’re not unreliable. However, they do have limited resolution. High accumulation-rate ice cores have higher resolution, but can only “see” back a few thousand years. Low accumulation-rate ice cores can “see” back 400-800 thousand years, but they have very low resolution.comment image

Reply to  ChrisDinBristol
July 1, 2017 11:45 am

If I remember well, Vostok has a resolution of ~600 years over 420,000 years, while Dome C is at ~560 years over the past 800,000 years.
While looking for the exact figures I found a response to the critique of Dr. Salby on ice cores reliability by Eric Wolff, from BAS and Cambridge;

Reply to  ChrisDinBristol
July 1, 2017 12:20 pm

BTW, I missed the discussion about the ice core resolution of some months ago, but while a sinusoid of up to twice the resolution will not be detected in an ice core, the current increase is either one-way and will be detected in every ice core, even with the worst resolution – be it with a lower amplitude, or it is part of a large sinusoid and then the wavelength is already over 600 years, again vivisble in every ice core, even with the lowest resolution…

Reply to  ChrisDinBristol
July 1, 2017 11:12 am

Hardly of influence, as the air in the ice is of similar compostion as the atmosphere at the moment that it is enclosed. Thus varying between about 180 and about 300 ppmv. As the bubbles at closing depth are about 10% of the ice volume and the ice volume is a tiny fraction of the atmospheric volume (at 1 bar), it may give only a change of a few ppmv when released at the opposite point of the temperature cycle…

Reply to  Ferdinand Engelbeen
July 2, 2017 5:57 pm

Thanks. You chaps (and chapesses) are an ongoing education . . .

July 1, 2017 3:58 am

Finally someone is saying what I have been saying for a long time.
The statement above are correct.
Whats missing, humans and animals alike need CO2 which controls the blood PH levels.
Without it we would not function.
The one thing thats missing is the NASA Saber project which seems that higher concentrations of CO2 actually protect the planet from solar burst.

July 1, 2017 11:56 am

What the author doesn’t take into account is that there is a little advantage that inland plants have, compared to the CO2 levels in the bulk of the atmosphere: CO2 in the first few hundred meters over land is biased higher compared to “background” (as measured in ice cores), in average but also at least a few hours in the morning, until photosynthesis takes more and more out of the air.
Here the monthly averages at Giessen, mid-west Germany which show some average 40 ppmv levels above background. Most of that is from soil bacteria, rotting vegetation and nightly respiration, but it may have helped some C3 plant in growth, even if it was only a few hours per day…

Reply to  Ferdinand Engelbeen
July 1, 2017 12:21 pm

I suspect that CO2 was not “well mixed” during glacial intervals, which are windy, with pronounced temperature gradients.
As areas with plant cover suck CO2 out of the air, masses would come in with more, particularly off of the ice sheets. Air with more CO2 is also heavier than those with O2 instead, if ever so slightly.

July 1, 2017 1:04 pm

Thoughts from 2009 – not all that bad for the time – a few corrections added later – details re C3 vs C4 and CAM plants, 180 ppm vs 200 ppm.
(Plant) Food for Thought (apologies – written too late at night)
1. “As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels – below 200 ppm – will cease to grow or produce.”'s_atmosphere
2. “The longest ice core record comes from East Antarctica, where ice has been sampled to an age of 800 kyr BP (Before Present). During this time, the atmospheric carbon dioxide concentration has varied by volume between 180 – 210 ppm during ice ages, increasing to 280 – 300 ppm during warmer interglacials…
… On longer timescales, various proxy measurements have been used to attempt to determine atmospheric carbon dioxide levels millions of years in the past. These include boron and carbon isotope ratios in certain types of marine sediments, and the number of stomata observed on fossil plant leaves. While these measurements give much less precise estimates of carbon dioxide concentration than ice cores, there is evidence for very high CO2 volume concentrations between 200 and 150 myr BP of over 3,000 ppm and between 600 and 400 myr BP of over 6,000 ppm.”
Questions and meanderings:
According to para.1 above:
During Ice ages, does almost all plant life die out as a result of some combination of lower temperatures and CO2 levels that fell below 200ppm (para. 2 above)? If not, why not?
Does this (possible) loss of plant life have anything to do with rebounding of atmospheric CO2 levels as the world exits the Ice Age (in combination with other factors such as ocean exsolution)? Could this contribute to the observed asymmetry?
When all life on Earth comes to an end, will it be because CO2 permanently falls below 200ppm as it is permanently sequestered in carbonate rocks, hydrocarbons, coals, etc.?
Since life on Earth is likely to end due to a lack of CO2, should we be paying energy companies to burn fossil fuels to increase atmospheric CO2, instead of fining them due to the false belief that 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 🙂

Reply to  Allan M.R. MacRae
July 3, 2017 9:03 am

According to this paper by Franck et al (Causes and Timing of Future Biosphere Extinctions, 2006) CO2 starvation is a highly plausible reason for eventual total biosphere extinction:

July 1, 2017 3:26 pm

Toward Pleistocene Park:
After the woolly mammoth, then the rhino, Irish elk and long-horned bison!
Not so sure about short-faced bears, cave bears, saber-tooth cats, cave lions, dire wolves, etc.

July 1, 2017 5:01 pm

“In fact, Earth’s atmosphere had only about 180 parts per million CO2, compared to today’s 400 ppm: 0.018% then versus 0.040% today.”
Think about that mate. 180 ppm put us in the freezer, 280 ppm is the norm during interglacials – and we’re currently over 400 ppm.
You don’t see that that indicates the acute sensitivity of planetary temperature to CO2 level?
You’d have to be blind not to see it.

Reply to  Jack Davis
July 1, 2017 8:09 pm

You have the cart before the horse. There is a sensivity of CO2 levels to planetary temperatures. This is well-known and understood.

Reply to  Jtom
July 2, 2017 11:19 pm

“Understood” by the science [snip] on this website – refuted by science.
[Reply: Certain pejoratives are prohibited on this site. Be nice and we won’t call you names either ~ mod ~ but some of you can guess who ~ yeah I’m back for a couple of months]

Reply to  Jtom
July 2, 2017 11:40 pm

K. Understood. Impressed you didn’t cull it completely.
Reply: Booyah ~ mod

Patrick MJD
Reply to  Jack Davis
July 2, 2017 12:24 am

“Jack Davis July 1, 2017 at 5:01 pm
180 ppm put us in the freezer, 280 ppm is the norm during interglacials…?
Evidence for this is where?

Reply to  Patrick MJD
July 2, 2017 11:14 pm

“180 ppm put us in the freezer, 280 ppm is the norm during interglacials…?
Evidence for this is where?”
It was stated in the article at the head of this discussion.

Reply to  Jack Davis
July 2, 2017 12:44 pm

Jack: Variation of atmospheric CO2 with temperature is unrelated to what effect CO2 has on temperature as a greenhouse gas. Even IF CO2 were not a greenhouse gas, its solubility in oceans as a function of temperature would remain.

michael hart
July 1, 2017 5:31 pm

Note that the pH changes associated with all that extra CO2 (concentrated in shrunken oceans) also didn’t cause terrible “‘ocean acidification” extinctions. The coral reefs are still with us.
The amount of extra CO2 would have come not only from the atmosphere itself but also from the water that was condensed in the ice sheets, because solid ice cannot contain the same amount of CO2 that can dissolve in liquid water (either fresh or saline).
Then there is all the extra carbon dioxide that would have come from the forests as they were swept from the landscape. Thus, massive changes in the carbon sources and sinks and yet no chemical disasters arising from CO2. This give sthe lie to the current scare stories about how extra CO2 would impact the oceans. The biosphere has seen it all before and took it in its stride.

Martin Hertzberg
July 2, 2017 1:55 am

Current CO2 measurements are direct air samples and are accurate. Vostok values are from bubbles trapped in ice for many centuries. Lots can happen to those trapped gases and so the absolute values for the Vostok data cannot be too accurate. However the relative values between Glacials and Interglacials are probably OK.

Patrick MJD
Reply to  Martin Hertzberg
July 2, 2017 5:52 am

“Martin Hertzberg July 2, 2017 at 1:55 am
Current CO2 measurements are direct air samples and are accurate.”
How many sites? Mauna Loa? How many meters above sea level?

Robert W Turner
July 2, 2017 9:01 am

Most crop plants are angiosperms and have evolved over the past 100 million years, not 400 million. Some crops, i.e. corn, are C4 pathway plants that evolved in the past 20 million years. C4 photosynthesis evolved independently in several plant families, suggesting that global CO2 levels directly led to this evolution.

Reply to  Robert W Turner
July 3, 2017 11:42 am

Corn is a hybrid of two other grass species. They evolved for millions of years, but corn was created by crossing them perhaps inside 10,000 years (exact date uncertain and some guesses as short as 5000 years). This article claims residue found about 9000:
The cross has been recreated in the lab, BTW. A big deal as this means a whole lot more genetic material is now available to corn breeders. Teosente and some other grass.
This doesn’t detract from your point, it only adds an interesting detail of the process and path. Many food crops are inter species hybrids. Look up the Triangle Of Wu, three species (mustard, cabbage, turnip) crossed in pairs to give the brassicas… kale, chois, rutabagas, broccoli, cauliflower, etc.

Reply to  Robert W Turner
July 3, 2017 12:03 pm

E. M.
You have more recent information than I, but IMO maize is not a hybrid at all, but simply results from domestication of teosinte by selective breeding (artificial selection). Indeed,their genes, ie protein-coding sequences, might well be the same.
Hybrids of maize and teosinte are used for research purposes, but in terms of “genes” they are variants of the same species.

Reply to  Gabro
July 5, 2017 1:03 am

Thankfully, opinions are of little importance.

MONTREAL — The scientific puzzle pieces are fitting together to form a definitive picture of the origin of corn, says a Duke University plant geneticist who has proposed that the world’s most important food crop originated in an ancient cross between two grasses.
Mary Eubanks described the latest evidence that corn, or maize, originated as a cross between teosinte and gamagrass, or Tripsacum, in a talk Friday, April 2, 2004, at a symposium on maize held at the annual meeting of the Society for American Archaeology ( in Montreal. Her research is supported by the National Science Foundation and the North Carolina Biotechnology Center.
Eubanks, an adjunct professor of biology, has developed evidence that modern corn, scientific name Zea mays, did not evolve solely from a Central American grass known as teosinte — traditionally the most widely held theory. Rather, her experiments clearly demonstrate that corn arose from a serendipitously viable cross between teosinte and gamagrass.

July 2, 2017 1:49 pm

wrt Gobbekli-Tepe. Cutting raw rock with only stone tools is immensely labor intensive. The question is how to feed these folks. Seems there are two possibilities. You get the work done fast, which means a lot of people working full time at it and not producing squat as food. So you hunt to feed them. How long until the area is hunted out? How far can you haul a dead deer, should you have to go further and further to find one, and still have it edible? Two days?
The alternative is to have a few people working for decades or centuries and so feeding them isn’t a problem. It does, however, presume a culture which will keep the effort going for decades or even centuries.
Rejigger the date of the Neolithic, seems like the best bet.

July 3, 2017 11:19 am

Loved your 1500 years book!
When I first got started looking at “global warming” I ran into Bond Events and similar periodic cycles. Then ran off to Barnes & Noble looking for more on “global warming”; saw the title, and had to buy it. That was the moment I turned from “puzzled seeker” to informed understanding.
Thank you for that.
Anyone who looks at the horrific conditions during glacials will understand cold is bad, horribly bad. Anyone who goes to vacation hotspots already knows warm is good. Very very good.
Just look at the preferred locations. Florida, Brazil, Italy, Australia, etc. etc. Hot, sunny, beaches and forests.
Where are the people in California? Not in the cold mountains, not in the cool north, but in the hot southern desert… Where do folks go to retire? Phoenix Arizona and southern Florida. I was in Phoenix when it was reported at 125 F at the airport and the tarmac taxiways were melting, so they shut down. The family went to a cactus garden in the morning, then the hotel pool that afternoon. Mornings and evenings were glorious!
(It was a bit funny in the pool, though… they had dark tile stripes so it solar heated, but that isn’t adjustable… the hot tub, though, by law had to be no more than 104 F… so we would dip in the hot tub to cool off! The pool was about 114 F. Get wet, then sit in the shade and you cool off a lot.)
Nobody in our party (nor anyone we met) was particularly bothered by the heat. This means that everywhere ELSE has a long ways to warm before they are too hot… At worst, you take a long lunch and siesta from about noon to 3 PM, dinner at 9 pm… like traditional Mexico…
The notion that hot is bad is just crazy and defies common experience. Very few people choose to vacation in Siberia in winter… many are found in Miami in summer.
That we are positioned at the very end of the interglacial cycle time line is the problem. That ought to be what folks work to fix. IFF CO2 were a “greenhouse gas” (an oxymoron as gasses convect but glass does not) then the proper thing to do is burn all the carbon we can find. Unfortunately, that is unlikely to stop nature from returning to the freezer…

Reply to  E.M.Smith
July 3, 2017 11:28 am

The Holocene is liable to last at least 3000 more years and possibly 30,000 or longer, depending upon which Milankovitch cycle rules.

Reply to  Gabro
July 3, 2017 12:21 pm

It is also just as valid to say it is already ending, given the historical cooling from the Holocene Optimum and the length of prior interglacials. I’ll take historical fact over hypothetical extrapolation of models, thanks…
The dominant state of global climate is glacial ( has been for about 1/2 million years of this Ice Age, with 100,000ish years of ice, then about 10,000 of warm). We are already below the level of insolation at 65N that keeps us warm. We are now in the unstable zone. If, at any time for any reason, we do not melt the north polar area in summer, we enter the next glacial. The only question is how much must stay snow covered through summer, and that amount decreases each year as obliquity changes.
Nobody knows when that day will come. Milancovitch gave us a method of understanding the mechanism, but not a stopwatch on the process. What we do know it that interglacials arrive in only one case: enough insolation in summer to melt the north polar glaciers. We are past that point in the cycle. It is over. Now it is just a waiting game to the first cold blip and then the plunge.
The Little Ice Age almost put us their. Some folks claim it was a Bond Event. IMHO, there is a half Bond Event cycle as well, and the L.I.A. was a half Bond Event (these show up in 750 or so year cycles of empires, wars, migrations, and famine through history). If that is valid, the next cooling will be a real full Bond Event, due to arrive after the present warm burst. Normally there is a warm spike, then a cold plunge. The present warm means the cold is comming… That could be as soon as this grand solar minimum. 540 A.D. + 1500 = 2040 A.D., at the outside. 536 + 1470 = 2006 A.D. as the earliest, which is about when “global warming” stopped… But these things are slow. Even a 750 year subcycle takes 10 lifetimes.
So you have a nice modeled conjecture, but I’d not bet on it with my life… It is just as likely that we get a full Bond Event in 20 years, the North freezes over, and the glacial begins.
FWIW, my best conjecture is that it holds off until about 2300 A.D. I won’t go into why, but there’s reason to think that’s going to be a cold turning point. (Lunar tidal changes of 1800 year cycles stir up cold ocean, or don’t, and that shifts currents).
IMHO, the most important warning shot was the L.I.A. The Roman Optimum was far warmer than now (they knew how to build central heating. It is missing from some of their homes in places that need it today) and the L.I.A. almost a glacial entry. Next cycle will be colder still. This isn’t a “static until it changes” process, it is a constant change to colder with a 1500 year sine wave overlay. Then an ice threshold glacial inception.
Now even if, by some magic, we avoid glacial inception for 3000 years, it will still be coldrr in the next L.I.A. than in the last one, and it will arrive on schedule. Either in a few years if it was a Half Bond Event, or in about 2600 A.D. if it was a full B.E.
Expecting continuous normal is as foolish as expecting continued warming. We are on a cycle machine in a downslope to cold. Exectly where in which cycle TBD…

Reply to  Gabro
July 3, 2017 12:33 pm

The problem is that historically, interglacials vary greatly in duration.
So far the 11,400 year-old Holocene hasn’t lasted as long as the previous interglacial, the 16,000-year Eemian, let alone the much longer interglacial of MIS 11. There have also been a few shorter than the Holocene since the mid-Pleistocene transition to longer glacial intervals, but they were more like double interglacials.
So history isn’t much of a guide.

Reply to  Gabro
July 3, 2017 1:26 pm

comment image
Shows past interglacials with a much sharper peak. IMHO, it was a meteor strike into the N.American ice field causing the Younger Dryas cooling that peak clipped ours. We have had an anomalous flat pattern due to that destruction of ice via impact.
The pattern of rapid down will resume, and looking at the width of peaks at the 0 line, the odds are highest for very soon. But as I pointed out above, exactly when is known to no one. It has a stochastic component. Volcanoes, meteor strikes causing lava flows or dust clouds, Bond Events arriving in sync with other cold pressures. One simply can not say when the end comes. All it would take is a shift of the Gulf Stream leading to ice build up. (As one example).
Now one might take solice from our flatter top, or become worried that we are already at the lower level of now. I’m hopeful the lack of downward momentum in temperatures is a benefit, but it could just as easily mean we can start the plunge without warning.
What is very clear is that the historical record gives much higher odds that we are very near the end and it is highly unlikely we have thousands of years left. Ice near Greece bringing down the Byzantine Empire, ice faires in England, year without a summer in New England: all those say we were on the edge of glacial inception. Orbital mechanics say the next dip will be even worse. Bad enough? That is not knowable.
So about “now”, or about 2300 A.D., or about 2600 A.D. are all very likely inception events (depending on the exact status of the Bond Event cycle and lunar cycle of orbit change). Could we get through those? Sure. But there are a lot of IFs… it is also possible that a 5000 year cycle must happen:
The interaction of Milancovitch cycles with lunar tidal cycles matters, and glacial inception can happen any ANY time they leave summer frozen in the northern hemisphere, since we are below the insolation limit.
I choose to look at the L.I.A and see a near miss. You choose to look at orbits and take comfort.
I see continued migration to a colder North from lower insolation. You choose to see stasis.
Cycles will continue. We are on the edge. It is a stochastic entry. Rolling dice is not predictable in details of any given roll…

Reply to  Gabro
July 3, 2017 1:37 pm

E. M.,
There is no convincing evidence of an impact at the YD and all the evidence in the world to see it as just another of the usual fluctuations during a normal deglaciation transition to yet another normal interglacial, cooler and so far shorter than the Eemian.
We have indeed been a cooling trend for at least 3000 years, but most likely have at least than long again before the next glaciation. Even if the next centennial-scale cool cycle be colder than the LIA, it still probably won’t take us back to glacial conditions. There is no reason to assume that we’re near a tipping point yet, based upon the tilt cycle, which appears to rule.
As noted, there are however those who favor eccentricity. If that cycle rules, then we’re in for a long warm spell, a la MIS 11. That would mean “natural” catastrophic climate change, with further melting of the Southern Dome of the Greenland Ice Sheet and maybe part of the West Antarctic Ice Sheet. But we’re talking tens of thousands of years.

Reply to  Gabro
July 3, 2017 2:02 pm is a good place to start looking.

Reply to  Gabro
July 3, 2017 2:16 pm

E. M.,
Been there. Done that. Nothing to see there.
It has all been hashed and rehashed repeatedly on WUWT.

July 3, 2017 1:52 pm

There is plenty of evidence for a Y.D. impact, if you choose to look. From the Clovis extinctions, to massive dust layers, to a platinum group metals mine under the likely impact spot, to scour marks, to craters from ejecta and much much more. It also explains the flash frozen mammoth and jumbled stratigraphy as a tidal wave of ice slush arrived where they were living…
I don’t care to argue the point, only point out it is there for those who care to look.

Reply to  E.M.Smith
July 3, 2017 1:58 pm

I’m familiar with the alleged “evidence”, most of which is bogus. And the bit that isn’t doesn’t lead to the desired conclusion.
It can’t possibly explain extinctions, since megafauna on islands closer to the supposed impact area survived, while those far too far away to have been killed on other continents were wiped out. And of course the Pleistocene megafaunal extinctions occurred over thousands of years, or tens of thousands if you factor in Australia. And even longer if you consider Holocene extinctions.
The YD was just another meltwater event, no different from those which preceded and followed in during the Pleistocene-Holocene transition and prior deglaciations during the Pleistocene. No special explanation required. The null hypothesis can’t be rejected.

Reply to  Gabro
July 3, 2017 2:16 pm

“The desired conclusion” is an interesting phrase. For me, no conclusion is “desired”, only reasonable based on logic and evidence, or not.
Then you leap to all sorts of megafauna extinctions when I only referenced the Clovis extinctions. North America only, and more surviving the further south you go.
Like I said, you either care enough to look, or will remain wilfully blindered. Not my problem in any case.
The likely cause was Encke breaking up. We enter the most dense remnants with a thousands year period…
It returns periodically and adds to our history…

Dynamical calculations show that, as a Taurid-like orbit precesses, the northern daytime intersection occurs just a little (a few centuries) before the southern nighttime one, and the southern daytime one just before the northern nighttime one. That is, the four intersections occur in two pairs, and the influx of material to Earth is enhanced during epochs lasting a few centuries and spaced by a few millennia. The term “coherent catastrophism” has been used by astronomers at Armagh and elsewhere to describe the idea that there are strong patterns in the influx of extraterrestrial material to Earth.

“Coherent Catastrophism”, eh? Two pairs, separated by a couple of hundred years, returning every ‘few millenia’. Sures sounds like that ‘two impacts’ in 2200ish BC that Timo was talking about with a couple of hundred years between them.

But I’m sure you will not look… nor see…

Reply to  Gabro
July 3, 2017 2:33 pm

E. M.,
As noted, the island megafauna clearly falsifiy the YDI extinction hypothesis. And of course the pattern of extinctions in North America, as well as everywhere else.
The only potential physical evidence for this highly improbable alleged event is a platinum spike found in Greenland. The problem is that for one meteorite to have deposited so much platinum, there would have to be a crater, of which there is no sign. Hence, it appears to be a coincidence. Platinum rains down all the time in small meteorites. Also, there is no telltale osmium and far too little iridium at the time of the YD. Nor has a platinum excursion been found outside of North America.

Reply to  Gabro
July 3, 2017 3:02 pm
Reply to  Gabro
July 5, 2017 1:23 am

Yup, firmly snapped shut … why I wasn’t interested in arguing about it.
Do note that rarely are craters a mile deep, and the ice was that deep, so any ice impact would not be expected to leave a crater, but the scour marks that are seen.
BTW, I read those articles at the time published, more or less. Some interesting points, but hardly definitive. They leave far too many unexplained loose ends.

of platinum – an element associated with cosmic objects like asteroids or comets – found by Harvard University researchers in an ice-core from Greenland in 2013.
The South Carolina researchers found an abundance of platinum in soil layers that coincided with the “Younger-Dryas,” a climatic period of extreme cooling that began around 12,800 ago and lasted about 1,400 years. While the brief return to ice-age conditions during the Younger-Dryas has been well-documented by scientists, the reasons for it and the demise of the Clovis people and animals have remained unclear.
“Platinum is very rare in the Earth’s crust, but it is common in asteroids and comets,” says Christopher Moore, the study’s lead author. He calls the presence of platinum found in the soil layers at 11 archaeological sites in California, Arizona, New Mexico, Ohio, Virginia, North Carolina and South Carolina an anomaly.
“The presence of elevated platinum in archaeological sites is a confirmation of data previously reported for the Younger-Dryas onset several years ago in a Greenland ice-core. The authors for that study concluded that the most likely source of such platinum enrichment was from the impact of an extraterrestrial object,” Moore says.
“Our data show that this anomaly is present in sediments from U.S. archaeological sites that date to the start of the Younger-Dryas event. It is continental in scale—possibly global—and it’s consistent with the hypothesis that an extraterrestrial impact took place.”

July 5, 2017 8:01 pm

Appears the Taurid Complex has yet another stream that we cross twice a year. Cheers –

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