From the UNIVERSITAT AUTONOMA DE BARCELONA and the “department of settled science” comes another global climate thermostat story. Just last week, we were told the Earth had no thermostat. Gotta love it when climate science is so robustly definite, eh?
Ice age thermostat prevented extreme climate cooling
Atmospheric CO2 concentrations swung over a range of 100 ppm (parts per million, by volume) during the ice ages. The exact processes behind this variation have been difficult to pinpoint, but it is known that changes in the storage of carbon by photosynthetic organisms played an important role.
“When we took a close look at measurements from ice cores, we noticed that atmospheric CO2 concentrations hovered close to 190 ppm during much of the past 800,000 years, but very rarely fell any lower,” said Sarah Eggleston, a researcher at the Institut of Environmental Science and Technology (ICTA-UAB) and co-author of the study. “This was surprising, because it suggests that these very low CO2 concentrations were quite stable. What’s more, we know that CO2 was often very high in the distant geological past, but we have no evidence that CO2 concentrations were ever lower than 190 ppm.”
“We know that, over hundreds of thousands of years, CO2 is regulated by slowly reacting with exposed rocks” explained Eric Galbraith, lead author of the study and an ICREA professor at ICTA-UAB. “But this would be too slow to explain the stability during periods of only a few thousand years, as we see in the ice cores. So it must have been some other mechanism that kicked in at very low CO2.”
The authors suggest that it was most likely the biosphere that maintained habitable temperatures, since at very low CO2 levels, plants and phytoplankton struggle to photosynthesize. Slower growth of these organisms would have meant less carbon in the soils and deep ocean leaving more in the atmosphere, and preventing CO2 concentrations from falling further. This might have prevented extreme cooling that would have led to Earth freezing over as a ‘snowball’.
However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.
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A lower limit to atmospheric CO2 concentrations over the past 800,000 years
Global temperatures and atmospheric CO2 concentrations varied widely over the glacial cycles of the past 800,000 years. But despite this variability, Antarctic ice cores have shown that CO2concentrations were very similar during all the coldest points of these cycles. Remarkably, the recurring minimum CO2 concentrations (190 ± 7 ppm) fall on the lower bound of any known in Earth history. Here we show that although the volume of terrestrial ice sheets was normally distributed over the past 800,000 years, as might be expected from the approximately normal distribution of the orbital forcing that drove the glacial cycles, Antarctic temperatures have a strong cold mode, whereas CO2 concentrations have both a cold mode and a central mode. Although multiple explanations are possible, the recurring CO2 minima and pronounced cold modes are consistent with a strong negative feedback to decreasing CO2 that resisted further cooling on timescales shorter than 10,000 years. We suggest that one possible negative feedback is CO2-limitation of photosynthesis, either directly or via CO2-limitation of N2 fixation, which could have inhibited further lowering of CO2 by reducing carbon storage.
Full paper: http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2914.html (paywalled)
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If climate change were caused by so called greenhouse gases then the gas of most concern would be H2O and not CO2. But there is no evidence that a radiant greenhouse effect exists anywhere in the solar system so the AGW conjecture is nothing but science fiction.
I’d hypothesise that the historic atmospheric CO2 minima of ~190ppm suggests an equilibrium model in which, as the earth and it’s oceans cool, increasing amounts of CO2 is released from the oceans causing atmospheric re-warming. Accordingly it is the ocean temperature vs. ocean CO2 concentration that buttresses this lower atmospheric equilibrium. There are other variables such as significantly lowered sea levels, higher volumes of land ice which mean less sea volume to absorb CO2.
An equilibrium for a CO2 maxima may or may not exist. Hopefully, at the point that all land ice melts, a maximum concentration of CO2 that can be absorbed by the ocean’s could be an upper equilibrium limit. But this would completely depend on absolutely no further burning of fossil fuels (or extinction of humans) and that we forests can regrow at a faster rate to act as a carbon sink. However there will be complications with ocean acidification, a much reduced land mass for those forests due to significantly higher sea levels, and a much larger sea volume to absorb atmospheric CO2.
Unfortunately, while we can hope for a maxima equilibrium, we certainly have one, but perhaps two examples of runaway greenhouse effects that have previously occurred! Definitely Venus. And possibly Mars.
There is no thermostat. Discussion of thermostats is just anthropomorphism. It is not science.
Do you… both Venus and Mars had an ocean of water. The one thing, at least that is different about the 2 is that neither one has a magnetic field. ( or very slight). Here on this planet, if you remember, the science back in the year 2000 that by now we should have been approaching a tipping point. The Bode formula that amplifies the temperature in the models requires an additional input of energy. Where are you getting that energy from ?
Further you don’t have the slightest idea with what’s happening with the co2 sinks. So many scientific conjectures from 2000 about co2 are no longer spoken of. And the rest of the really hard questions aren’t addressed. How do you address the last 60 years of co2 following temperature? How do you address the ice core samples co2 lags temperature by 800 years ? Manipulate the data? How do you address the year over year growth of co2 by 1 billion metric tons and the co2 ppm per year is not reflected in the the current record ? Something is definitely not right. I was fully expecting that co2 ppm for 2016 to be 5 or possibly 6 ppm, from the amount of anthropogenic co2 and from an el nino. They either manipulated last year’s co2 record or there is something serious going on that no one has a clue about.
We didn’t have a runaway greenhouse effect when co2 was 1700 ppm. Unfortunately, since that time, or fortunately for us, the world did just the opposite, it got colder.
No one ever mentions 14CO2 is continuously created in the upper atmosphere during quiet sun periods.
Anyway, can someone please point me to an explanation, real science please, of how radiation from CO2 in the cooler atmosphere can warm the much warmer earth below. It certainly can’t warm 70% of the water covered earth, so that implies, to my layman thinking, that only 30% of the CO2 in the atmosphere is doing all the currently claimed anthropogenic global warming.
Richard111, here is an explanation, real science, of how radiation from CO2 in the cooler atmosphere can warm the much warmer earth below (and it certainly does warm both the oceans and the land):
https://wattsupwiththat.com/2016/10/25/mit-traditional-incandescent-light-bulbs-reinvented-may-make-a-comeback/#comment-2327676
Thanks daveburton. Colour me translucent as that lot went right through me.
Equating CO2 in the atmosphere with a doped composite crystal mirror in a hi tech light bulb is going too far.
The fundamental reason cooler things do not raise the energy of warmer things is entropy. Exchanges of photons take place, but the system works to reduce the gradient–the energy of position–the potential energy.
I would have thought this process was too obvious to get a paper published about it. It is just CO2 Fertilization Feedback (“greening”).
People forget that it works both ways:
1. The more CO2 there is in the atmosphere the faster plants remove it. (Reduces warming.)
2. The less CO2 there is in the atmosphere the slower plants remove it. (Reduces cooling.)
Negative feedbacks do not just reduce warming, they also reduce cooling. In other words, they increase climate system stability.
There are always oxidation processes (fires, rotting organic matter, animal respiration, etc.) going on, which produce CO2. So when the photosynthesis rate drops below the point where the plants can keep up and use as much CO2 as is produced, the CO2 level goes up, causing the photosynthesis rate to increase. That feedback loop limits how low CO2 levels can get.
Every schoolchild learns that animals use O2 and produce CO2, and plants do the opposite. But have you ever wondered why there are more than 500 O2 molecules in the atmosphere for each CO2 molecule? Nearly all of the oxygen in the atmospheres of Venus and Mars is in the form of CO2, and almost none is O2, but on Earth it’s just the opposite. Why is that?
It is because Venus and Mars are dead planets. But on planet Earth carbon-hungry living things have used up nearly all the CO2, to get the carbon, discharging the O2 as a waste product. The plants outnumber us animals, and they used up the CO2 until they ran out, practically speaking. They used up CO2 until the level got so low that the photosynthesis rate was reduced to rough equilibrium with the CO2 production rate. It is a very obvious, very fundamental, negative feedback system. The chronic shortage of CO2 is the fundamental limit on plant growth, on planet Earth.
This statement from the article is nonsense: “the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”
CO2 Fertilization Feedback works both ways. With CO2 high, as it is now, CO2 Fertilization Feedback is removing a large portion (AR5 estimates 27-29%) of anthropogenic CO2 emissions from the atmosphere, each year. The only reason that CO2 levels are continuing to climb is that we are producing prodigious amounts of CO2. It’s not that the negative feedback isn’t working, its simply that we’re currently overwhelming it with the huge amounts of CO2 we’re releasing.
That can’t go on forever. We’ve only added about 120 ppmv of CO2 to the atmosphere, and CO2 fertilization feedback is already removing CO2 from the atmosphere very rapidly — just not as rapidly as we’re adding it. But as CO2 levels climb, the negative feedbacks which remove it operate faster and faster, making it progressively more difficult to raise CO2 levels. That’s why I doubt that mankind will ever manage to drive CO2 levels much above 600 or 700 ppmv.
When CO2 levels go up, two things happen:
1. The warming effect of additional CO2 diminishes logarithmically.
2. The CO2 removal rate by natural processes, including “greening” and dissolution in the oceans, increases.
So it is easy to see why it is an inherently stable system.
Venus and Mars are dead planets because there is no magnetic field to protect them from the solar wind.
Still no word on why we had a MWP and a LIA. Outside of a Yellowstone going off, the orbit of the earth, the tilt, activity of the sun, a large rock falling out of the sky, where we are in the galaxy, it’s stable.
rishrac wrote, “Still no word on why we had a MWP and a LIA.”
It could be solar effects, at least in part. We don’t have good sunspot observations from during the MWP and earlier, but there’s at least a noticeable correlation between increasing solar activity and the Earth’s emergence from the LIA.
http://www.sealevel.info/Sunspot_Numbers_2015_whiteBG.png
http://www.sealevel.info/resources.html#solar
The recent warmup, also referred to as the current warm period, CWP, has implications on AGW. AGW has asserted that temperatures are solely controlled by co2. When asked about the MWP and the LIA, their answer was that it was local and not world wide. After it was shown that both were indeed world wide, the next line was that the MWP wasn’t as warm as it is now. The evidence indicates that it was warmer. And there is no question the LIA was cold.
The problem for AGW is what was happening then to make it warmer that isn’t happening now. It obviously wasn’t co2. If it was, they’d have to point to a source. My research into the co2 record has me wondering if the co2 record over the last 1000 or so years is correct. I’m wondering if they didn’t flat line the co2 record along with the temperature line. In the last 60 years there is a delta movement in the co2 that moves with temperature. I am certain of that.
{Sigh!} Pollution is a real problem, and “Eric”‘s sky-dragon-slayer gibberish is a prime example. It’s thread pollution. (Is that you, Doug?)
[no, it’s not Doug, but another person known to us who uses fake names, fake emails, and fake IP addresses to get his inane comments through. Comments deleted due to site policy violations, thanks for the heads-ups – mod]
It amazes me that it is so often overlooked that the earth itself is a heat source. Ice is also an insulator. The combination means that glaciers and ice caps are always melting from the bottom, and a ‘snowball earth’ is doomed from beneath, regardless of the composition of the atmosphere.
“However, the study did not reveal a corresponding regulation during the warm portions of the ice age cycles, suggesting that the Earth does not have a similar mechanism to prevent rapid warming.”
The mechanism to prevent rapid warming is called clouds.
Themostat, I’m surprised these global warming types don’t blame it all on a pair of dead AA batteries!
Thermostats are ok when they limit cooling…