Amplification of Global Warming by Carbon-Cycle Feedback Significantly Less Than Thought, Study Suggests
from ScienceDaily (Jan. 28, 2010) — A new estimate of the feedback between temperature and atmospheric carbon dioxide (CO2) concentration has been derived from a comprehensive comparison of temperature and CO2 records spanning the past millennium.
The result, which is based on more than 200,000 individual comparisons, implies that the amplification of current global warming by carbon-cycle feedback will be significantly less than recent work has suggested.
Climate warming causes many changes in the global carbon cycle, with the net effect generally considered to be an increase in atmospheric CO2 with increasing temperature — in other words, a positive feedback between temperature and CO2. Uncertainty in the magnitude of this feedback has led to a wide range in projections of current global warming: about 40% of the uncertainty in these projections comes from this source.
Recent attempts to quantify the feedback by examining the co-variation of pre-industrial climate and CO2 records yielded estimates of about 40 parts per million by volume (p.p.m.v.) CO2 per degree Celsius, which would imply significant amplification of current warming trends.
In this week’s Nature, David Frank and colleagues extend this empirical approach by comparing nine global-scale temperature reconstructions with CO2 data from three Antarctic ice cores over the period ad 1050-1800. The authors derive a likely range for the feedback strength of 1.7-21.4 p.p.m.v. CO2 per degree Celsius, with a median value of 7.7.
The researchers conclude that the recent estimates of 40 p.p.m.v. CO2 per degree Celsius can be excluded with 95% confidence, suggesting significantly less amplification of current warming.
Journal Reference:
- David C. Frank, Jan Esper, Christoph C. Raible, Ulf Büntgen, Valerie Trouet, Benjamin Stocker, & Fortunat Joos. Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate. Nature, 2010; 463 (7280): 527 DOI: 10.1038/nature08769
Full story here at Science Daily
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hro001 (14:02:45) :
I think she has it around, just like the temperature-CO2 relationship…
The Earth has been cooling down (first). When the air is colder, less water can be loaded into that water. It would then be normal to find less water in the stratosphere. This is why in winter it is dryer. In fact, the upper troposphere has declined by 17% from 1948 to 2008 at the 400 mb pressure level. The absolute humidity follows temperature and not the other way around. I would never be able to heat up my house by evaporating water in it, in fact it would cool it down.
Where do these people get their diploma? boxes of crackerjacks?
I note that the feedback effect is measured in ppm CO2 in the atmosphere per degree Celsius. It seems to me that this is only half the loop. I would think the degrees Celsius temperature increase per one ppm CO2 increase would be the other half. I am guessing that would be a multiplier on the order of .0026 (about 1/380) to calculate the open loop gain of the feedback system. This would yield a net sub critical open loop gain of about .02 — far below the greater than unity open loop gain required for a run-away effect with positive feedback. Is this correct?
Chris H at 13:39, I have doubts about CO2 in ice cores as well. Where is the proof that the concentration of gas in a bubble trapped deep in ice is the same concentration as the atmosphere it was derived from? This seems to be the assumption of the scientists studying ice cores, but in the modern era, I don’t trust their assumptions without proof anymore.
Little error in my previous post… it should read “When the air is colder, less water can be loaded into that AIR.”
As can be seen on the image at the top CO2 varies with latitude. It is lowest at the poles mainly due to dissolution of CO2 into the oceans and no production of CO2 from terrestial sources. The ice core data is biased to towards low CO2. This is particularly shown by the disgraceful hockey stick like curve of Keeling. Beck,2007 showed (from actual accurate measurements) (see here http://www.biomind.de/realCO2/papers.htm ) that CO2 levels in the northern hemisphere around 1940 were similar to present levels, there also may have been higher levels a bit less than present around 1840. The recent paper by Massen and Beck,2009 (same source as above) shows how the past measurements relate to actual background CO2 levels which should silence any knowledgable scientific criticism of the 2007 paper. Proxies of CO2 or temperature can never match actual precision measurement made with all supporting data (such as wind speed, wind direction, temperature, pressure, time, location, insolence etc).
If actual measurements are considered over some 180years it will be found that there is no measureable connection between CO2 and temperature. The fact that over the last 10 or so years that CO2 has been increasing while temperatures have been steady or declining should be proof of that.
It will be very interesting over the next 10 years if sea surface temperature continue to decline to note if CO2 levels will decline which maybe expected from the natural cyclical variations of CO2 shown by past measurements.
I suspect that authors of the letter to nature were actually looking for a proof of a CO2 -temperature connection. It is a pity they have not published there work on a blog where it would be available for public scrutiny
Jeff L (13:58:40) :
If I read this post right, they have reduced the feedback by a factor of about 5x (40/7.7 = 5.19).
So instead of the IPCC forecast of a 4 deg C rise in temps over the next 100 years, we would be closer to 0.8 deg C …. right?
I think probably – wrong. This isn’t the the main “feedback” effect. That comes in the form of increased atmospheric water vapour, i.e. CO2 warms atmosphere -> warmer atmosphere can hold more moisture. A result from the Climate models is that relative humidity remains constant. If correct concentration of IR absorbing water vapour in the atmosphere will increase.
If there is a CO2 feedback factor incorporated into the models (is there??) it looks, from the numbers, to be at most about 20%-30% of the total.
John from MN (14:16:00) :
If I am not mistaken this is just one of several positive feedbacks the scientists use in their models to show such a large expected increase in Global Tempertures that are caused by increasing co2. And this feedback is a very small one. I see this as no game changer. But it is refreshing that the “Science is not Settled”!!!!!!!!!!……..John…..
I think you have it about right. This study doesn’t seem to be of any particular significance either way.
[quote Ray Boorman (14:48:55) :]
Where is the proof that the concentration of gas in a bubble trapped deep in ice is the same concentration as the atmosphere it was derived from?
[/quote]
There’s also the the assumption that each layer of melting and refreezing seen in the ice cores equals “Winter/Summer”. Is this really the case? It seems to me that “Melt/Refreeze” = “Hot/Cold”, which isn’t necessarily the same as “Winter/Summer”. It can get hot and cold more than once per year.
So these “800,000” year ice core records may not actually be 800,000 years. They may not even be close to that.
I’d have to say that for Ice Cores, I agree with Tom Wigley that they’re nearly 100% useless as a climate proxy.
But wait. I thought the science was settled. Now I’m all confused.
After following the Science Daily link, I found this Related Story:
Am I reading this right? Only about seven months ago, there was revealed a linear relationship between “carbon” and temperature, leading to a maximum amount that civilization should be allowed to release, for all time? And this really was published in Nature, as straightforward honestly-true science?
——–
@ur momisugly Lucy Skywalker (14:31:47) :
I have read now how the models of carbon isotopes used for tree ring reconstructions should not be absolutely trusted. Then there is the idea that a trace gas in an air bubble in ice should stay at the same concentration for hundreds and thousands of years. And even in the recent past, we can see what was done to the thermometer readings.
It is truly a testament to the utter weakness of AGW theory that we can tear it apart using their own data, even that which we can clearly see has been biased in their favor or should otherwise be considered far from perfectly accurate.
The gain is too small. There is a lot more gain from the CO2 -> warming -> water vapor –> warming –> water vapor –> … feedback loop.
400ppm to 500ppm leads to thermal runaway? Not credible.
kadaka (15:25:08) :
“Matthews, together with colleagues from Victoria and the U.K., used a combination of global climate models and historical climate data to show that there is a simple linear relationship between total cumulative emissions and global temperature change.”
In essence they might have just confirmed what the guys at CRU and GISS did in generating the hockey stick… If their relationship is based on the manipulated global temperature data, it is worth nothing.
I haven’t had time to wander down to the library to read the original paper, but if they are using the unreasonably featureless temperature reconstructions of the various hockey sticks over the time period 1050 to 1800, then actual CO2 feedback could be zero or even negative.
Talking about warming being exaggerated, we have fog in Wellington that has grounded planes and this is the second time it has happened in a week. Now fog in Wellington may not be unusual, but fog in Wellington at the end of Jan, when we are in the height of our summer? – I would imagine that is unusual.
John Finn (15:00:45) :
I have to admit I didnt have time to scrutinize the details of the paper so I might be somewhat off-base the magnitudes in my comment, but the author’s conclusion was that climate sensitivity to CO2 is much lower than used in climate models currently – that I am sure of.
That being said, I do recall reading somewhere else ( I wish I could remember the reference, but I cant at this time – someone else feel free to post a reference) that forecasted temperature rises in the models were dominated by feedbacks – something like 3 deg C of the total 4 deg C temp rise forecast by 2100 was from feedbacks. So if we reduce that 3 deg C by substantial amount (need to review the paper in more detail to quantify), then you have eliminated the majority of the forecasted warming.
My main point is that other independent datasets suggest exactly the same thing – the the climate sensitivity to CO2 is much lower than what is modeled thus the magnitude of any warming will be significantly less than represented
As I see it the feedback effect relates to a global mean temperature. If we increase the CO2 in the atmosphere one part per million, then on the assumption that we get one degree Celsius global mean temperature increase per each doubling of the CO2 concentration, I am assuming that a one PPM increase will cause a .0026 degree Celsius increase in temperature.
Given that we see a 7.7 PPM increase in CO2 concentration per degree Celsius, I am assuming we would see .02 PPM additional CO2 concentration increase caused by the resulting temperature increase.
The closed loop feedback gain would be 1/(1-.02) or 1.0204 PPM net CO2 increase per PPM that we actually add to the atmosphere.
“it’s less than we thought”
I have no problems with this as long as it’s unprecedented.
At least, it’s robust!
According to the commonly discussed theory, why wouldn’t this continue to runaway?
Because temperature, energy, and power are not a linear relationship. The amount of power in watts/m2 required to maintain a 1 degree rise in temperature increases with temperature in degrees K raised to the power of 4 multiplied by a constant. This is due to any object being heated up radiating energy back at its environment. The equation is for an ideal Black Body, which the earth isn’t, but close enough to make the point:
273 K (0 degrees C) + 1 degree => 4.7 watts/m2
283 K (10 degrees C) + 1 degree => 5.2 watts/m2
293 K (20 degrees C) + 1 degree => 5.8 watts/m2
303 K (30 degrees C) + 1 degree => 6.4 watts/m2
So the system can’t run away because an exponential increase in energy is required to maintain a linear increase in temperature.
At the same time, CO2 increases suffer a diminishing effect. The CO2 can only absorb the energy being radiated at it. Additional CO2 can only absorb with the original CO2 left behind. So increasing amounts of CO2 have steadily decreasing amounts of energy to absorb. If the relationship were strictly linear, you could absorb more energy than what is being emmited. Einstein would come back from the grave to see how you did it.
Water vapor is slightly more complicated as it is a greenhouse gas and the amount the atmosphere can “hold” increases exponentially with temperature, about doubling for every 10 degree C rise in temperature. But is suffers from the same law of diminishing returns as CO2. The more it absorbs, the less is left to work on.
At end of day ALL greenhouse processes hit an absolute max, while the amount of energy required to generate another 1 degree increase keeps going up. Hence no runaway or tipping point. UNLESS you have enough energy to boil the oceans. In which case humanity will have ceased to exist long before you got there.
Ladies and Gentlemen, please! When someone on the world stage is attempting to leave the room by crawling on hands and knees on the floor, through an angry mob, and attempting to be as inconspicuous as they possibly can, do not kick and spit at them, think of their innocent loved ones and the fact that they’ll be working at Walmart for the nex thirty years under an assumed name.
“Rudolf Kipp (12:51:30) :
The German Der Spiegel had a story on this yesterday. They did admit, that the feedback effect would be smaller than previously thought, but:
There would be absolutely no reason to take back any previous warning, because:[…]”
Great! The more confused the reasoning becomes, the faster people will just refuse to believe it anymore! They’re arguing themselves into contradictions faster than you can say enough already.
“”” Lucy Skywalker (14:31:47) :
Chris H (13:39:26) : I presume that these 1000 year old “atmospheric” CO2 levels come from gas bubbles in Antarctic ice cores? CO2 is very soluble in water and diffuses very quickly through aqueous solutions. I find it very difficult to believe it hasn’t equilibrated to a very large extent with the air and must, therefore be a very poor reflection of the CO2 level at the time the bubble formed.
Someone please tell me I’m wrong. “””
Well the problem is that CO2, and other things like salt, is a whole lot less soluble in the solid phase of H2O; aka ice.
When a typical liquid freezes, any minor impurities in it segregate into a portion in the liquid, and a portion in the solid phase, and typically the equilibrium greatly favors the impurity remaining mostly in the liquid phase. This is not unlike the way Henry’s law dictates the equilibrium between components of the gas phase (atmosphere) and the liquid phase (ocean, to set the solubility of CO2 in the ocean.
This “Segregation coefficient” typically highly favors the impurity molecules remaining in the liquid phase.
Now I am sure some PhD chemist Post Grad, will trundle out an example of where the impurities abhor the liquid phase, and clamor to climb aboard the soild side of the interface. Well all such inputs are invited; I love learning stuff all the time.
Suffice it to say, that in the dim distant past, I used to work for a company that made multi kilograms of very high purity single crystal Gallium Arsenide by the so-called gradient freeze process, which is a variant of the Horizontal Bridgeman method of growing a single crystal out of a melt. And in the process, as the liquid/solid interface moved along the growing crystal; all of the crud in the compound, maybe as much as one part in a million, congregated in the liquid, which slowly got crudddier as the crystal grew, and the liquid phase shrank; but the solid crystal was amazingly free of impurities.
And just for good measure; since we were very green even back there in the 1970s, we recycled all of our scrap Gallium Arsenide, and epitaxial Gallium Arsenide Phosphide wafer scraps to reclaim the raw Gallium, which is a normal by product of the Aluminium smelting business.
And for the final clean-up of the reclaimed gallium, we purified it using a fractional crystallization process, whereby we froze the Gallium, to once again segregate out impurities into the remaining “slag” that was left over after freezing.
The effect is so striking that the final crystallized raw gallium was 7-nines purity; aka 99.99999% pure Ga metal (which can be either solid or liquid at room temperature). That was even better stuff, than we could purchase from our industrial raw materials suppliers (who made really good stuff).
So CO2 is not very welcome in water ice; and it is this high abhorence of the solid phase for such interloper molecules, that ensures (to the extent that it does) that the CO2 in the atmosphere bubbles contained in voids in the ice, diffuses so slowly through the solid ice, that it can be entombed for geological time scales with little loss.
Now that still leaves the open question of just how good a job the undertaker did of embalming that CO2 in the first place, and preserving its character for long enough to build an ice casket around it.
So yes I think it is fair to be somewhat suspicious of ice core gas compositions; but mostly as to the compositions and amounts; and less so to the actual timing of events.
But thermal runaway from CO2; start worrying about that around the time when this planet gets rid of all of its oceans.
Until then “It’s the Water; stupid !” (not directed at anyone in particular.)
273 K (0 degrees C) + 1 degree => 4.7 watts/m2
283 K (10 degrees C) + 1 degree => 5.2 watts/m2
293 K (20 degrees C) + 1 degree => 5.8 watts/m2
303 K (30 degrees C) + 1 degree => 6.4 watts/m2
Also, remember that the above is for an increase from THAT starting point. The amount of energy needed for the total temp change is cumulative. I was just making the point about the incremental. To look at it another way:
273 => 283 = 49.5 watts/m2
273 => 293 = 104.6 watts/m2
273 => 303 = 165.6 watts/m2
IPCC claim => doubling CO2 = 3.7 watts
IPCC claim => results in tripling from water vapour = 11.1 watts
IPCC claim => about a 3 degree rise
But if you double it again, you do NOT get another 11.1, you will get something less, while the amount of w/m2 to get a 1 degree rise keeps going up.
I forgot to say that when growing a single crystal out of a melt of high purity materials, it is a fact of life that the temperature at the liquid/solid interface is almost exactly equal to the freezing/melting temperature for that material. Hey I use the word “almost” to give myself some “wiggle room”
What do I know, there may be some “work function” or the like in quantum mechanical parlance; that offsets by some amount; but basically, that is the definition of melting/freezing temperature; the temperature at which the two phases in contact are in equilibrium; neither growing nor shrinking.
And as we all remember, a recent bunch of rocket scientists blowing gigantic holes in Antarctic floating ice, (using hot water or steam to burn the holes), to measure the water temperature; made the remarkable new discovery, that the water temperature adjacent to the ice was very close to the freezing temperature of salt water; who would ever have imagined that could be so.
And they likely discovered that with help from a government grant , ultimately coming out of my tax dollars; or yours even.
What this abstract doesn’t do is quantify the time scale in which such feedback takes place. It is famously (by now) known that CO2 lags temperature by 800 years. Not that it takes 800 years for the Henry’s Law constant to change when temperature changes — but that is roughly how long the global system takes to approach equilibrium when a radical change is wrought upon that constant by a temperature change.
Assuming this feedback is derived from the correlated CO2 after the 800-year lag, then one has to moderate the feedback, on a short timeline, by even more than this. In 100 years only a fraction of the CO2 feedback will manifest. So, while a feedback of (let’s say) 8 ppm is the technical consequence of a 1 degree C increase in temperature, under the most basic linear interpolation (wrong I know, but this is only for discussion) perhaps only 1 ppm actually shows. The effect of 1 ppm versus 380 ppm of an extremely weak GHG is less than negligible — even the modellers can’t forcefully extract any significant warming from that!
“”” M. Simon (12:42:56) :
Since the response to CO2 is a log function it implies that the positive feedback effect will decline with increasing concentrations. And in any case it is a minor factor compared to water vapor. “””
Can you cite a reference to any graph of Log (CO2) verus global mean surface temperature (T) that plots as a straight line.
Well I mean a graphs that is a better fit to the data, than say a linear CO2 versus Temperature or even a parabolic fit (either way up).
We have since the precambrian some 600 million years ago, some sort of proxy data for CO2 in the atmosphere covering a range from around 7000 ppm to a low of well below the recent 280 ppm which is considered sacrosanct. That si maybe five octaves of CO2 doubling, so that shoulkd yield a wing ding logarithmic graph verus temperature.
So please SOMEBODY show us a plot of any such logarithmic relationship, ever having been observed.
In recent decades, of actual measured data, we have so far seen less than 1/2 of one octave of CO2 doubling; so we are not in too good a shape to say it is a logarithmic relationship, rather than linear or any other ersatz mathematical function. Heck for all I know the relationship might better fit a Legendre Polynomial or maybe a Bessel Function or Tchebychev Polynomial.
Let’s have a show and tell of people’s logarithmic relationship measured data.
Otherwise, be done with this “climate sensitivity” mythology.