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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In my example, it will not continue to run-away because a 2.04% increase is *all* you get from positive feedback. Using the values I have assumed, the open loop gain appears to be about 2% of the gain required to cause a run-away effect. Also, the logarithmic CO2 temperature sensitivity will reduce the open loop gain even more as the CO2 concentration increases.
I am surprised that my calculated open loop gain works out to be a number 50 times less than the run-away point given the public worry about this.
For the people pondering the water vapour “positive feedback”: This is pure fabrication. Higher GHG leads to heat trapped closer to surface. If the energy is closer to the surface, it cannot be at the same time higher up, in other words, heating below means cooling above, all other things being equal. This leads to the mysterious drying of the stratosphere that the good people at Nature are still pondering about. A reduction in water vapour caused by an increase in CO2. NEGATIVE feedback there. See Ferenc Miskolczi. Don’t have my link collection handy; search for Miskolczi in WUWT’s search box.
As the feedbacks get discredited one by one, the GCM programmers will have a harder and harder job to make their models do a correct hindcasting and at the same time still project runaway meltdown for the future. Yes, i do assume that that is their explicit mission to preserve their funding. Probably they can only manage these conflicting goals by introducing more and more invention, i.e. fudge factors into the models.
Water vapour a ‘major cause of global warming and cooling’
http://www.dailymail.co.uk/news/article-1246904/Water-vapour-responsible-slowdown-global-warming.html
Water vapour a ‘major cause of global warming and cooling’
By David Derbyshire, Daily Mail
Last updated at 11:34 PM on 28th January 2010
Climate scientists have overlooked a major cause of global warming and cooling, a new study reveals today.
American researchers have discovered that the amount of water high in the atmosphere is far more influential on world temperatures than previously thought.
Although the findings do not challenge the theory of man-made global warming, they help explain why temperatures can rise and fall so dramatically from decade to decade.
Breakthrough: Scientists have discovered a link between humidity and the global temperature
Breakthrough: American scientists have discovered a link between water vapour and the earth’s temperature
The study, published in the journal Science, says a 10 per cent drop in humidity 10 miles above the Earth’s surface explains why global temperatures have been stable since the start of the century, despite the rise in carbon dioxide in the atmosphere.
And a rise in water vapour in the 1980s and 90s may also explain why temperatures shot up so quickly in the previous two decades, they say.
Water vapour has long been recognised as an important greenhouse gas. Like methane and carbon dioxide, it absorbs heat from the sun that would otherwise be reflected back into space, keeping the planet warm.
However, most computer models that predict climate concentrate on the levels of water lower down in the atmosphere.
Dr Susan Solomon, of the US National Oceanic and Atmospheric Administration, said: ‘Current climate models do a remarkable job on water vapour near the surface.
‘But this is different — it’s a thin wedge of the upper atmosphere that packs a wallop from one decade to the next in a way we didn’t expect.’
Observations from weather balloons and satellites show that ‘stratospheric water vapour’ increased in the 1980s and 1990s and dropped after 2000.
The changes took place in a narrow altitude region of the atmosphere where they would have the biggest impact on climate.
The reasons why water vapour rises and falls remain a mystery, the scientists say. However, the study estimates that the drop in water vapour since 2000 caused surface temperatures to rise 25 per cent more slowly than they would have done otherwise.
And the increase in stratospheric water vapour in the 1990s is likely to have accelerated the rate of global warming by around 30 per cent, the scientists say.
The stratosphere is a region of the atmosphere from about eight to 30 miles above the Earth’s surface. Water vapour enters the stratosphere mainly as air rises in the tropics.
Dave Britton from the Met Office said the study highlighted the complexity of climate science. ‘But it does not challenge the basic science that carbon dioxide and other greenhouse gases released from human activity are warming the planet,’ he said.
Dr Vicky Pope, head of climate science at the Met Office, said: ‘Whatever’s causing this change from decade to decade is having an influence at the surface. But it is a small variation on top of the long term increase in manmade greenhouse gases.’
If Planet Earth had no carbon-based life, then C02 would have only geology to sequester and release it.
But it does have carbon-based life, and any man-made attempts to sequester it also sequesters life itself.
Has any of these anti-Carbon Dioxide bents ever stopped to consider just how little Carbon-Dioxide in now present in the atmosphere?
Yes, it is less than they thought, in more ways than one.
OK. So a doubling of CO2 may raise the actual temp about 1C. Where do we start?
at 10 ppm?
50 ppm?
137 ppm?
If my world starts at 10 ppm and yours starts at 100 ppm, by the time I get to your starting point of 100 ppm, my world should be about 4.2C higher then yours at 100!!!!
Where does this CO2 doubling thing start?
well no doubling CO2 concentration always gets you the same “radiative forcing” however the amount required to double is different.
273->546
and then
546->1092
see that?
At least that’s how the theory goes.
This obviously invalidates all current AGW climate models. They will have to go back to the raw data and start again. Oh….
Ahh you mean the feedback, yeah that’s correct, the feedback weakens.
I stand corrected.
And now this: http://www.nature.com/news/2010/100128/full/news.2010.42.html
“Water vapour could be behind warming slowdown
Mysterious changes in the stratosphere may have offset greenhouse effect.
A puzzling drop in the amount of water vapour high in the Earth’s atmosphere is now on the list of possible culprits causing average global temperatures to flatten out over the past decade, despite ever-increasing greenhouse-gas emissions.”
This part is also very interesting: “In 1999, researchers at the University of Reading, UK, reported similar numbers to Solomon and her colleagues, suggesting that the increase in stratospheric water vapour could have boosted warming by 40% compared with carbon dioxide alone”
After tens of billions of dollars spent on AGW research they now have cast iron evidence. Unfortunately cast iron is very brittle, especially in cold weather, and tends to fall apart if struck!
Why not comment on the paper itself instead of articles based on the paper? This is not about climate sensitivity, but on defining the constraints on one feedback (carbon cycle sensitivity). It is based on temperatures and CO2 levels from the last millennium; reconstructions (and modeling) that seem to be reconstructions with which people here disagree. The caveat is that YMMV: release of CO2 may be different at higher temperatures. It is interesting to note that Knutti & Hegerl noted that sensitivity based on the last millennium tended to be on the low side, so maybe these results are consistent with the earlier papers.
RE Leo G (18:16:11) :
You can start anywhere.
OK. So a doubling of CO2 may raise the actual temp about 1C. Where do we start?
IPCC => 280 ppm = normal
IPCC => 560 ppm = double = 3.7 watts = +1 degree
“Anticlimactic (18:20:34) :
This obviously invalidates all current AGW climate models. They will have to go back to the raw data and start again. Oh….”
Too expensive. You just patch up what you have and hope nobody will ever get hold of the source code.
John Finn (15:00:45) :
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.
Which, according to observed data, hasn’t occurred.
well no doubling CO2 concentration always gets you the same “radiative forcing” however the amount required to double is different.
273->546
and then
546->1092
see that?
At least that’s how the theory goes>
Uhm no. The feedback weakens as per your 2nd comment, but doubling doesn’t double the forcing. Let’s say earth is radiating an extra 40 watts to space. double the CO2 and it grabs 10% of that. 4 now being retained and 36 going to space. double it again. It grabs another 10% of what’s left which is…3.6. I don’t know how the exact math would work out (George E Smith where are you?) but you get the drift. As the amount of energy already absorbed goes up, the chances of any given co2 molecule intercepting it go down. Even if it WAS linear… there’s only 40 watts to go get in the first place.
“davidmhoffer (18:43:44) :
[…]
Let’s say earth is radiating an extra 40 watts to space. double the CO2 and it grabs 10% of that.”
Wrong. The CO2 greenhouse effect is nearly saturated; an LWIR ray is absorbed after 10m or so if it is in the absorption band of CO2. Practically no LWIR ray can pass the entire atmosphere without ever hitting a CO2 molecule. This is already the case with pre-industrial levels. The reasoning of the warmists re the extra “forcing” by CO2 increase is that more layers of absorption are added like more blankets on a bed and that makes the warming go up. And that might even be the case even though i never saw empirical evidence. They only got the waper vapour feedback wrong. The sign of it.
Ohmygawd! CO2 is less filling? This is like chocolate lite! I am gobsmacked (like the word lots and lots but whatthehelldoesitmean)! Ya know that graph that shows CO2 as % part of the atmosphere? The one with the supposed line at the bottom of the graph (can’t even see it with cheater glasses on). Are they saying that CO2-caused global warming is just a light-weight? More like mousse compared to pudding?
By the way, that new jello mousse, the decadent chocolate kind with only 60 calories? I know it’s just whipped filled-with-air pudding and I’m paying more for less, but gawdamighty it is good with red wine.
Every day (every shift lol) I check out WUWT and thank my lucky stars I am surrounded by people such as Ed, George, Tilo, Jeff L, Steven, Leif, Lucy, Roger, davidmhoffer et al. Of course our host and the mods. The gloriously funny commentary. The wit and wisdom. The side issues, OTs and diversions.
I would go stark staring mad(der) in the face of a seemingly relentless attack on my instincts by the mainstream and alarmists if not for the aforementioned’s capacity to explore and explain the manifold aspects of the nature of Nature’s most wonderful atom and the seemingly endless interactions and compound relationships it has with almost everything on this ball of rock.
Having read as much as I can absorb, for as long as possible before asking; When did the very first, mythical if you will, doubling occur?
I understand that of the $billions spent on investigating warming, thus far, there is such piffling return on investment regarding the real physics of CO2 in atmosphere, but surely, if it is of such pressing urgency that the world’s economy should be spavined and contorted so as to pivot about just this one of its qualities then it should be the only significant investigation ongoing – or am I missing something?
TIA
Wrong. The CO2 greenhouse effect is nearly saturated
Won’t argue that Dirk. Was just trying to explain IF it wasn’t what the scenario would be. Point being that there IS a saturation point, and the closer you are to hitting it, the bigger the boost you need to get the same percentage of what’s left.
Is it possible that the lower level of water vapor in the stratosphere could be the result of ‘seeding’ of water droplets in the lower reaches of the stratosphere (9–12 km) from commercial airliners?
It would be ironic if air travel actually removed greenhouse gasses from the atmosphere.
Wouldn’t that be a hoot!
Come to think of it, they say:
“Balloon and satellite observations show the amount of water vapour in a layer about 16 kilometres high declined after 2000. The stratosphere extends from about 13 to 48 kilometres above the Earth’s surface.
“The reason for the decline is unknown, according to researchers led by Susan Solomon of the National Oceanic and Atmospheric Administration in Washington, D.C. They report their findings in Thursday’s online edition of the journal Science.”
So they don’t know.
I bet they would rather drink hemlock then even suggest that the increase in air travel is actually cooling the planet.
estimates of 40 p.p.m.v. CO2 per degree Celsius
I don’t want to pay $30+ to read the paper [or do it on Stanford time], but isn’t this backwards? I would have thought the estimate should have been of degrees Celsius per ppmv of CO2. Is this just me getting it backwards?
Actually amusing to see the mental gymnastics applied to try to say this work either has no effect on current theory or actually reinforces it. The world of spin has made it from the political to the scientific.
By the way, the AO went negative again and Arizona got D-U-M-P-E-D on with snow! Mother nature check-mates CO2.
“Leif Svalgaard (19:22:32) :
estimates of 40 p.p.m.v. CO2 per degree Celsius
I don’t want to pay $30+ to read the paper [or do it on Stanford time], but isn’t this backwards? I would have thought the estimate should have been of degrees Celsius per ppmv of CO2. Is this just me getting it backwards?”
Two parts of a feedback loop, they only talk about CO2 here. More CO2 increases greenhouse effect and raises temperature. Raised temperature leads to more CO2 outgassing by a warmer ocean.
This feedback (with a low gain and the new study even reduces that some more) probably even exists though it doesn’t do much. like a very faint echo.