From The Hockey Schtick:
A paper under discussion for Earth System Dynamics finds the transient climate response [TCR] to CO2 is 1.3°C per doubling of CO2 levels, about 35% less than claimed by the IPCC mean estimate and the same as determined by another recent paper by Otto et al finding a TCR of 1.3°C.
The authors say:
“assess the origin of these differences [between the IPCC high TCR estimates and lower estimates from this paper and others] and highlight the inverse relation between the derived anthropogenic temperature trend of the past 30 years and the weight given to the [natural] Atlantic Multidecadal Oscillation (AMO) as an explanatory factor in the multiple linear regression (MLR) tool that is usually employed. We highlight that robust MLR outcomes require a better understanding of the AMO in general and more specifically its characterization. Our results indicate that both the high- and low end of the anthropogenic trend over the past 30 years found in previous studies are unlikely and that a transient climate response with best estimates centred around 1.3°C per CO2 doubling best captures the historic instrumental temperature record.”
Earth Syst. Dynam. Discuss., 5, 529-544, 2014
www.earth-syst-dynam-discuss.net/5/529/2014/
doi:10.5194/esdd-5-529-2014
G. R. van der Werf and A. J. Dolman
Abstract:
VU University Amsterdam, Faculty of Earth and Life Sciences, Amsterdam, the Netherlands
Abstract. The instrumental surface air temperature record has been used in several statistical studies to assess the relative role of natural and anthropogenic drivers of climate change. The results of those studies varied considerably, with anthropogenic temperature trends over the past 25–30 years suggested to range from 0.07 to 0.20 °C decade−1. In this short communication we assess the origin of these differences and highlight the inverse relation between the derived anthropogenic temperature trend of the past 30 years and the weight given to the [natural] Atlantic Multidecadal Oscillation (AMO) as an explanatory factor in the multiple linear regression (MLR) tool that is usually employed. We highlight that robust MLR outcomes require a better understanding of the AMO in general and more specifically its characterization. Our results indicate that both the high- and low end of the anthropogenic trend over the past 30 years found in previous studies are unlikely and that a transient climate response with best estimates centred around 1.3 °C per CO2 doubling best captures the historic instrumental temperature record.
I’m shocked! Shocked to learn that yet more real science has actually been going on!
Equilibrium CS is probably about the same, ie scarcely more than the effect from doubling CO2 alone (280-560 ppm), over half of which effect has already occurred since c. AD 1850. The supposed huge positive feedbacks from water vapor & any other source have always been unsupported phantom fantasies.
Dana to the misrepresentation!
Nice to see there are no disagreements in climate science (sarc off).
Otter (ClimateOtter on Twitter) says: “Dana to the misrepresentation!”
Thanks. Made me laugh.
It’s really probably more like 60-70% less than what the IPCC says.
It still makes no sense since the recent temperature variation in our high emissions era is so closely mirrored in the former one, and temperature saw-toothed *down* just as emissions finally boomed after WWII:
http://www.woodfortrees.org/plot/hadcrut4gl/from:1955/to:2013/plot/hadcrut4gl/from:1895/to:1954
Since CO2 rose about 30% since WWII that would add 0.35° extra warming since then, but even up-adjusted Climategate University’s global average shows no such big boost in warming versus the low CO2 spike before it, only perhaps 0.2° extra, which stepping back mathematically indicates sensitivity of only 0.74° not 1.3°.
Bob says “Nice to see there are no disagreements in climate science (sarc off).” YUP, we wouldn’t want anybody to get the strange idea that there was no Imperial Consensus about the Truth of AGW, would we?
Correction: I have to discount the 10% boost in CO2 prior to 1940, which would have added 0.13° to that early spike, so the new spike really can be said to be 0.33° extra big compared to the *natural* part of the older one, quite close to their sensitivity claim after all.
…then again, sensitivity could still be zero due to negative feedbacks or unappeciated physics but natural variation may still have caused most all of the curve, given that even bigger transient warm spikes litter the last 30K years in the Greenland ice core, the last 3500 years being playfully plotted here:
http://s6.postimg.org/zatdndwq9/image.jpg
What exactly did they use for their “linear” anthropogenic term? CO2 concentration? Log of CO2 concentration? If it’s there I missed it.
The instrumental surface air temperature record…has been so jiggered to show faster warming
…and this is still all we could squeeze out of it
Let me see,…… remove all the unjustified “adjustments”, factor in the poor station siting, include known geological data, and presto; zero CS. ( Oh yes, I forgot to add; ignore the ridiculously inadequate GCM’s as per rgbatduke ).
Genuflection in. Gospel out?
So if the next 30 odd years are cooler than today, will the sensitivity drop to zero or go negative?
Given the quality of our current temperature record, can we honestly claim warming, [cooling] or no can say?
The claimed trends being less than the noise on the signal, it takes a lot of gall to make any definitive claims from this data.
1.3C? We’re doomedish.
spellcheck loves me.. cooling..or no can say.
NikFromNYC says:
May 8, 2014 at 5:02 pm
That’s why in real science, rather than Climate Science (TM), CACA has been repeatedly what we call “falsified” (in both the technical & ordinary senses of the word). In fact, it was born falsified, since data from c. 1945 to its birth c. 1977 already showed the hypothesis false.
Anthony.
This sensitivity thing is something that has confused me (I’m easily confused) for a long time. When I studied energy transfer at university, we used curves based on work by Leckner (Leckner, 1972) and earlier work by Hottel (1927) and Hottel and Sarofim (1967). These models for [AB sorption] of EMR versus concentration of CO2 showed that the [AB sorption] for CO2 (unlike water) plateaued (well nearly plateaued as there is always an increase in absorbance with an increase in concentration). This would be a sensitivity of almost 0. The CO2 level was at a path length of about 200 bar.cm which corresponds to atmospheric CO2 of about 300 ppm. So the question I have for Mosher and his buddy the telescope guy. Can they explain to a dimwit like me, what conditions are necessary to move from:
the [AB sorption] as modeled by Leckner, which shows a somewhat hyperbolic relation between CO2 and [AB sorption], with the asymptote nearly parallel to the concentration axis,
to the [AB sorption] as modeled by Ramanathan, which shows a more parabolic/logarithmic relation?
At lower concentrations (400 ppm and lower) the results are so close, they can be called identical. At higher concentrations, Leckner’s work shows near 0 sensitivity. Leckner’s curves are used by combustion, mechanical, chemical and metallurgical engineers to design things that work. Ramanathan’s are used by climate scientists to design climate models that over-estimate global warming. I think (could be wrong, often am) Myhre et. al. 1998 is more recent that Ramanathan’s work and is the source of the 5.35ln[CO2] equation.
For those interested in how all the physics of this stuff works, I direct them to the blog to the right called “scienceofdoom”. Excellent reference for radiative physics.
Mods: I’ve made a minor mistake in a technical term above. Wherever I say “adsorption”, one should substitute AB sorption. It will be interesting to see if anyone picks up on this.
[Like that [AB sorption] or [absorption] ?? First doesn’t look right. Mod]
John Eggert:
You seem to be stuck on a basic point that Roy Spencer addresses here – http://www.drroyspencer.com/2014/04/american-thinker-publishes-a-stinker/
The basic point is this: For determining forcing, the issue is not one of the absorption saturating. The issue is one of how high you have to go in the atmosphere until it is optically transparent enough that radiation emitted can escape to space without being absorbed again. This height rises as you increase CO2 levels and, along with the lapse rate in the troposphere, this means emission occurs from higher, colder regions of the atmosphere where (because the intensity of emission is an increasing function of temperature) means that the emission to space is less.
Nice one John Eggert -at least one commenter who has some understanding of heat transfer. (adsorption and absorption are different chemical engineering subjects)
I make another point, no one has proved that the 280ppm CO2 atmospheric concentration prior to 1960 is correct. Everyone is ignoring the measurements made by well qualified scientists (some recognised with Nobel prizes) with instruments whose accuracy had been checked and errors understood. (see here http://www.biomind.de/realCO2/realCO2-1.htm) If the concentration as measured by W Kreutz and others around 1941 was about 390ppm then it points to a sensitivity in the period 1940 to 2014 of zero. Measurements of CO2 and temperature back around 1850 have doubts about being representative of the world and the extent of errors but there is equally no evidence the CO2 level was 280ppm.
Discussing a word or subject such as sensitivity based on guesses or hypotheses is futile. Lots of factual information with knowledge of errors are required for one can make a sound analysis..
Well this is more in line with what I think we should be talking about when it comes to Climate Change. Again this is still a little on the conjecture end as there may be numerous other items that play a role in temperature that have amplified the signal we have thus seen but it is getting closer to where I understand the numbers to be.
It is funny to see people say that skeptics are deniers of climate change when in reality I think the correct term is realist. Now I am happy to talk to people about the benefits of increasing both the temperature and CO2 versus the trade offs when we are not talking 6 – 10 degrees celsius of warming…
The science is settled. These guys must be deniers to still be working on climate sensitivity to CO2. Let me guess they were paid by the Koch brothers and Big Oil. [/sarc]
Eggert
What IR wavelengths are they measuring in Leckner et al models? What are the full absorption lengths? Show me the graphs and equations used in these models. You can observe “saturation” in lab experiments but it is not true for the atmosphere because it is 10,000 meters thick while the lab apparatus is one or a few meters in length.
Hi Cementafriend:
do you know why there was a large peak in the CO2 concentration in 1941 on the website of Ernst-Georg Beck?
“One other outcome of these MLR analyses is that most of the temperature increase over the past 100 years is of anthropogenic origin, whether the AMO is included or not and whether the anthropogenic shape is linear or follows the forcing estimates. This indicates that there is no combination of natural factors that can better match the observed temperature pattern than one with a large anthropogenic influence.”
AMO and anthropogenic warming rates, G. R. van der Werf and A. J. Dolman