I’m taking the weekend off, as I need to do some climate unrelated work, which is physical, and always good for the soul, and I need to spend time with my family, who often get neglected due to the amount of time I put into this blog.
Guest posters are welcome to post stories.
Feel free to discuss topics within site policy.
See – owe to Rich says:
October 20, 2013 at 2:48 am
Is there a natural ocean “lapse rate” down to a constant 4K at some depth where the densest waters reside, and if so would the depth at which 4K is reached
==========
Ferd Berple says: isn’t 4K the temp of liquid helium at atmospheric pressure? 🙂
Sorry, that was a typo – I meant 4degC as that is the temperature at which water achieves maximum density, and slides to the bottom of the ocean.
Now you can get back to my main question: how would equilibrium in the ocean change given an immediate and static 1 degree heating of the atmosphere?
Rich.
Ferdinand Engelbeen says:
October 20, 2013 at 5:03 am
MikeB says:
October 20, 2013 at 5:25 am
_Jim says:
October 20, 2013 at 6:43 am
Thanks for the replies.
richardscourtney says:
October 20, 2013 at 7:30 am
the changes in those ratios don’t “mimick the increase in human emissions” but are wrong by a factor of 3.
The factor 3 is not of the slightest interest to show that human emissions are the cause of the increase. That is only the diluting factor, caused by the deep ocean circulation, which is a lot higher in quantity (but lower in d13C difference with the atmosphere, to the positive side) than the human emissions (which are strongly negative in d13C).
If the deep ocean circulation was the real cause of the increase of CO2 in the atmosphere, then the 13C/12C ratio would go the other way out:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/deep_ocean_air_increase_290.jpg
An increase from 40 to 290 GtC in deep ocean circulation (total circulation from 150 to 450 GtC) over the past 50 years is needed to mimick the 3-fold increase of human emissions since 1960. But that violates the observed 13C/12C ratio…
The main other possible source, vegetation is a proven sink for CO2. Thus if you have an alternative that doesn’t violate one or more observations, I want to know that…
There are multiple periods of millions of years and of thousands of years when the planet was cold when atmospheric CO2 levels were high and periods when the planet was warm and CO2 levels were low. Over the last decade there has been a cottage industry of warmists scientists (The scientists how write on the RealClimate blog appear again and again as principal authors or co-authors of the revision papers. The same RealClimate authors attempt to attack the alternative explanation for what causes cyclic and abrupt climate change.) who have been working to revise the proxy data to force correlation. For example recently an entire ice epoch was eliminated the problem of how to explain an ice epoch (cold period of millions of years) that occurred when atmospheric CO2 was roughly 5 to 10 times greater than current.
One solution to a paradox is to attempt to make it go away by re-interpretation the data. If the paradox is real, attempts to make it disappear block the progress of science.
If the paradox is real, there is a mystery, some fundamental basic assumption(s) concerning either the CO2 forcing mechanism or concerning the atmosphere which causes the CO2 forcing mechanism to saturate.
Connected with the scientific mystery of why the CO2 mechanism saturates is the alternative explanation of what causes the past ice epochs and the current glacial/interglacial cycle which is processes that change the amount of cosmic ray flux (CRF is also called galactic cosmic rays GCR. CRR/CRF are mostly high speed protons that are believed to be created by super nova. As the solar system travels around the galaxy it bobs in and out of the galactic plane. CRF/GCR increases by a factor of roughly 4 to 5 times for millions of years when the solar system passes through the galaxy plane. The ice epochs correlate with the periods of high CRF/GRF) which changes modulate planetary cloud cover is the explanation. There is unequivocal smoking gun evidence that changes in GCR/CRF modulate planetary temperature For example, there are cycles (Dansgaard-Oeschger cycles, 23 cycles have been found which is the limit of the proxy data analysis) of warming and cooling in the paleo record with a periodicity of 1500 years. Those cycles of warming and cooling correlate with high and low cycles of CRF/GRF.
As most are aware there has been a sudden change to the solar magnetic cycle. It appears the solar magnetic cycle is going to enter into a Maunder like minimum that has in the past lasted for 50 to 100 years. As result of that change CRF/GRF has started to increase. If the GCR/CRF modulation of planetary cloud theory is correct there should now be the start of planetary cooling, with the majority of the cooling occurring at high latitudes. (GCR/CRF modulation of planetary clouds is greater at high latitudes as GCR/CRF is blocked at low latitudes by the geomagnetic field. For some unexplained reason there is a delay of roughly 10 to 12 years from the time the solar cycle changes and the cooling occurs. For some unexplained reason the high latitude temperature changes correlate with the length of time of the solar magnetic cycle.) The magnitude of the cooling (assuming cooling occurs) will settle multiple questions concerning the CO2 forcing mechanism and the alternative CRF/GCR and solar magnetic cycle of planet temperature. There is now the first observational evidence of anomalous cooling at high latitudes.
http://nsidc.org/data/seaice_index/images/daily_images/S_stddev_timeseries.png
http://www.solen.info/solar/images/comparison_recent_cycles.png
http://cosmicrays.oulu.fi/webform/query.cgi?startday=02&startmonth=09&startyear=1980&starttime=00%3A00&endday=10&endmonth=10&endyear=2013&endtime=00%3A00&resolution=1440&picture=on
CO2 Vs Planetary Temperature Geological time
http://www.geocraft.com/WVFossils/PageMill_Images/image277.gif
http://mysite.science.uottawa.ca/idclark/courses/Veizer%20Nature%202001.pdf
Evidence for decoupling of atmospheric CO2 and global climate during the Phanerozoic eon
Certain intervals of the Earth’s history, such as the Middle Cretaceous (about 100 million years (Myr) ago) are characterized by fossil and geologic indicators of global warmth, and by voluminous deposits of volcanic rocks and other indicators of abundant volcanism. Volcanoes are a chief source of CO2 to the atmosphere, so it is reasonable to conclude that atmospheric pCO2 was elevated during such times. However, the times of greatest volcanic activity may not correlate directly with times of greatest warmth3. Moreover, unlike the Pleistocene, there is no direct evidence for CO2 levels in earlier times. Numerical carbon-cycle models that calculate ancient CO2 levels, and pCO2 proxies derived from the isotopic composition of marine organic matter or carbonate nodules in ancient soils, or from the density of stomata on fossil leaves, do generally support the relationship between climate and atmospheric pCO2 on geologic timescales7.
http://www.phys.huji.ac.il/~shaviv/Ice-ages/GSAToday.pdf
Celestial driver of Phanerozoic climate?
We find that at least 66% of the variance in the paleotemperature trend could be attributed to CRF variations likely due to solar system passages through the spiral arms of the galaxy. Assuming that the entire residual variance in temperature is due solely to the CO2 greenhouse effect, we propose a tentative upper limit to the long-term “equilibrium” warming effect of CO2, one which is potentially lower than that based on general circulation models.
This is an example of a Realclimate scientist attacking the alternative theory. Meteorites where analyzed to determine how much GCR/CRF has varied in the past and to confirm that the timing of those changes correlated with the past ice epochs.
http://www.phys.huji.ac.il/~shaviv/ClimateDebate/RahmReply/RahmReply.html
RECONSTRUCTING COSMIC RAY FLUXES —The starting point of SV03 is a reconstruction of cosmic ray fluxes over the past 1,000 Myr based on 50 iron meteorites and a simple model estimating cosmic ray flux (CRF) induced by the Earth’s passage through Galactic spiral arms ([Shaviv, 2002; Shaviv, 2003]). About 20 of the meteorites, making four clusters, date from the past 520 Myr, the time span analysed in SV03. The meteorites are dated by analysing isotopic changes in their matter due to cosmic ray exposure (CRE dating [Eugster, 2003]). An apparent age clustering of these meteorites is then interpreted not as a collision-related clustering in their real ages but as an indication of fluctuations in cosmic ray flux (CRF). One difficulty with this interpretation is that variations in CRF intensity would equally affect all types of meteorites. Instead, the ages of different types of iron meteorites cluster at different times [Wieler, 2002]. Hence, most specialists on meteorite CRE ages interpret the clusters as the result of collision processes of parent bodies, as they do for stony meteorites (ages _ 130 Myr) to which more than one dating method can be applied.
A Great Lesson
By the DUKE OF ARGYLL.
The Theory of the young naturalist was hailed with acclaim. It was a magnificent generalization. It was soon almost
universally accepted with admiration and delight. It passed into all popular treatises, and ever since for the
space of nearly half a century it has maintained its unquestioned place as one of the great triumphs of reasoning
and research. Although it illustrious author has since eclipsed this earliest performance by theories and
generalizations still more attractive and much further reaching, I have heard eminent men declare that, if he had
done nothing else, his solution of the great problem of the coral islands of the Pacific would have sufficed to
place him on the unsubmergeable peaks of science, crowned with an immortal name.
And now comes the great lesson. After an interval of more than five-and-thirty years the voyage of the Beagle has
been followed by the voyage of the Challenger, furnished with all the newest appliances of science, and manned by a
scientific staff more competent to turn them to the best account. And what is one of the many results that have
been added to our knowledge of Nature-to our estimate of the true character and history of the globe we live on? It
is that Darwins theory is a dream. It is not only unsound but it is in many respects directly the reverse of the
truth. with all his conscientiousness, with all his caution, with all his powers of observations, Darwin in this
matter fell into errors as profound as the abysses of the Pacific. All the acclamations with which it was received
were as the shouts of an ignorant mob. It is well to know that the plebiscites of science may be as dangerous
and as hollow as those of politics.
…
In a recent article in this review I had occasion to refer to the curious power which is sometimes exercised on
behalf of certain accepted opinions, or of some reputed prophet, in establishing a sort of Reign of Terror in their
own behalf, sometimes in philosophy, sometimes in politics, sometimes in science. This observation was received as
I expected it to be-by those, who being themselves subject to this kind of terror, are wholly unconscious of the
subjection.
…
Nevertheless, the disproof of a theory which was so imposing, and had been so long accepted, does read to us the
most important lessons. It teaches us that neither the beauty-nor the imposing character-nor the apparent
sufficiency of an explanation may be any proof whatever of its truth. – Nineteenth Century.
PopSci Archive Viewer | Popular Science
http://www.popsci.com/archive-viewer?id=ziIDAAAAMBAJ&pg=243&query=coral
Fun interesting read.
Jim asks me to name a program that was repealed because of failure. The war on gun and ammunition makers and the war on big tobacco companies, two attention grabbing, unpopular restrictions to personal freedoms.
The really big deal bi-partisan haunted house that needed attention was left in place to fester. Because campaign contributions definitely rearranged the priorities whilst all eyes were trying to focus sharply on hanging chads.
http://www.nytimes.com/2008/11/17/business/economy/17gramm.html?pagewanted=all
We voters had a man who wanted to go to Washington without pay and straighten the mess up because he saw our boat drifting towards the rocks of powerful advocacy and lobbying groups. He got trashed. Porn pictures of his daughter were like a Karl Rove fornication performance enhancement drug. In my opinion.
cynical_scientist says:
October 19, 2013 at 3:38 pm
“With regard to Schwarzenager lobbying for a change to the constitution to enable him to be POTUS, surely there are more urgent priorities for reform.
How about fixing the broken senate filibuster rules which essentially completely break democracy. How about a line item veto to cut back on the extent of back room dealing and pork clauses riding through in omnibus legislation. How about looking at instituting proportional voting for one of the houses. How about a single transferrable vote system in the presidential primaries. Why is it possible to get the constitution amended to deal with Schjawrzanagers trivial petty and self-serving desire to stand for president whereas it is not possible to address serious structural issues. The US system of government is currently dysfunctional. Does anyone honestly think that a foreigner being unable to stand for president is the biggest problem?”
————————————————————————————————
The U. S. government is not a democracy. It is a Representative Republic. The Founders of our Country purposely set up a system that makes change difficult and has checks on the majority in order to protect the minority. Imagine if change was easy, the majority would pass a host of laws and then 2 years later if the other party takes over, they change all those laws and implement their own. Then when the first party takes over again, they change those laws and institute the ones they had before. Utter chaos every thing a party moves from minority to majority. Keep in mind that every budget crisis is manufactured to prevent a new budget from being voted on where it would have to be scrutinized. Instead, simply pass continuing legislation to keep the same budget in place with “relief” that the government will stay open. They fool most of the people all of the time.
Ferdinand Engelbeen:
re your post at October 20, 2013 at 9:23 am.
You may be right that the recent rise in atmospheric CO2 concentration is caused by the anthropogenic emission, or you may be wrong. But you do your case no good by pretending your case is better than it is.
In reply to my pointing out that the magnitude of the isotope ratio changes are not the clear evidence you asserted by my writing
you have replied
As I said to you about this on the other thread only yesterday
And what I said was
Richard
What legislation was this? That was repealed by congress? Please be specific about which federal laws (PL ‘Public Law’ or US Code, etc via congressional acts which) were repealed. Name something on the magnitude of the ACA in particular (something the size and as large as the ‘Social Security’ act for instance.)
BTW, note, pls moniker “_Jim”. This aids in search on the thread as well as there are several “Jims” that post on WUWT. TIA
.
Ed fails to note how ‘popular the Income Tax is … yet, has it been overturned? Once the FSA (Free Stuff Army) starts getting cared-for by Obamacare the ACA will never be repealed … seniors squawk to high heaven at the sound that Sos Sec might be be ‘reformed’ even …
.
See – owe to Rich says:
October 20, 2013 at 9:10 am
See – owe to Rich says:
October 20, 2013 at 2:48 am
Is there a natural ocean “lapse rate” down to a constant 4K at some depth where the densest waters reside, and if so would the depth at which 4K is reached
==========
Ferd Berple says: isn’t 4K the temp of liquid helium at atmospheric pressure? 🙂
Sorry, that was a typo – I meant 4degC as that is the temperature at which water achieves maximum density, and slides to the bottom of the ocean.
That’s true of freshwater but not seawater which has maximum density at it’s freezing point (which depends on salinity).
Zaphod says:
October 19, 2013 at 3:26 pm
“Can anyone help?
I’m an engineer, not a scientist. For 30 years I’ve relied on New Scientist to keep me in touch.
I am seriously disappointed with NS in recent years. They are totally sold on the CAGW religion, plus they’ve gone all arty, and Social Sciencey. NS has sold its body. ”
A little short in the social science and cosmologist-end-of-the-world-scenario departments… but on the other hand, more hard science than you thought to exist…
http://www.innovations-report.com/
richardscourtney says:
October 20, 2013 at 9:54 am
Richard, the dilution with a factor 3 of the d13C decrease caused by fossil fuel burning is not more proof that humans are not the cause of the increase in the atmosphere than the afct that only halve the emissions (as quantity) are measured as increase in the atmosphere…
It would be more interesting if the d13C levels were getting more negative than expected from fossil fuel burning or positive, because that would prove that either vegetation was a net source or that the deep oceans were the cause of the increase…
Ferdinand Engelbeen
re your post at October 20, 2013 at 10:45 am.
The interesting point is that the carbon cycle is not adequately understood for the cause of the recent rise in atmospheric CO2 concentration to be known.
I would like to know what it is. You are certain the cause is the anthropogenic emission, and you may be right (or not). But my point was that you do not promote your case by overstating it.
Richard
Thoughts on science and politics excerpted from Willing Slaves of the Welfare State, an essay by C.S. Lewis, from God in the Dock: Essays on Theology and Ethics (1970), first published in The Observer on July 20, 1958:
….Again, the new oligarchy must more and more base its claim to plan us on its claim to knowledge. If we are to be mothered, mother must know best. This means they must increasingly rely on the advice of scientists, till in the end the politicians proper become merely the scientists’ puppets. Technocracy is the form to which a planned society must tend. Now I dread specialists in power because they are specialists speaking outside their special subjects. Let scientists tell us about sciences. But government involves questions about the good for man, and justice, and what things are worth having at what price; and on these a scientific training gives a man’s opinion no added value. Let the doctor tell me I shall die unless I do so-and-so; but whether life is worth having on those terms is no more a question for him than for any other man… On just the same ground I dread government in the name of science. That is how tyrannies come in. In every age the men who want us under their thumb, if they have any sense, will put forward the particular pretension which the hopes and fears of that age render most potent. They ‘cash in’. It has been magic, it has been Christianity. Now it will certainly be science. Perhaps the real scientists may not think much of the tyrants’ ‘science’– they didn’t think much of Hitler’s racial theories or Stalin’s biology. But they can be muzzled… We have on the one hand a desperate need; hunger, sickness, and the dread of war. We have, on the other, the conception of something that might meet it: omnicompetent global technocracy. Are not these the ideal opportunity for enslavement? This is how it has entered before; a desperate need (real or apparent) in the one party, a power (real or apparent) to relieve it, in the other… All that can really happen is that some men will take charge of the destiny of the others. They will be simply men; none perfect; some greedy, cruel and dishonest. The more completely we are planned the more powerful they will be. Have we discovered some new reason why, this time, power should not corrupt as it has done before?
William Astley says:
October 20, 2013 at 9:24 am
Connected with the scientific mystery of why the CO2 mechanism saturates is the alternative explanation of what causes the past ice epochs and the current glacial/interglacial cycle which is processes that change the amount of cosmic ray flux
It is generally accepted that glaciations are caused by planetary influence on the orbit of the Earth. No cosmic ray fluxes involved.
As most are aware there has been a sudden change to the solar magnetic cycle.
No, the solar cycle is just low, which has happened many times before, about every 100 years for the past 300 years. Nothing wrong with the cycle.
Why is it that Ferdinand and Richard Courtney always feel the neurotic need to take over WUWT threads. Help me Jimbo and Janice.
CD (@CD153) says:
October 20, 2013 at 7:18 am
“As a regular visitor to WUWT, I have often seen one or more of the Laws of Thermodynamics mentioned on occasion. I have read elsewhere in the past that the CAGW narrative violates one or more of these Laws. However, I do not recall if that issue was ever directly discussed here, and was wondering if the CAGW narrative does indeed violate one or more of the Laws. Please understand that I am a non-scientist, so please forgive my ignorance here if this issue was in fact covered in the past. Please, if you would, discuss this in terms that any lay person can understand.”
There are people who claim that CO2AGW violates the laws of thermodynamics; they are a fringe group called the Slayers. They claim that a cool object cannot increase the temperature of a warmer object even by means of radiation.
I think it’s a weak and maybe false argument against CO2AGW, as the warmists could still claim that enhanced CO2 simply delays cooling to space.
So better arguments have to be found. The best one being that the climate models have been proven to be junk; and that therefore the Null hypothesis holds until refuted. In other words: If the warmists think they know what’s going on then they should make PREDICTIONs. They tried, and they failed; ball’s in their court.
“Also, I recall reading elsewhere about the Law of Diminishing Returns (LoDR) as regards CO2. Is this one of the Thermodynamic Laws? The LoDR, as I understand it, states that CO2′s effect diminishes as a greenhouse gas as the level of it in the atmosphere increases and that, at 400 PPM, CO2 has already done most of its “damage” (if in fact it does any at all). So CO2 as a greenhouse gas should be a non-issue because of the LoDR among other reasons. Correct?”
LoDR is not a natural law but just a description of anything that ceases to be effictive, like the US taking on more debt. The CO2 logarithmic effect is caused by the fact that most absorption lines are saturated (mean free path length of photons smaller than thickness of atmosphere); and only at the edges are they partially saturated at given partial pressure. As partial pressure of CO2 rises , these edges become slightly more saturated (probability of absorption of photon is smaller one, but rises with increasing CO2 concentration). The effect is called “Pressure broadening of absorption lines”.
@richardscourtney.
I would like some help in tidying up my statement of the null hypothesis. As you saw above I stated:-
” – anthropogenic CO2 emissions are NOT causing catastrophic climate change.
Or – natural variation is causing climate change.”
It seems that my first statement requires breaking into two parts –
a) anthropogenic CO2 emissions are NOT causing the rise in atmospheric CO2 levels
b) rising atmospheric CO2 levels are NOT causing catastrophic climate change
The alternative statement requiring falsification is :-
” natural variation is causing climate change.”
My understanding is that the science (of the carbon cycle and of climate drivers) is currently not in a position to falsify any of those three statements.
Do I have this right and complete?
GeeJam says:
October 20, 2013 at 11:45 am
“Why is it that Ferdinand and Richard Courtney always feel the neurotic need to take over WUWT threads. Help me Jimbo and Janice.”
Open threads are fair game.
lsvalgaard says:
October 20, 2013 at 8:52 am
geran says:
October 20, 2013 at 5:04 am
this is an OPEN thread, duh….
Yeah, sure, you and everyone are allowed to make fools of themselves.
Of course “everyone” also includes you 🙂
GeeJam says:
October 20, 2013 at 11:45 am
Why is it that Ferdinand and Richard Courtney always feel the neurotic need to take over WUWT threads. Help me Jimbo and Janice.
Some people have investigated a few items of the whole AGW story more in depth than others…
I have looked into the use of human aerosols in climate models, which were used to “tune” the models to follow the slight cooling of temperature in the period 1945-1975. That is one of the reasons that the models nowadays are far too high in their “projections” as they implemented a far too high sensitivity for aerosols and thus for CO2…
Another hobby of mine was looking if the increase of CO2 in the atmosphere is man-made or not. As human emissions fit all observations, that is with high probability the case.
If somebody then comes with an altenative which is based on non-relevant or wrong assumptions or which doesn’t fit one or more observations, I will react on that. Because such reargard fights weakens the arguments of skeptics on items where the AGW science is not that rock solid: the influence of the increase of CO2 in the atmosphere on temperature (“climate sensitivity”).
Thank you Dirk, but Ferdinand and Richard are not purely confined to open threads. I admire them both but we sometimes need a layman’s viewpoint of what is happening. All of us should be singing from the same hymn sheet – unilateral agreement that CAGW is a complete scam.
And most people missed my factual post 12 hours ago because Anthony’s team of excellent moderators were rightly checking my statistics. It’s gone through and accepted.
http://wattsupwiththat.com/2013/10/19/weekend-open-thread-8/#comment-1453624
farmerbraun says:
October 20, 2013 at 11:57 am
It seems that my first statement requires breaking into two parts –
a) anthropogenic CO2 emissions are NOT causing the rise in atmospheric CO2 levels
If you imply that failing one observation is enough to falsify that statement, then we agree.
The alternative statement is that anthropogenic CO2 emissions are causing the rise in atmospheric CO2 levels. Until now that fits all observations… See an oversight at:
http://www.ferdinand-engelbeen.be/klimaat/co2_measurements.html#The_mass_balance
farmerbraun:
I am answering your request to me at October 20, 2013 at 11:57 am.
Actually, I like your succinct statement of the climate null hypothesis. However, since you ask, this is how I explain it. (And there is nothing stopping GeeJam from skipping past it.)
The Null Hypothesis says it must be assumed a system has not experienced a change unless there is evidence of a change.
The Null Hypothesis is a fundamental scientific principle and forms the basis of all scientific understanding, investigation and interpretation. Indeed, it is the basic principle of experimental procedure where an input to a system is altered to discern a change: if the system is not observed to respond to the alteration then it has to be assumed the system did not respond to the alteration.
In the case of climate science there is a hypothesis that increased greenhouse gases (GHGs, notably CO2) in the air will increase global temperature. There are good reasons to suppose this hypothesis may be true, but the Null Hypothesis says it must be assumed the GHG changes have no effect unless and until increased GHGs are observed to increase global temperature. That is what the scientific method decrees. It does not matter how certain some people may be that the hypothesis is right because observation of reality (i.e. empiricism) trumps all opinions.
Please note that the Null Hypothesis is a hypothesis which exists to be refuted by empirical observation. It is a rejection of the scientific method to assert that one can “choose” any subjective Null Hypothesis one likes. There is only one Null Hypothesis: i.e. it has to be assumed a system has not changed unless it is observed that the system has changed.
However, deciding a method which would discern a change may require a detailed statistical specification.
In the case of global climate no unprecedented climate behaviours are observed so the Null Hypothesis decrees that the climate system has not changed.
Importantly, an effect may be real but not overcome the Null Hypothesis because it is too trivial for the effect to be observable. Human activities have some effect on global temperature for several reasons. An example of an anthropogenic effect on global temperature is the urban heat island (UHI). Cities are warmer than the land around them, so cities cause some warming. But the temperature rise from cities is too small to be detected when averaged over the entire surface of the planet, although this global warming from cities can be estimated by measuring the warming of all cities and their areas.
Clearly, the Null Hypothesis decrees that UHI is not affecting global temperature although there are good reasons to think UHI has some effect. Similarly, it is very probable that AGW from GHG emissions are too trivial to have observable effects.
The feedbacks in the climate system are negative and, therefore, any effect of increased CO2 will be probably too small to discern because natural climate variability is much, much larger. This concurs with the empirically determined values of low climate sensitivity.
Empirical – n.b. not model-derived – determinations indicate climate sensitivity is less than 1.0°C for a doubling of atmospheric CO2 equivalent. This is indicated by the studies of
Idso from surface measurements
http://www.warwickhughes.com/papers/Idso_CR_1998.pdf
and Lindzen & Choi from ERBE satellite data
http://www.drroyspencer.com/Lindzen-and-Choi-GRL-2009.pdf
and Gregory from balloon radiosonde data
http://www.friendsofscience.org/assets/documents/OLR&NGF_June2011.pdf
Indeed, because climate sensitivity is less than 1 .0°C for a doubling of CO2 equivalent, it is physically impossible for the man-made global warming to be large enough to be detected (just as the global warming from UHI is too small to be detected). If something exists but is too small to be detected then it only has an abstract existence; it does not have a discernible existence that has effects (observation of the effects would be its detection).
To date there are no discernible effects of AGW. Hence, the Null Hypothesis decrees that AGW does not affect global climate to a discernible degree. That is the ONLY scientific conclusion possible at present.
Richard