By Roy W. Spencer, Ph. D., October 11th, 2009
It is claimed by the IPCC that there are ‘fingerprints’ associated with global warming which can be tied to humanity’s greenhouse gas emissions, as if the signatures were somehow unique like real fingerprints.
But I have never been convinced that there is ANY fingerprint of anthropogenic warming. And the reason is that any sufficiently strong radiative warming influence – for instance, a small (even unmeasurable) decrease in cloud cover letting in slightly more sunlight starting back in the late 1970’s or 1980’s– would have had the same effect.
The intent of the following figure from Chapter 9 in the latest (AR4) version IPCC report is to convince the reader that greenhouse gas emissions have been tested against all other sources of warming, and that GHGs are the only agent that can cause substantial warming. (The snarky reference to “proof” is my addition.)
But all the figure demonstrates is that the warming influence of GHGs is stronger than that from a couple of other known external forcing mechanisms, specifically a very small increase in the sun’s output, and a change in ozone. It says absolutely nothing about the possibility that warming might have been simply part of a natural, internal fluctuation (cycle, if you wish) in the climate system.
For instance, the famous “hot spot” seen in the figure has become a hot topic in recent years since at least two satellite temperature datasets (including our UAH dataset), and most radiosonde data analyses suggest the tropical hotspot does not exist. Some have claimed that this somehow invalidates the hypothesis that anthropogenic greenhouse gas emissions are responsible for global warming.
But the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source. Anomalous heating gets spread throughout the depth of the troposphere by convection, and greater temperature rise in the upper troposphere than in the lower troposphere is because of latent heat release (rainfall formation) there.
For instance, a natural decrease in cloud cover would have had the same effect. It would lead to increased solar warming of the ocean, followed by warming and humidifying of the global atmosphere and an acceleration of the hydrologic cycle.
Thus, while possibly significant from the standpoint of indicating problems with feedbacks in climate models, the lack of a hotspot no more disproves manmade global warming than the existence of the hotspot would have proved manmade global warming. At most, it would be evidence that the warming influence of increasing GHGs in the models has been exaggerated, probably due to exaggerated positive feedback from water vapor.
The same is true of the supposed fingerprint of greater warming over land than over the ocean, of which there is some observational evidence. But this would also be caused by a slight decrease in cloud cover…even if that decrease only occurred over the ocean (Compo, G.P., and P. D. Sardeshmukh, 2009).
What you find in the AR4 report is artfully constructed prose about how patterns of warming are “consistent with” that expected from manmade greenhouse gases. But “consistent with” is not “proof of”.
The AR4 authors are careful to refer to “natural external factors” that have been ruled out as potential causes, like those seen in the above figure. I can only assume this is was deliberate attempt to cover themselves just in case most warming eventually gets traced to natural internal changes in the climate system, rather than to that exceedingly scarce atmospheric constituent that is necessary for life of Earth – carbon dioxide.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
John S. (11:24:31) :
tallbloke (01:05:25):
You’ve got the essential points entirely right. But oceanic mixing from near-surface thermalization of solar radiation readily extends downward only to ~100m, which is the ballpark thermocline level.
Or a bit less in the tropics. But much deeper in the temperate latitudes. James Annan (AGW oceanographer) thinks subducting currents in the poleward regions mix the heat downwards. I don’t know, but it seems to me that the ocean fluid is much more mobile than theory suggests, somehow.
William,
once the “peer-review” process re-opens itself to impartial submission and referees, perhaps Dr. Spencer will do so. However what has been educational in this exercise is to see a credibility transition from standard “peer-review” publications to online dialog between rational people – including scientists like Spencer – on blogs like this. Heartening for those who admire democratic debate.
It takes a margin of intelligence to know when you’re being fed a one-sided argument. By attempting to co-opt the media and peer publication process, alarmists destroyed their own credibility. Open debate is the foundation of scientific method. When debate was silenced, alarmists sowed the seeds of their own demise.
Roy Spencer (04:41:15) :
You say:
“erlhapp:
The heating in the upper troposphere is not from water vapor at that level, but rising from below condensing and releasing latent heat. It is BECAUSE the specific humidity is limited at 200 mb that water ascending to the level must be precipitated out. Also, remember the heat capacity of air at 200 mb is only 20% of that at 1000 mb (less air to heat), which helps amplify a temperature rise.”
Roy,
Latent heat is released at cloud condensation level and at that point the energy goes into either radiation or convection. Most of that latent heat release is close to the surface as low as 850hPa.
In the atmosphere above tropical rainforest areas that give rise to heavy daily cycles of evaporation (moisture transpired by plants) outgoing long wave radiation is as low as it is at the poles because the convective activity cools the air via decompression as you well know. (I learned this from you) The air at 200hpa is no warmer over the Amazon than it is over the East Pacific where warming is the result of compression (descending air) and the energy pickup from UV light exciting ozone which is in greater concentration in downdraft areas. Am I wrong? I will check it out using NCEP /NCAR data.
I would suggest that there is a greater flux in temperature at 200hPa in the downdraft area over the cool ocean and this is a result of changing ozone content and changing OLR. It should be more in one half of the year than the other.
I would further suggest that the flux in temperature at 200hPa will be reflected in a sympathetic change in sea surface temperature as a result of changing ice cloud density. Specific humidity at 200hPa is relatively invariable by comparison with temperature. So, as the air warms, reflective ice particles disappear and the ocean will warm.
I would suggest that ,regardless of location, the amplification of the temperature rise at 200hPa is due to excitation of ozone by outgoing long wave radiation. That radiation is heaviest in the downdraft areas. The amplification over the east Pacific should be greater than over the Amazon.
Just thinking out loud here but there are many things that can be easily checked.
The Team has moved on. The Tropical Tropespheric Footprint is soooooo 2007. Like Gavin said a year ago or so, they weren’t really serious. Not even the iconic Artic Ice Melt is really that important. The Crisis De Jour is really just that. No need to spend all that time, effort and money attempting to verifying something that The Team really doesn’t think is all that important.
tallbloke (15:20:15):
Downward mixing well below the thermocline, which is seldom found much deeper than 100m anywhere before disappearing completely at high latitudes , is a very sluggish process, quite inconsequential in its climatic effect. Widespreasd subduction of surface waters is a red herring, accepted only by ignoranti in physical oceanography, such as Al Gore. What little sinking occurs is due purely to density differences developed in limited areas, under rather special conditions. The wind-driven circulation is orders of magnitude more important than the thermohaline in redistributing near-surface heat poleward, rather than downward.
@ur momisugly RW (06:12:35) :
You beat me to it. How does a slight decrease in cloud cover cause stratospheric cooling? Increasing GHGs does even when ozone depletion is considered.
See: http://www2.sunysuffolk.edu/mandias/global_warming/greenhouse_gases.html#stratospheric_cooling
Here is an excellent thread from Skepticalscience.com on the subject of measuring GHG influences on climate:
http://www.skepticalscience.com/How-do-we-know-CO2-is-causing-warming.html
Finally, if decreasing cloud cover is suggested as the reason for global warming what the heck is going on in the past century, especially the past few decades, that did NOT happen in the past 2000 years? Today’s warming climate is doing so at rates that “natural” forcings seem not to be able to explain.
“Extraordinary claims require extraordinary evidence.” The claim of cloud cover has been made but where is the extraordinary evidence?
@ur momisugly william (13:46:47) :
All of this makes for a very interesting discussion. But yet, no one contributing to this blog has published any of these refutations to AGW warming in a reputable peer review journal. If all of this is so obvious and easy to prove then who here is going to write and publish the refutation?
EXACTLY! It never ceases to amaze me that if the anti-AGW points were so obvious then why do they not appear in journals? Most of the anti-AGW arguments are analogous to: “I see a bird flying so I just proved there is no gravity!”
Scott Mandia:
“EXACTLY! It never ceases to amaze me that if the anti-AGW points were so obvious then why do they not appear in journals?”
Exactly NOT. I just provided a peer reviewed paper to william to read [of course he didn’t; his mind is already made up], debunking AGW in my 13:46 post above. You seem to ready to believe only what you want to believe.
And please don’t link to clearly dishonest blogs, OK? When an alarmist blog calls itself “Skeptical science”, and then posts the same rubbish as realclimate, they are being disingenuous right off the bat. We’re not fools here.
Alarmists hang their collective hats on the ridiculous presumption that a tiny trace gas controls the climate and will lead to runaway global warming and climate catastrophe. Is that silly, or what? They probably believe that CO2 controls the Sun, too: click
Dr Spencer:
I very much appreciate you making the point that the so-called “hotspot” is not a fingerprint that distinguishes the mechanism of AGW from other warming mechanisms. I have said this countless times on this site but people will probably be more receptive to you saying it. I do have a few comments / questions though:
(1) As RW points out, the stratospheric cooling is a unique signature…or at least one that distinguishes it from an increase in solar irradiance. What about a decrease in low cloud cover…What would be the expectation for the stratospheric temperature trend in that case?
(2) It is important to emphasize that if the models are wrong about the “hotspot”, then they are wrong in a pretty subtle way because (as pointed out by Santer et a. 2005), the amplification of the surface trends as one goes up in the troposphere is seen quite clearly in the data for temperature fluctuations on timescales of months to a few years. It has always seemed kind of difficult to me to explain why processes that operate on the timescales of hours to days lead to the amplification on this longer timescale but then not on the multidecadal timescales. And, of course, the fact that the amplification is clearly seen for timescales where the data is very trustworthy and only is difficult to detect on the multidecadal timescale where the data is less trustworthy (because you face the very difficult issue of dealing with artifacts that can affect the secular trends) seems to point in the direction of data problems, which was also what the CCSP report thought.
(3) In regards to what the missing hotspot would mean, you say: “At most, it would be evidence that the warming influence of increasing GHGs in the models has been exaggerated, probably due to exaggerated positive feedback from water vapor.” Actually, it seems to me that the most direct effect of the hotspot missing would be that the NEGATIVE lapse rate feedback is being exaggerated…I can’t really see any way around that given that this feedback is based directly on the notion that the warming in the upper troposphere will be greater than at the surface! It seems to me that the implication about the water vapor feedback being incorrect is more indirect. I understand that a lot of the same convective physics goes into both of these feedbacks, but the argument to get from the temperature profile to the water vapor feedback is certainly more complicated with more room for other possible resolutions. Furthermore, we have independent evidence from the satellite record that the upper troposphere appears to moisten about as the climate models predict (e.g., from Soden and Dessler), although admittedly the evidence is again most persuasive for fluctuations on roughly annual timescales as opposed to for the multidecadal trends.
O’s Peace Dividend Report (formerly Goreacle Report) from the GWN, the Land of the Broken Hockey Stick. (Go, Steve.)
The frost moves up the window pane, Canuck Ned Pratt said.
The “expert'” has more: Goreacle is “”shattering” them,”.
…..
“Cold snap grips B.C., sets dozens of records again on Thanksgiving
The early-morning reading of 0.9 degrees Celsius was a low for Oct. 12 since weather records began being kept decades ago.
“I’ve counted in excess of 80 cold-temperature records set throughout the long weekend [across the province],” said Environment Canada meteorologist and Global BC weather expert Mark Madryga on Monday.
In many cases, the lows aren’t just slipping slightly below old records but “shattering” them, he said.
He cites Williams Lake, where the morning low of minus 13 broke the old 2002 record of minus 6.5.
“And most of these weather stations go back 50 or 60 years or more,” he notes.”
http://www.calgaryherald.com/technology/Cold+snap+grips+sets+dozens+records/2092744/story.html
Smokey says:
Actually, I think it is you who are being disingenuous by calling yourself a “skeptic”. As I have illustrated many times, you seem to be about the least skeptical person on the planet when it comes to some supposed piece of evidence that supports your own pre-conceptions. I think it is great that the side which the real science is on should attempt to take back the use of the word “skeptic” or “skeptical”, which has been badly misappropriated by those who are just dead-set against entertaining the possibility that AGW is real.
What is silly…and actually quite frustrating…is that only yesterday I linked to a peer-reviewed paper that showed that the more recent data that your figure is based on shows that the correlation illustrated in that figure breaks down dramatically (and that it actually starts to break down even in the time period shown by that figure but is hidden by some errors in doing the interpolation at the endpoint). Thus, the warming over the last ~30 years cannot be explained by this supposed correlation between solar cycle length and temperature. Yet, you link to that figure again again! That seems like willful ignoring of evidence to me.
Smokey, just to remind you, here is the link: http://magee.vsb.bc.ca/dsheldan/climate/pdf/Laut_2003.pdf It is worth noting that one of the original co-authors of the paper containing the data that you showed (Lassen) was on the new paper that updated that data in 2000 ( http://www.uwmc.uwc.edu/geography/globcat/globwarm/solar-00.htm ) and his co-author on that new paper notes, “The curves diverge after 1980 and it’s a startlingly large deviation. Something else is acting on the climate.” And, although he says they can’t be sure what is responsible, he says, “It has the fingerprints of the greenhouse effect.”
Would this work as a fingerprint? Scroll down to the graph. Notice the decreasing temperature averages. Is that a fingerprint?
http://www.wrh.noaa.gov/pdt/
brrrrrrrrrrrrrrrrrrr
William,
“If cloud feedbacks turn out to be positive then it will be game over for the skeptical argument.”
What if cloud feedbacks turn out to be negative? What would that mean to “the skeptical argument”? You are implying that the determination of the value of “the skeptical argument” lies in the future. WRONG! The skeptical argument is directed towards the lack of scientific method of today, regardless of what will be (scientifically) proven in the future.
Joel Shore (17:50:05),
I think you’re actually going to throw a tantrum if you can’t get skeptics to believe in your arguments. You haven’t provided any solid, real world evidence that CO2 causes anything more than minor warming. If that. And if CO2 only causes little or no warming [the jury is still out on that, despite stamping your foot about it], then it’s best if the world stops its crazy rush toward self destruction, led by AGW fanatics terrified of a real debate.
For those who worship at the altar of climate peer review, here are a few of the many skeptical papers out there [and there would be plenty more if the peer review process wasn’t tightly controlled by a rent-seeking AGW grant clique]:
CONCLUSIONS:
• All examined long records demonstrate large overyear variability (long‐term fluctuations) with no systematic signatures across the different locations/climates.
• GCMs generally reproduce the broad climatic behaviours at different geographical locations and the sequence of wet/dry or warm/cold periods on a mean monthly scale.
• However, model outputs at annual and climatic (30‐year) scales are irrelevant with reality; also, they do not reproduce the natural overyear fluctuation and, generally, underestimate the variance and the Hurst coefficient of the observed series; none of the models proves to be systematically better than the others.
• The huge negative values of coefficients of efficiency at those scales show that model predictions are much poorer that an elementary prediction based on the time average.
• This makes future climate projections not credible.
• The GCM outputs of AR4, as compared to those of TAR, are a regression in terms of the elements of falsifiability they provide, because most of the AR4 scenarios refer only
to the future, whereas TAR scenarios also included historical periods.
More on climate peer review:
Another peer reviewed paper debunking AGW: link
Exposé of UN “peer review”: link
CO2 lags, does not lead, temperature [Peer reviewed]: pdf
Climate models have no credibility [per reviewed]: link
The real reason for the low number of skeptical papers being accepted by the AGW clique: click
Many more peer reviewed papers here debunking AGW: click. [Cue the ad homs]
It’s time for Joel to write his article, instead of always taking his impotent pot shots from the sidelines. Whaddya say Joel me boy? Got what it takes? Or is hit ‘n’ run always your style?
Joel Shore (17:50:05) :
“I think it is great that the side which the real science is on should attempt to take back the use of the word “skeptic” or “skeptical”, which has been badly misappropriated by those who are just dead-set against entertaining the possibility that AGW is real.”
Joel – “real science” eh? I’m a skeptic when I see garbage like this:
http://www.giss.nasa.gov/tools/modelE/
passed off as “proof” of AGW for policy makers (i.e. our government), so they can fool the public into passing confiscatory taxes and burdensome regulations as a way to “fix” the global warming problem.
But I really can’t blame the people in the climate industry for advancing the AGW meme – it has proven to be very lucrative for those involved…
Scott. The problem with this conjecture is that c02 effects work to saturation in the lower troposphere – so adding or subtracting quantities (changing their concentrations) doesn’t affect what happens in the stratosphere, since the same amount of radiation comes through to the stratosphere anyway. Adding more c02 or water vapour doesn’t affect how much heat exits the atmosphere. At mid troposphere this heat is emited in different directions, so it doesn’t cause more heat.
There is also a flaw with the notion that some 30% of c02 is anthropogenic – Oceans emit 27 times that of anthropogenic sources per year, and land emits 8 times as much, mainly through decay and respiration. that leaves anthropogenic at 4% max. The isotopic mass balance allegedly calculates it at that figure… However, if you’re using ice measurements from ice as the standard for how much c02 there is today as opposed to before measurements began -then there is much dubious science involved – from the method of measuring ratios of hydrogen and nitrogen – the method of how they are obtained (crushing ice in a vacuum causes gases to diffuse with the gases they are escaping with), and the fact that stability of molecules in ice changes over time – with the tendency of c02 to deplete to a lesser optimum. Not only the peaks, but the averages.
The only way ot measure atmospheric c02 is direct measurement, and this has been going on for quite sometime
The nominal conclusion of the above is that ice cores indicate a 30% increase today, whereas pre (and post) 1957 back to 1810 measurements by chemical and spectroscopic methods show similar figures, or excessive figures of today
Ah, fingerprints to go with the carbon footprint ‘eh….. This whole AGW thing is loaded with comedy if one is in the mood… LoL:-)
Smokey: I think thou dost protest too much. Having been caught red-handed using the same deceptive graph a day after I last shot it down, you have now gone off on a tangent!
As for your post, I count 4 links to what you call “peer-reviewed” papers. Two of them are really links to the same paper (one a version that was apparently not peer-reviewed published in a conference proceedings and the other version published in a hydrology journal that I don’t think normally publishes on climate science). One is a link to something at ICECAP that comments on Hansen’s 1988 paper but I see no evidence of being peer-reviewed.
And, the final one is a link to Caillon et al published in the journal Science no less. The problem, however, with the Caillon article is that it does not contradict AGW in any way. It just shows that temperature started to rise before CO2 levels did in the ascent out of the glacial period ~240,000 years ago. Since it has been understood since the mid-1970s that the trigger of the glacial – interglacial cycles is orbital oscillations, this was not really very surprsing. The last paragraph in their paper is worth quoting in full:
“Skeptics” are in the awkward position of having to say, “Look at this paper but make sure you ignore the final paragraph!”
Joel, Joel, Joel. Saying that your version of science can beat up his version is soooooo grade school. Your side does not have a monopoly on; what phrase did you use, “I think it is great that the side which the real science is on…”, what is real science. From what I have seen here, you have a Ph.D. in physics, but correct me if I am wrong. Regardless, please act as if it is more than a degree in Piled Higher and Deeper.
Scott Mandia (17:12:24)
“Today’s warming climate is doing so at rates that ‘natural’ forcings seem not to be able to explain.”
These few words describe my picture. Consider the (non-Mann!) hockey stick graphs. Not only is the blade higher, it is also STEEPER than for other warmings in the past 2000 years.
This would seem to reduce “the possibility that warming might have been simply part of a natural, internal fluctuation (cycle, if you wish) in the clilmate system.”
Jan veizer was published in science mag – how he got through the peer reviewing / censorship process is a mystery.
Perhaps he didn’t put the AGW disclaimer in the final paragraph to get past the censors, which they all seem to do!
P Wilson (18:21:02) :
Scott. The problem with this conjecture is that c02 effects work to saturation in the lower troposphere – so adding or subtracting quantities (changing their concentrations) doesn’t affect what happens in the stratosphere, since the same amount of radiation comes through to the stratosphere anyway. Adding more c02 or water vapour doesn’t affect how much heat exits the atmosphere. At mid troposphere this heat is emited in different directions, so it doesn’t cause more heat.
Not true, CO2 absotption is not saturated in the troposphere, absorption in the atmosphere is approximately proportional to log([CO2]).
See for example: http://i302.photobucket.com/albums/nn107/Sprintstar400/CO2spectra.gif
Phil. (19:50:36) :
P Wilson (18:21:02) :
Scott. The problem with this conjecture is that c02 effects work to saturation in the lower troposphere – so adding or subtracting quantities (changing their concentrations) doesn’t affect what happens in the stratosphere, since the same amount of radiation comes through to the stratosphere anyway. Adding more c02 or water vapour doesn’t affect how much heat exits the atmosphere. At mid troposphere this heat is emited in different directions, so it doesn’t cause more heat.
Not true, CO2 absotption is not saturated in the troposphere, absorption in the atmosphere is approximately proportional to log([CO2]).
Carbon dioxide cannot absorb energy per molecule ad infinitum. There are limits for every level of concentration of carbon dioxide in the atmosphere, depending on the Pp it exerts for the whole. The greatest lie from AGW idea is that the carbon dioxide absorptivity at its current concentration in the atmosphere is the same as if the concentration of the carbon dioxide in the atmosphere was 100%.
Even if the carbon dioxide concentration in the atmosphere was 100%, its limit of absorptivity would be 0.3, which is nothing in comparison with methane and water vapor absorptivities at their current concentrations in the atmosphere.
P Wilson (19:30:24) :
Jan veizer was published in science mag – how he got through the peer reviewing / censorship process is a mystery.
Perhaps he didn’t put the AGW disclaimer in the final paragraph to get past the censors, which they all seem to do!
I cannot find Jan Veizer published in Science Magazine, but only a mention by Richard Kerr. Would you be so kind as to tell me the title of Veizer’s article?