Arguments
Lindzen Illusion #7: The Anti-Galileo
Posted on 13 May 2011 by dana1981
Richard Lindzen is one of the most prominent and widely-referenced climate scientist "skeptics". After all, there is a scientific consensus about anthropogenic global warming, so there are few climate scientist "skeptics" to choose from. Lindzen has researched climate science for four decades, since the field really began to grow and develop in the early 1970s, has published hundreds of peer-reviewed papers, works at a prominent academic institution (MIT), and has been a "contrarian" for most of his career.
So his combination of expertise and "skepticism" make Lindzen an appealing figure to "skeptics". He's even been compared to Galileo quite frequently. But there's one major difference between Galileo and Lindzen: Galileo was right.
Galileo's positions were based on and supported by scientific evidence. Other scientists at the time also recognized that Galileo was right and supported by the evidence. In this post we will see that Lindzen, on the other hand, has a history of consistently being wrong on climate issues, and his positions are contradicted by the scientific evidence and observational data.
Lindzen's Evolution
In his 1989 MIT Tech Talk, Lindzen summarized his many climate contrarian positions at the time:
- Earth hasn't warmed as much as expected
- the surface temperature record is wrong
- global warming is not a concern
- climate sensitivity is low
- the water vapor feedback is negative
- the cloud feedback is negative
- global warming is just due to internal variability
- water vapor is the most important greenhouse gas
Over the years, Lindzen's views have evolved somewhat, and some of these positions have fallen by the wayside. Let's examine how his 1989 positions compare to his current views, and how they stack up against the observational data. You would think a scientist's views would match observational reality, but as we will soon see, that's simply not the case for Lindzen.
Earth hasn't warmed as much as expected - this remains one of Lindzen's favorite arguments, which he makes in media articles on an annual basis to this day. But as we saw in Lindzen Illusion #1, there is simply no truth to this argument. When we consider all factors, including aerosol cooling and ocean thermal inertia, both of which Lindzen neglects in making this argument, we see that the planet has warmed almost exactly as much as climate models expect.
The surface temperature record is wrong - as we saw in Lindzen Illusion #2, in 1989, Lindzen didn't even put the GISTEMP observed warming trend (0.5 to 0.7°C since 1880) within his range of possible warming trends (-0.2 to +0.4°C since 1880). As we now know, and as Lindzen would now admit, James Hansen and GISTEMP were right, and Lindzen was wrong. The surface temperature record was and is accurate.
Global warming is not a concern - this argument is of course fundamental to global warming "skepticism", and thus one which Lindzen continues to subscribe to. However, it's based on a conglomeration of Lindzen's many other incorrect arguments, and as shown in Lindzen Illusion #3, his arguments against taking action to reduce GHG emissions are based on logical fallacies and a lack of understanding of economics.
Climate sensitivity is low - this continues to be Lindzen's bread and butter argument, but as illustrated in Lindzen Illusion #2, temperature projections using low sensitivity simply don't match the observed warming trend. Additionally, Lindzen Illusion #1 showed that the warming we've seen so far is inconsistent with low climate sensitivity. Lindzen Illusion #4 demonstrated that nothing credible we've seen so far suggests sensitivity is nearly as low as Lindzen claims. His low sensitivity argument seems to be based on little more than his own fundamentally flawed paper.
The water vapor feedback is negative - as we saw in Lindzen Illusion #4, Lindzen argued that water vapor could be a negative feedback due to a drying of the upper atmosphere until the mid-1990s, but had begun to reverse this position by the end of the decade. Indeed, recent observational evidence has been consistent with the climate model projection of a strongly positive water vapor feedback.
The cloud feedback is negative - Lindzen Illusion #4 also discussed that Lindzen continues to believe the cloud feedback is strongly negative. However, his "infrared iris" hypothesis has not withstood the test of time, and numerous recent studies have been inconsistent with a strongly negative cloud feedback.
Global warming is just due to internal variability - Lindzen continues to argue that internal variability may account for most of the global warming over the past century. However, Lindzen Illusion #5 revealed this argument's Achilles heel: the oceans (including the deep layers) are warming too. If the surface warming were simply due to heat moving around the internal climate system, from oceans to air, then the oceans would be cooling. Moreover, we saw that Lindzen's argument was based on a misrepresentation of other climate scientists' work.
Water vapor is the most important greenhouse gas - although Lindzen no longer downplays the role of CO2 in the greenhouse effect, he continues to downplay its role as a global temperature driver, and many "skeptics" still argue that water vapor is a far more important greenhouse gas than CO2. However, as highlighted in Lindzen Illusion #6, two recent NASA GISS studies demonstrated that CO2 plays a far larger role in the greenhouse effect than Lindzen claimed in 1989, and more importantly, is "the principal control knob that governs the temperature of Earth".
In short, of Lindzen's eight 1989 arguments listed above, he has effectively admitted that he was wrong on three points (temperature record accuracy, water vapor feedback, importance of CO2 as a greenhouse gas), but continues to make the other five. However, none of these remaining five arguments mesh with observational reality. But a useful question comes to mind, given the frequency with which "skeptic" arguments contradict each other: are these surviving arguments contradictory or self-consistent?
Lindzen's Consistently Cloudy Vision
Lindzen's surviving arguments are: Earth hasn't warmed as much as expected, global warming is not a concern, climate sensitivity is low, the cloud feedback is negative, global warming is just due to internal variability. And indeed, we can create a consistent depiction of the climate system with these arguments.
A strongly negative cloud feedback would allow for a low climate sensitivity, which would explain how the large anthropogenic GHG radiative forcing could have a small impact on global temperatures. If the anthropogenic influence were overestimated, then Earth wouldn't have warmed as much as expected. But if GHGs aren't driving global warming, there must be another cause. Lindzen explains the warming through the natural internal variability of the climate system (although as Swanson et al. (2009) note, a climate system with larger internal variability will also tend to be more sensitive to external forcings). And if the warming is just natural variability, it will soon reverse itself, and thus is of no concern.
So Lindzen does present a mostly coherent, consistent alternative hypothesis to the anthropogenic global warming theory. There's only one problem: as discussed above, every single one of these arguments is inconsistent with the observational evidence. You may have also noticed that every single one of Lindzen's positions have underestimated or downplayed anthropogenic global warming, which suggests they may be based on contrarianism rather than scientific evidence.
Lindzen has constructed a house of cards, with his incorrect conclusion (global warming is of no concern) sitting atop a series of incorrect beliefs which are each contradicted by the observational evidence. Indeed, when asked by then-Senator Al Gore why he believed water vapor and clouds generate a negative feedback in a 1991 Congressional hearing (Page 71), Lindzen responded:
"as far as we can tell every model predicting an excess of 2 degrees [sensitivity to doubled CO2] is predicting more [warming] than we already have seen."
In short, Lindzen's "no concern" argument is based on his "low sensitivity" argument, which is based on his "clouds are a large negative feedback" argument, which is based on his "Earth hasn't warmed as much as expected argument. It's just one huge chain of wrong arguments based on other wrong arguments, finally leading to a very wrong conclusion.
With this history of being wrong, the comparisons to Galileo seem wholly inappropriate. There is of course nothing wrong with being occasionally mistaken in science. The problem arises when a scientist is consistently wrong and fails to learn from the corrections advanced by other scientists or by nature, especially when we're asked to believe that he is right and virtually every other scientific expert is wrong.
Galileo was not a contrarian who was purely motivated to contradict Catholic beliefs. Galileo's key feature is that his conclusions were dictated by the scientific evidence. If anything, Lindzen is the anti-Galileo, as his conclusions seem to be based on pure contrarianism instead of scientific evidence. Indeed, this seems to be a common feature among self-proclaimed global warming "skeptics", which is likely why Lindzen is held in such high regard despite his dismal climate record.
NOTE: clicking John Cook's snazzy Lindzen Illusions button at the top of the post will take you to our comprehensive Lindzen page (short URL http://sks.to/lindzen), with tabs for Lindzen's quotes, articles, arguments, our Lindzen blog posts, and relevant external links. It's identical in format to the Monckton Myths page
The one critique I have is that I gathered on the prior post in this series that Lindzen postulates a lower sensitivity to CO2 levels than to orbital changes. I would like to see a treatment of that if you have time.
My first thoughts on the matter are that orbital forcings are initiated by albedo changes, and we have already seen large albedo changes as a result of CO2 induced warming. So, if I am correct, again, there is actual evidence that counters Lindzen's model of the world. Although, I don't know if the albedo changes we have already seen are greater or larger than Milankovitch cycle induced changes.
I also recall reading that, from a mathematical perspective, the amount of forcing that an M. cycle produces is smaller than the W/m^2 forcing that some level of increased CO2 produces. That could be another tack to take.
Thanks Again.
I'd also like to mention that I emailed Dr. Lindzen to offer him the chance to respond to the Lindzen Illusions series.
I think there are good odds of it being in
Lindzen, R. S.: 1993, 'Paleoclimate Sensitivity', Nature 363, 25-26.
But, I suspect getting a copy of that will require a subscription to Nature or access to a university library that I don't currently have.
I'd like to add a couple of other fators which, I think, come into these kinds of discussion.
1/ selection bias.
As you say, Galileo was right - we know that to the nth degree with hindsight. But there have been many - often brilliant - scientists who've made wrong 'strong' assertions. How does one know, for someone makeing strong and public claims, that theyre like Galileo and not, for example, like Eric Laithwaite? I superb chap, who, for years, held onto the belief that gyroscopes violate Newtons laws. Or like the late Freddy Hoyle a giant amongst cosmologists, who never really gave up on the expansionary universe?
I'm not going to get into lists ;), but I'd not be surprised if there where more cleaver chaps who held out for wrong ideas than ones who struck gold!
2/ The second point is that it is not unusual for people to hold onto wrong beliefs when the benefit of doing so - e.g. lime-light, a following etc - is greater than the detriments - e.g. looking daft to other people. This point was called "being strategically wrong" as analysed by Robert Kurzban in "Why Everyone (Else) Is a Hypocrite: Evolution and the Modular Mind By" in which he noted that Stephen Jay Gould - who we all know and love - sustained a completely ill founded assault on evolutionary psychology for many years, despite criticisms, not only from them, but from his own! This is a good read.
I remind people of Poptech... the value of his list - his fame, 'voice', internet-presence etc. not only depended on the list but the list being wrong and, therefor, the arguments it generated. It was in his best interest for the list to be wrong! A good list summarizing the number of papers published supporting AGW to a greater or less degree, or even a better use of statistics or clearer analysis (as we all suggested)... would not have brought him any fame and attention, upon which he thrived!
yes he sort of says it in that letter to Nature you refer to (which is a response to a Hoffert and Covey paper describing a calculation of a value for climate sensitivity (2.3 oC per doubling of CO2)[*]). Lindzen asserts that temperature changes are dominated by changes in the nature of heat transport (air and oceans), and suggests that Milankovitch cycles, which themselves result in very minor changes in total insolation, are amplified by changes in this heat transport.
Referring to these heat transport processes as "dynamic fluxes" Lindzen says:
He states that atmospheric heat fluxes depend on Hadley circulation in the tropics, which
In other words Lindzen is asserting that the Milankovitch cycles and their effects on glacial-interglacial series are amplified by heat transport changes, and these don't need any significant contribution from radiative forcing from variations in [CO2]. He states:
Hoffert and Covey are pretty robust in their response!
* Martin I. Hoffert, Curt Covey (1993)Palaeoclimate sensitivity Nature 363, 26-26.
That is a pretty mind boggling hypothesis by Lindzen! I have not read Hoffert and Covey's Only tiny external forcing to set off huge global warming/cooling without the aid of a CO2 feedback? Does he at least accept the feedback from changes in albedo?
I have a major problem with his hypothesis, how the heck does the redistribution of a tiny increase of energy amplify the warming. Surely the additional heat is just redistributed by these meridional fluxes? This seems to be the same logical fallacy that internal climate oscillations are driving long-term trends. His hypothesis may , at best, describe long-term regional changes in temperature, but not long-term global trends.
Anyways, I am probably missing some even more disturbing issues, but that is all that came to mind off the top of my head.
You should probably add that Richard Lindzen is part of that consensus - his published works indicate AGW due to CO2.
The response to Lindzen's critique (that I quote from) of Hoffert and Covey's paper (whch was in fact published in 1992, and not 1993 as in my post above), by Hoffert and Covey is very interesting. It pretty much tears apart Lindzen's conjecture, and is astonishingly modern; it could have been written yesterday, and gives a pretty up to date account of energy balance, ice age cycles and radiative forcing.
Incidentally Hoffert and Covey's original paper cited in my post above, refers to another of Lindzen's subsequently falsified assertions; Hoffert and Covey say:
The sonde data disagree.
And, so do observations of emissions.
The water vapor channels from satellites depict the energy at which water vapor emits to space.
Spatially anyway, the highest levels of water vapor emission are from the sub-tropics. The dynamics ( who'd have thought, dyanmics? ) of subsidence account for this, of course, but spatially, if one looks at regions excluding high clouds ( which are far more important radiatively than gasses ), then higher surface temperatures correspond to greater emissions from water vapor. Lower surface temperatures correspond to lower emissions from water vapor.
The correlation is less than with the window emissions or with the wings of CO2 emissions, but this is negative feedback.
There is loads of data from satellites that indicates an increase in upper troposphere water content pretty much as expected from enhanced greenhouse induced tropospheric warming. See for example:
Dessler, A. E., Z. Zhang, and P. Yang (2008), Water-vapor climate feedback inferred from climate fluctuations, 2003–2008 Geophys. Res. Lett., 35, L20704
here
Gettelman A and Fu, Q. (2008) Observed and simulated upper-tropospheric water vapor feedback J. Climate 21, 3282-3289
here
Buehler SA (2008) An upper tropospheric humidity data set from operational satellite microwave data J. Geophys. Res. 113, art #D14110
here
Brogniez H and Pierrehumbert RT (2007) Intercomparison of tropical tropospheric humidity in GCMs with AMSU-B water vapor data. Geophys. Res. Lett. 34, art #L17912
here
Santer BD et al. (2007) Identification of human-induced changes in atmospheric moisture content. Proc. Natl. Acad. Sci. USA 104, 15248-15253
here
[*] Soden BJ, et al (2005) The radiative signature of upper tropospheric moistening Science 310, 841-844.
here
who state:
“Although an international network of weather balloons has carried water vapor sensors for more than half a century, changes in instrumentation and poor calibration make such sensors unsuitable for detecting trends in upper tropospheric water vapor (27). Similarly, global reanalysis products also suffer from spurious variability and trends related to changes in data quality and data coverage (24)."
I suspect another, possibly more important piece of work, for this discussion, is referenced by Covey as
Kirk-Davidoff, D. B. and Lindzen, R. S.: 1993, Paper presented at the American Geophysical Union
annual Fall .Meeting, San Francisco, CA.
which might also be known as
Kirk-Davidoff, D.B., and R.S. Lindzen, 1993: On the Role of Meridional Energy Fluxes
in Climate Change. Oral Presentation, Fall Meeting of the American Geophysical Union.
http://www.atmos.umd.edu/~dankd/CV.pdf
I have not found a publication of that paper by the same name. I'm wondering if dankd the poster here is Daniel Kirk-Davidhoff, the primary author of the paper above, and if so, if he could shed some light on the different mechanics between orbital and GHG forcings.
Any good?
(I'm sitting for my Clinate "skeptic" exams. Think I'll pass?)
Not that it matters, but I think the odds are against it.
As for your reference to Poptech's list, I'll admit to some curiosity about it, but he lost me when he claimed to have a better understanding of what some papers mean than the persons who wrote them.
19 - yes, it is curious and fascinating...
(see slide 15 for contradictory trends between two satellites )
As to RAOB, I'm sure you're familiar with the Paltridge paper
There are problems with sonde data, notably spatial coverage and instrumentation change. But even in recent decades, as the instrumentation has become more uniform, the sonde data do not show positive feedback.
One should also look further.
People assume that when humidity increases, infrared emission to space decreases. But we observe the opposite. Excluding cloudy areas, the moist subtropics emit more to space than do the dry polar regions. It is temperature and vertical variation of humidity that govern earth's emission amount and not to total water vapor.
Make the world more like the subtropics and it will cool off because it will emit more energy to space.
Make the world more like the polar regions and it will warm up because it will emit less energy to space.
I can't believe anyone would still put forward the Partridge paper as evidence/argument for anything.
For example, the radiosonde reanalysis of McCarthy et al (2009) does show a positive water vapour response to tropospheric warming. Likewise the reanalyses described by Dessler and Davis (2010). Likewise with the new radiosonde analyses described in Dai et al. (2011).
Paltridge et al is not a particularly convincing example for your argument. After all the authors themselves conclude:
I don't think one can dismiss the very large body of work from satellites and now from raiosonde reanalysis that global warming is accompanied (amplified) by enhanced tropospheric water vapour.
Make the world more like the polar regions and it will warm up because it will emit less energy to space. "
This is one of the more outrageous statements you've made. You are, I hope, aware of the T^4 relationship between temperature and power emitted? Of course the tropics emit more energy, they are warmer!
I would rather not turn the polar regions into tropics, myself - it would have rather harsh consequences for the middle latitudes, let alone the present tropics.
Moist air emits less energy than dry air at any particular temperature, ClimateWatcher. Predicted, tested, proven.
Just to connect some dots, that is the same link posted by dankd, whom I suspect is the same climate researcher who studied under Lindzen as a graduate student about the time that the 1993 discussion and unpublished AGU presentation were written.
So, I suspect that Dan has a better understanding of what Lindzen's views are, or were, than anyone other than Lindzen himself. Which makes the AGU presentation, where he is the primary author and Lindzen the second, interesting.
Paltridge et al. found that specific humidity in the NCEP/NCAR reanalysis declined between 1973 and 2007. However, this reanalysis is incredibly biased and almost certainly inaccurate for several reasons.
1) Other reanalyses indicate that the long-term water vapor feedback is positive, as chris noted.
2)The NCEP/NCAR reanalysis was solely dependent on radiosonde humidity measurements to constrain upper tropospheric humidity. As you note, there are problems with these measurements.
3) While the NCEP/NCAR reanalysis showed that the long-term water vapor feedback is negative, it also indicated that the short-term feedback is positive. This makes very little physical sense.
4) Newer reanalyses include improvements that are designed to increase the fidelity of long-term trends. Thus, the NCEP/NCAR reanalysis is not as accurate as the newer reanalyses which indicate the existence of a positive feedback.
Dessler and Davis (2010) - full paper
On the other hand, Lindzen is at the rump end in the march of climate science. Fifty-sixty years ago, his no-significant-CO2-effect position was the consensus position among climate scientists. It has since declined to only 3% (or 1%, with 2% don't know).
This distinction is of obvious interest to those who don't know much climate science, and are looking for other indications of validity.
Those who would champion Richard Lindzen need to find another analog. In the history of science are there any examples of scientific positions that have declined to 3% participation, yet eventually prevailed?
Copernicus or Ohm might do. The sad part being that their "being right" was only received recognized after they died.
http://en.wikipedia.org/wiki/Georg_Ohm
Dana - this is a GREAT article. Thank you. I really like the what he said then, what he says now, and where is right and wrong setup. It feels much fairer than the original - tear apart his 1989 positions.
[dana1981] Thanks!
Indeed (ignoring the fact that Ohm is a pretty poor example of controversy in science!) ... Again the point is that history contains examples of people who swam against the tide - some where right, some wrong, some right about some things and wrong about others (which includes Newton and Einstein), some recognized as right before they died, others after, others where just plain wrong...
You have to justify - over and above "doesn't agree with the consensus" - why you think X is like Y, and justify it against the relevant history of science.
Just saying "The maverick in science is often correct" without the justification is gibberish or propaganda... As I mentioned above, Laithwaite was, to some degree, "The maverick in science is often incorrect"... Why isn't he like that?!?!?
Of course, for people who aren't used to doing a careful analysis and argument, such throwaway lines come naturally (see the blog links in the above article). I'd hope that SkS commentators would function at a higher level.
"An analog much harder to find is a mob that admits its mistake.
You're being a little hard on the likes of Drs Lindzen (and e.g. Spencer and Christy). I wouldn't call them a "mob" even if their actions are rather ill-considered. Perhaps you meant that they have a tendency to incite "mobs"! Maybe a bit of British-style kettling
would be in order....
Actually Drs Spencer and Christy didn't so much "admit their mistakes" as have them pointed out in a manner that was impossible to deny (see pages 972/3).
Just saying "The maverick in science is often correct" without the justification is gibberish or propaganda...
You could say "the Maverick in science who is correct is more often remembered by posterity than the maverick who is wrong".
Every individual and their circumstances and social/scientific environment is different. So Wegener's studies were done at a time when there was neither a particularly strong scientific imperative to address the apparent physical, geological and environmental relationships between several adjacent continental margins, nor any political imperative whatsoever to do so.
And whereas Wegener's ideas were right in essence (those inter-continental margin relationships were real and the result of actual juxtapositions in the deep past), Wegener couldn't propose any sort of realistic mechanism, and this differs from the situation today, re the evidence base that informs us on climate change, and the false evidence base that drives Lindzen-style analyses.
Wegener's mechanistic proposals were rightly rejected (he suggested that the continents might be driven through the oceanic crust under the gravitational influence of the moon, for example). And he was inherently incorrect in that continents don't "drift". Rather they "piggy-back" on the plates to which they are very firmly attached....
Lets say the first firm indications for AGW piled up between the mid 70's and late 80's based on very rudimentary measurements compared to what's available today. I recall that even in the early 90's many scientists in associated fields where still unsure (in my direct experience, the European earth-observation crowd where still 'more measurement needed' in the mid 90's), till now where there is pretty broad based consensus, except for a few stragglers in the science community...
... and a pile of nutters in the public sphere, of course.
Whereas it seems that Wegener's ideas were soundly rejected at the time (in fact he had some supporters who were very important in geology/geophysics), and he was only vindicated after his death when new discoveries forced reassessment of his ideas, Hansen and Broecker were reinforcing an already quite well understood subject. Their insight was to strongly grasp the significance of the growing atmospheric CO2 levels, in the 1970's (Broecker) and 80's (Hansen), and to foresee the likely future consequences. And their contributions were not so much ignored/ridiculed, as considered not to be terribly important (at the time; I think that's about right). In fact their attempted ridicule (largely Hansen) occurred considerably later when the evidence base concerning the consequences of enhanced greenhouse gas levels became sufficiently strong, that some powerful interest became concerned that steps might be taken to do something about the problem...
"ignoring the fact that Ohm is a pretty poor example of controversy in science"
Considering that "Ohm's Law" was rejected for being too simple, and then turned out to be spot on, not sure where you're coming from. Here is another link:
http://www.corrosion-doctors.org/Biographies/OhmBio.htm
Still, if you like; I'm not fussed about that, I'm fussed about the justification of the comparison based on history if science etc. Clearly the simplicity of ohms law isn't that - there's nothing nearly as simple about climate science!
So, we're still awaiting your detailed justification for your suggestion.
Excellent!
Although maybe you being less then generous to the substantial improvements in climate systems simulations, models etc.
I'd love to see an equally detailed [attempt at a] comparison between Galilao and Lindzen!
Of course no such comparisons work in all details. Still, such details provede more insight than a the sort of thin posted on wuwt etc.
If Lintzen's last name wasn't MIT, who would pay attention to him?
I had not been to wuwt in ages, but as a result of your post I went there.
Bob Tisdale has an excellent post on OHC verses a model. I read what Tamino posted, and will only say that he degrades himself in his response.
There is a def divergence, at this time, between observations of OHC and the models.
However, this discussion is off topic. Please stick to the content of the article.
Trends since 1979 are all below the IPCC "low scenario" rate.
Trends since 2000 are all below the IPCC ".2 C per decade for all scenarios" rate.
One for Lindzen.
2. the surface temperature record is wrong
SST and MSU are pretty close to land rates ( except for the high outlier GISS ) UHI effect does exist, but it is not a huge part of the temperature averages.
3. global warming is not a concern
Concern reflects emotion, not a scientific quantity.
But we know the recent rate is quite similar to the early twentieth century rate.
We know that Northern Hemisphere temperatures were higher for millenia during the Holocene Climatic Optimum, a time which corresponded to the advancement of human civlization.
And we know that humans and all the other species of life on earth evolved through all the glacial/stadial changes.
Pretty hard to get worked up about this when there are so many real problems to be concerned about.
4. climate sensitivity is low
Well, the lower warming rate from 1. indicates this to be true.
But nobody can be sure. Why? Because we don't know how much energy earth is receiving, mostly because we don't know how much the earth reflects away:
And we don't know how much earth is emitting:
The uncertainty in the balance is larger than the projected forcing from a CO2 doubling.
5. the water vapor feedback is negative
There are reasons to believe this to be so.
There is great uncertainty as to whether or not water vapor is increasing or decreasing ( the sonde data indicate drying aloft, but are subject to instrumentation changes over time, some satellites indicate increasing, some indicate decreasing humidity )
But beyond that, water vapor is a dynamic quantity.
It gets pushed around in the atmosphere, mostly pushed toward the equator by polar air masses.
And water vapor, by its mere presence, works against an increase. That's because if water vapor injects into the upper atmosphere, which was previously arid, that region of atmosphere then radiates more effectively and cools. This cooling allows subsidence to occur. And subsidence then dries this layer.
The total column water vapor might increase, but the top of this layer would emit just as effectively as with a lower total column water vapor.
6. the cloud feedback is negative
Since the meager attempts to create a long term trend of cloudiness disagree in sign ( some indicate increasing cloudiness, others indicate decreasing cloudiness ) I don't think anyone can justify a conclusion on what has actually happened. And since cloud formation depends on some many processes from the macro ( synoptic scale convergence ) to the micro ( condensation nuclei ) and in between, I have a difficult time with any theory predicting any change in cloudiness.
7. global warming is just due to internal variability
Since we don't actually know the energy balance well enough ( see above ) pretty much all attribution is a fairy tale.
On the other hand, look at the 97-98 El Nino. Temperatures changed by almost 1 degree C, but oceanic heat content didn't show a pimple. This was internal variability. The warming rate from 1910 through 1945 is about the same as the recent rate. And that was natural variability.
8. water vapor is the most important greenhouse gas
CO2 is significant, largely because of the band from which emissions to space leave from the stratosphere. That's a big deal because that makes the energy level that leaves from CO2 much lower and mostly (though not completely) independent of the surface temperature.
H2O vapor, on the other hand, diminishes with height. It is the vertical variation of temperature coupled with the vertical variation of the emitting constituent that determines the energy that leaves earth.
In this regard, forcing from water vapor is constrained and coupled to the surface temperature while CO2 emissions are not, and in this way CO2 is more 'important'.
On the amount of 'greenhouse effect', my understanding is the relative importance goes:
Clouds > Water Vapor > CO2
The question of 'importance', we might agree, is secondary to what will actually happen with changes in CO2.