I don’t like to comment about the information stemming from “Watts up with That” because no one in their right mind gets information from such a source, and by doing so I’m only allowing nonsense to set the tone in the climate debate, but Anthony Watts has a recent post about the water vapor feedback which I felt compelled to elaborate on.
I have little to say about the graphical approach or the cited paper at the bottom by Paltridge et al. I have already expressed concern over the usage of Re-analysis data for Relative humidity information, especially for older data. I’m particularly skeptical of sharp decreases in RH closer to the surface where the physics of the water vapor budget of the lower troposphere involves a tight thermodynamic coupling of the surface and atmosphere.
[edit, see update] McIntyre has his own post
The bottom line is that there is much better evidence from other sources showing a powerful water vapor feedback, and even the paper by Platridge et al. warn to be cautious of the results. I have posted on the progress in understanding the WV feedback as it has evolved over the decades through improved theoretical, observational, and model-based approaches, and I see no reason why all that should be thrown out the window right now. There’s lots of literature providing good evidence of a strongly positive water vapor feedbacks (e.g., Soden et al 2005 and Dessler et al 2008) and more through treatment is given in the IPCC AR4 report and NAS report on feedbacks.
What if relative humidity were in fact on the decline?
Anthony Watts and CA make it out to be self-evident that this should mean a negative climate feedback, but it’s not self-evident. His citation to Miskolczi is pretty much a credibility-destroyer. Admittedly, some of this confusion may arise from a very poorly worded abstract by Paltridge et al. more than anything. But the very title of Watts’ post is therefore misleading (even though he says “then water vapor ‘may’ cause a negative feedback” later on).
Relative humidity is given as a percentage,
RH = 100*(Vp/SVp)
Which is a ratio of the total water vapor content to the saturation vapor pressure (the latter can be thought of as an “upper limit” to the possible water vapor concentration in the atmosphere, due to the limits imposed by temperature).
The water vapor feedback doesn’t happen because of changes in relative humidity, it happens because of changes in specific humidity (Vp). The reason relative humidity is important though is because it tells you how the change in water vapor content scales with the change in saturation vapor pressure at a higher temperature. It’s possible to have relative humidity drop but still have an increase in the saturation pressure, and depending on which one of those wins out tells you whether Vp is larger or smaller. So, if RH were actually declining, it could simply be that the water vapor feedback is positive but less powerful than the mainstream science suggests.
Earth’s paleoclimate history is incompatible with a negative water vapor feedback. Long-term outlooks over geologic time on climate sensitivity, the inferred sensitivity through looking at the Last Glacial Maximum and other observations, millennial scale outlooks or even the strength of the seasonal cycle show that the Earth’s equilibrium temperature is not insensitive to change (ironically, we are always reminded of this by those who argue global warming must be natural).
Update I’m withdrawing a particular comment I wrote in my thread on McIntyre and “iffy” data which is seen in the comments. My apologizies. I still think Watts implied such where he writes “…ignored for the most part by the mainstream climate community, even going so far as to having a debate over the paper’s source of data (NCEP reanalysis of radiosonde data) and declaring the data to be too ‘iffy’.” Really, I think this was the main concern, and there is no need to jump back to GISS “issues.” With a more clear reading, I think McIntyre has been a bit more sensible about this, at least up until the post gets into the “Paltridge viewpoint.”
Climate Change 
NASA’s very own data of specific humidity right here:
http://members.shaw.ca/sch25/Ken/Optical%20Depth%20Data.xls
QED
Response– Same kind of data– chris
“”Watts and McIntyre (who has his own post ) make it out to be a bad thing that people are concerned with “iffy” data””
This isn’t true at all.
We are still here an`t we.
Thanks Robert Wood.
I have been looking for this data for a long time. Thanks again.
One thing I did with it was calculate the weighted average relative humidity (from 1050MB to 300MB) and it produces a decline of 4.0% (percentage points) which again is inconsistent with the global warming models. Specific Humidity is more-or-less constant.
For these levels, GISS Model E projects a 1.3% decline in RH. (The models need to have slightly declining relative humidity with increasing temperature or they would not be stable – runaway ice planet or runaway greenhouse without this assumption).
Response– Where do you get your information from? This is absurd.– chris
To put it all together, a 4.0% decline in relative humidity (and, in fact, a stable specific humidity means there is NO water vapour feedback at all) and doubling CO2 only results in an increase of temps of 1.2C or so (which is what the actual temp trend to date says the number should roughly be as well – circle completed.)
Response– Neglecting other feedbacks. But how can you say “what the actual temp trend to date says the number should roughly be as well?” Such a claim is rather bold given the large uncertanties in aerosol forcings, and “Heating in the pipeline.”– chris
Thanks for the kind words.
Response– I’m a grumpy guy– chris
“Watts and McIntyre (who has his own post ) make it out to be a bad thing that people are concerned with “iffy” data”
This claim is borderline libelous. Certainly McIntyre has said exactly the opposite in the very thread of which you speak.
But the reality is that “iffy” data is the norm in climate science. Climate scientists don’t generally have the luxury of short duration experiments that can be conducted in a laboratory, so they use what they have.
McIntyre, in particular, is used to dealing with papers that make statistical inferences from incredibly spotty data* without any meaningful caveats.
In this instance we have a paper that analyzes spotty data and does a very good job of discussing the caveats. In would be absurd for him NOT to compare the two.
But that doesn’t entitle you to claim that McIntyre “make it out to be a bad thing that people are concerned with “iffy” data”. It is a false claim, and should be retracted.
*sadly, incredibly spotty data [a decidedly unscientific phrase] in this context includes:
1. Using data which many or all prior peer reviewed articles have characterized as being of unacceptably poor quality
2. Using data which has been hand edited to maintain consistency with conclusions that were not supported by the actual measurements
Response– Retracted. By the way, I think the large issue was in the quality of data. I do see that McIntyre has been much more sensible about acknowledging this, but Watts’
post remains fraught with blatent errors and implications which cannot be taken out of this issue (starting from the very title). I should not group the two together, but I did, and I hope I don’t do it again– chris
Are you seriously claiming that significant climate change is impossible if, over time frames on the order of decades, short term negative water vapor exists?
Existing climate models do depend on positive water vapor feedback to explain the magnitude of historic climate change.
But invalidating those models does not somehow invalidate the history of Earth’s climate. It simply means that Scientists don’t fully understand the mechanisms behind climate change.
Response– The Earth is very insensitive with no water vapor feedback (let alone a negative one) since it acts to amplify other things. Almost all of climate science and the evolution of the Earth is out the window. Sorry, I just don’t buy that our understanding is that far off– chris
Chris,
There is no “heating in the pipeline.” If you have followed the discussions on ocean heat content, you would know the oceans have not warmed since 2002. There was heating in the pipeline during the 1990s, to be sure. But it just is not true today.
Response– Oh please. A monotically increasing warming trend in the oceans year-after-year is not necessary for thermal intertia physics to apply. The oceans actually have their own variability. Most of these arguments stem on hand picking a few years of data to make outrageous claims. Can you not see this? — chris
I came here because of the link you provided at CA, but I stopped reading your comment after the first line. Whatever errors may occur at WUWT, the notion that anyone who believes anything they read there is “not in their right mind” is the sort of comment that marks you as just another emotion-dominated, ad hominem-addicted alarmist.
When your crowd succeeds in destroying our civilization — when we are all shivering and starving in the dark — I wonder what lies you’ll tell yourself to evade the knowledge of the enormity of the evil you will have wrought on mankind?
Response– What did I say about his site that is untrue?– chris
If it turns out that additional CO2 with water-vapor feedback does *not* cause much warming, then that begs the question — what drove strong warming events in the Earth’s past? An excellent example is the Paleocene Eocene Thermal Maximum (PETM) event. What is a plausible physical explanation for the PETM if greenhouse-gas forcing is to be discounted?
And about three million years ago, sea-levels were on the order of 25 meters higher than they are now. If greenhouse-gas induced warming is to be discounted, then what is a plausible mechanism that would cause enough ice to melt to raise sea-levels that much?
Discounting the CO2/water-vapor mechanism raises far more problems than just conflicts with climate-model results. It eliminates the most plausible physical cause for many of the well-documented (via paleontological evidence) events in the Earth’s past.
Chris: “What if relative humidity were in fact on the decline?”
As you say, if RH was in decline that would imply that feedback was becoming *less* positive, not necessarily that it would become negative.
To my mind, this may help explain some of the historical data, namely that a colder Earth was more sensitive to changes in radiative forcing than the current one is.
In any case, it is very hard to see how a 7% increase in water vapor can increase CO2’s impact by 100% or more. If we take a pretty reasonable (IMO) 15W/m2 for a doubling of water vapor(and assume a generally logarithmic distribution), we see that a 7% increase should result in an increase in GH feedback of ~ 1.5W/m2 **([ln(1.07)/ln(2)]*15W/m2).
Given that the bare forcing for CO2 is 1.2C/(3.7w/m2) this should give us approximately, 0.4-0.5C as water vapor feedback warming.
Cheers, 🙂
Response– Actually it provides an amplicative factor of about 2. This essay I wrote may help– chris
“I don’t like to comment about the information stemming from “Watts up with That” because no one in their right mind gets information from such a source”
As Groucho said, “I resemble that remark!” — me and the thousands of others who voted WUWT the 2008 Weblog Award Winner for Best Science Blog. And if you belittle that award, I’ll counter with my thoughts on the Academy Award for Best “Documentary.”
Response– You should read some of Tamino’s work on Watts’ so-callled “science” such as here, here, here, here, , here, and this one. Watts (as per his comment to me at WUWT) feels as though this poor anaylsis is “an opinion.” It’s not. Seriously, go to his site, and pick a post (like his recent Roger Pielke an warming in the pipeline post). Chances are, it’s just wrong or misleading. Webblog awards don’t help it.– chris
I was intrigued by the spreadsheet data referenced by Robert Wood in the first comment – it’s the first document of this sort which has made me think twice about AGW for a while. Then I found on the same site:
http://members.shaw.ca/sch25/FOS/Climate_Change_Science.html
which contains a lot of statements which cause me to fail to trust that spreadsheet. My suspicion is that it’s valid data as far as it goes but there’s something important missing. Is it simply that the increase in absolute humidity low down is more significant from the point of view of an IR photon than the greater decrease in absolute humidity higher up or is there something else going on?
His reference to the source of the humidity data is now broken. Any ideas on a better source?
After five glacial periods over 650,000 years(The Pleistocene) the level of CO2 in the atmosphere has been around 290 PPM. Today it is around 380 ppm. We know that we have been living at a comfortable temperature for all of nature’s species to exist. Now the Earth is warming and that signal has been increasing. Adding to that a water vapor feedback of 7% is huge. Deforestation, is adding CO2 to the atmosphere. All of the cryosphere is melting, and ocean acidification has already killed one half of the great coral reef. When you say that we have CO2 in the pipeline I presume you are talking about all of the CO2 in the oceans that hasn’t processed out yet.
I have read that it will take millennia for things to return to normal, if we stopped using fossil fuels today. With 380 PPM in the atmosphere the world is getting warmer. The CO2 in the atmosphere is absorbing outgoing long wave radiation (OLR), and redirecting it back to earth. The sun contributes 0.12 gross watts per meter squared of warming and CO2 contributes I.90 gross of warming watts per meter squared. That‘s how global warming is measured. This heat is called global warming. The problem that I have with Anthony Watts is that he fudges the facts around the constant signal of Global Warming. If it’s not the water vapor as a feedback than it’s the weather stations. Weather stations are only one way to view warming. What about radiosonde data from balloons, observational data, or satellite data. They all can’t be wrong? Together they make a strong case for Global Warming. Anthony Watts’s children and grandchildren will look back at him someday and wonder why he was so weird. If you only have faith in Natural Variations and God in your wallet, then there I can see the logic. Today deniers either don’t know the science, or are afraid of some world order, as if China, Russia and the U.S. ever got along, as they couldn’t even accomplish the Kyoto treaty. They laugh at the IPCC because they think the U.N. wrote it. The International Panel on Climate Change was funded by the U.N. and scientists were paid according to their pay grade. The IPCC is an independent body. Thousands of scientists from all over the world got it; the reason that Anthony watts has never tackled global warming is that there is no science to prove against it. In the past there was a time when the world was warmer, and a time it was colder but weather is local. Paleoclimate records have proven that.
Think about the American Natives that live in Alaska, and are now being moved out of their habitat, and the millions more that will die of deseases, and the American Southwest becoming a desert. Water stress in California is now an emergency, as the gulf stream is beng pushed up by too much rain in the tropics.
Deniers should spend more time learning about climate and less time defending the past. They are, loud and so irrelevant. The comment from W.U.W.T was most telling. They had Nothing to say? As usual.
KIPP
Chris, I haven’t worked my way through the whole paper yet, but can you point me in the right direction here. Assuming my numbers from above are in the ballpark, I get a feedback from WV of about 1/3 the magnitude of the CO2 forcing. This gives us a net warming from CO2 and WV of 1.5C – (1C/(1-1/3)).
Cheers, 🙂
Ok, I spoke too soon here, I should’ve read a bit further. I think I see that you are using a water feedback of 0.5 (and an albedo change of 0.2). To get to the 0.5 number, don’t we have to assume either that WV feedback is not (essentially) proportional or that the amount of feedback per doubling is approximately 18-19W/m2 of WV?
Further, and maybe I am demonstrating my ignorance here, doesn’t this whole approach(ie the sum of an infinite series) neglect the fact that it takes energy to turn liquid water to vapor? When the temperature goes up, some of that energy goes to vaporize water. Since this amount is a constant, (ie 2.27MJ/kg I believe) and the energy increase from GH gas is proportional to its logarithm, this should lead to a shrinking f over time.
Response– The logarithmic forcing relationship for any greenhouse gas (depending on the atmospheric context) is because of the underlying radiative physics, specifically the decay of absorption from the primary absoprtion band and a shift toward the “wings.” It’s not because of latent heat.
The importance of water vapor increase with temperature is to reduce the slope of the Outgoing Longwave Radiation vs. T curve, making the climate more sensitive to radiative forcing of any sort. Further, the ability to double the Earth’s sensitivity holds true at a wide range of Earth-like conditions.– chris
Cheers, 🙂
Oops. Above should read “… not (essentially) proportional *to the logarithm of its concentration*.
Cheers, 🙂
http://www.agu.org/pubs/crossref/2009/2008GL036703.shtml
High-CO2 cloud radiative forcing feedback over both land and ocean in a global climate model
Abstract:
A positive feedback on high-latitude winter marine climate change involving convective clouds has recently been proposed using simple models. This feedback could help explain data from equable climates, e.g., the Eocene, and might be relevant for future climate. Here this convective cloud feedback is shown to be active in an atmospheric GCM in modern configuration (CAM) at CO2 = 2240 ppm and in a coupled GCM in Eocene configuration (CCSM) at CO2 = 560 ppm. Changes in boundary conditions that increase surface temperature have a similar effect as increases in CO2 concentration. It is also found that the high-latitude winter cloud radiative forcing over land increases with increases in surface temperature due to either increased CO2 or changes in boundary conditions, which could represent an important part of the explanation for warm continental interior winter surface temperatures during equable climates. This is due to increased low-level layered clouds caused by increased relative humidity.
[quote]Response– The logarithmic forcing relationship for any greenhouse gas (depending on the atmospheric context) is because of the underlying radiative physics, specifically the decay of absorption from the primary absoprtion band and a shift toward the “wings.” It’s not because of latent heat.[/quote]
Yes, I think I get the basics of the radiative side of the issue, I am curious about the evaporative side of the issue. If there were no evaporation, some of the energy from a forcing or feedback would go into raising the temperature, right? Thus, it follows that any feedback temperature increase has two parts
1. Energy is used to vaporize water
2. Energy is returned from the greenhouse effect
Since 1 is more or less constant per kg of vapor and 2 decreases logarithmically per kg of vapor, we should see a shrinking sensitivity to vapor as the concentration rises.
Also, just to return to issue of the radiative effect of WV, what is the amount of feedback supposed to be for a doubling of WV? I thought the ratio of GH effect was 4:1 vapor to CO2 overall, which should lead to a value for the feedback from a doubling of WV of ~15W/m2(3.7W/m2*4). However, you seem to be arguing for a higher ratio than this.
Thanks for all your help.
Cheers, 🙂
OH!
This is probabley the funniest site I have read.
Let me see: The American southwest will become a desert! Thanks for the heads up. I lived there and thought it was a desert. I guess I was imagining what I lived through.
Wait! The climate on the earth has been stable for how long before man decided to cause problems? What globe have you been examining it sure was not this one!
I really have to come back to learn more. I do enjoy fantasy!
Response– Next time you come back, please do try to make some sense– chris
Like others, I dropped by to check-out your blog. Maybe I missed it, but the only thing I have to go on as far as you as a person is your comments.
Did I miss a link titled, “About me”, or something similar?
Thanks.
Response– I’m no one special; no reason to pay any attention.– chris
“Response– I’m no one special; no reason to pay any attention.– chris”
Fair enough. I will wait until you have matured for about 8 or 9 years, return and see if you have any opinions of your own.
Later…
“Response– I’m no one special; no reason to pay any attention.– chris”
Fair enough. I will let you mature for anothe 8 or 9 years, return, and see if you have opinions of your own.
Response- Is there nothing related to the post (or topic of climate) you want to talk about?– chris
Mike Davis: Governor Schwarzenegger said there were two reasons for water stress in California, and the Southwest where they grow crops. The lack of snow in the Sierra Nevada Mountains, and the expansion of the tropics leaving the Southwest and California to more water stress, and drought.
Much of the Southwest where crops are grown will become more arid
as they rely on it’s aquifur to survive.Calfornia is the largest producer of vegetables. “Most importantly, poleward movement of large-scale atmospheric circulation systems, such as jet streams and storm tracks, could result in shifts in precipitation patterns affecting natural ecosystems, agriculture and water resources,” they say. Read more below about your fantasy. KIPP
http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGLL_enUS315US315&q=expansion+of+rainforest+and+water+stress+in+california
Chris:Looks like anonymous is spreading out in his effort to be the worlds
most scientifically challenged denier. If he knew one tenth of what you know he would be twice as intellegent as he is now.I hope these dumb comments are taken for what they are worth. The deniers have finally lost their battle to stall science and are very frustrated. If they love the natural variations so much,, why the hell don’t they leave the natural order alone. It was fine before strip mining, deforestation, and clean coal technology,my favorite oxymoron. KIPP
It is the actual measurement in of its self that RH is misleading.
what amount is talked about? .5? .7?
can be explained by RH
now
Anonymous: Usually over at accuweather stirring up trouble. He doesn’t know any science of his own.If he had one tenth of your intellegence he would be a little smarter but just doesn’t like science in general, and especially doesn’t like Obama for his creative genius in running our country.
Chris:In My Photography career I have met many interesting people.Akio Morita, the co-founder of Sony, Frank White an excellent Photographer with Time Life, and Jason Robards an Academy Award winning Actor. They all had one thing in common like you. They were very modest. Now you are being attacked by deniers who don’t know any science at all. How ironic and desperate these people are. I have purchased the text books you have suggested and am learninng as fast as I can. But your extensive knowledge in so many different sciences, is why I come back to learn more. Keep up the good work, we know the implications of wasting time. Thanks,KIPP
I also just dropped in – googled you from your comment on RC. Without any “about me” information, I’m not apt to listen to any of your opinions… the “about” part is an important element of developing credibility, especially in the climate blogosphere.
Response– I’m student of the atmospheric sciences, with most of my education in climate change coming outside of formal training. I don’t have an authoritiative position or publications in peer-reviewed references. As such, any “About Me” is not bound to sound impressive, and I’d rather have people judge this site on the content. I’m just an interested blogger, and I have the education to make remarks about general aspects of climate change science. Essentially everything I say is not new, but rather can be found in the literature by those people who you might be “apt to listen to” (and thus are not really my opinions); I’m just putting it in easier-to-understand fashion in a more accessible site. — chris
Mike Davis:
While your watching Fantasia or other quality genre, why don’t you read and learn. This is how the growing areas in the Southwest are drying up. The Sierra Nevada mountains lack of snow coupled with precipitation patterns from the Tropics was the reason. The areas in the Southwest now, that are used for agriculture are becoming too arid, and Las Vegas is giving it suburbanites a tax break not to grow grass. Also Governor Schwarzenegger has pronounced that California is in a state of Emergency due to water stress.
Also I have noticed that Watts goes after weather station data. as if observational,radiosonde Weather ballons and satellite data wasn’t good enough. Mike, Anthony Watts is not God just because he thinks he is.
KIPP
“Most importantly, poleward movement of large-scale atmospheric circulation systems, such as jet streams and storm tracks, could result in shifts in precipitation patterns affecting natural ecosystems, agriculture and water resources,” they say.
http://www.independent.co.uk/environment/climate-change/expanding-tropics-a-threat-to-millions-761326.html
In the Blogosphere you will find some of the most excellent papers and articles if anyone were to bother to read them.Because Chris Colose has said that his training is not in Geophysics,his ability to explain Science and his scope of learning far exceeds anyone that I have ever read in any blog. Just read some of his last papers which you will find in archives and past blogs.Or don’t you want to know more about science. Anthony Watts and Steve McIntyre can’t even come near the amount of knowledge that Chris has. Another modest man is Hank Roberts who doesn’t hang a shingle, but knows so much more than most of us put together. It’s easy to criticize, but harder
to have the knowledge that they both possess. KIPP
Chris,
Isn’t the real problem with the humidity issue and the responses at Watts that they are calling a one-year drop in humidity the end of AGW? A one year drop or rise in anything = nothing of consequence if not viewed within the framework of long-term trends, no?
Response– Not really, since the re-analysis by Paltridge et al. goes back many decades. The larger problem is that the re-analysis is not useful for evaluating long-term humidity trends.
Going off-topic here, sorry, but I’d be interested in your take on, specifically, the use of MAGICC using the default of 3C for sensitivity in this post at The Oil Drum: http://europe.theoildrum.com/node/5084
Also, the paper intentionally ignores feedbacks. The upshot is the author states we *may* be able to ignore even Kyoto, though he calls, in the final analysis for moving away from FFs. He does this, however, not because of climate concerns, but for energy-related ones. This is not bad in and of itself, but it strikes me as irresponsible to set AGW up as a phantom menace, if you will. Also, sceptics will seize on such comments as proof wee should do nothing about AGW.
Again, it all comes down to the chosen sensitivity. MAGICC is capable of using up to 6C for sensitivity, so the question is, why did the author go for 3C?
Cheers
Response– There are lots of issues raised by you and the link. The equilibium climate sensitivity for a doubling of CO2 is roughly 3 degrees C (the IPCC AR4 puts the range at 2 to 4.5 C) and this is including feedbacks (it’s about 1 degree C with no feedbacks). 6 C is very likely too high. The “first doubling” is usually something like 560 ppm, since the pre-industrial background was roughly 280 ppm.
Keep in mind though that a key focus of your oil drum link involves emissions and therefore how concentrations evolve over time, which becomes a different question. This depends on socio-economic decisions (e.g., do we dig up all the coal we can get or do we get into alternative energy?), and it also depends on the lifetime of an extra pulse of CO2 in the atmosphere. Usually not modelled (or very poorly so) are natural GHG feedbacks such as methane releases from permafrost which can kick up concentrations even more.
So, the temperature rise “by 2100” is different than the temperature rise “for a doubling of CO2” since the second one specifies a given change in atmospheric composition, whereas “by 2100” not only involves the climate uncertainty, but the socio-economic uncertainty as well (which means we really can make a difference!), and we don’t really know if concentrations will be lower or higher than 560 ppm.– chris
Wait a minute, we have people like Watt and others, not scientists, getting people fawning all over them despite their tendency to error, but as soon as a scientist says that having a “who I am” page is distracting from the science and debate, people start claiming they aren’t going to pay any attention to his opinion (edit– I’m not a scientist. Sorry to disappoint).
Wake up folks, science doesn’t care about opinion, neither does CO2, or indeed gravity, so moaning about Chris not having a “who am I ” page just demonstrates an inability to engage with the issue and a lack of understanding of how science works. (at least ideally, and we should be striving towards this ideal all the time)
Guthrie:I would you second your emotion. CO2 is no lover of persons, and knowledge gained at some Antarctic station is never peer reviewed by a Penguin. Much of observational data is collected by a variety of people dedicated more to Science than some accepted Scientists. Some scientists and others who study in the field could spend their whole life on one specie, only to return to their Country to find that someone else had already published an article about what they just discovered. Reality is cruel that way,and these people are brave and deserve our respect. KIPP
Anyone read the full paper I mentioned earlier yet?
Response- I looked at it briefly. Interesting, though I’m not sure how important it is– chris
Thanks Chris — all I can see is the abstracts, unless I go to a library that has the journal, so I appreciate your having taken a look.
Based on 35 years of direct involvement in radiosonde humidity measurement, I am very surprised that anyone is making an effort to use those measurements for climate analysis purposes.
The basic quality just is not there. Neither the basic sensor physics nor the recording procedures support such endeacour. No amount of statistical or other torture can extract meaningful long term information from those measurements. The well known theory (higher sea surfce temperature results in higher atmospheric water vapor content) beats any on-site RH measurement as to accuracy.
In the olden times (perhaps even today on some stations, for I know) the RH sensor was so called “goldbeater skin” – a fancy name for processed sheep’s long intestine. On many other stations the standard was strands of human hair (blondes preferred to dark ones for obvious reasons). Both types had very slow response due to their mass and thickness, and an extreme temperature dependence. Overall poor accuracy and repeatability.
Enter several new technologies, with microns thick layers of synthetic sensor materials. Much better in some respects, but sensitive to such effects as incident solar heating (obviously dependent on time of day and cloudiness) or wetting by water droplets within clouds. Again varying thermal time constants and new formulations of materials and methods of computation from time to time, not very well documented.
RH measurement was not a priority. The WMO accuracy requirement used to be “better than 15 %RH” . The users were primarily interested in seeing qualitative items, such as cloud base and cloud top heights. As to the weather forecasting models, humidity is not an input parameter. It varies strongly on a sub-grid scale, and the models produce credible humidity fields anyway (as was explained by the modelers).
As a result, the global long term RH data base is nothing to rely on. Digging deep into it, one may find some subsets of limited interest. I.e. there are maybe three instrument models that were used in some significant parts of the network and that remained rather well standardized over some periods of time (i.e. 25 years). These series might contain some usable information, if the relevant accuracy issues are properly investigated.
Another issue is that the “relative humidity” in fact is two distict parameters. “RH with respect to ice” is lower than “RH with respect to water”, and both are relevant in the atmosphere, depending on the circumstances. Neither is directly descriptive of radiation forcing.
A poor measurement does not overturn good theory. The experience is that if there is a strong disagreement between a well established theory and some measurements, it is wise to check the measurements first. A point that is repeatedly proven. (I.e. see the next item on this site)
I believe in fact that global RH is variable to some extent. It is a possible descriptor of the dwell time of WV in the atmosphere, which obviously varies a bit. Sources of WV move around, El-Nino/La-Nina being an extreme example, and the residence times then change with wind patterns. Tracking such variability should be possible using new saellite sensors.
Your comment: I don’t like to comment about the information stemming from “Watts up with That” because no one in their right mind gets information from such a source…”
Thanks for the cheap insult aimed at me. I have yet to find a professional attitude an any pro AGW blog and I can now remove the bookmark I just saved before I waste any time ever coming back here.
Response– Okay bye.
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