Here’s an interesting paper that breaks with consensus. The only problem is that it is being 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”. You can read all about that debate at Climate Audit called “
A peek behind the curtain“. It is a firsthand account of the attempt at publishing from one of the authors, Garth Paltridge. Here is how he characterized the debate at a conference:
Those ‘against’ (among them a number of people from GISS) simply said that the radiosonde data were too ‘iffy’ to report the trends publicly in a political climate where there are horrible people who might make sinful use of them. Those ‘for’ simply said that scientific reportage shouldn’t be constrained by the politically correct.
Since most of the objections seemed to be coming from GISS, who has a surface data set that one could also describe as “iffy”, I find their argument rather humorous.
What is really interesting though is this graph presented in comments at CA by Ken Gregory:
Ken writes:
“The relevant discussion of the water vapour effect from the IPCC Fourth Assessment Report (Chapter 8 page 632):
The radiative effect of absorption by water vapour is roughly proportional to the logarithm of its concentration, so it is the fractional change in water vapour concentration, not the absolute change, that governs its strength as a feedback mechanism. Calculations with GCMs suggest that water vapour remains at an approximately constant fraction of its saturated value (close to unchanged relative humidity (RH)) under global-scale warming (see Section 8.6.3.1). Under such a response, for uniform warming, the largest fractional change in water vapour, and thus the largest contribution to the feedback, occurs in the upper troposphere.
This means that changes in specific humidity in the upper troposphere (300 – 700 mb) may be very significant even though the amount of water vapour there is low due to the cold temperatures.
If relative humidity remains constant, CO2 induced warming would cause increasing specific humidity and a strong positive feedback. But if relative humidity is actually falling (due to water vapour being displaced by CO2 as per Miskolczi) then water vapour may cause a negative feedback. The specific humidity has declined dramatically in 2008 at ALL levels in the troposphere.
I do not know the accuracy of the NCEP reanalysis data on upper tropospheric humidity, but the direct measurement of humidity by weather balloons seems preferable to the very indirect determination from satellite data.”
I agree. Here is more on the paper and it’s conclusions. – Anthony
New Paper Suggests Long-Term Water Vapour Feedback is Negative
(1) Environmental Biology Group, RSBS, Australian National University, GPO Box 475, Canberra, ACT, 2601, Australia
(2) Johns Hopkins University, Baltimore, MD, USA
(3) Centre for Australian Weather and Climate Research, Hobart, TAS, Australia
The Abstract states:
The National Centers for Environmental Prediction (NCEP) reanalysis data on tropospheric humidity are examined for the period 1973 to 2007. It is accepted that radiosonde-derived humidity data must be treated with great caution, particularly at altitudes above the 500 hPa pressure level. With that caveat, the face-value 35-year trend in zonal-average annual-average specific humidity q is significantly negative at all altitudes above 850 hPa (roughly the top of the convective boundary layer) in the tropics and southern midlatitudes and at altitudes above 600 hPa in the northern midlatitudes. It is significantly positive below 850 hPa in all three zones, as might be expected in a mixed layer with rising temperatures over a moist surface. The results are qualitatively consistent with trends in NCEP atmospheric temperatures (which must also be treated with great caution) that show an increase in the stability of the convective boundary layer as the global temperature has risen over the period. The upper-level negative trends in q are inconsistent with climate-model calculations and are largely (but not completely) inconsistent with satellite data. Water vapor feedback in climate models is positive mainly because of their roughly constant relative humidity (i.e., increasing q) in the mid-to-upper troposphere as the planet warms. Negative trends in q as found in the NCEP data would imply that long-term water vapor feedback is negative—that it would reduce rather than amplify the response of the climate system to external forcing such as that from increasing atmospheric CO2. In this context, it is important to establish what (if any) aspects of the observed trends survive detailed examination of the impact of past changes of radiosonde instrumentation and protocol within the various international networks.
The paper concludes:
It is of course possible that the observed humidity trends from the NCEP data are simply the result of problems with the instrumentation and operation of the global radiosonde network from which the data are derived. The potential for such problems needs to be examined in detail in an effort rather similar to the effort now devoted to abstracting real surface temperature trends from the face-value data from individual stations of the international meteorological networks. As recommended by Elliot and Gaffen (1991) in their original study of the US radiosonde network, there needs to be a detailed examination of how radiosonde instrumentation, operating procedures, and recording practices of all nations have changed over the years and of how these changes may have impacted on the humidity data.
In the meantime, it is important that the trends of water vapor shown by the NCEP data for the middle and upper troposphere should not be “written off” simply on the basis that they are not supported by climate models—or indeed on the basis that they are not supported by the few relevant satellite measurements. There are still many problems associated with satellite retrieval of the humidity information pertaining to a particular level of the atmosphere—particularly in the upper troposphere. Basically, this is because an individual radiometric measurement is a complicated function not only of temperature and humidity (and perhaps of cloud cover because “cloud clearing” algorithms are not perfect), but is also a function of the vertical distribution of those variables over considerable depths of atmosphere. It is difficult to assign a trend in such measurements to an individual cause.
Since balloon data is the only alternative source of information on the past behavior of the middle and upper tropospheric humidity and since that behavior is the dominant control on water vapor feedback, it is important that as much information as possible be retrieved from within the “noise” of the potential errors.
Like this:
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Leif Svalgaard (09:02:44) :
It has warmed, so even with the same amount of water vapor, RH will go down. The change [a couple of per cent] looks reasonable for ~1 degree warming.
That was my first thought as well. The 700 hPa plot suggests a warming of about 1 C. But the 400 hPa plot drops from about 42% to 37% and the 300 hPa plot drops from about 47% to 37%. If we assume that temperatures at those altitudes are roughly in the -30 C – -40 C range, we need a temperature increase of at least 2 C (if my calculations are right) to see those drops in relative humidity if the amount of water stays the same. Has there been a 2 degree warming at those altitudes since 1948?
Need the absolute humidity, or temperature at those mb levels. Anyone have the data source?
philincalifornia (09:24:51) : The “no positive feedback = game over for AGW” is correct. Nailing down the level of negative feedback is extremely important, probably THE most important aspect there is. Spencer has a paper on it, but he doesn’t explain the movement of his squiggly lines well enough to have a lot of people “get it”. I’ve discussed it with him and offered to write a program to show atmospheric conditions & maps as you move along the lines, but he didn’t bite. Doing the study with a smaller focused area (column of air) in dynamic conditions (sun, clouds, convection, etc truly separating radiative and non-radiative feedbacks, would I think put the final nail in the positive feedback coffin.
There is no doubt in my mind that the feedback is negative. I think the IPCC knows it, and they’re determined to undermine any evidence that comes along. The stakes are truly life or death for them because positive feedback is THE single factor that underpins the whole supposed catastrophe (and the largest single factor that causes all GCM’s to fail).
Take away +feedback, then only minor temp increases are possible, no need for mitigation, economic study of impacts, tax revenue from CO2, lobbyists, transfer of wealth, etc. The entire manufactured calamity and everything surrounding it (the livelihood of thousands) implodes.
Talk about a bailout that could actually have a positive ROI…
I personally think there is no single more important element for the economic future of the planet than determining the direction and magnitude of this feedback. If it’s negative and we can prove it, we might be able to stop the madness and ward off the economic carnage that is about to happen through CO2 regulation. We could probably save science in the process.
If the NCEP data is correct, then it is interesting that RH continued to fall even while the globe wasn’t warming during the ’50s, ’60s, and part of the ’70s; this suggests that changing H20 concentration is not dependent on temperature, but perhaps on CO2 concentration, as suggested by Miskolszi.
Thanks Ken for the graphs.
So it seems that the absolute humidity at high altitude has decreased but increased at very low and ground level. From the relatively stable high altitude temperatures, we can guess that generally it has rained more, thus maybe helping in cooling down the atmosphere. The increased humidity and temperature at ground level or near ground level seems to be the good ol’ blck body experiment. Is it a coincidence that the ground and humidity increased with the sun’s increased in activity since the LIA? The upper atmosphere does not look like it has problems getting rid of the excess heat.
Too bad the concentration of CO2 is not reported at the different altitudes. It would be surprizing that it’s concentration is homegenous in the atmosphere since it is usually relative to the other species.
This is fascinating… And we don’t really have a handle on the most basic science of water vapor in this ‘settled science’ rodeo…
Just for fun, I poke a few at the “satellite data” in GIStemp here:
http://chiefio.wordpress.com/2009/03/05/illudium/
especially if you are a Marvin the Martian fan 😉
Now how do we get a satellite to measure humidity…
Can someone who is more familiar with the numbers post what percent of forecast warming is due to positive water vapor feedback? My recollection is that it was somewhere around 2/3rd’s of the forecast warming. So just by going neutral, you would eliminate 2/3rds of the the forecast warming. And of course, if the feedback is actually negative, you loose even more of the warming – you might even loose it all and find that CO2 has no net effect on atmospheric temperatures.
The importance of this research can not be over-emphasized if it is correct.
Perhaps the models should also factor in some relative humility
Ross (09:39:10) :
“The only problem is that it is being 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”.”
One wonders how much publicity this paper would have gotten if the “iffy” data resulted in positive feedback.
Am I the only one that finds it odd that real recorded data are claimed to be too “iffy” yet artificial synthetic dare I say it, fabricated, data are fine in GIStemp?
Oh, and I’m also one of the folks struggling with why RH and absolute would behave as described. I would have thought it was just the number of water molecules, not their relationship to the carrying capacity of the air… but maybe it’s not intuitive.
And I’m still peeved that GISS can’t even get their heads around the fact that data recorded in whole degrees F can not compute accuracy in 0.01 C. How can they criticize real data and use fantasies to do it?
http://chiefio.wordpress.com/2009/03/05/mr-mcguire-would-not-approve/
Re
Shawn H. (10:58:57) :
Gary (09:23:12) :
“The radiative effect of absorption by water vapour is roughly proportional to the logarithm of its concentration, so it is the fractional change in water vapour concentration, not the absolute change, that governs its strength as a feedback mechanism.”
Can someone provide an explanation in simple terms why this is so? And how rough is “roughly”? Is the correlation R2 = 0.9 or 0.3?”
The way I think of it myself is to assume that there are a finite number of photons available to be absorbed by a finite number GH gas molecules. Thus, if in the first X meters of travel 75% of the photons are absorbed, then in the second X metres 0.75*(1-0.75) will be absorbed and so on and so forth.
Water differs from other GH gasses (like CO2) in that it varies dramatically by altitude, hence the “roughly” part.
Cheers, 🙂
The logarithm growth has to do with the line profile of the spectral lines (spectral lines aren’t sharp, they’re bell shapped like this http://en.wikipedia.org/wiki/Voigt_profile )
Once the concentration is sufficient so that the center of the line is 100% opaque (absorbs light completely) the center of the line can’t absorb more, however the wings can absorb more with increased concentation of the molecule. As more molecules are added, the wings grow deeper and wider logarithmically with the concentration, so the total opacity of the molecule increases logarithmically with concentration.
Michael D Smith
I personally think there is no single more important element for the economic future of the planet than determining the direction and magnitude of this feedback.
I agree whole heartedly with this. What I find difficult to understand is why, apparently, so few scientists are giving the subject their attention. Is it lack of data? It couldn’t be because the IPCC (and followers) knows it, as you say?
It doesn’t much matter if the radiosondes are accurate or not, as long as any errors consistent and they have the trend right.
“Here is more on the paper and it’s conclusions. – Anthony”
its
Well I haven’t digested the above to the point where I can say I know what they are talking about; BUT (sorry about the caps foinavon) !!
I just go back to Wentz et al, July 2007 SCIENCE.
“How much more Rain will Global Warming bring ?”
According to Wentz (RSS, Santa Rosa CA), a 1 deg C increase in mean global surface temperature results in a 7% increase in global evaporation, total atmospheric water content, and total Global precipitation.
The GCMs on the other hand agree with Wentz on the 7% increase in total atmospheric water content; but claim that the increase in global evaporation and global precipitation (which must be equal) is only 1-3%, as much as seven times lower than the total atmospheric water increase.
Now that does not sound to me like a formula for declining relative humidity, having the total increasing 7 times faster than the rate of input and output?
But all that aside; whether water vapor can itself produce negative feedback (as well as positive feedback); water in the form of clouds (solid and liquid) can most certainly lead to negative feedback (surface) cooling. Seen any peer reviewed papers on the warming observed when a cloud passes in front of the sun, lately ?
So if water vapor too can produce negative feedback as well as clouds; that doesn’t hold out much hope for a positive feedback enhancement of puny CO2 effects.
At least one mechanism where water can produce cooling, is in the direct absorption of incoming solar spectrum radiation starting at about 750 nm in the (very) near IR. Something like 45% of the total air mass zero solar spectrum energy is above 750 nm, and with all the water bands starting out there and continuing to beyond 20 microns, the water may take out fully half of that 45%. (I can’t integrate by eye).
That leads to warming the atmosphere directly; which presumably also leads to convective transport into the upper reaches of the atmosphere, were condensation and maybe freezing will dump out huge amounts of latent heat to radiate to space.
CO2 on the other hand only has very weak molecular absorptions in the tail of the solar spectrum; so has little direct effect on the incoming solar energy.
I’d sure like to know more about this above report and research.
Well I’ve always believed that water is king and has full control of the earth’s temperature (other than the sun bringing the food).
George
coaldust (10:43:10) : If the warming is constrained by negative water vapor feedback, sounding this alarm is akin to yelling fire in a crowded theater where the fire is nicely contained inside a fire box.
I like your analogy, but given that the ‘fire’ is a simulated one in a computer, I’d change it to “nicely contained on the movie screen”…
Ross wrote:
“One wonders how much publicity this paper would have gotten if the “iffy” data resulted in positive feedback.”
A million times more, give or take an order of magnitude.
“…as suggested by Miskolczi.”
Ferenc Miskolczi’s equations got a lot of attention for a brief time last year, but there seems to be nothing in his work to explain why CO2 would displace H2O or otherwise cause its concentration to be reduced. If it remains a “just so” story, then Miskolczi’s equations remain as an indication of a place to look but not a solution to the question.
Steinar Midtskogen (10:58:58) : If we assume that temperatures at those altitudes are roughly in the -30 C – -40 C range, we need a temperature increase of at least 2 C (if my calculations are right) to see those drops in relative humidity if the amount of water stays the same. Has there been a 2 degree warming at those altitudes since 1948?
If I’m following this right, you are saying that as the temperature goes up, the RH goes down, and the GHG potential goes down with it, all else held static.
Isn’t that, on the face of it, negative feedback? THE dominant GHG drops in activity as temperatures rise? It can’t be that simple…
This is all well and good, but there’s one question I’ve never heard adequately addressed.
Let’s stipulate for the moment that more Co2 absorbs radiation, which warms the atmosphere, which increases evaporation rates, which increases the humidity, which increases the radiative absorption potential from the surface.
However, isn’t the most significant effect of increased evaporation and humidity increased cloud formation?? Doesn’t the reduction of radiation reaching the surface by clouds more than overwhelm any minor increased capacity for absorption?
Are these not the same people that warn us of the danger of nuclear winter?? Do they not need some ‘nuclear summer’ scenario for consistency?
Is it not on balance cloudier in tropical regions than arid desert regions? And this makes it hotter??
It seems entirely plausible to my simple mind that increased temperature leads simply to faster cloud formation, more frequent rainfall, more plant growth, more oxygen, et cetera.. Hawaiification, if you will.. 🙂
Isn’t that really more likely than humidity induced deserts?
Who woulda thunk that Gaia knew how to control her thermostat?
By the way, NCDC has the February numbers for North America. This February was a bit warmer than last February.
Back to common sense: Lower humidity means colder weather.(when you find that water is down under your frozen feet)
So, Ken Gregory @10:42:30, NASA has the data that falsifies the global warming model
It would be interesting to see the integral of the total vertical water amount on that graph as well as well as the integral of the heat of vaporization.
How about we change relative humidity to dewpoint? That would tell us if there was actaully more or less vapor in the atmosphere, independent of temperature.
This chart shows the greatest water concentration losses at the least pressures highest altitudes therefore suggesting a warming and evaporation to the even less water populated lower stratosphere.
Interestingly and a a bit of an aside. water levels in the lower to higher stratosphere are supposed to have Risen over this time scale or certainly the last thirty years. it has been deemed responsible for cooling in the lower and mid stratosphere as a result of the development of clouds and the prevention of ozone formation. this chart shows the greatest water concentration losses at the least pressures therefore suggesting a warming and evaporation to the even less water populated lower stratosphere.
perhaps these stratospheric clouds (formed at lowest temperatures eg 2008)are affecting whats below and/or (in warmer times) secondly have been enjoying the enhanced transportation of moisture from the trophosphere upwards as a result of a warmer trophosphere.
other effects can be large scale volcanic eruptions apparently obviously these are obviously more imortant for the stratosphere although there may be a diffusion down to the top levels of the trophosphere.
as for a cooler 2008 proably less moisture reaching any part of the upper atmosphere.
some papers for startospheric water vapour ….
Increase in lower-stratospheric water vapour at a mid-latitude Northern Hemisphere site from 1981 to 1994
by S. J. Oltmans & D. J. Hofmann
also there seem to be many works by Forser and Shine amongst others on this topic in the stratosphere