Spencer on water vapor feedback

The image above shows the first results from the Ocean Surface Topography Mission (OSTM)/Jason-2, Advanced Microwave Radiometer: a global map of the amount of water vapor in the atmosphere beneath the satellite from June 22–28, 2008.

Five Reasons Why Water Vapor Feedback Might Not Be Positive

By Dr. Roy Spencer

Since it has been a while since I have addressed water vapor feedback, and I am now getting more questions about it, I thought this would be a good time to revisit the issue and my opinions on the subject.

Positive water vapor feedback is probably the most “certain” and important of the feedbacks in the climate system in the minds of mainstream climate researchers. Weak warming caused by more carbon dioxide will lead to more water vapor in the atmosphere, which will then amplify the weak warming through water vapor’s role as the atmosphere’s primary greenhouse gas.

Positive water vapor feedback makes sense intuitively. Warmer air masses, on average, contain more water vapor. Warmer air is associated with greater surface evaporation rates, which is the ultimate source of almost all atmospheric water vapor.

And since water vapor is the atmosphere’s main greenhouse gas, most scientists have reasonably inferred that climate warming will be enhanced by increasing water vapor amounts. After all, water vapor feedback is positive in all of the IPCC climate models, too.

But when one looks at the details objectively, it is not so obvious that water vapor feedback in the context of long-term climate change is positive. Remember, it’s not the difference between warmer tropical air masses and cooler high-latitude air masses that will determine water vapor feedback…its how those air masses will each change over time in response to more carbon dioxide. Anything that alters precipitation processes during that process can cause either positive or negative water vapor feedback.

Here are some of those details.

1) Evaporation versus Precipitation

The average amount of water vapor in the atmosphere represents a balance between two competing processes: (1) surface evaporation (the source), and (2) precipitation (the sink). While we know that evaporation increases with temperature, we don’t know very much about how the efficiency of precipitation systems changes with temperature.

The latter process is much more complex than surface evaporation (see Renno et al., 1994), and it is not at all clear that climate models behave realistically in this regard. In fact, the models just “punt” on this issue because our understanding of precipitation systems is just not good enough to put something explicit into the models.

Even cloud resolving models, which can grow individual clouds, have gross approximations and assumptions regarding the precipitation formation process.

2) Negative Water vapor Feedback Can Occur Even with a Water Vapor Increase

Most atmospheric water vapor resides in the lowest levels, in the ‘turbulent boundary layer’, while the water vapor content of the free troposphere is more closely tied to precipitation processes. But because the outgoing longwave radiation is so much more sensitive to small changes in upper-layer humidity especially at low humidities (e.g. see Spencer & Braswell, 1997), it is possible to have a net increase in total integrated water vapor, but negative water vapor feedback from a small decrease in free-tropospheric humidity. See #4 (below) for observational support for this possibility.

3) Cause Versus Effect

Just because we find that unusually warm years have more water vapor in both the boundary layer and free troposphere does not mean that the warming caused the moistening.

There are a variety of processes (e.g. tropospheric wind shear causing changes in precipitation efficiency) which can in turn alter the balance between evaporation and precipitation, which will then cause warming or cooling as a RESULT OF the humidity change – rather than the other way around.

This cause-versus-effect issue has been almost totally ignored in feedback studies, and is analogous to the situation when estimating cloud feedbacks, the subject of our most recent paper.

Similar to our cloud feedback paper, evidence of causation in the opposite direction is the de-correlation between temperature and humidity in the real world versus in climate models (e.g. Sun et al., 2001).

4) Evidence from Radiosondes

There is some evidence that free tropospheric vapor has decreased in recent decades (e.g. the Paltridge et al., 2009 analysis of the NCEP Reanalysis dataset) despite this being a period of surface warming and humidifying in the boundary layer. Miskolczi (2010) used the radiosonde data which provide the main input to the NCEP reanalysis to show that the resulting cooling effect of a decrease in vapor has approximately counterbalanced the warming influence of increasing CO2 over the same period of time, leading to a fairly constant infrared opacity (greenhouse effect).

Of course, water vapor measurements from radiosondes are notoriously unreliable, but one would think that if there was a spurious drying from a humidity sensor problem that it would show up at all altitudes, not just in the free troposphere. The fact that it switches sign right where the turbulent boundary layer pushes up against the free troposphere (around 850 mb, or 5,000 ft.) seems like too much of a coincidence.

5) The Missing “Hot Spot”

Most people don’t realize that the missing tropospheric “hot spot” in satellite temperature trends is potentially related to water vapor feedback. One of the most robust feedback relationships across the IPCC climate models is that those models with the strongest positive water vapor feedback have the strongest negative lapse rate feedback (which is what the “hot spot” would represent). So, the lack of this negative lapse rate feedback signature in the satellite temperature trends could be an indirect indication of little (or even negative) water vapor feedback in nature.

Conclusion

While it seems rather obvious intuitively that a warmer world will have more atmospheric water vapor, and thus positive water vapor feedback, I’ve just listed the first 5 reasons that come to my mind why this might not be the case.

I am not saying that’s what I necessarily believe. I will admit to having waffled on this issue over the years, but that’s because there is evidence on both sides of the debate.

At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is.

=================================================

Be sure to check out Dr. Spencer’s book:

The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists

Highly recommended – Anthony

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Baa Humbug

At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is.

So the science isn’t settled then? sigh

John Galt

I wonder if we could get Dr. Spencer to comment on the latent heat effect of the water cycle. As water evaporates from the surface, it carries latent heat with it, cooling the surface. Convective transport of this water vapor to higher altitudes effectively moves that energy around the greenhouse effect. When that vapor condenses, it not only removes the vapor, but emits that stored latent heat at a higher altitude, bypassing much of the greenhouse effect. If higher temperatures drive more evaporation and precipitation, then they also drive greater convective transport of latent heat. At least, that’s what appears to me.

kim

I think I’ve never heard so loud
The quiet message in a cloud.
And now I hear so loud so clair
Resounding clarion in the air.
==================

John R T

My question reflects personal experience and recent comments on a blog:
more moisture in summer air still produces uncomfortable perceptions of heat;
more moisture while sailing led to severe hypothermia one summer in Seattle;
clothes air-dry indoors, here in San Jose Costa Rica, even during the wet season.
¿Would discussions of water vapor effects be more understandable to non-scientists were the focus on energy? Joules? Calories?

Neil

How come this missing “hot spot” isn’t being shouted from the rooftops, regarding AGW?
Here, surely, is one testable hypothesis of AGW. It failed this test, so the entire theory must be discarded and reworked.
Or has direct observation been retired as a scientific method and replaced with statistical extrapolation?

Rows and floes of angel hair
And ice cream castles in the air
And feather canyons everywhere
I’ve looked at clouds that way
But now they only block the sun
They rain and they snow on everyone
So many things I would have done
But clouds got in my way
I’ve looked at clouds from both sides now
From up and down, and still somehow
It’s cloud illusions I recall
I really don’t know clouds at all

Ok, if there is a decline in free tropospheric water vapor, could that mean an increase in stuff is bringing it down in the form of rain? Dust, ash, ions, pollen and spores, etc.

Ian H

What John Galt said. Also more clouds leads to more sunlight being reflected straight back out into space.

Dinostratus

Roy, I’m not sure if you read these comments but regarding your cloud feedback data, I’d suggest contacting Stewart Daw at ORNL to see if he can help with the data. He is very good at analyzing data from non linear systems. Your data reminds me of stuff he looked at about twenty years go.
John Galt – Bypasses the greenhouse effect? Let’s think about this. Latent heat effects aren’t always easy to figure out. So the ocean gets hotter, evaporates a bit more, the vapor travels up the atmosphere, collects a bit more radiation along the way and then heats up the upper atmosphere as it condenses. The upper atmosphere is now hotter and with a higher water mole fraction, absorbs more radiation…. No, that’s the case for global warming. I’m not sure why it would bypass the greenhouse effect What it may do though is reduce the temperature difference between the upper and lower atmosphere, make it more homogeneous. More liquid water falling would also make the atmosphere more homogeneous. More water vapor would lower the altitude where the water vapor starts to condense. Interesting. There’s something here that may explain the missing tropospheric “hot spot” but I’m not quite sure what.

Dinostratus

Neil – It failed it a long time ago. It’s one of the big problems with climate models. I’m not sure how they’ve addressed it. Lindzen would talk about this frequently.

Ian H

Bizarre schemes to build fleets of robot ships to put salt spray into the air and seed clouds to increase the Earth’s albedo are somehow regarded as viable proposals to combat global warming. Yet the increasing cloud cover caused directly by warming itself is not regarded as a cause of significant negative feedback. Consistency check anyone?

I wonder if Roy Spencer might be interested in the rather good correlation I found between specific humidity at the tropopause and solar activity:
http://tallbloke.files.wordpress.com/2010/08/shumidity-ssn96.png
Discussion here:
http://tallbloke.wordpress.com/2010/08/08/interesting-correlation-sunspots-vs-specific-humidity/
If solar activity is playig a role in controlling the level of humidity in the upper atmosphere at the boundary between the troposphere and the stratosphere, it would seem to me that the strong levels of solar activity in the latter half of the C20th may have had a much bigger part to play in ‘global warming’ than a calculation of the change in TSI at the top of the atmosphere would account for in simple energy terms such as those frequently cited by Leif Svalgaard.

Konrad

If water vapour feed back were strongly positive, the Earth’s temperature would have spiralled out of control during the Roman Climatic Optimum and the Mediaeval Warm Period. This clearly did not happen. Vapour /condensate heat pipes in computer heat sinks work. Climate models assuming positive water vapour feedback do not.

AJB

“I will admit to having waffled on this issue over the years, but that’s because there is evidence on both sides of the debate.”
You and everyone else, Roy. This is the key issue yet we seem no nearer to solving it than we were ten years ago. Meanwhile huge sums are being wasted on yet more anecdotal observation to support a meme based on a few tenths of a degree rise in temperature (cause unknown) over a period of time that gets ever shorter as the odd wheel falls off. And the economic hinterland behind it grows more massive by the day.
This to me defines “Climate Science” – the business of reinforcing anecdotal evidence to support conjecture, supposition and an agenda while avoiding pursuit of the truth.
Surely it is not that difficult to roll out a programme to sort this issue out based on sound empirical evidence. In a rational world, is that not what the IPCC and all the rest ought to be doing? How much would it cost to improve water vapour measurements from the radiosondes you mention compared to launching yet more satellites to confirm water freezes and thaws seasonally by varying amounts? If you want to play with satellites how about a matrix of them to replace the aging ERBE and measure the earth’s radiation budget directly and accurately over the entire globe? The key question is why this hasn’t already been done as a matter of urgency.
Why, when it’s supposedly the survival of the human race that’s at stake? Hang the cost. There’s only so much spleen grease and post normal clap trap one can swallow before the obvious kicks in I’m afraid, no need for conspiracy theories.

Dinostratus says:
September 14, 2010 at 11:55 pm (Edit)
Roy, I’m not sure if you read these comments

I think Roy is busy enough doing science running his own blog. Why not drop by and post your comment on the original thread?
http://www.drroyspencer.com/2010/09/five-reasons-why-water-vapor-feedback-might-not-be-positive/

stumpy

More moisture in the air, more clouds, rain, storms, which seek to remove the latent head and ensure stability. If these systems didnt exit, the earths atmosphere would have gone nuts a long time ago. Its no coincidence that the moonson permanently sits over the area of the earth recieiving the most energy.
You cant have more evaporation, cloud cover and rainfall whilst also having more warmth, it just doesnt work!

Kiminori Itoh

Thank you Dr. Spencer for your thoughtful and stimulating article. I read Paltridge et al. paper according to your suggestion, and understood your idea that precipitation may induce low specific humidity in upper-air.
One question on your statement. You explain the lacking of warming at the tropical upper troposphere as indirect evidence of the negative feedback, but there is an interesting recent article: R. J. Allen and S. C. Sherwood, “Warming maximum in the tropical upper troposphere deduced from thermal winds,” Nature Geoscience VOL 1 JUNE 2008, 399-403. Allen and Sherwood claim that reanalyzed temperature deduced from wind fields rather coincides with the warming at the upper troposphere which is predicted by models.
Of course, the warming at the troposphere upper air may be different matter from the climate sensitivity, but I wonder whether or not their result is consistent with your explanation on the effect of the precipitation.

Brent Hargreaves

Step by step we are approaching a refutation of the Global Warming Myth.
The two major battlefields are Feedback and Sensitivity.
Prove that negative feedback operates, and the hotter the world gets the more it cools, and the IPCC claims of positive feedback and tipping points are demolished.
Prove that there are forcings more significant than greenhouse gases, such as solar, such as aerosols, such as some as-yet unidentified forcing, and the IPCC’s other iconic graph – the bar chart on p.136 showing GHGs and trivial also-rans – is discredited. It’s too early to say “it’s the Sun, stupid”, but the astrophysicists are boarding the troopship.

John Marshall

Latent heat is most important. Evaporation needs latent heat so will cool the surface from which the water is being removed. Once in the atmosphere this heat is given up during the condensing into cloud. It is cloud that has both positive and negative feedbacks depending on situation and acts as a regulatory control on climate. Water vapour will carry heat around the atmosphere, as latent heat. once this heat is released, during condensation, it is free to warm the surrounding atoms in the atmosphere or escape to space.

Spector

As I have stated earlier, I personally suspect that role played by earthshine emitting/absorbing (greenhouse) gases at the tropopause level may be being underestimated as a mechanism for removing convected heat from the atmosphere. I would think that the most important spectra may be those lines that have a 50 percent chance of getting out from that level at the typical temperature of 220 K as I believe these should have the highest relative emissivity.
The important parameter for measuring how effective convection is as a thermal regulator of surface temperatures would be a determination of how the effective surface temperature, as controlled by the adiabatic lapse rate from the tropopause temperature, would change as a function of the total energy being convected upward. This would account both for tropopause altitude changes and temperature changes with increasing upward convected thermal energy. I do not know if anyone has ever attempted to estimate or determine this.

Guy

Mike D. at 11:36 should have credited his words. I believe their creator was Joni Mitchell.
Now that I have seen latent energy brought up: should the quantity of energy needed to melt ice and evaporate water be somehow included in the calculations of percent increase in temperature? In other words, if ice goes from -1C to water at 1C it has increased in temperature only two degrees Kelvin, but its energy absorption is a rather large multiple of this. I feel a bit like the spectator who runs out on the field when I ask this, but it is something that I have been wondering for some time.

Robert of Ottawa

Again, positive feedback, if it exists in the climate system, would have caused the Earth to fry, or freeze, billions of years ago.

John Galt

Dinostratus,
I’ll try to respond. First I think it’s the air over the ocean, not the ocean itself, that’s warming, minor point. I think you’re not considering the magnitude difference between specific heat and latent heat. The specific heat of water is 1 cal/g-K. The heat of vaporization is 539 cal/g. That 539 cal then, rather than trying to radiate from the surface, through the rather dense, ghg laden atmosphere, moves by convection, which is unaffected by the greenhouse effect. At some higher altitude, above much of the greenhouse effect, the water vapor precipitates, releasing this 539 cal. This energy is now able to radiate upward with much less greenhouse effect. This is what I mean by going around the greenhouse effect. It works much like a heat pipe, which is much more effective than radiation. A small additional effect is that the water falls back to the surface at a lower temperature than it left at, adding a few more cal’s of cooling.
During the time the water vapor is in the atmosphere, it’s a positive radative feedback. The evaporation/precipitation cycle is a negative convective feedback. The longer the cycle is, the greater the radiative effect will be wrt the convective effect. As the evaporative effect becomes greater, due to surface warming, the cycle will shorten, precipitation will increase. This should move the positive/negative balance toward negative.
I haven’t tried to calculate how much delta warming a given mass of water contributes per day vs. the latent heat it moves. I suppose I should, but I expect Dr. Spencer already has that answer. I do know, just from peeling the lid off of something from the microwave, that the latent heat of water is nothing to trifle with.

I posted this comment at Roy Spencer’s blog, still in moderation:
——–comment——

At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is..

I think it’s very complicated and I can’t comment on “most researchers” whereas you would probably know a lot of them – plus their papers may well be more cautious than their general views.
But the papers I’ve read don’t appear to deal with it simplistically and do cover these same questions. Of course some of the papers I’ve read are “Spencer & Braswell 1997″, Lindzen, but also Soden & Held, Sun & Oort, Bony & Duvel, Ramanathan, many others.
In Clouds and Water Vapor Part Two I cited Held and Soden (2000):

To model the relative humidity distribution and its response to global warming one requires a model of the atmospheric circulation. The complexity of the circulation makes it difficult to provide compelling intuitive arguments for how the relative humidity will change. As discussed below, computer models that attempt to capture some of this complexity predict that the relative humidity distribution is largely insensitive to changes in climate.

Held and Soden have their point of view but in theirs and most of the papers I don’t see a simplistic approach.
—end of comment—
Water vapor feedback is a complex subject. You can see the approach of the great Ramanathan in Clouds and Water Vapor – Part One. For those who don’t simplistic answers, it’s worth taking a look. Many interesting comments as well.

Ceri Phipps

Water vapour can not be a positive feedback as there is no limit to available water and consequently if it were a positive feedback the atmosphere would be saturated with respect to water vapour which it is not.
If the atmosphere warms, the amount of water vapour it can hold increases, therefore if there were a positive feedback it would not matter what caused the warming, it would kick of a positive feedback until the atmosphere became saturated with water vapour. This should, therefore, have happened in the last El Nino event, which it clearly didn’t.
The idea that water vapour can be a positive feedback makes no scientific sense. It is blatantly obvious that there is a large negative feedback that keeps it in balance. Clouds and rain seem the most obvious.

JTinTokyo

Dr . Spencer is asking the most important question of all and thinking about the possible answers(s). He, and others asking similar questions, know that the “science is (not) settled”. With an open mind, we look forward to further work in this crucial area!

Geoff Sherrington

Is there a published global summary of annual surface precipitation over the years, like there is an effort to have a global temperature summary? If so, could this help solve some questions raised above? Ditto relative humidity?

Iren

Ferenc M. Miskolczi’s paper Greenhouse Effect in Semi-Transparent Planetary Atmospheres published in the Quarterly Journal of the Hungarian Meteorological Service in 2007 explores the effects of humidity.
http://met.hu/doc/idojaras/vol111001_01.pdf
“Abstract—In this work the theoretical relationship between the clear-sky outgoing infrared radiation and the surface upward radiative flux is explored by using a realistic finite semi-transparent atmospheric model. We show that the fundamental relationship between the optical depth and source function contains real boundary condition
parameters. We also show that the radiative equilibrium is controlled by a special atmospheric transfer function and requires the continuity of the temperature at the ground surface. The long standing misinterpretation of the classic semi-infinite Eddington solution has been resolved. Compared to the semi-infinite model the finite
semi-transparent model predicts much smaller ground surface temperature and a larger surface air temperature. The new equation proves that the classic solution significantly overestimates the sensitivity of greenhouse forcing to optical depth perturbations. In
Earth-type atmospheres sustained planetary greenhouse effect with a stable ground surface temperature can only exist at a particular planetary average flux optical depth of 1.841 . Simulation results show that the Earth maintains a controlled greenhouse effect with a global average optical depth kept close to this critical value. The broadband
radiative transfer in the clear Martian atmosphere follows different principle resulting in different analytical relationships among the fluxes. Applying the virial theorem to the radiative balance equation we present a coherent picture of the planetary greenhouse effect.”
SPPI published a paper last December by another Hungarian scientist, Miklos Zagoni, discussing Miskolczi’s work, which was based on actual observations and measurements. You might recall that Miskolzci was a senior scientist at NASA, which refused to publish his work. The SPPI paper can be found here –
http://scienceandpublicpolicy.org/originals/co2_cannnot_cause.html?Itemid=0

Dave Springer

Dinostratus says:
September 14, 2010 at 11:55 pm
Transport of energy from surface to altitude by latent heat of evaporation not only bypasses the greenhouse effect it reverses it. Once the heat is released at altitude via condensation the greenhouse gases below it now serve to insulate the surface from the heat of the cloud so instead of the GHGs keeping the surface warmer in this case it is keeping it cooler.

Ceri Phipps says:

Water vapour can not be a positive feedback as there is no limit to available water and consequently if it were a positive feedback the atmosphere would be saturated with respect to water vapour which it is not..
The idea that water vapour can be a positive feedback makes no scientific sense. It is blatantly obvious that there is a large negative feedback that keeps it in balance. Clouds and rain seem the most obvious.

It doesn’t make intuitive sense for those used to thinking about control systems – positive feedback usually leads to some kind of runaway system.
However, in the case of the climate there are also some non-linear negative feedbacks – surface radiation increases in proportion to the forth power of (absolute) temperature. If you analyze the system mathematically, a higher range of potential positive feedback leads to a thermal runaway. The lower range of positive feedback leads to amplified warming (compared with no feedback), and of course, negative feedback leads to reduced warming.
This doesn’t mean that water feedback is a positive feedback. But the idea isn’t mathematical or scientific madness.

Harold Pierce Jr

Below is a comment that I recently posted on Roy Spencer’s blog.
RE: The Positive Water Feedback Hypothesis
At 14 deg C and 1 atm .pressure, 1 cu. meter of air has 12.1 g of water vapor for 100% humidity. If the temperature of the air is increased to 15 deg C, 1 cu. meter will now have 12.8 g of water vapor for 100% humidity , a small increase of only 0.7 g or 6.7% of water vapor. However, 100% humidity only occurs if it is raining or snowing or if there is dense fog. So how does the enormous amounts of surface water enter the atmosphere?
The wind is the force that transports surface water into the atmosphere and is far more important than simple evaporation of water in still air. When wind blows over a body of water, the surface will cool but water will still be transported into the air. Due to their momentum the much heavier nitrogen and oxygen molecules and argon atoms just blast the lighter water molecules out the surface water into the air. The lake effect is due to strong winds blowing water vapor from warm surface water onto the usually colder land.
Changes in air pressure are also more important than a slight increase in air temperature as is shown on an aneriod barometer. An air pressure drop of a few inches (ca 60 mm) of mercury will often cause rain or snow. If pressure increases, the air becomes dry. The heat of vaporization of liquid is depends mostly on external pressure. The low air pressure in tropical a cyclone causes enormous quantities of water to “flash evaporate” into the air as it moves into warm coastal waters.
Clouds are liquid water in the air and depending on local temperature, pressure and humidity, they can readily release water vapor into the air or drop excess moisture as rain, snow or ice pellets. On average cloud cover in the atmosphere is about 65%.
Clouds also contain atmospheric gases and can transport these, in particular CO2, from one local to an other local where these gases can be released into the air or be deposited on the surface in rain drops.
Over land transpiration from plants contributes to the local humidity as does respiration from all plants and animals which includes soil organisms such as bacteria, fungi, worms and insects.
I don’t recall reading that climate models take the above into account.

Edward Bancroft

“Warmer air is associated with greater surface evaporation rates….”
Yes, but other effects have such as wind speed have large impacts on evaporation rate. Wind can dry the surface (that is evaporate water) on cold days/nights quicker than warmer days/nights with no wind. The GHG IR effect is of little relevance where wind dominates.
Spector says:
“As I have stated earlier, I personally suspect that role played by earthshine emitting/absorbing (greenhouse) gases at the tropopause level may be being underestimated as a mechanism for removing convected heat from the atmosphere. ”
This is something that is not often referred to, as the energy transfer diagrams never seem to include the effect of IR active gases on the absorption/re-radiation of IR receivedfrom the sun. Nor do they really consider what happens at night, when GHG’s are for the most part atmospheric coolers.

Edward Bancroft:

This is something that is not often referred to, as the energy transfer diagrams never seem to include the effect of IR active gases on the absorption/re-radiation of IR receivedfrom the sun. Nor do they really consider what happens at night, when GHG’s are for the most part atmospheric coolers.

I don’t know about energy transfer diagrams but the climate models all take into account the radiatively-absorbing gases on absorption of solar radiation.
In fact, even the best known one, by Kiehl and Trenberth shows 1/3 of the solar radiation being absorbed by the atmosphere.
At night? Well, I don’t know what diagrams you are referring to, but in the case of Kiehl and Trenberth for example, this is a globally, annually averaged diagram, so you won’t see day and night. But once again, this is climate basics so it is considered in every climate model.

Bill Illis

We don’t know if water vpour is increasing as predicted.
We don’t know if increased water vapour is producing or will produce a net warming as predicted.
Since it is expected to be responsible for close to 2.0C of the warming by 2100, it is a little strange that we still don’t have any evidence to say one way or the other.

cohenite

The range of GMST over the Earth’s history has been ~ 12-15C; today’s GMST of ~ 15C is at the lower end of the scale; some of the periods in the past featured very high levels of CO2 and extensive or no glaciation. If combined feedbacks were positive the Earth would now either be a snowball or like Venus, with Venus being the more likely scenario because of the growing sun over this time. CO2 cannot be the agent of change because it does not have the causal correlation with temperature; water, however does; and water must be a moderator of temperature trend given the relatively low range of GMST.
The science should be about water but unfortunately there is not a buck in it; at least to the same extent as CO2.

Ulric Lyons


3) Cause Versus Effect
Just because we find that unusually warm years have more water vapor in both the boundary layer and free troposphere does not mean that the warming caused the moistening.
There are a variety of processes (e.g. tropospheric wind shear causing changes in precipitation efficiency) which can in turn alter the balance between evaporation and precipitation, which will then cause warming or cooling as a RESULT OF the humidity change – rather than the other way around.”
________________________________________________
If one takes a look at the months with the greatest +ve deviations from normals in unusually warm years, higher solar wind speeds will be evident.
The major rainy periods this summer so far, 2nd and 4th week of July, 2nd half of August, and the past few days, had lower solar wind speeds, providing the drop in temperature required to increase volume of summer rainfall.
http://www.lmsal.com/solarsoft/latest_events/

The idea that water vapor acts as feedback to magnify the effects of CO2 is like saying a flee can control the direction of a horse. It is much more likely that water vapor and condensed moisture (clouds) is taking CO2 for a ride and controlling it’s global distribution in the process. http://www.kidswincom.net/CO2OLR.pdf.

Edward Bancroft

From scienceofdoom:
“In fact, even the best known one, by Kiehl and Trenberth shows 1/3 of the solar radiation being absorbed by the atmosphere.
At night? Well, I don’t know what diagrams you are referring to, but in the case of Kiehl and Trenberth for example, this is a globally, annually averaged diagram, so you won’t see day and night. But once again, this is climate basics so it is considered in every climate model.”
My take on this: The K&T diagram shows the 1/3 absorption, but does not say in which energy bands it takes place. If it is shorter wavelength, there is no GHG/IR re-radiation. It does show emitted radiation, but the diagram implies that the source of this radiation is from the surface/clouds, not the re-radiation of the incoming energy in the upper atmosphere.
The day/night effects are lumped together, but it would be instructive to see them separated so that the compensating IR heating/cooling effects can be clearly shown.
As a style criticicism, the K&T diagram also attempts two analyses on the same image. Namely, on the left there is an energy analysis in direct W/m2. On the right it also uses W/m2, but as part of a black body cloud/surface interchange, with the apparently anomalously large numbers actually being correctly expressed artefcats of the blackbody dynamics.

It is good to see the topic move to the area that makes the most sense, only by understanding the role that water liquid/vapour equilibrium plays in moderating our climate will we be better able to predict the outcome from variable energy inputs into the system.
John Galt
I agree with you that water vapour provides for effective movement of heat energy through the atmosphere. And, huans have used it continuosly since the invention of the steam engine. A quick browse of the steam tables for the latent and sensible energy transferred from a source at an initial temperature and pressure to a destination at final temperature and pressure will show just how effective water vapour is in this regard.

Ulric Lyons says:
September 15, 2010 at 5:48 am
The major rainy periods this summer so far, 2nd and 4th week of July, 2nd half of August, and the past few days, had lower solar wind speeds, providing the drop in temperature required to increase volume of summer rainfall.
http://www.lmsal.com/solarsoft/latest_events/

The second half of August wasn’t all that rainy where I live.

Tilo Reber

Nice work, Roy.

Jeff L

Given the change in CO2 over the last 100 yrs & the expected water vapor feedback in the models, wouldn’t we have expected significantly more warming than we actually have observed? And if that is the case, this would strongly argue that the water vapor feedback is significantly less than is in the models. Which of course would also imply that the forecast temp increase in the future is significantly overdone & that pretty much blows up the catastrophic AGW case, doesn’t it? Water vapor feedback is a critically import issue.

Joseph Day

Let’s add a little more to Harold Pierce Jr’s post. Water is lighter than oxygen and nitrogen. Thus, moist air is less dense than dry air. We focus on heat making air rise. Yes, heat helps water evaporate, but the wet air is lighter anyway. That helps lift it to higher cooler altitudes. When moist air cools enough, the air is saturated and clouds form.
Wet air is less dense and must rise through drier air, all else being equal. Thus, we have a strong mechanism for transporting heat. In this case, the heat of evaporation / condensation. It works like a refrigerator. It will operate until the temperature at the surface drops sufficiently, or there is not enough water to make clouds. Seasonal hurricanes are the perfect illustration.
With 70% of the Earth covered by oceans, I think we have enough ‘refrigeration’ capacity to stop worrying about climate hysteria. 250 million years ago, the center of Pangaea was an enormous desert, lacking water to cool it. Obviously, the Earth’s oceans didn’t dry up. The areas of Pangaea that did receive rainfall were very fertile. We have the fossil record to prove that. And we are here.
If there were a way for a positive feedback mechanism to kill us, it would have done so already over the almost 4 billion years life has existed on Earth. Stop worrying about it. Oh, that’s right, some of us need the grant money, so keep worrying, and keep paying.

As per usual I’m prolly missing something, but water vapor isn’t a coolant.
Water is a coolant, just try it in a desert, or hell spill your water on your crappy ski pants high up in the mountains at minus 20 but I guess a big commercial freezer works too. When in the jungle in the summer time everyone present want those instant 15 minute showers, cool things down a bit… however afterwards it get warmer due to the water vapor raising from the ground, cloths drying, and what not. In the desert it really is the same you just doesn’t really notice the difference when the splash in the face that cooled things down for a micro second is then vapor in the atmosphere, the vaporization process is felt as cooling though.

Slabadang

Its obvious there is a negative feedback!
I wonder if the whole climate science isn`t starting by passing over the river to fill the bucket with water. When clouds form it’s because of heat, and they protect the earth from further heating by radiating back the incoming solar radiation. The daily observations from the tropics confirm this every morning and every afternoon.
Of cource there are “time lags” and smaller aerosolic influenses as well as the oceans heating circles in the thermostatic effects. But in the end the negative feedback from water vapour dominates and we land around the historical top records as “worst” (best?) case.
From the historical data we have, its interesting to observe that there seems to bee a “soft roof” for how high the temperature on earth can get (with the same solar output) this is an indication that the hotter i gets the harder it gets to get even hotter.
My simple answer is that the total amount of water on earth is the allways present allways reliable functioning thermostat protecting us from owerheating.Its when you try to calculate and understand why and how the details in the thermostat works that you may be lost on your way. Its much easier to find and understand factors why it can get so much cooler.

Canadian Mike

IMO Cohenite hits the nail on the head. As an engineer I have studied feedback systems and positive feedback results in system failure. We know this for a fact. If CO2/H2O forcing was positive we would have become Venus a long time ago when CO2 levels were many times what they are now. How can scientists continue to say “we have no real ideal how water vapor, by far the strongest greenhouse gas, responds to increasing temperatures but we’re pretty sure it’s catastrophic” despite the evidence all around them. At what point do reasonable people call bullcrap?

jorgekafkazar

Fred H. Haynie says: “The idea that water vapor acts as feedback to magnify the effects of CO2 is like saying a flee can control the direction of a horse. It is much more likely that water vapor and condensed moisture (clouds) is taking CO2 for a ride and controlling it’s global distribution in the process…”
Does rain scrub CO² from the atmosphere?

jorgekafkazar said on Spencer on water vapor feedback
September 15, 2010 at 10:03 am
Yes, clouds do absorb CO2. Relatively pure rain will have a pH that is roughly in equilibrium with the atmospheric concentration (between 5 and 5.5). Some CO2 will be returned to the ocean surface in rain. Some will be transported up in towering clouds where the water freezes and releases CO2 to the upper atmosphere. This process of evaporation/condensation/freezing will occur many times as an air mass containing clouds goes from the equator to the poles. http://www.kidswincom.net/climate.pdf.

Enneagram

Humidity shorcircuits condensers….

Enneagram

How do any of us negative feedback ourselves when too hot? With water. Water refreshes. Do some alien “peers” think differently? Probably,…. if cold-blooded.