Here is some interesting news; according to data from NOAA’s Earth System Laboratory, atmospheric water vapor is on the decline globally.
You’ve probably heard many times how water vapor is actually the most important “greenhouse gas” for keeping our planet warm, with an effectiveness far greater than that of CO2.
It is generally accepted that the rank of important greenhouse gases is:
- water vapor and clouds which causes up to 70% of the greenhouse effect on Earth.
- carbon dioxide, which causes 9–26%
- methane, which causes 4–9%
- ozone, which causes 3–7%
Note the range of uncertainties, on water vapor some say the percentage goes up to 90% with reduced numbers on the other three.
It is absolutely true that water vapor is the gas most responsible for the “greenhouse effect” of our atmosphere. Greenhouse gases let short-wave solar radiation through the atmosphere, but impede the escape of long-wave radiation from the Earth’s surface. This process keeps the planet at a livable temperature: Without a suitably balanced mixture of water vapor, CO2, methane, and other gases in the atmosphere, Earth’s average surface temperature would be somewhere between -9 and -34 degrees Fahrenheit, rather than the balmy average 59 degrees it is today.
This graph then from NOAA’s Earth System Research Laboratory, showing specific humidity of the atmosphere up to the 300 millibar pressure level (about 8 miles altitude) is interesting for it’s trend:
Click for original source of the graph
[UPDATE2: After reading comments from our always sharp readers, and collaborating with three other meteorologists on the graph, I’m of the opinion now that this graph from ESRL, while labeled as “up to 300mb only” is misleading due to that label. The first impression I had would be from the surface to 300mb i.e. the “up” portion of the label, but on the second thought I believed the label was intended to be numerical meaning “zero to 300mb” or from the top of the atmosphere down as opposed from the surface up as we normally think of it. The values looked like anomaly values, but are inthe range of absolutes for that elevation also.
Thanks to some work by commenter Ken Gregory, looking at other ways this and similar graphs can be generated from the site, it has be come clear that this is a level, not a range from a level. The label ESRL placed “up to 300mB was intended to list the availability of all data levels. Thus there is no 200mb data.
This demonstrates the importance of labeling a graph, as without any supplementary description, it can be viewed differently than the authors intend. A better label would be “at 300mb” which would be unambiguous. ESRL should correct this to prevent others from falling into this trap.]
For some background into atmospheric absorption efficiency of the electromagnetic spectrum, this graph is valuable:
Note the CO2 peak at 15 microns is the only significant one, as the 2.7 and 4.3 micron CO2 peaks have little energy to absorb in that portion of the spectrum. But the H2O (water vapor) has many peaks from .8 to 8 microns, two that are fairly broad, and H2O begins absorbing almost continuously from 10 microns on up, making it overwhelmingly the major “greenhouse gas”.
Here is another graph looking at it in a different way:
Click for a larger image
Note that water vapor plays quite a role in keeping the planet cool by absorbing some percentage of incoming radiant energy.
The yellow line is what we’d get without an atmosphere, and the blue line what we get with it. Sunlit temperatures on the earth’s surface are substantially less than those on the moon (up to 123°C) because our atmosphere intercepts some incoming solar short-wave radiation as well as some outgoing long-wave infrared.
So when we see atmospheric water vapor dropping as shown in the NOAA ESRL graph above, you know it has to have an effect on our overall planetary energy budget, the question that will be argued is; “how much”?
h/t: Thanks to atmospheric physicist Jim Peden, and also to Barry Hearn, and Alan Siddons for some of the graphs and background to this post.
UPDATE: See part2 of this post here
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Thanks Anthony,
I’ve been looking for this data for a long time. If possible can we see other levels of the atmosphere.
Generally, this is another area where the models are wrong as the assumption is that specific humidity remains constant. And this is a key assumption to the sensitivity estimates for GHGs.
It seems the models are getting too many specific assumptions/outputs wrong such as tropical troposphere, Antarctic, and temperature trends, in general, to be reliable.
Doesn’t decreased water vapour fly in the face of positive feedback in global warming theory.
I seem to recall that the worry from increased CO2 is that it causes positive feedback of increased water vapour, and therefore could cause run away global warming.
This seems to contradict that as CO2 levels continue to rise and now water vapour levels are decreasing.
“Greenhouse gases let short-wave solar radiation through the atmosphere, but impede the escape of long-wave radiation from the Earth’s surface.”
“Sunlit temperatures on the earth’s surface are substantially less than those on the moon (up to 123°C) because our atmosphere intercepts incoming solar short-wave radiation as well as outgoing long-wave infrared.”
I must be missing something because in the beginning you said greenhouse gases let through short-wave, and then later said they intercept short-wave.
On one hand they warm the planet (pass through solar short-wave and absorb earth-radiated long-wave), and on the other they cool the planet (intercepts incoming solar short-wave).
You’ll have to clear that up for me.
REPLY: The let in some, they intercept some. Its two way partial mirror, otherwise we’d never see stars or stay warm
raypierre @ur momisugly realclimate talked about anthropogenic GHG’s and strong water vapour feedback in 2005
The authors then subtract off the part of the downward infrared radiation increase attributable to temperature and water vapor increase, and thus estimate the part due directly (as opposed to via feedbacks) to the increase in anthropogenic greenhouse gases such as CO2. They estimate this to be about one third of a Watt per square meter. This is not in bad agreement with estimates from detailed radiation models run by the authors, which say that the change in surface radiation due to the 12ppm CO2 increase between 1995 and 2002 should be about one fourth of a Watt per square meter. It is striking that the changes in the Earth’s surface radiation budget due to anthropogenic greenhouse gases are so profound that they can be directly observed on a regional scale, over such a short time period. So far, so good. Physics seems to be working as it should, and climate scientists seem to be basing their understanding of climate change on rock-solid physical principles….I’m wondering if there needs to be some rethinking on this.
Very interesting. I have a related question. Anthony explained the greenhouse gas very well. If GHGs absorb long wave radiation reflected back toward space, isn’t there a diminshing return as GHG concentrations increase? Think of it this way, I have a window film that blocks 50% of the light. The first sheet I put on the window reduces the visible light by 50%. The next sheet only 25% (50% of 50%), the third 12.5%, the fourth 6.25% and so on.
If that analogy is right, we would expect that the first 100ppm of CO2 to produce the MOST warming. Is there something wrong with my reasoning? At some point adding more GHGs will have almost no effect on the energy absorbed.
REPLY: Your reasoning is spot on, CO2’s effectiveness as long-wave reflector with concentration is logarithmic
That graph is for the global average. It seems that regional patterns would be important to know before drawing conclusions.
Its probably not reasonable to expect the models to match short-term trends. They are not built that way.
We now have roughly 30 years of satellite data though, but I mostly see matches to Hadley or GISS “adjusted” data. The matches there appear to be reasonable for some model runs (the ones that assume CO2 reduction or stasis).
My trust of GISS is somewhat compromised (can’t image why) and MSU data has its own problems, but these pale compared with the surface station problems.
So who is working with MSU data to calibrate their models?
I haven’t looked into this too deeply, but I can’t help noticing that the water vapor graph looks somewhat like the sunspot graphs that we’ve seen. If there was some sort of correlation of sunspots to water vapor that might go a long ways in explaining why a low amount of sunspots or a quiet solar cycle seems to create mini ice-ages.
This is just off the top of my head, so don’t flame me if it actually sounds silly. Just thought I’d put it out there.
“Your reasoning is spot on, CO2’s effectiveness as long-wave reflector with concentration is logarithmic”
As would water vapor, right?
“That graph is for the global average. It seems that regional patterns would be important to know before drawing conclusions.”
Why would regional patterns matter when we’re talking about GLOBAL warming?
This is an amazing assertion by NOAA…. And based on past manipulations by NASA/NOAA, I find it VERY suspect and stinks like a hog farm. For openers, why did NOAA wait so long before announcing the drop in humidity? According to the above chart, the big drop began around 1958.
For the past year, I’ve spent hundreds of hours pouring over research papers on the various forms of water (solid, liquid, and vapor) in our atmosphere for an article on “The Mysterious Climate Project.” Quite frankly, each time I think I have a handle on it along comes another research paper or scientist with still another figure. The above article states water vapor and clouds cause up to 70% of the greenhouse effect on earth. Before I go on, blog members should realize the “volume” and the “effect” are two different animals! You can have all the volume you want (Argon for example), but if it has little or no effect it’s immaterial.
During the course of my research, I’ve received dozens of papers and letters from well known atmospheric physicists and climatologists who believe the “effect” figure should be closer to 95%. So how does this square with the above? I don’t know. Are some of my figures already outdated? Possibly. The truth of the matter seems to be that climatology is such an infant science, we essentially know VERY little of the subject. For the simplistic Pogies to run around like a bunch of chickens with their heads cut off screaming the sky is falling, simply shows how intellectually challenged they really are.
As the Pogies continue witnessing their AGW claims go up as so much smoke, it appears they are embarking on a crusade of minimizing every other variable associated with the climate in order to make CO2 look more important than it is.
If I were young and just entering college, my major would be atmospheric physics. It is virgin, it is challenging, it is intriguing, and it is the wild wild west all over again! To me, atmospheric physics and its associated fields remind me of that knock ’em dead, good looking redhead with a tight butt and a sexy swish in her walk! Okay, okay, maybe not that much, but close to it!
Jack Koenig, Editor
The Mysterious Climate Project
http://www.climateclinic.com
REPLY: There was no “announcement” per se, this was a data plot from the ESRL website that became self evident from the recently released data and upgraded web site that allowed such examinations by members of the public.
Henrik Svensmark has written extensively on the relationship between the sun’s magnetic field and cloud formation; unfortunately, I’m out the door for an appointment and can’t post any links now.
How can this be? Burning all that gas, oil and coal which makes the evil CO2 that warms the Earth also produces vast amounts of water vapor. So it can’t decrease.
Unless human activities aren’t such a big deal.
Blasphemy!
A bit more OT: It looks like we are close to saturation on inbound absorbtion (for CO2). How close to 100% are we on outbound radiation? Shouldn’t be much at near IR, what about the 15u stuff?
This is a Question.
If we assume (I hate that word always gets me in trouble) that water vapor is at 1000 ppm and that it falls by 50% to 500 ppm the current thought that it causes warming then the warming caused by water vapor would decrease by 12.5% causing lower water vapor content as cooler air tends to be drier. then the air could lose another 50% down to 250ppm and this could cause an additional 25% cooling causing another reduction of temp causing the air to condensate reducing water vapor again if another 50% we lose an additional 50% ability to warm and so forth. I wonder if the modelers put this in their computations. I know that the figures I am using are not correct but just food for thought. It would seem that with the sun possibly having influence on water vapor our problem might be run away cooling not runaway warming. (Ice ages again) I know that my figures are exaggerated but If Gore can as truth why can’t I in a question while admitting that they are exaggerated?
Come on Sun
Bill Derryberry
Ok, GHGs let through some short-wave (visible and very-near infra) and absorb others. They keep in/out the strong majority of the infrared bands, and H2O keeps in/out just about all the microwave range stuff.
Cool, I guess I just got confused on terminology. Blocking a small portion of the short-wave stuff doesn’t sound like it does much “cooling”. Maybe it just doesn’t warm as much as it might, which I guess is pretty much the same thing as having a cooling effect.
Would you happen to have any charts that show the bands of radiation that the Earth puts out? Does Earth radiate infrared pretty uniformly across wavelengths, or does it radiate in particular wavelengths?
I could see a significant difference in effects if Earth happens to primarily radiate at the 6 micron wavelength of infrared where H2O is the only thing that really keeps that in, compared to if Earth radiates more at 4 microns where it’s primarily CO2 that keeps the radiation in.
Or Earth may radiate in a smooth grade of wavelengths, and we can do relatively easy average-calculation of what effect the dropping H2O might have on keeping in infrared radiation.
Anthony, you say “Without a suitably balanced mixture of water vapor, CO2, methane, and other gases in the atmosphere, Earth’s average surface temperature would be somewhere between -9 and -34 degrees Fahrenheit, rather than the balmy average 59 degrees it is today.”
Actually, in his book Roy Spencer has recently reminded people of a paper from 1964 by Manabe and Stickler, where they calculated the surface temperature with major greenhouse gases and natural convection at about 140 F. The lapse rate is also almost double what is actually observed. It is the resulting weather that accelerates the transport of heat from the surface to the top of atmosphere, reduces the lapse rate to the observed values of about 6.5 K/km, and regulates the surface temperature at around 59 degrees F. It is a subtle difference, but shows that weather processes are a huge stabilizing feedback mechanism to the global climate. You don’t need much of a change in cloud cover or precipitation efficiency to have a dramatic impact on surface temperature.
REPLY: Correct, weather is part of the global heat transfer mechanism, hurricanes and thunderstorms do quite a bit of this transport.
Pardon me, I do not understand, what the globally averaged relative humidity really means. E.g.; values of order 0.2 and somewhat less imply clear sky situations all year long. Or try to estimate the latent heat content in the atmosphere from these numbers, by using globally averaged mean temperatures. You probably get enormous fluctuations which do not make any sense. Humidity saturation increases exponentially with temperature. How meaningful is it to just take the average over exponential functions? Finally, it is the absolute humidity which determines any water vapor greenhouse effect. It is also the absolute humidity, which determines the amount of latent heat, transported into the upper troposphere by convection and which, according to R.S. Lindzen may more or less bypass the blocking of radiation cooling by the greenhouse gases.
Anthony — I believe you are wrong on the primary reason for higher peak temperatures on the moon. While the earth’s atmosphere (clear sky) absorbs about a quarter of incoming solar radiation before it hits the surface (~1365 W/m^2 at the top of the atmosphere, ~1000 W/m^2 at the surface), remember that this energy is still absorbed in the earth “system”.
Remember that the moon’s day/night cycle is a month long in earth terms, so its “daylight period” is two weeks long. This gives plenty of time to get the surface cooking. Think of how hot the earth’s surface would get in the afternoon of a month-long day.
Time-averaged, the moon is cooler than the earth, one of the key pieces of evidence saying there is a natural greenhouse effect on earth.
REPLY: Excellent point, one which I hadn’t considered. That duty cycle does indeed change the issue.
This is very interesting. As the basic CO2 incriminator is the feedback mechanism between water vapor and temperature rise this is another nail on the coffin of anthropogenic CO2. One does not need a sophisticated analysis to disprove a correlation with the monotonic CO2 rise of the last decades.
It is amazing that they were sitting on such data and never checked their feedback hypothesis.
Thanks for finding it for us.
Anthony,
Do you have a link for the original data for this? I’ve found lots of huge gridded datasets, but nothing as simple as this annual/monthly global mean.
Thanks
Paul
REPLY: This is from web plotting automation similar to yours, I’ll see if I can backtrack the raw data.
Anthony et al, if water vapor is dropping it’s effect should first be felt in the tropics. Do we have cooling there?
Secondly, dropping water vapor is a sign of cooling somewhere, oceans, troposphere, polar regions, temperate regions. So where do we have cooling? We think we have cooling in the seas and the troposphere, South pole any other areas? Perhaps they are enough.
Here is a nice chart on the W/M^2 of sunlight: http://www.spacewx.com/solar_spectrum.html
http://www.spacewx.com/images/Solar_spectrum_144px.jpg
Notice that most of the energy contained in sunlight is in the 1,000 (10^3) to 10,000 (10^4) nm range (1 to 10 mircon respectively). Where is CO2’s range???? two small isolated peaks below 10 mircons and one larger above 10 microns. And where is the H20 range??? Spanning most of the range of sunlight. That in itself should negate the silly argument about CO2 absorption and emission driving H20. It’s just plain deceptive to even maintain the position.
For those of you math challenged, here is a nm to mircon calculator: http://www.unitconversion.org/length/nanometers-to-microns-conversion.html
GHG alarmists obsess about positive feedbacks. They obsess about positive feedbacks that don’t exist. The ones that do exist generally result in several thousand feet of continental ice covering half of North America.
Locri — yes that was my thought as well. However after looking around for some time, and reviewing papers about what Svensmark has proved, I get this — When you take into account the Svensmark cosmic ray effect then a possible theory begins to come to the fore. Could it be that sunspots are just an indicator, not the prime mover for cooling, the real player might be cosmic rays and low level cloud formation and subsequentially higher precipitation.
Sunspot number would likely be the prime forcing for warming, because of the direct radiative effect of CMEs and increases in the solar wind. So just having sunspot numbers go down, like in a normal solar minimum, may not provide enough forcing for cooling. Consider, there have been periods of low sunspot activity without any cooling correlation before, a normal sunspot minimum for instance.
What we have here is the unique observed event of the lowered sun’s magnetic component.
Try this line of reasoning — The sun goes quite, caused primarily due to a drop in the sun’s magnetic field, increasing the incidence of cosmic rays on Earth’s atmosphere, this in turn increases low level clouds, which produces more rain, which then cools Earth. The missing link was the cosmic rays and cloud formation theory which was provided by Svensmark..
Anthony – the decrease in specific humidity at ~6 miles (300mBars) is very interesting and the site you linked to is pretty neat. However, before jumping to too many conclusion re: feedback etc., you might want to check the trends in specific humidity at lower atmospheric levels. 600 -900 mbars seem pretty flat, but 950 mbars, and particularly 1000 mbars show very clear increasing trends over the time period in question. From eyeballing the g/Kg numbers, it appears that the lower troposphere is gaining more water than the upper troposphere is losing. That’s just eyeballing it though, and maybe it balances out. Keep up the good work.
BobN
REPLY: As I understand this data, this is data up to 300 mb, not at 300 mb. I’ll dig a little deeper though to be sure.
What we need is a graph showing heat capacity in watts/ppm at given temperatures and heat absorption rate of change in watts/ppm.
Water vapor absolutely dwarfs CO2.
Water is also a working fluid for heat transfer from the Earth’s land and ocean into space. When it condenses from water vapor into clouds, it releases huge amounts of heat. The reverse is true when fog or clouds dissapate.
Everyone is familiar with a cold can of soda having water condense on it on hot humid days, thus warming the can. Then there is the nighttime convergence of dewpoint and air temps which prevents nights from getting cold.
CO2 does not do this.