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
I am enjoying Ken Gregory’s comments on Miskolczi’s theory of semi-transparent atmospheres. David Stockwell has an interesting posting commenting on Anthony’s article worth looking at providing a little more explanation of Miskolczi’s relevance to the current discussion.
Anthony, thanks for correcting your post. Could you also kindly correct my name from Kevin to Ken? Thanks.
In my previous posting, I had promised to post a composite graph of specific humidity at various elevations. On second thought, specific humidity varies greatly at different elevations, so the line at 300 mb shows as an almost straight line at the bottom of the graph due to the large scale range. Expanding the scale at the 300 mb line would show the identical line shown in the lead post.
The specific humidity graph is here:
http://members.shaw.ca/sch25/FOS/GlobalSpecificHumidity.jpg
and the relative humidity graph is here:
http://members.shaw.ca/sch25/FOS/GlobalRelativeHumidity.jpg
I had previously asked if it was possible to insert graphs directly into posts. I got no reply. I had copied the appropriate tag codes (from ClimateAudit.org) but that didn’t work. There are no “img” tags shown in your tag list.
All climate models use a completely absurd assumption that specific humidity is constant when CO2 concentrations increase. This violates fundamental energy conservation laws. There are not separate energy balance equations for different greenhouse gases. There is not one set for water vapor, and a different set for CO2; there is one set of energy balance equations for the total atmosphere including the sum of all greenhouse gases.
Why is the relative humidity at 300 mb at 38% and not at 60% or 95%, or vary randomly? It is at its value due to the laws of physics, which are not included in the climate models. The energy conservation principles controls the strength of the greenhouse effect, not just one particular gas, so changing the amount of CO2 will cause an offsetting change in H20. Water specific humidity would be constant only if other greenhouse gas concentrations are held constant.
A summary of the correct energy balance laws that control the strength of the greenhouse effect is here:
http://hps.elte.hu/zagoni/Proofs_of_the_Miskolczi_theory.htm
I can’t resist. If increases in CO2 increase precipitation then we get a double bonus for plant growth. There seems to be some serendipity going on. Even if land gets soggy, it will be good for rice, which the Chinese will appreciate.
I think these articles talk about some of the issues in this blog.
http://www.igbp.kva.se/documents/NL_69-6.pdf
http://www.pbs.org/wgbh/nova/transcripts/3310_sun.html
Evaporation rates are down but its probably due (certainly recently) to increased particulate pollution.
I created a graph of global relative humidity of levels of each 100 mb from 300 to 700 mb here:
http://members.shaw.ca/sch25/FOS/GlobalRelativeHumidity300_700mb.jpg
This expanded scale more clearly shows the declining relative humidity.
Remember that the highest curves, 300 mb and 400 mb are most important, as these are in the predicted hot spot and at the characteristic emission level. Water vapor changes near the surface have little effect on the greenhouse effect because long wave-length photons captured here and emitted would be recaptured again and would not escape to space.
Apart from simple logic that the constant relative humidity assumption used in climate models is ridiculous (as previously discussed), this graph proves it to be false, and that water vapor is a strong negative feedback, not a positive feedback.
Ken, Do you have any thoughts on how this (obvious) drop in relative humidity relates to specific humidity, and the relative merits of specific vs relative humidity in looking at thermodynamic effects of changes in water vapor in the atmosphere? Your earlier graphs of specific humidity appeared to show no decline, and perhaps a slight increase.
Hi David,
I have read your excellent four part critique of the Miskolczi theory at our website Niche Modelling at http://landshape.org/enm/radiative-equilibrium-miskolczi-part-4/
This is a must read for anyone concerned about the world spending trillions of dollars to slow emissions of a completely beneficial by-product of industrialization – CO2.
If CO2 were held constant, an increase of external Sun forcing would cause specific humidity to increase with increasing global temperatures, but there should be little or no change to relative humidity. Increasing the Sun’s forcing would also increase the greenhouse effect. The greenhouse effect G would increase by 1/2 of the increase in the Sun forcing F, where F in net of albedo, so includes the Svensmark’s theory of the Sun changing the amount of cloud cover via cosmic rays.
When we say there is an almost constant greenhouse effect, we mean it is constant despite increasing CO2 assuming a constant external forcing (Sun and albedo).
In the real atmosphere, the increasing CO2 and increasing Sun’s forcing over most of the 20th century would also cause the specific humidity to increase. At lower elevations specific humidity has increased, but this has little effect on the greenhouse effect as the large amount of water vapor already captures all LWR. At higher elevations specific humidity has decreased. We expect overall the specific humidity to increase due to increasing Sun forcing and decreasing relative humidity especially at higher elevations due to increasing CO2 concentrations.
Previous message, should be “your website Niche Modeling”.
I posted a non-technical review (no equations!) of the Miskolczi theory with discussion of the falling specific humidity titled “The Saturated Greenhouse Effect” on the Friends of Science website here
http://www.friendsofscience.org/index.php?id=222
Please provide critical comments.
Thanks
Ken, thanks for the kind words, although it is unfinished and going to take another 4 posts at least to get through even the radiative equilibrium part of M’s paper. I thought your review of AGW issues was the best I have seen. I will certainly give you my thoughts on your Miskolczi piece after I have read it.
The water vapor story is obviously a major piece of the puzzle and I should come to grips with the issues and the facts surrounding it. Your explanation above seems to suggest that papers claiming increase in water vapor and positive feedback, and facts showing relative humidity declining, could both be right. It seems contradictory on the face of it.
Please note – I have corrected the plot in my earlier post
Apologies for a totally off topic post but I don’t know any other way of bringing it the the attention of this blog.
This site/papers on sustainable energy gives a lot of facts based the UK energy usage which appears to kick a lot of holes in the wind/tidal power argument as a viable alternative source http://www.withouthotair.com/
Ken Gregory wrote: “Hi David, I have read your excellent four part critique of the Miskolczi theory at our website Niche Modelling at http://landshape.org/enm/radiative-equilibrium-miskolczi-part-4/
This is a must read for anyone concerned about the world spending trillions of dollars to slow emissions of a completely beneficial by-product of industrialization – CO2.”
I agree this is a “MUST READ,” but first, readers might wish to read Ken’s great article found at http://www.friendsofscience.org/assets/documents/The_Saturated_Greenhouse_Effect.htm.
Jack Koenig, Editor
The Mysterious Climate Project
http://www.climateclinic.com
If John McLondon’s quote of NOAA “Also, while we have good atmospheric measurements of other key greenhouse gases such as carbon dioxide and methane, we have poor measurements of global water vapor,” is correct (and I have no reason to doubt it), it means we know bugger all about something thought to contribute 70 – 90% of the “greenhouse effect” and yet it has been possible to create the illusion that we should be “spending trillions of dollars to slow emissions of a completely beneficial by-product of industrialization – CO2.” (McGrats). That’s the real concern about “global warming”
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