The Role of Water Vapor in Climate Change

Craig James Blog ^ | March 31,2007 | Craig James

[DouglasKC]

The Role of Water Vapor in Climate Change

Posted By Craig James @ March 31st, 2007 under All Blog Posts, Craig James.

 

You have probably heard the comment that if it wasn’t for the greenhouse effect, the Earth’s average temperature would be around zero degrees Fahrenheit instead of the 57 degrees we currently enjoy. Obviously, the greenhouse effect is a good thing. But of course, the current questions is: can we get too much of a good thing?

There are five main greenhouse gases (gases that trap the Earth’s long wave radiation and produce a warmer climate). These naturally occurring plus human generated greenhouse gases include water vapor (H2O), Carbon Dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3), plus a few other minor ones. What I have found is that the generally accepted numbers for the contribution of water vapor to the greenhouse effect is 60- 70%. It varies somewhat depending upon cloud cover but everyone agrees water vapor plays the major role in the greenhouse effect. You can find a technical discussion of the subject in this article in the Bulletin of the American Meteorological Society. If you don’t want to wade through all the technical jargon, the main thing I want to point out from the conclusion of this paper is “in discussing increases in greenhouse gases and their impact on climate change, the dominant contribution of water vapor to the current greenhouse effect is often overlooked.”

That is an amazing statement. There is just a brief mention in the latest IPCC Summary that water vapor in the atmosphere has increased due to greater evaporation because of warmer temperatures, but a more significant discussion of the role of water vapor can be found in the IPCC report released in 2001. If the atmospheric water vapor concentration increases as a result of a global warming, then it is expected that it will enhance the greenhouse effect further. This is called a positive feedback. Here is what the IPCC report says about water vapor feedback:

Water vapour feedback continues to be the most consistently important feedback accounting for the large warming predicted by general circulation models in response to a doubling of CO₂. Water vapour feedback acting alone approximately doubles the warming from what it would be for fixed water vapour (Cess et al., 1990; Hall and Manabe, 1999; Schneider et al., 1999; Held and Soden, 2000). Furthermore, water vapour feedback acts to amplify other feedbacks in models, such as cloud feedback and ice albedo feedback. If cloud feedback is strongly positive, the water vapour feedback can lead to 3.5 times as much warming as would be the case if water vapour concentration were held fixed (Hall and Manabe, 1999).

The climate models had better be getting the water vapor feedback correct or the projected warming may be too high by a factor of 2 to 3.5. This doesn’t sound like something that should be “overlooked”. While it is certainly true more evaporation will take place in a warmer world, there are many meteorologists who believe “the average amount of water vapor that resides in our atmosphere is not controlled by evaporation. Instead, it is controlled by precipitation (rain and snow) systems.” This quote comes from Dr. Roy Spencer, principal research scientist at the University of Alabama in Huntsville in an article at this site.

Here is what a study by NASA has to say on the subject:

The study cites satellite observations showing the rate that warm rain depletes clouds of water is substantially higher than computer models predicted. This research may help increase the accuracy of models that forecast rainfall and climate. The rate water mass in a cloud rains out is the precipitation efficiency. According to the study, when it comes to light warm rains, as sea surface temperature increases, the precipitation efficiency substantially increases.

Here is Dr. Spencer’s concluding comment on the subject:

I believe that it is the inadequate handling of precipitation systems — specifically, how they adjust atmospheric moisture contents during changes in temperature — that is the reason for climate model predictions of excessive warming from increasing greenhouse gas emissions.

It appears very possible, therefore, that the increased amount of water vapor in the atmosphere gets “precipitated out” by an increase in rainfall efficiency of precipitation systems, thereby lowering the amount of water vapor feedback the models are currently projecting, which results in LESS warming than the models are predicting. Here is another of the many reasons why I feel we shouldn’t formulate public policy and enact carbon taxes based on the still inadequate computer models.

Additional comment added on April 5: Please check out this weblog from Roger Pielke Sr. for more on the subject of water vapor. Roger is currently a Senior Research Scientist in CIRES and a Senior Research Associate at the University of Colorado-Boulder in the Department of Atmospheric and Oceanic Sciences (ATOC) at the University of Colorado in Boulder (November 2005 -present). He is also an Emeritus Professor of Atmospheric Science at Colorado State University.

[DouglasKC]

Water vapor is responsible for up to 70% of the greenhouse gases!!! Whoduh thunk?

[hophead]

PING

[DManA]

Then it’s a polutant and the EPA must regulate it.

[amigatec]

bttt

[dirtboy]

Breathing too much water can kill you.

[IrishCatholic]

bookmarked.

[DManA]

We need water offsets. For instance, if I give up bathing then I should be able to sell my rights to the water I WOULD have used to someone who cares about offending others.

[miele man]

bookmarked also

[<1/1,000,000th%]

Again science points to the dangers of dihydrogen monoxide.

[henkster]

The IPieceofCCr@p, Al Gore and the egghead priest/prostitute scientists all refuse to recognize the following facts:

1. 100,000-40,000 years ago, mile-thick ice sheets covered much of the Northern Hemisphere
2. 20,000-40,000 years ago a warming period began, which melted these ice sheets.
3. During the period of about 1000-1400 A.D., the Medieval Warm Period allowed for prolonged human settlement of Greenland, which is still not feasible today due to the cold climatic conditions.
4. About 1300-1400 the earth entered what is know as “The Little Ice Age,” from which it is still emerging.
5. The above worthies cannot properly identify the causes of all of the above, and thus cannot state that those causes are not the predominant movers of climate change today.

Those are just my 5 fun historical facts to trot out whenever confronted by the “True Believers.”

[steve8714]

Try to pass water vapor instead of the other stuff.

[Wuli]

Doug:

A really great post.

An observation - too many scientists live and work in an information bubble that provides a feedback loop of self-reinforcing thinking, while much of what could be learned and observed, outside that bubble, is ignored.

“Incomplete” is the outstanding accomplishment of the scientific thinking that emerges from these bubbles - like the bubble the man-made global warming advocates in “science” live and breath under.

[Reeses]

Global warmers hate to discuss clouds and snow because these act as giant natural mirrors bouncing sun heat back out to space. They especially don’t want to talk about man-made clouds and snow and the role of wind blown sand, dirt, and pollution which increase their formation. GWers are afraid to even research and model clouds because then the Luddite party would be over.

[Smedley]

Water vapor is responsible for up to 70% of the greenhouse gases!!! Whoduh thunk?

Ida thunk it to be higher - still do

[Tenacious 1]

Ping for later reply

[P-40]

I like to have really humid air in my greenhouse during the winter. It holds the heat better.

[HardStarboard]

>>>Breathing too much water can kill you.<<<

Water-boarding terroriwst suspects will contribute to global cooling. This is how we beat GW and the WOT at the same time.

Brilliant, simply Brilliant Hardstarboard; have another Guinness.

[BIGLOOK]

Bump

[Tenacious 1]

Ping to Curiosity,

Note, per our previous thread, that there is still very credible and objectionable scientific data and research that challenges the impact of Man Made CO2.

If you would like to debate these finer issues, then there is real progress being made. But as I said, Labeling us as “GW deniers” for citing debatable science behind the causes of global warming proves that the current alarmists propaganda has crossed the line from scientific in nature to religious. When science is thrown out and debate is stifled, then one can only rely on faith. I, therefore, question your “faith” in Man Made Global Warming.

(Note: I am not turning this into religious discussion as I am a devout Catholic. But use theses “radical” words to emphasize a point.)

[Smedley]

The most important players on the greenhouse stage are water vapor and clouds. Carbon dioxide has been increased to about 0.038% of the atmosphere (possibly from about 0.028% pre-Industrial Revolution) while water in its various forms ranges from 0% to 4% of the atmosphere and its properties vary by what form it is in and even at what altitude it is found in the atmosphere. In simple terms, however, the bulk of Earth's greenhouse effect is due to water vapor by virtue of its abundance. Water accounts for about 90% of the Earth's greenhouse effect -- perhaps 70% is due to water vapor and about 20% due to clouds (mostly water droplets), some estimates put water as high as 95% of Earth's total greenhouse effect. The remaining portion comes from carbon dioxide, nitrous oxide, methane, ozone and miscellaneous other "minor greenhouse gases." As an example of the relative importance of water it should be noted that changes in the relative humidity on the order of 1.3-4% are equivalent to the effect of doubling CO2.

http://www.junkscience.com/Greenhouse/