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Memories of the 28th Century

Water Vapor Versus Imagination

Rating: 6 votes, 5.00 average.
It has been known for a fairly long time that clouds are made of water in the form of vapor and small droplets. It is also well-known that clouds reflect solar radiation away from Earth. It is also well-known that water vapor is the main "greenhouse" gas in the Earth's atmosphere; in addition to being more effective in holding infrared radiation; it is also one of the more common components of the atmosphere, usually the third most common component after nitrogen and oxygen.

With its double role in regulating the Earth's temperature water vapor warms the Earth. It is estimated that the Earth's atmosphere would have an average temperature of about -18 C degrees (or 0 Fahrenheit), if there were no greenhouse gases. Water vapor brings that average up to about 56.5 degrees Fahrenheit, and the most recent average temperature is 58.3 F. In the recent past it was calculated that "Earth's surface would average about 33 C colder, which is about 59 F below the present average of 14 C (57 F).[2][3][4]"* Water vapor accounts for about 97 percent of the total (natural plus man-emitted) greenhouse warming of the planet. See, e.g., John Houghton's The Physics of Atmospheres, 3rd edition, Cambridge University Press, 2002.

Obviously there is disagreement as to how much warming which gas adds. A large part of the disagreement seems to be a result of water being a very variable component of the atmosphere. The percentage water vapor in surface air varies from .01% at -42 C (-44 F)[26] to 4.24% when the dew point is 30 C (86 F) (Michael B. McElroy "The Atmospheric Environment" 2002 Princeton University Press p. 36 example 4.1)

There is also the matter of how much of a greenhouse gas Carbon Dioxide is. Greenhouse potential is proportional to dipole moment, and CO2 has a zero dipole moment. Other surces assign a dipole moment to CO2 not because it actually has one, but that it can vibrate in a way that can have a very slight dipole moment at some points during its vibrations. There appears to be no experiemental or empirical data for assigning a dipole moment to CO2. Based on this and using the standard, more or less, values for atmospheric concentrations for the most important greenhouses, it looks like H2O contributes about 98% to the greenhouse effect. O3 and CO (see table). But the percentages vary with the amount of water in the atmosphere. In desert regions the contribution might be as low as 85%, while in the dampest regions it is higher than 99%. When I calculated greenhouse gas potential based on dipole moment and concentration, only ozone, carbon monoxide, and water have any effect at all, but I did not include the extremely minor constituents such as flourocarbons. (See table)
Name dipole moment in ppmv greenhse potential
Argon 0 9,340 0
Carbon dioxide 0 397 0
carbon monoxide 0.122 1 0.122
Helium 0 5.24 0
Methane 0 1.79 0
Neon 0 18.18 0
Nitrogen 0 780,840 0
Oxygen 0 209,460 0
ozone 0.53 8 4.24
Water 1.85 50,000 92,500

Even if CO2 had some small greenhouse effect, the contribution from CO2 is fairly uniform around the world, but it is absorbed by water and by plants, so there is less CO2 over large expanses of water, such as the South Pacific and over large areas of vegetation, such as the rain forests of South America and Africa and the extensive forests of Siberia, Canada, and some other regions, but the greenhouse potential is so small, and the atmospheric concentrations are so low that CO2 simply does not have much greenhouse potential. And the dipole moment of CO2 is usually given as 0 (zero), so its greenhouse potential is extremely also zero. Methane (CH4) is another gas that is usually assigned a greenhouse potential but it has no dipole moment, and it is an even smaller component of the atmosphere than CO2, so it would contribute a vanishingly small amount to the greenhouse effect, if it did have greenhouse potential.

In addition to being the main greenhouse gas, water also has the contrary effect of forming clouds when concentrations of water vapor reach high levels, and clouds reflect solar radiation back into space. While clouds form over most of the Earth at some times, they form almost daily in some regions in the course of the day, as solar heat evaporates water from ground sources, and the vapor rises to a level where it condenses and accumulates into clouds. The daily formation of clouds is very common in tropical areas, and the clouds keep those areas from becoming uncomfortably warm.

While there is no doubt that there is and always has been climate change, the rises in temperatures over the longer term are governed by the solar output. While atmospheric water vapor holds heat in the atmosphere, that effect is self-limiting, because above certain concentrations water vapor condenses into clouds that cool the Earth by reflecting solar radiation back into space.

To satisfy themselves, some researchers have assigned greenhouse gas potential to Carbon Dioxide that greatly exceeds the level that might be derived from the gass physical characteristics. I have read the explanations of that action, and the rationale can be summed up as '0Its so because we say it's so.' After creating a dipole moment for CO2, its backers dreamed up a new version of the carbon cycle that kept CO2 in the atmosphere for centuries, rather constantly recycling it through the well-known cycle. No one has found any evidence that the carbon cycle changed, but that is no reason to change a good story.

There are lies and big lies. It appears that the climate change myth is a big lie, because it was made up out of the whole cloth. Small lies can be based in fact, but the more I look into climate change the less factual information I find behind it.


Fairly thorough explanation of greenhouse gases

A not as good explanation

A look at the numbers very good

Updated 08-11-2015 at 03:45 PM by PeterL