Re: AAPG on Global Climate Change

J. Taylor wrote:
On 18 Feb 2007 19:56:47 -0800, "Daryl Krupa" <icycalmca@xxxxxxxxx>
wrote:

Very good Daryl, it is so hard to detect those subtle ad hominem.

It is completely irrelevant it was a personal website or the
occupation of owner of it.

What do you have to say about the pie?

JT

I would say it makes a very nice Pacman graphic, though it is the wrong color. *|:-)

If folks are looking for a well-researched overview of the subject of atmospheric composition/change etc.,with lots of data in a readable format, but without only a tiny ax to grind, (what if scenarios presented as predictions, not as inevitabilities) I recommend Global Environment: Water, Air and Geochemical Cycles, By Elizabeth and Robert Berner.

They quite ably explain, using hard numbers from journal and academic sources, how the atmosphere works and what threatens it in a text which is quite readable to college freshmen or reasonably well-educated high schoolers. I refer people to it all the time--you can't explain change without knowing from what it is changing.

No one disputes water vapor is a very effective or influential greenhouse gas. The graphic on the final page showing water vapor as the overwhelming contributor to the greenhouse effect is likely correct when looking at the big picture (greenhouse effect as moderating temperatures, acting as an insulator, redistributing humidity, etc.) It is misleadingly used on the card, because it implies that because water vapor is quite important in the greenhouse effect,(true) it is also a large source of correlated directional temperature change (false).

The difficulty with quantifying water vapor as greenhouse gas with a changing and humanly negative impact is because
a) water vapor acts differently depending upon residence in which atmospheric layer;
b) it has an average residence time in the atmosphere of 11 days;
c) while there are decent weather records of daily relative humidity (dependent on dew point), there are very scarce long-term records of absolute humidity, since it is quite variable even over a 24 hr period(from less than 0.01% to 3% of the atmosphere,depending on latitude, altitude and weather conditions;
d) water vapor is comes from a wide variety of sources, and picking apart anthropogenic water vapor (additions from irrigation, industrial processes and increase due to breakdown of more complex human produced gases) is extremely difficult;
e) the water vapor feedback mechanism, while understood qualitatively is poorly understood quantitatively;
f)clouds are water vapor, but water vapor as clouds,or as ice has a different effects on heat transfer than diffused aerosol water vapor, including dissipation;
g) even people who claim atmospheric water vapor is rising have few mechanisms to correlate a specific human activity to a quantifiable specific increase (possibly stratospheric disturbance due to air flight, but that's the only being proposed)(anyone seen any studies on change in atmospheric water vapor due to irrigation?);
h) in short, the effects of human perturbation of the hydrologic cycle and on the amount of atmospheric water vapor seem a reasonable assumption, but this perturbation is very small (the butterfly in the tornado) compared to the movement of water vapor by solar energy and wind.

See below:

http://lwf.ncdc.noaa.gov/oa/climate/gases.html#wv

Water Vapor

"Water Vapor is the most abundant greenhouse gas in the atmosphere, which is why it is addressed here first. However, changes in its concentration is also considered to be a result of climate feedbacks related to the warming of the atmosphere rather than a direct result of industrialization. The feedback loop in which water is involved is critically important to projecting future climate change, but as yet is still fairly poorly measured and understood.

As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the relative humidity can be higher (in essence, the air is able to 'hold' more water when its warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'. However, huge scientific uncertainty exists in defining the extent and importance of this feedback loop. As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up). The future monitoring of atmospheric processes involving water vapor will be critical to fully understand the feedbacks in the climate system leading to global climate change. As yet, though the basics of the hydrological cycle are fairly well understood, we have very little comprehension of the complexity of the feedback loops. 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, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries, though satellite measurements, combined with balloon data and some in-situ ground measurements indicate generally positive trends in global water vapor."

See also:
http://www.nsc.org/EHC/climate/ccucla6.htm
.

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