Wednesday, August 27, 2008

The Atmosphere and CO2

The explanation is that 150 years ago the atmosphere was made up of 99.96%
nitrogen, oxygen and argon and today it is still 99.96% nitrogen, oxygen and
argon. The concentration of CO2 in the atmosphere is so small that an increase
from 280ppmv to 400 ppmv (parts per million by volume) does not affect the
concentration of the major components.
Argon points out a very interesting fact.
There is over 25 times more argon in the atmosphere than CO2 but CO2 emissions
are millions of times more than argon emissions.
This is because argon is an inert gas that forms from the radioactive decay of
potassium40. It has been doing this for the entire 4.5 billion year history of
the Earth but it is an inert gas with no where to go so it has just collected
in the atmosphere.
CO2 on the other hand is always being added and removed from the atmosphere
through the "carbon" cycle and has come to an equilibrium concentration that is
very small. Human contribution to the atmospheric concentration of CO2 is
minute compared with the natural sources and the scientific evidence points to
warming being a cause of increase in CO2 concentration not the result of it.
(Close inspection of the geological records shows that warming always leads
increase in CO2 concentration.)
Two processes remove CO2 from the atmosphere. THe first is photosynthesis which
uses the energy of the sun to undo the "burning process" (oxydation) that
created CO2 from oxygen and carbon. The carbon is added to the plant and the
oxygen is returned to the atmosphere.
The second process takes CO2 dissolved in the oceans and combines it with
calcium to form calcium carbonate (CaCO3) that forms sea shells and other forms
of limestone deposits.
Perhaps it would be beneficial to refine the geological perspective to the paleo-botanical perspective and examine the history of the plant community. When vascular plants first evolved. about 425 million years ago (Cooksonia), CO2 levels were about 3000 ppm. Gymnosperms evolved between 385 and 365 million years ago under CO2 concentration of near 4000 ppm and angiosperms evolved with CO2 levels of 2200 ppm about 165 million years ago. These earlier plant forms used C3 photosynthetic pathway better adapted to higher CO2 concentrations. However, as CO2 levels approached present day levels of 274 to 400 ppm, many of the C3 plants exhibited stress due to CO2 starvation. As a result of this environmental stress, two new photosynthetic pathways evolved; the C4 pathway and CAM. C4 plants first evolved up to 50 million years, they did not reach significant numbers until about 8 million years ago Crassulacean acid metabolism or CAM, which is typically of the cactii, evolved even more recently, apparently to counter the effect of CO2 starvation. As CO2 levels rise above recent lows, most plants grow more efficiently and harbor water resources more effectively. Hot houses typically increase CO2 levels to 1000 to 1500 to promote growth rates. CO2 and plants They thrive at 1000 ppm in green houses.

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