I heard this the other day and thought it interesting and amusing enough to post here.
Plants absorb CO2 and animals eat plants and CO2 gets turned into coal and oil and limestone, so CO2 gets gradually removed from the atmosphere. Vulcanism releases CO2 into the atmosphere, but over the eons the trend has been downwards. So, eventually, won’t there come a point where there is too little CO2 in the atmosphere to support life as we know it? The amount of CO2 in the atmosphere today is very very small indeed. So, isn’t it to Earth’s longer term benefit to release that stored CO2 so it can be re-used? There would, of course, be no immediate benefit, but what about in (hundreds of) millions of years’ time?
Take the following with a grain of salt; I read the book a while back. IIRC:
In the very long run (next few hundred million years or longer), volcanism will slow and ultimately stop as the Earth’s core continues to cool. At that point the level of CO[sub]2[/sub] will decrease until it can no longer support plant life, which will likely lead to the end of life on Earth.
This process competes with the gradual increase in the Sun’s output, which will eventually evaporate the oceans and increase surface temperatures to the point where life is no longer possible.
It’s anyone’s guess as to which phenomena will end life on Earth: the end of plant life, or the end of the oceans.
In the long run, IIRC, the authors discount any CO[sub]2[/sub] added to the air by burning fossil fuels. The time scales are too different. Anything we do in the short term (next few thousand years) will not significantly affect things hundreds of millions of years out.
(However, the authors do discuss the possibility of short-term increases in CO[sub]2[/sub] levels in mitigating the effects of the next ice age–after all, we are in an interglacial period. I have been meaning to start a GD thread on this for some time, but haven’t ever gotten around to it.)
Indeed…Even though a small fraction of what we emit is likely to remain around quite a long time by our standards ([), these are still short times compared to the sort of timescales being talked about.
Also, it should be pointed out that on geologic timescales, there [url=http://en.wikipedia.org/wiki/Faint_young_sun_paradox]are hypothesized to be](]estimates are that 7% will remain after 100,000 years[/url) some negative feedback processes that would keep the CO2 levels from dropping too low for very long: