The theory of anthropogenic global warming is a useful theory, but it is, on the whole, a sub-theory – a set of hypotheses born out of the larger concept of a planetary climate that effects and is effected by the life that moves within it.
The easiest way to see this in action is by looking at CO2 levels as seasons change in the northern hemisphere. When trees drop their leaves in the winter, CO2 levels in the atmosphere increase across the entire planet. As new leaves form in the spring, and photosynthesis increases, CO2 levels drop as more carbon is fixed into solid plant matter.
Looking further ahead in time, we can see that as global temperatures increase, and winters become ever milder, plants that do NOT drop their leaves will have an advantage over those that do – they will be able to continue gathering resources and reproducing year round, and rather than cold, our seasons here in New England will be dictated, as they are in the tropics, by availability of water.
The net effect of this will be that as CO2 achieves over-abundance, as the climate warms, evolutionary pressures will favor a shift towards forests that have a higher level of carbon fixation. Without any intention of doing so, the biosphere will be pushed into a role of attempting to mitigate the vast amounts of carbon being pumped into the atmosphere by humanity.
This is basically the Gaia theory proposed by James Lovelock, and it’s a solid one. The more you study life, the more you come to recognize that each organism is tied in some way to another, which is tied to another, which is tied to another, and so on in a web of biological interaction that surrounds the planet Earth like a spider’s silk wrapped around a fat, juicy fly. mmmmm. Excuse me, I have to go eat something now.
Anyway, as I was saying, the Gaia theory states that the atmosphere and biosphere interact in such a way as to maintain acceptable conditions for life as we know it on this planet. Occasionally, something will happen that will adjust the planetary climate onto a different stable level, one warmer or colder than what we currently experience, but still within the boundaries needed by life. As I may have mentioned, I’m not TOO worried that life will end, just the human part of it.
So, the Gaia theory works so far. Theories gain acceptance as they are tested, used, and re-used to great effect. We don’t hesitate to use hammers to hit things because they’ve been around and in use for millennia. We have a useful tool here, and given that the climate is currently CHANGING, we need to use it.