Another consideration that people always seem to miss is that, even if you assume that the production of greenhouse gasses by man is having a negative impact on the climate, our ability to increase CO2 output (or even to maintain it) is very limited because we're at a point where cost effective fossil fuels have (mostly) been exploited. We're already at a point where our ability to increase the supply of conventional energy is not meeting the increased demand of this energy, which is the primary reason why in the middle of a deep recession the price of Oil remains high (when you look at it from a historical perspective) ... even if we tapped every fossil fuel based energy source in the world, within the next 20 years we would hit a point where we have a shrinking supply of fossil fuel based energy sources and any increased demand will only translate into skyrocketing energy costs.
Knowing that (if we're very lucky) we will be able to produce 10% to 25% more energy from fossil fuels before we (essentially) hit peak production, how are we going to get to outputting 2 to 4 times as much CO2 as is assumed by the climate models that project doom for our planet?
Realistically, we're going to hit a point in the very near future where the average price of oil will hit $100 and remain above that until it is phased out; and from there it will most likely ramp up to $400 or $500 before we can mass produce cost effective alternative energy sources to phase out oil; which is something that throwing more money at will (probably) not have that much of an impact on, because the technology has to be developed to make it better which is something that just takes time. Much like 9 women can not have a baby in one month, you can't just have more companies working at trying to find a "Breakthrough" in alternative energy to make it come along any faster.
A lot of the efforts to prevent "Global Warming" are pointless even if you consider it to be a man made problem, and will probably only result in a very painful and expensive transition being dramatically more painful and expensive; and if people are forced to make a choice between driving to work, feeding their family, or heating their homes it is unlikely that they will have the spare money needed to pay for their children to have a better future.
