WATER is responsible for 90% of the earth's greenhouse effect (water vapor and clouds). The remaining 10% is caused by CO2 and other gasses. Humans are only responsible for about 3% of the CO2 being emitted into the atmosphere each day.

My point is that all this focus on CO2 is irrational. The effect of H2O totally swamps out any pitiful human contribution of CO2. What are we gonna do? Cover the oceans?

Notwithstanding the difficulty and dubious usefulness of trying to measure the global average air temperature accurately, a half a degree C change in over 100 years is not exactly what I would consider catastrophic. The local temperature here changes over the course of a single day by at least an order of magnitude more than that.

The climate of the earth is not static. Nor should it be. I'm convinced that had they been alive at the time, some people would be shouting for us to save the dinosaurs from extinction.

Source: http://www.junkscience.com/Greenhouse/