It's Water Vapour, Stupid

Here.

Excerpt:

One of my intuitive objections to the theory of global warming has been the role of carbon dioxide as a trigger mechanism, the driver of changes in the earth's atmosphere. Yes I recognize that levels of carbon dioxide have risen from around 260 ppm to 360 ppm, but I still can't grasp how a gas that represents less than 0.04% of the atmosphere dictates the climate for the whole planet.
...
So why would a trace gas be so crucial? And when did carbon dioxide go from irrelevant to the dominant driver of climate? (For example: past geological records indicate carbon dioxide levels in excess of 7,000 ppm and no correlation with temperature; Gore's famous graph where carbon dioxide lags behind temperature changes by 800 years; and, the more recent disconnects of carbon dioxide levels from temperature changes throughout the past century).