[TigersEye]

The problem with this argument is that you then have to come up with a recent natural mechanism that's sequestering the CO2 we know human activity has produced in the last few hundred years. (We have good enough surrogates for CO2 production that we know it has to have been considerable, ...

Not considerable...

Sources of Greenhouse Gases

NOTE: "Human additions" represent such a small percentage of the total Greenhouse Effect (0.28%) that they are barely visible in this "pie chart" at the scale represented.

[edsheppa]

What does water vapor have to do with whether or not human emissions of CO2 account for the recent considerable increase in atmospheric concentration?