Nice discussion...well said. Dennis, your positions are reasonable but in the past I get nervous because I know, by checking directly myself, that ExxonMobil was behind some global warming skeptic stuff. So, the natural cycles and solar variability may all be good science, but it will be mis-applied. My order of what is important would be different than yours: CO2, methane, (and possibly increased water vapor as feedback to warming) are the most important factors to warming. Natural cycles (oceanic for example) and solar may be significant, but less so than the greenhouse gases.

The climate change we are liable to see this century may be faster than even during the last deglaciation. Otherwise, Mike has already made the same points I would have (7 billion reasons why it matters now).

Chris