The temperature vs. solar cycle chart?
If so, up until the 1990s, the climate scientists say that solar effects accounted for 1/3 to 1/2 of the warming since the late 1800s -- i.e., up to the mid-1940s, when it appears other effects kicked in to cause the slight cooling over the next couple of decades. I.e., the CO2 effect wasn't as strong as now, and there is a lag time in response, too (probably).
Why did these other factors have such sway over global temperatures up until the last 10-20 years? Are CO2 levels suddenly shooting off the charts and only now capable of overwhelming all these other factors?
What the Sun does is out of our control. SO2 aerosols in industrialized countries were markedly reduced in the 1970s due to clean air and acid rain concerns. Same with a lot of plain ol' smoke (black soot). And, CO2 is significantly higher in concentration in the atmosphere now than 20 years ago. It's not "shooting off the charts", but any effect that it's creating is increasing, too.
Also, didn't this link, posted previously by another FReeper, indicate that there are much greater forces at work in the production of atmostpheric CO2 than man? This fact, when combined with the fact that CO2 levels themselves are only a small piece of the global temperature puzzle, should cause the alarm over anthropogenic CO2 production to decrease to approximately zero.
Mankind is the primary source of the imbalance between input and output from the atmosphere. The imbalance is the cause of the increase in atmospheric CO2 concentration (and we are indebted to the oceans, which have absorbed about 50% of the CO2 that has been produced by fossil fuel burning). This can be easily proven by the Suess effect (isotopic dilution).
Water vapor is a GHG, and the most important, but water vapor responds to radiative forcing -- it is so big a constituent in the atmosphere that mankind has no appreciable effect on water vapor input/output. But radiative forcing does have an effect, a positive feedback. In an interesting paper (subject of a FR thread in the past year, I think), a study confirmed that the water vapor feedback is positive -- which hadn't been conclusively shown before that -- and also showed that the modeling assumption of the mathematical expression of the positive feedback probably overestimated it. I bet the modelers are still working on an improved formulation of this aspect.
Man has little to do with atmospheric CO2 levels.
But... man has everything to do with the increase in atmospheric CO2 levels from 280 ppm to the current level. That's a rock-solid inescapable certainty. Below 280 (and sometimes a lot lower, in glacial periods) -- that's the natural climate system.
Atmospheric CO2 levels have little to do with global temperature change.
That's the subject of our discussion now -- how much of a global temperature increase will be induced by rising atmospheric CO2 concentrations. Only the most diehard, ardent skeptics maintain that there will be a zero effect. In case you hadn't noticed, there has a been a change in the tenor of argument from the notable skeptics, people like Patrick Michaels, Richard Lindzen, and Roy Spencer. They are basically saying two things: the temperature increase in the next century will be on the low-end of the predictions, and mankind should have nothing to fear from that.
I would heartily wish them to be right. But I've been tuned into this issue for awhile, and I just can't give them the benefit of the doubt.
Personally, I'm not concerned. I have a great trust in the fact that the various forces on and around earth are quite capable of recovering from and adjusting to any activities engaged in by mankind. A volcano erupting or tectonic plate moving has a far more profound effect on our planet than anthropogenic CO2 levels.
I predict that the Global Warming hype will eventually become something like the "flat earth" maps of years gone by with the "There be dragons here" warnings at the edges. It will be seen historically as another in a long line of fear-based overreactions to the unknown.
I appreciate your thoughtful and well-researched answers, both marks of an intelligent gentleman. However, I remain unconvinced.