"Though scientists know with a great degree of certainty that atmospheric CO2 levels drive climate change, there are certain mismatches in the geologic record, such as the Ordovician ice age -- originally thought to have begun 443 million years ago -- that seem to counter that view."

pwokenyaw says: Not many climate doubters would dispute this statement, instead they dispute (lamely) whether the current level of forcing is sufficient to cause change.

I think most "climate doubters" would dispute this statement. But if you replace the word "drives" with a "fairly strong correlation" you won't get much dispute from me. The problem with saying CO2 drives climate change is that most of the record shows that rising CO2 levels follows global temperature rise. I'm unaware of an instance [though the Ordovician period *might* be an exception] of high CO2 level subsequently causing increasing global temperature. Now, even a "climate doubter" such as myself wouldn't argue that increasing CO2 by 20 times the current level wouldn't have significant effect the Global temperature. Though at a yearly increase of 2 ppm of CO2 it would require centuries to double and thousands of years [assuming a steady increase of 2 ppm, {which I think is unlikely- especially if humans remain at the current technological level or higher}].

"The status of the evidence is that much supports the idea that we are having dangerous effects on climate, with little evidence to the contrary. This study removes yet another piece from that "little evidence" pile. If this study is wrong, the predominance of evidence continues to be that we are taking enormous risks."

The evidence shows that we are in a long period of warming, but there is a shortage of evidence that shows that human activity is having a significant influence on global temperature.