Well, duh. Historically, there haven't been sudden new sources of CO2. Temperature changes were caused by other things, and CO2 followed that, by completely dif

Well, duh. Historically, there haven't been sudden new sources of CO2. Temperature changes were caused by other things, and CO2 followed that, by completely different mechanisms than greenhouse gases. Rather, higher temperatures melt permafrost, reduce vegetation, and speed decay. It could just as easily have been that different mechanisms caused CO2 to decrease rather than increase. Unfortunately for us, higher temperature does increase CO2 -- which means that by forcing CO2 we're setting up a positive feedback loop. The atmosphere has more than one effect going on. Adding a new one causes different things than the past ones did.