We do know that climate changes can happen quite rapidly, and the CO2 and temperature curves track so closely that using the ice core methods the cause and effect is largely lost in the variations.

Just guessing, and using common sense, I look at the even spacing of the cycles and it seems to me that there would be a much greater probability of some astronomical or other factor shoving temperature around than something that would create CO2 cycles like that.

Ironically, the most recent warm period that was the best opportunity for civilization to develop may be the worst timing in the cycles for suddenly dumping a lot of extra CO2 into the air. Kind of like jumping straight up when your roller coaster car hits the top of a loop.

BTW, my position is that even if there were no connection at all between human burning of fossil fuels and global warming, there are still plenty of other good technological and political reasons to start backing off from burning huge quantities of oil and coal.