I have been reading through some of the older papers concerning CO2 levels in the 20th and century, CO2 residence times, and the carbon cycle. (The papers this linked to article and paper are referencing. Another source is the 2300 papers Ian Plimer references in his book Heaven and Earth.) What I found is interesting. CO2 Residence Time, Source of 20th Century CO2, Could CO2 levels start to drop? Why did the Ocean level increase in the 20th century? Could ocean levels drop? If the residence time for CO2 in the atmosphere is short, then the majority of the 20th century CO2 increase does not have to be anthropomorphic. Did anything changed in the 20th century that could have increase CO2 in the atmosphere? If that hypothesis were correct, then if the forcing function that increased CO2 in the 20th century diminished, CO2 levels could drop or at least stop rising. i.e. The CO2 levels in the atmosphere could be delinked from anthropomorphic emissions. http://www.co2science.org/articles/V12/N31/EDIT.php Because of the argument going on about global warming people are caught up with arguing one side or the other, which makes it difficult to see or discuss the problem situation. There are multiple paradoxes associated with the paleo climatic data, the geological data, and the current observations that appear logically connected. One of the puzzles to explain is why in the past have CO2 levels increased and decreased. Another is why ocean levels have increased in decreased in the past. A basic analysis shows the Himalayan/Tibet plateau hypothesis does not explain the reduction in CO2 in the Cenozoic. There is obviously something that resupplies a form of carbon to the atmosphere. The question is what stabilizes the amount of CO2 in the atmosphere. A short residence time for CO2 allows the 80 times atmosphere CO2 in the oceans to buffer changes to help regulate the amount of CO2 in the atmosphere so it does not fall to dangerously low levels. Something else is regulating the amount of CO2 in the atmosphere. Something else is controlling amount of carbon that is released into the atmosphere. As noted in the Sloan Deep Carbon there is evidence immense inputs of C12 rich carbon into the planet. If you look at paleo data for the last 500 million years. The planet cools, ice sheets form and then after the ice sheets form the CO2 level drops.