So Zeebe's study does not appear to answer the question of how long it took to establish the original warming or what the magnitude of the original warming was relative to the CO2 feedback. (skepticalscience.com)
We know how much a given amount of carbon dioxide will warm the atmosphere, but that warming sets into motion a variety of changes in the Earth system that can either exacerbate or mitigate the original warming. (giss.nasa.gov)
The net effect is a greater (reflecting) albedo, less sunlight reaching the surface, and therefore a negative feedback that reduces the original warming from increasing CO2. (americanthinker.com)