The Critics Say: “CO2 lags behind temperature by centuries in the glacial-interglacial cycles, so clearly CO2 does not cause temperatures to rise, temperatures cause CO2 to rise.”

Just a bit of illogic here. But don't think the simplicity of the explaination means it will sway any of the die-hards.

A close examination of the CH4, CO2 and temperature fuctuations recorded in the
Antarctic ice core records does in fact reveal that yes, the temperature moved first in what is, when viewed coarsely, a very tight correlation. But what is not correct is to say the temperature rose and then 800 years later the CO2 rose. These warming periods lasted for 5000 to 10000 years (the coolings lasted ~100kyrs) so for the majority of that time (~90%) temperature and CO2 rose together. This means that this wonderful archive of climatological evidence clearly allows for CO2 acting as a cause while also revealing it can be an effect.

The current understanding of those cycles is that changes in orbital parameters (
Milankovich and other cycles) caused greater amounts of summer sunlight in the northern hemisphere. This is a very small forcing. But it caused ice to retreat in the north which changed the albedo increasing the warmth in a feedback effect. Some ~800 years after this process started, CO2 concentrations in the atmosphere began to rise and this also amplified the warming trend even further as another feedback mechanism.

You can also go here: for a discussion by climate scientists of exactly this question but with greater technical detail and full references to the scientific literature.

So, CO2 did not
trigger past warmings, but it did contribute to them, and according to climate theory and model experiments, Greenhouse Gas forcing was the largest factor in the ultimate change.One thing that this says for the future is that we may well see additional natural CO2 come out of the woodwork as whatever process that took place repeatedly over the last 650K yrs begins to play out again. The likely candidates are outgassing from warming ocean waters, carbon from warming soils and methane from melting permafrost. A1b1_d6