This is an issue that is often misunderstood in the public
sphere and media, so it is worth spending some time to explain
it and clarify it. At least three careful ice core studies have
shown that CO2 starts to rise about 800 years (600-1000 years)
after Antarctic temperature during glacial terminations. These
terminations are pronounced warming periods that mark the ends
of the ice ages that happen every 100,000 years or so. Does this
prove that CO2 doesn’t cause global warming? The answer is no.
The reason has to do with the fact that the warmings take about
5000 years to be complete. The lag is only 800 years. All that
the lag shows is that CO2 did not cause the first 800 years of
warming, out of the 5000 year trend. The other 4200 years of
warming could in fact have been caused by CO2, as far as we can
tell from this ice core data. The 4200 years of warming make up
about 5/6 of the total warming. So CO2 could have caused the
last 5/6 of the warming, but could not have caused the first 1/6
of the warming.