Showing from 200 to 11000 years ago, the subsequent graph is based on ice core data, readily visible in files hosted on the servers of the U.S. National Oceanic and Atmospheric Administration (NOAA):GISP 2 and EPICA Dome C:

Over the past few hundred thousand years of ice core data, a “medium” time
scale in this sense, CO2 superficially appears to change in step with
temperature if a graph is so zoomed out as to not show sub-millennial time
scales well:

A record of temperature and atmospheric CO2 over the past 400,000 years is preserved in the Vostok Ice Core and is shown in the figure on the right.

It can be seen that there have been a series of large fluctuations in temperature (the Ice Ages), accompanied by large changes in atmospheric CO2.

It is thought that these large temperature fluctuations are triggered by Milankovitch cycles - variations in the earth's orbit that change the amount of energy from the sun that reaches us.

However, on their own, these cycles are not enough to explain the changes in temperature.

The full explanation seems to be that the small change in temperature caused by the changing orbit are amplified by natural processes on earth. These cause CO2 to be released from the oceans and the biosphere, causing an increased greenhouse effect.

This is described more fully in this article from the New Scientist (see also Shackleton 2000). For more details on the timing of changes in CO2 and temperature, click on the figure.