Milankovich cycles and CO2

Source

This graph of the last 400,000 years of global temperature, CO2 and sea level derived from ice cores doesn’t look like it was created randomly, but rather by a clock mechanism.

Fifty years before we knew how to create such a graph the work of a scientist named Milankovitch indicated that when we got our act together we would see Earth’s orbital cycles, which operate on time scales of tens to hundreds of thousands of years, in the record.

But what Milankovitch didn’t expect is that when there was more sunlight at high Northern latitudes, processes like ice melt caused oceans to warm and release CO2 which made even the Southern hemisphere warm, although it was getting less sunlight.
The only way to explain this is with C02, so a story that didn’t start out to be about CO2 became one. 

CO2, methane, and ice sheets were feedbacks that amplified global temperature change causing these ancient climate oscillations to be huge, even though the climate change was initiated by a very weak forcing. 

The physics doesn’t change now that we are rapidly increasing atmospheric CO2, in fact ice is melting all over the planet and methane is beginning to escape the permafrost.

Hat tip to Erik Frederiksen

Note the unprecedented surge in atmospheric CO2 over the last 100 years, and the beginning of the temperature response.

See also this video (start at about 6 minutes in) which gives an excellent perspective of glacial flow and the risk of the melting icecaps.