Other records show us that major changes in atmospheric circulation and climate were experienced all around the northern hemisphere.
Antarctica and the Southern Ocean experienced a different pattern, consistent with the idea that these rapid jumps were caused by sudden changes in the transport of heat in the ocean.
Methane concentration also tracks the glacial-interglacial changes, probably because there were less wetlands in the colder, drier glacial periods.
Ice core measurements allow us to extend this way back into the past.
In an Antarctic core (Law Dome) with a very high snowfall rate, it has been possible to measure concentrations in air from as recently as the 1980s that is already enclosed in bubbles within the ice.
Its concentration is now much more than double its pre-industrial level.
This is mainly due to the increase in emissions from sources such as rice fields, ruminant animals and landfills, that comes on top of natural emissions from wetlands and other sources.
At this time, there was a huge ice sheet (the Laurentide) over northern North America.