Over the last 55 million years, climate has become increasing colder in an uneven series of steps. Ice sheets did not start to become established at the poles until about 3 million years ago. When we think of climate change on a time scale this large, we must also remember that the continents were in different locations than in the modern world. Data from the oxygen isotope record of the Greenland ice sheet demonstrate that the climate that we know has exhibited unusual warmth and stability compared to the historic record. During the last glacial, climate exhibited swift and short-lived changes.
Some variability is on the time scale of decades to hundred of years.
The record also suggests that this same variability might have been present during the last interglacial. Return to top.