Professor Iain Stewart explains how the temperature of the earth is affected by its orbit round the sun, and the tilt of its axis. This was a theory put forward by James Croll. Professor Stewart draws the changing orbit of the earth around the sun on a sandy beach. He explains why this causes temperatures to fall and how this can be exaggerated by the changing tilt of the earth.

This clip is from:
The Big Freeze
First broadcast:
14 December 2010

Use to introduce the concept of Quaternary climate change, either to inform discussion of current climate change issues or to explain the cyclical nature of glacial periods.