This article uses flash animations to illustrate ideas. You'll need the free flash player to view these . If you're on a modem connection they may take a little time to load, please be patient.
What if we associate weather types (for example, cloud cover) with each number on the die?
Try rolling the dice in the animation, again explore what happens as the number of rolls increases.
As when there were numbers on the sides of the die, you can't predict what the weather will be on the next throw. Climate is defined as being the average of the weather over a long (typically 30 years) period of time. The 'climate' of this die is 50% cloud cover. A single throw of 0% or 100% cloud cover won't affect the climate very much if you are taking the average of 100s of throws. In the same way we can have a very hot summer one year, and a very wet one the next, without the climate, the weather we expect to happen, necessarily changing.
"Climate is what we expect, weather is what we get"
So why do the weather forecasters never get it totally right? Mostly because the weather is a 'chaotic' system.
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Content last updated: 13/12/2005
About our expert
Sylvia Knight - a climate scientist - works with the climateprediction.net project, which is trying to produce the most complete forecast of 21st century climate ever attempted. She is responsible for communicating the aims and results of the experiments to as wide an audience as possible.
Sylvia has a degree in Natural Sciences and a PhD in Meteorology, and is co-author of the Open University short course Weather and Climate Modelling.
