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.
So, what's a chaotic system? The animation below uses the analogy of rabbits breeding to illustrate the difference between a chaotic system and one that isn't. Let's start out with a non-chaotic system - simply adjust the slider on the left to pick a starting number of rabbits in the warren and watch how the population changes with time. Try a few different starting numbers and see what the impact of changing this is on the population size.
Whatever number you choose, the population should grow until it reaches 32 and then stabilise - this is the maximum number of rabbits this warren can support.
But, the weather isn't this simple - it's chaotic. What does this mean? Let's find out by having another go at the animation. By clicking on the 'chaotic model' tab we can then see what the impact of changing the starting condition (the initial rabbit population) is.
As you should have seen, this time, the number of rabbits in the warren varies haphazardly. How many rabbits are there at the end? Now vary the starting number by just 1 and start the animation again. How many rabbits are there at the end this time? Even though the change in the initial population size was very small, the final population size can be very different.
The weather is also chaotic - very small changes to the starting conditions can lead to completely different weather patterns developing. This observation led Ed Lorenz to suggest that the flap of a butterfly's wings in the Amazon rainforest could lead to a tornado in Texas. It is very unlikely, but it could.
This means that, to make a perfect weather or climate forecast, we need to know what the atmosphere is doing currently, down to the scale of individual butterflies flapping their wings, which is obviously impossible!
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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.
