At the 1972 American Association for the Advancement of Science convention , Lorenz presented his paper , “ Predictability : Does the Flap of a Butterfly ’ s Wings in Brazil Set off a Tornado in Texas ?,” which he reprints in his 1993 book Essence of Chaos . He discusses the difficulty of accurately predicting weather patterns , asking ,
How can we determine whether the atmosphere is unstable ? The atmosphere is not a controlled laboratory experiment ; if we disturb it and then observe what happens , we shall never know what would have happened if we had not disturbed it . Any claim that we can learn what would have happened by referring to the weather forecast would imply that the question whose answer we seek has already been answered in the negative . ( 182 )
Lorenz documents how weather forecasters compare two predictive simulations : one based on the “ actual weather ” and one based on what would have happened owing to “ slightly different initial conditions ” affecting the outcome ( 182 ). He asserts that the weather system is essentially unstable because of its period doubling , which leads to prediction errors ( 182 ). He attributes sensitivity to initial conditions and the human error of poor observation to the difficulty of accurately predicting weather patterns . Lorenz accounts for the mathematical , computer-modeled aspects of weather forecasting , concluding that the final purpose is to make “ not exact forecasts but the best forecasts which the atmosphere is willing to have us make ” ( 184 ). Lorenz ’ s query into the limited predictability of weather is significant in the context of this paper because it asks us how we might adequately determine all the strange attractors that were part of the initial Manhattan Project and which have
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