Tim Palmer discusses Ed Lorenz the man and his work, and compares and contrasts the meaning of the 'Butterfly Effect' as most people understand it today, and as Lorenz himself intended it to mean. Meteorologist Ed Lorenz was one of the founding fathers of chaos theory. In 1963 he showed with just three simple equations that the world around us could be both completely deterministic and yet practically unpredictable. In the 1990s, Lorenz's work was popularised by science writer James Gleick who used the phrase "The Butterfly Effect" to describe Lorenz's work. The notion that the flap of a butterfly's wings could change the course of weather was an idea that Lorenz himself used. However, he used it to describe something much more radical -- he didn't know whether the Butterfly Effect was true or not.

Tim Palmer is Royal Society Research Professor in Climate Physics at the University of Oxford.