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Summary Article: Lorenz, Edward (1917-)
From Encyclopedia of Global Warming and Climate Change

EWARD LORENZ IS an American mathematician and meteorologist who pioneered the chaos theory. Lorenz conceptualized the strange attractor notion and termed it the “butterfly effect.” He is well-known for his work in the dynamics of atmospheric circulations, and the first to recognize what is now called chaotic behavior in the mathematical modeling of weather systems. In the words of the committee that presented him the Kyoto prize in 1991, Lorenz has established “the theoretical basis of weather and climate predictability, as well as the basis for computer-aided atmospheric physics and meteorology.” The committee went on to compare the impact of Lorenz's discovery of “deterministic chaos” on a wide range of basic sciences to that of the ideas of Sir Isaac Newton. Lorenz's discovery of the sensitivity of weather predictions to the input is often invoked by global warming skeptics to challenge computer-based scenarios which continue to predict an exponential temperature increase on earth.

Born in West Hartford, Connecticut, on May 23, 1917, Lorenz received his undergraduate degree in mathematics from Dartmouth College in 1938, a masters degree in mathematics from Harvard University in 1940, the SM in meteorology from the Massachusetts Institute of Technology (MIT) in 1943 and the Sc.D. in meteorology in 1948. It was while serving as a weather forecaster for the U.S. Army Air Corps in World War II that he decided to do graduate work in meteorology at MIT. Upon his return from the war, he joined the staff of what was then MIT's Department of Meteorology in 1948. Seven years later he was appointed to the faculty as an assistant professor. He was promoted to professor in 1962 and was head of the department from 1977 to 1981. He became an emeritus professor in 1987.

In the early 1960s, in the course of his work on weather systems, Lorenz found that he was getting chaotic results from some of his calculations. Studying weather patterns, he realized that weather did not always change as predicted. He experimentally discovered that if he made two runs using the same initial conditions, but specified his input conditions in one to three decimal places, rather than two, or four rather than three, he always got different weather predictions. Small variations in the initial values of variables in his 12 variable computer weather model would lead to extremely different weather patterns. This sensitive dependence on initial conditions came to be known as the butterfly effect. In Lorenz's weather models, almost any two nearby starting points, indicating the current weather, will quickly diverge trajectories and quite frequently will end up in different “lobes,” which correspond to calm or stormy weather. The shape this model took, with its twin-lobed outlook, gave rise to the somewhat ironic “butterfly effect” metaphor: the flapping of a butterfly's wings in Mexico today may cause a tornado in Kansas tomorrow.

Convinced that these inconsistencies were not caused by faulty data or computer errors, he began to study chaos itself. His early insights, published in his 1963 paper, “Deterministic Nonperiodic Flow,” marked the beginning of a new field of study. Some scientists have since asserted that the 20th century will be remembered for three scientific revolutions: relativity, quantum mechanics, and chaos. The study of the rules of chaotic disorder is making an impact, not only on the field of mathematics, but in virtually every branch of science: biological, physical and social. In terms of the atmosphere, it has led to the conclusion that it may be fundamentally impossible to predict weather beyond two or three weeks with a reasonable degree of accuracy. For this conclusion, Lorenz is often a starting point for global warming critics. They point out that Lorenz's “butterfly effect” leads to predictions that may depart significantly over time from what happens in the real world, if the input conditions cannot be specified to arbitrary accuracy.

During leaves of absence from MIT, Lorenz has held visiting research or teaching positions at the Lowell Observatory in Flagstaff, Arizona, the Department of Meteorology at the University of California at Los Angeles, the Det Norske Meteorologiske Insitutt in Oslo, Norway, and the National Center for Atmospheric Research in Boulder, Colorado. He was elected to the National Academy of Sciences in 1975, and his groundbreaking research has won numerous awards, honors and honorary degrees. In 1983, he and former MIT Professor Henry M. Stommel were jointly-awarded the $50,000 Crafoord Prize by the Royal Swedish Academy of Sciences, a prize established to recognize fields not eligible for Nobel Prizes. His other honors include the Elliott Cresson Medal from the Franklin Institute in 1989, the Rossby Research Medal of the American Meteorological Society in 1969, and the Society's Meisinger Award in 1963. In 1991, he was awarded the Kyoto Prize in earth and planetary sciences.


Chaos Theory, Computer Models, Massachusetts Institute of Technology

  • Lorenz, Edward “Deterministic Nonperiodic Flow,” Journal of the Atmospheric Sciences v. 20/2: 1960.
  • Lorenz, Edward, The Essence of Chaos (University of Washington Press, 1993.).
  • Palmer, Tim, “Global Warming in a Non-Linear Climate. Can We Be Sure?” Europhysics News (March/April 2005).
  • Prono, Luca
    University of Nottingham
    Copyright © 2012 by SAGE Publications, Inc.

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