Edward Norton Lorenz

1917-

American Mathematician and Meteorologist

Edward Norton Lorenz is known for his pioneering work on chaos theory as a way of explaining atmospheric science. He established the theoretical basis of weather and climate predictability as well as the tools used for computer-aided atmospheric physics and meteorology. His "butterfly theory" influenced a wide-range of basic sciences and has contributed to significant changes in the ways that scientists view nature, the universe, and the future direction of mathematics and science.

Lorenz was born May 23, 1917, in West Hartford, Connecticut. He graduated from Dartmouth College with an undergraduate degree in mathematics (1938) and later earned a master's from Harvard (1940) and a Ph.D. from the Massachusetts Institute of Technology (1948). He taught mathematics at Harvard during the 1941-42 academic year and served as a weather forecaster with the U.S. Army Corp from 1942-46.

In 1946 Lorenz began his meteorology career at the Massachusetts Institute of Technology (MIT) in the department of meteorology. He was influenced by MIT meteorologists Carl-Gustav Rossby (1898-1957) and Vilhelm Bjerknes (1862-1951), both highly regarded weather scientists. Their work emphasized a physical-dynamical interpretation of atmospheric movement and provided the first systematic model of theoretical and practical meteorology. This system of weather forecasting was used extensively by the U.S. Weather Bureau and the military during World War II.

While a visiting scientist at Harvard (1950), his research focused on the idea of atmospheric energy balance. Later, this research on the theoretical basis of dynamic and statistical systems became part of a joint research effort between UCLA and MIT in statistical weather prediction ("MIT Statistical Forecasting Project"). At the conclusion of the forecasting project in 1959, Lorenz was promoted to associate professor, and his research began to focus on weather prediction using computer modeling.

Lorenz saw the chance to combine mathematics, the recently developed computer, and meteorology and set out to design a mathematical model of the weather—a set of differential equations that represented changes in temperature, pressure, wind velocity, etc. He developed a model containing 12 equations and in 1961 began a project to simulate weather patterns using a computer. Lacking much memory, the computer was unable to create complex patterns, but it was able to show the interaction between major meteorological events such as tornadoes, hurricanes, easterlies, and westerlies. Lorenz began to see patterns emerge and was able to predict with some degree of accuracy what weather pattern would occur.

While carrying out an experiment, Lorenz made an accidental discovery that eventually became known as "deterministic chaos" or the "Butterfly Effect." His experiment began using an identical set of numbers, but when the data was inputted for the second time, the new run was not identical to the first as expected. Although initially the same, the data slowly changed after many computations and became an entirely different set of numbers representing a totally different weather system. Lorenz realized this occurred because of minute errors that had been unintentionally programmed into the computer when the numbers were rounded off. Therefore, Lorenz had unexpectedly discovered that no matter how much information he gathered, his weather prediction could be wrong.

In the early 1970s he wrote a paper examining the hypothesis that "the flap of a butterfly's wings in Brazil can set off a tornado in Texas." This paper, presented at the convention of the Global Atmospheric Research Program at MIT in 1972, suggested that some very minor, small undetectable influence could lead to something detectable after a sufficient period of time. With this Butterfly Effect, Lorenz concluded that weather is generally unpredictable beyond a 14-day period and even then subject to change.

In 1983 Lorenz and colleague Henry Stommel received the Crafoord Prize from the Royal Academy of Sciences in Sweden. In 1991 Lorenz received the Kyoto Prize and in 1992 he was the first recipient of the American Geophysical Union's Revelle Medal for achievements in understanding atmospheric process and determining climate.

LESLIE HUTCHINSON