Lorenz spent the entirety of his scientific career at the
Massachusetts Institute of Technology. In 1948, he joined the MIT Department of Meteorology as a research scientist. In 1955, he became an assistant professor in the department and was promoted to professor in 1962. From 1977 to 1981, Lorenz served as head of the Department of Meteorology at MIT. In 1983, the MIT Department of Meteorology and Physical Oceanography merged with the Department of Geology to become the current MIT Department of Earth, Atmospheric and Planetary Sciences, where Lorenz remained a professor before becoming an emeritus professor in 1987.
Atmospheric circulation In the late 1940s and early 1950s, Lorenz worked with
Victor Starr on the General Circulation Project at MIT to understand the role the weather system played in determining the energetics of the general circulation of the atmosphere. From this work, in 1967, Lorenz published a landmark paper, titled "The Nature and Theory of the General Circulation of the Atmosphere," on
atmospheric circulation from an energetic perspective, which advanced the concept of
available potential energy.
Numerical weather prediction In the 1950s, Lorenz became interested in and started work on
numerical weather prediction, which relied on computers to forecast weather by processing observational data on such things as temperature, pressure, and wind. This interest was sparked, in part, after a visit to the
Institute for Advanced Study in Princeton, New Jersey, where he met
Jule Charney, then head of the IAS's Meteorological Research Group and a leading dynamical meteorologist at the time. (Charney would later join Lorenz at
MIT in 1957 as a professor of meteorology.) In 1953, Lorenz took over leadership of a project at MIT that ran complex simulations of weather models that he used to evaluate statistical forecasting techniques.
Chaos theory In 1961, Lorenz, with the assistance of
Margaret Hamilton, was using a simple digital computer, a Royal McBee
LGP-30, to simulate weather patterns by modeling 12 variables, representing things like temperature and wind speed. He wanted to see a sequence of data again, and to save time he started the simulation in the middle of its course. He did this by entering a printout of the data that corresponded to conditions in the middle of the original simulation. To his surprise, the weather that the machine began to predict was completely different from the previous calculation. The culprit: a rounded decimal number on the computer printout. The computer worked with 6-digit precision, but the printout rounded variables off to a 3-digit number, so a value like 0.506127 printed as 0.506. This difference is tiny, and the consensus at the time would have been that it should have no practical effect. However, Lorenz discovered that small changes in initial conditions produced large changes in long-term results. Lorenz's discovery, which gave its name to
Lorenz attractors, showed that even detailed atmospheric modelling cannot, in general, make precise long-term weather predictions. His work on the topic, assisted by
Ellen Fetter, culminated in the publication of his 1963 paper "Deterministic Nonperiodic Flow" in
Journal of the Atmospheric Sciences, and with it, the foundation of
chaos theory. In the book "The Essence of Chaos," in the chapter "Our Chaotic Weather" from 1993, authored by Edward Lorenz and
Krzysztof Haman, the authors delved into the challenges of weather forecasting. The work discusses the consequences of chaos in the atmosphere and its impact on weather prediction. They describe a scenario in which meteorologists, in the computer age, generate
multiple long-term weather forecasts based on different yet similar initial atmospheric conditions. Differences in the forecast results arise due to the sensitivity of the system to initial conditions. Lorenz's insights on deterministic chaos resonated widely starting in the 1970s and 80s, when it spurred new fields of study in virtually every branch of science, from biology to geology to physics. In meteorology, it led to the conclusion that it may be fundamentally impossible to predict weather beyond two or three weeks with a reasonable degree of accuracy. However, the recognition of chaos has led to improvements in
weather forecasting, as now forecasters recognize that measurements are imperfect and thus run many simulations starting from slightly different conditions, called
ensemble forecasting. Of the seminal significance of Lorenz's work,
Kerry Emanuel, a prominent meteorologist and climate scientist at MIT, has stated: the
Buys Ballot Award in 2004, and the
Tomassoni Award in 2008. In 2018, a short documentary was made about Lorenz's immense scientific legacy on everything from how we predict weather to our understanding of the universe. A reprint book containing invited papers on butterfly effects was published to celebrate the 50th anniversary of the metaphorical butterfly effect. ==Personal life and death==