Solomon, Susan (1956- )

American atmospheric chemist

Susan Solomon played a key role in discovering the cause of a major threat to the earth—the loss of the protective ozone layer in the upper atmosphere. Ozone protects all life on Earth from large amounts of damaging ultraviolet radiation from the sun . Solomon, an atmospheric chemist, was first to propose the theory explaining how chlorofluorocarbons, gases used in refrigerators and to power aerosol spray cans, could in some places on the globe lead to ozone destruction in the presence of stratospheric clouds .

Solomon said in an interview with Lee Katterman that she recalls "exactly what got me first interested in science. It was the airing of Jacques Cousteau on American TV when I was nine or ten years old." Solomon said that as a child she was very interested in watching natural history programming on television. This sparked an interest in science, particularly biology. "But I learned that biology was not very quantitative," said Solomon in the interview. By the time she entered the Illinois Institute of Technology, Solomon met her need for quantitative study by choosing chemistry as her major at the Illinois Institute of Technology. A project during Solomon's senior year turned her attention toward atmospheric chemistry . The project called for measuring the reaction of ethylene and hydroxyl radical, a process that occurs in the atmosphere of Jupiter. As a result of this work, Solomon did some extra reading about planetary atmospheres, which led her to focus on atmospheric chemistry.

During the summer of 1977, just before entering graduate school at University of California at Berkeley, Solomon worked at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. She met research scientist Paul Crutzen at NCAR, who introduced her to the study of ozone in the upper atmosphere. In the fall at Berkeley, Solomon sought out Harold Johnston, a chemistry professor who did pioneering work on the effects of the supersonic transport (SST) on the atmosphere. Solomon credits Crutzen and Johnston for encouraging her interest in atmospheric chemistry. After completing her course work toward a Ph.D. in chemistry at Berkeley, Solomon moved to NCAR to do her thesis research with Crutzen.

She received a Ph.D. in chemistry in 1981 and then accepted a research position at the National Oceanic and Atmospheric Administration (NOAA) Aeronomy Laboratory in Boulder, Colorado. Initially, Solomon's research focused on developing computer models of ozone in the upper atmosphere. Ozone is a highly reactive molecule composed of three atoms of oxygen . By comparison, the oxygen that is essential to the metabolism of living things is a relatively stable combination of two oxygen atoms. In the upper atmosphere between about 32,000 and 100,000 feet altitude, a layer of ozone exists that absorbs much of the sun's deadly ultraviolet radiation, thereby protecting all life on Earth.

In 1985, scientists first reported that, during the months of spring in the Southern Hemisphere (September and October), the density of the ozone layer over Antarctica had been decreasing rapidly in recent years. The cause of this hole in the ozone layer was unknown and many scientists began to look for its cause. In 1986, the scientific community wanted to send some equipment to Antarctica to measure atmospheric levels of ozone and nitrogen dioxide. Much to the surprise of her scientific colleagues, Solomon volunteered to travel to Antarctica to get the needed measurements; until then, she had concentrated on theoretical studies, but the chance to understand the cause of the ozone hole prompted Solomon to take up experimental work. Solomon led an expedition to Antarctica during August, September, and October of 1986, where she and co-workers measured the amounts of several atmospheric components, including the amount of chlorine dioxide in the upper atmosphere. The level of this atmospheric chemical was much higher than expected and provided an important clue in determining why the ozone hole had appeared. Back at her NOAA lab in Boulder, Solomon wrote a research article that provided a theoretical explanation for the ozone hole. Solomon showed how the high level of chlorine dioxide was consistent with fast chemical destruction of ozone triggered by reactions occurring on stratospheric clouds. The extra chlorine dioxide was derived from chlorofluorocarbons released into the atmosphere from sources such as foams and leaking refrigeration equipment. Solomon returned to Antarctica for more measurements in August of 1987. Her explanation for the cause of the ozone hole is now generally accepted by scientists, and has led many countries of the world to curtail the production and use of chlorofluorocarbons.

Solomon's scientific studies to uncover the likely cause of the ozone hole have led to public recognition and many awards. In 1989, Solomon received the gold medal for exceptional service from the U.S. Department of Commerce (the agency that oversees the NOAA) She has testified several times before congressional committees about ozone depletion and is increasingly sought out as an expert on ozone science and policy (although the latter role is one she does not welcome, Solomon admitted in her interview, since she considers herself a scientist and not a policy expert).

Solomon was born on January 19, 1956, in Chicago, Illinois. Her father, Leonard Solomon, was an insurance agent. Susan's mother, Alice Rutman Solomon, was a fourth-grade teacher in the Chicago public schools. Solomon continues to study the atmospheric chemistry of ozone and has added Arctic ozone levels to her research subjects.

See also Chloroflurocarbon (CFC); Global warming; Greenhouse gases and greenhouse effect; Ozone layer and hole dynamics; Ozone layer depletion