Paul Jozef Crutzen (Dutch pronunciation: [pʌul ˈjoːzəf ˈkrʏtsə(n)]; 3 December 1933 – 28 January 2021) was a Dutch meteorologist and atmospheric chemist. In 1995, he was awarded the Nobel Prize in Chemistry alongside Mario Molina and Frank Sherwood Rowland for their work on atmospheric chemistry and specifically for his efforts in studying the formation and decomposition of atmospheric ozone. In addition to studying the ozone layer and climate change, he popularized the term Anthropocene to describe a proposed new epoch in the Quaternary period when human actions have a drastic effect on the Earth. He was also amongst the first few scientists to introduce the idea of a nuclear winter to describe the potential climatic effects stemming from large-scale atmospheric pollution including smoke from forest fires, industrial exhausts, and other sources like oil fires. He was a member of the Royal Swedish Academy of Sciences and an elected foreign member of the Royal Society in the United Kingdom.
Early life and education Crutzen was born in Amsterdam, the son of Anna (Gurk) and Josef Crutzen. In September 1940, the same year Germany invaded The Netherlands, Crutzen entered his first year of elementary school. His classes moved around to different locations after the primary school was taken over by the Germans; during the last months of the war he experienced the 'winter of hunger' with several of his schoolmates dying of famine or disease. In 1946 with some special help he graduated from elementary school and moved onto Hogere Burgerschool (Higher Citizens School). There, with the help of his cosmopolitan parents he became fluent in French, English, and German. Along with languages he also focused on natural sciences in this school, graduating in 1951; however his exam results did not qualify him for university scholarships. Instead, he studied Civil Engineering at a Higher Professional Education school with lower costs, and took a job with the Bridge Construction Bureau in Amsterdam in 1954. After completing military service, in 1958 he married Terttu Soininen, a Finnish university student whom he had met a few years earlier and moved with her to Gävle, a tiny city 200 km north of Stockholm where he took a job at a construction bureau. After seeing an advertisement by the Department of Meteorology at Stockholm University for a computer programmer, he applied, was selected, and in July 1959 moved with his wife and new daughter Ilona to Stockholm.
Beginning of academic career In the 1920's Norwegian meteorologists began using fluid mechanics in analyse weather, and by 1959 the Meteorology Institute of Stockholm University was at the forefront of meteorology research using numerical modeling. The theories were validated in 1960 by images from TIROS, the first weather satellite. At that time, Stockholm University housed the fastest computers in the world with the BESK (Binary Electronic Sequence Calculator) and its successor, the Facit EDB. Crutzen was involved with the programming and application of some of those early numerical models for weather prediction, and also developed a tropical cyclone model himself. Working as a programmer at the university, he was able to take other lectures and in 1963 applied for a PhD program with a thesis combining mathematics, statistics and meteorology. Although intending to extend his cyclone model for his thesis, around 1965 he was asked to help US scientists with a numerical model for the distribution of oxygen allotropes (atomic oxygen, molecular oxygen and ozone) in the stratosphere, the mesosphere and the lower thermosphere. This involved studies of stratospheric chemistry and the photochemistry of ozone. His PhD awarded in 1968, Determination of parameters appearing in the "dry" and the "wet" photochemical theories for ozone in the stratosphere, suggested that nitrogen oxides (NOx) should be studied. His thesis was well-received and led to a post-doctoral fellowship at the Clarendon Laboratory of the University of Oxford, on behalf of the European Space Research Organisation (ESRO), the precursor of ESA.
Research career Crutzen conducted research primarily in atmospheric chemistry. He is best known for his research on ozone depletion. In 1970 he pointed out that emissions of nitrous oxide (N2O), a stable, long-lived gas produced by soil bacteria, from the Earth's surface could affect the amount of nitric oxide (NO) in the stratosphere. Crutzen showed that nitrous oxide lives long enough to reach the stratosphere, where it is converted into NO. Crutzen then noted that increasing use of fertilizers might have led to an increase in nitrous oxide emissions over the natural background, which would in turn result in an increase in the amount of NO in the stratosphere. Thus human activity could affect the stratospheric ozone layer. In the following year, Crutzen and (independently) Harold Johnston suggested that NO emissions from the fleet of, then proposed, supersonic transport (SST) airliners (a few hundred Boeing 2707s), which would fly in the lower stratosphere, could also deplete the ozone layer; however more recent analysis has disputed this as a large concern. In 1974 Crutzen received a prepublication draft of a scientific paper by Frank S. Rowland, professor of Chemistry at University of California, Irvine, and Mario J. Molina, a postdoctoral fellow from Mexico. It concerned the possible destructive effects of chlorofluoromethanes on the ozone layer. Crutzen immediately developed a model of this effect, which predicted severe depletion of ozone if those chemicals continued to be used at that current rate.
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