Paul Jozef Crutzen (; 3 December 1933 – 28 January 2021) was a Dutch meteorologist and atmospheric chemist. He was awarded the Nobel Prize in Chemistry in 1995 for his 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. After many delays and school switches caused by events in the war, Crutzen graduated from elementary school and moved onto "Hogere Burgerschool" (Higher Citizens School) in 1946, where he became fluent in French, English, and German. Along with languages he also focused on natural sciences in this school, from which he graduated in 1951. After this he studied Civil Engineering at a technical school, completed his military service, and married. In 1958, he moved his young family to Gävle. Research and 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 (), 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