Articles | Volume 23, issue 24
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18 Dec 2023
Opinion | Highlight paper |  | 18 Dec 2023

Paul J. Crutzen – a pioneer in Earth system science and a founding member of the journal Atmospheric Chemistry and Physics

Rolf Müller, Ulrich Pöschl, Thomas Koop, Thomas Peter, and Ken Carslaw

Paul Jozef Crutzen was a pioneer in the atmospheric sciences, a kind-hearted and humorous person with empathy for the private lives of his colleagues and students, and a man who upheld the highest scientific standards for himself and for others. He made fundamental scientific contributions to a wide range of scientific topics in all parts of the atmosphere, from the mesosphere to the stratosphere and from the stratosphere to the troposphere. In particular, he was the first to describe the NOx-driven ozone depletion cycle in the stratosphere, he was among the first to develop the idea of chemical formation of ozone in the troposphere, he provided key concepts to explain the “ozone hole”, and he made fundamental discoveries about the effects of biomass burning on the troposphere. Understanding and addressing the causes of anthropogenic air pollution and climate change were the driving motivations for his scientific work. In his work, he did not shy away from challenge and provocation. His work on smoke from fires after a potential nuclear war inspired new research on a concept now known as “nuclear winter”. He also initiated the reopening of the debate on “geoengineering” – a concept now referred to as “climate intervention”. He also brought the term “Anthropocene” to the popular debate. Moreover, he had a strong influence on atmospheric science through his educational role; there is a very large number of outstanding scientists who started their career with scientific work with Paul. In 2000, Paul was among the founders of the journal Atmospheric Chemistry and Physics, which was unique at the time in providing public discussion of published preprints as well as what we now call “open access” to published articles. Paul's work on human impacts on atmosphere and climate has had a profound impact on the environmental policies of many countries for decades. In the future, his work will continue to be a guide for generations of scientists and environmental policymakers to come.

1 Introduction

Paul Crutzen was always full of scientific ideas that he pursued and also shared generously with colleagues and students. He was also a very hard-working individual; when he focused on a particular scientific problem, he could forget the world around him. Despite all of his concentration on science, he always had time for his family and never forgot how important the private lives of his colleagues and students were. You could always discuss the events of the day with him, from political issues to the weather and sports.

Particularly impressive about Paul's scientific achievements is the range of different topics in atmospheric science to which he made fundamental contributions (Müller2022; Fishman et al.2023); a short overview is given below in Sect. 2.2. Paul's research interests included topics in the mesosphere, the stratosphere, and the troposphere, with a particular emphasis on the issues of climate change and air quality (e.g. Fishman and Crutzen1978; Fishman et al.1979a, b); in this context, the role of aerosol particles – including black carbon – became a focus of his work (e.g. Lelieveld et al.2001; Ramanathan et al.2001). Moreover, he was involved in the first studies on the global effects of a thick smoke layer in the atmosphere produced by fires caused by a possible nuclear war (Crutzen and Birks1982; Birks and Crutzen1983). This work inspired research on “nuclear winter” starting in the mid-1980s (e.g. Turco et al.1983; Aleksandrov and Stenchikov1983; Robock1984; Covey et al.1984). Paul also sparked a new debate by breaking the taboo regarding a possible cooling of the climate by increasing the Earth's albedo through stratospheric sulfur injections (Crutzen2006). Finally, he popularised the term “Anthropocene” as the epoch dating from the commencement of geologically significant human impact on the Earth's system (Crutzen2002; Crutzen and Steffen2003; Crutzen and Müller2019; Benner et al.2021; see also Sect. 4).

Paul was a key figure in establishing the journal Atmospheric Chemistry and Physics (ACP). ACP has been a pioneer in transparent peer review since it was founded in the year 2000 (Pöschl2004, 2012; Ervens et al.2023). The special issue “20 years of Atmospheric Chemistry and Physics”, of which this paper is a part and which celebrates more than 20 years of ACP, contains two papers that are directly related to topics that Paul brought up. These two papers are on the global consequences of a possible nuclear exchange (nuclear winter; Robock et al.2023) and on climate intervention (Visioni et al.2023).

Paul Crutzen himself provided a very good description of his life and of his scientific work in his published Nobel lecture (Crutzen1996) on the occasion of the 1995 Nobel Prize in Chemistry, which he shared with Mario J. Molina and Frank Sherwood Rowland. Shorter biographical texts are also available (Möllers et al.2015; Lelieveld2021; Moortgat et al.2021; Rodhe2021; Solomon2021; Zalasiewicz et al.2021; Zetzsch2021). Moreover, there are two more recent and detailed memoirs describing Paul's life and his scientific achievements (Müller2022; Fishman et al.2023; see also, last access: 14 December 2023). Finally, there is a book (Lax2018) on the recent history (1959–2000) of the Max Planck Institute (MPI) for Chemistry (“Otto-Hahn-Institut”) in Mainz, where Paul worked from 1980; this book also contains a wide range of information on Paul's research during this period.

2 Paul Crutzen: the person and the scientist

2.1 The person

Paul Jozef Crutzen was born in Amsterdam on 3 December 1933 and passed away in Mainz on 28 January 2021. He was the son of Anna Gurk and Jozef Crutzen. In Amsterdam, on 14 February 1958, he married Terttu Soininen; Paul and Terttu have two daughters, Ilona and Sylvia, and three grandchildren (Müller2022). There is no doubt that Paul was a very hard-working man. He once said “see, this is the life of a scientist, always working”. He was very dedicated and demanded the same of his collaborators and students. If the only opportunity to talk science with him was on a Saturday afternoon, you had no choice but to accept his invitation and come to the office. However, this intensity also meant that he was always very interested in the work of colleagues and students; you could count on a well-elaborated reply from Paul in a very short time frame to any scientific text you sent him, be it a paper draft, parts of a doctoral thesis, or any other kind of text.

Nevertheless, no matter how much Paul concentrated on his scientific work, he always had time for his family (Fig. 1). He himself mentioned that weekends were reserved for family, especially during the time when his daughters were young. The entire Crutzen family has fond memories of family gatherings, weekends, holidays, and vacations with Paul. For his colleagues, Paul was a very pleasant person to be with, and science was not necessarily the main subject of conversation. One could chat with Paul over a coffee or an evening meal on many other topics that he was interested in, such as sports. For example, he was always well-informed about the performance of the Dutch ice-skating team and was interested in football,1 particularly with respect to the performance of the top team of his hometown (Ajax Amsterdam). Moreover, he followed the football team of the town that he moved to in 1980 (1. FSV Mainz 05) and watched matches live in the Mainz stadium.

Figure 1Paul Crutzen with his daughter Ilona in 1961 (picture courtesy of Ilona Crutzen).

2.2 The scientist

Paul's scientific achievements are too numerous and their scope too broad to be covered in detail in this brief note (for more information, see e.g. Crutzen1996; Müller2022; Fishman et al.2023). However, stratospheric ozone chemistry, in general, and NOx chemistry, in particular, were what started his scientific work, even before his doctoral research (Müller2022). He proposed the ground-breaking idea that reactions catalysed by NO and NO2 control the ozone concentration in the middle stratosphere (Crutzen1970), according to the following catalytic cycle:


Here, the sum of NO and NO2 is defined as NOx=NO+NO2 and O indicates that an oxygen atom in its ground state (O(3P)).

The discovery of this mechanism in 1970 was a crucial step towards facilitating a quantitative description of the chemistry of the stratospheric ozone layer; prior to Paul's discovery, the dominant catalytic loss cycle of stratospheric ozone (DN, through Reactions 1 and 2) was not known (Fig. 2). It is now known that DO, the reaction O3+O2O2, originally proposed by Chapman (1930), is only a minor sink of stratospheric ozone and that HOx-induced catalysis is important only close to the tropopause and above about 45 km (e.g. Portmann et al.2012; see also Fig. 2). The recognition that chlorine (DCl) also catalytically contributes to stratospheric ozone loss came a few years after the discovery of the NOx-induced cycle (Molina and Rowland1974).

Figure 2Dependence of various production and destruction reactions on altitude: the left-hand panel presents the mean reaction rates; the right hand-panel shows the relative importance of the individual contributions to ozone loss in the gas phase. DO represents the Chapman reaction (the reaction O3+O), DN represents NOx catalysis (Reactions 1 and 2), DH represents HOx catalysis (by H, OH, and HO2), and DCl represents ClOx catalysis (Molina and Rowland1974). Moreover, P denotes production of odd oxygen (by the reaction O2+hν) and D denotes total ozone destruction. The dominant ozone loss cycle in the stratosphere (DN) was not known prior to Paul's work (Crutzen1970). (Figure adapted from Crutzen et al.1995, and Grooß et al.1999; figure courtesy of Jens-Uwe Grooß.)

The recognition of the strong effect of NOx on stratospheric ozone had a major impact, as emissions of NOx caused by a possible fleet of supersonic planes was the first stratospheric ozone depletion issue that was studied (Johnston1971; Crutzen1972). Paul also investigated how tropospheric nitrogen-containing compounds (like N2O) can enter the stratosphere and cause the formation of stratospheric NOx (Crutzen and Ehhalt1977; Müller2021). He initiated the first studies on the budget of N2O in the atmosphere and how it is influenced by human activity (Crutzen and Ehhalt1977).

Tropospheric chemistry, in particular the chemical production of ozone in the troposphere, was of great importance to Paul (Crutzen1996; Fishman et al.2023). The OH radical (Levy1971; Crutzen and Zimmermann1991; Crutzen1996) is responsible for the oxidation of CH4 (and many other compounds emitted into the atmosphere). It was found that, in environments containing sufficient NO, the methane oxidation chain could produce ozone in large quantities – compared with the downward flux of ozone from the stratosphere to the troposphere (Crutzen1973; Chameides and Walker1973). At that time, very little was known about the homogeneous and heterogeneous reactions affecting the methane oxidation chain in the troposphere; therefore, initial conclusions remained uncertain (Crutzen1974b). However, some years later, along with Jack Fishman and Susan Solomon, Paul presented observational evidence of strong in situ tropospheric ozone production (Fishman and Crutzen1978; Fishman et al.1979b). Later, Paul's work on tropospheric ozone led him to realise the importance of biomass burning for the chemistry of the atmosphere (Crutzen et al.1979; Crutzen and Andreae1990).

Paul's work on smoke from fires after a possible nuclear war and the absorption of sunlight by the smoke (Crutzen and Birks1982; Birks and Crutzen1983) introduced the concept that the use of nuclear weapons would have global impacts that go far beyond the more obvious direct effects. This work inspired substantial research activity: Turco et al. (1983) and Aleksandrov and Stenchikov (1983), soon followed by Robock (1984) and Covey et al. (1984), calculated the surface temperature response to fires after a nuclear war and introduced the term nuclear winter (see also Robock et al.2023). Paul's original intention, however, at the outset of these studies (Fishman et al.2023) was to explore the impact of nitrogen oxides, which might form as a result of a possible nuclear war, on stratospheric ozone, a concept that had been discussed earlier (e.g. Whitten et al.1975). Paul counted his contribution to this field as important from a political point of view. Indeed, along with John Birks, Jeannie Peterson, Alan Robock, Carl Sagan, Georgiy Stenchikov, Brian Toon, and Richard Turco, he was presented with the 2022 Future of Life Award (, last access: 14 December 2023) by the Future of Life Institute. The award was presented to this team for reducing the risk of nuclear war by developing and popularising the science of nuclear winter.

After the impact of chlorofluorocarbons (CFCs) on stratospheric ozone was identified (Molina and Rowland1974), Paul published a modelling study on this topic in the same year (Crutzen1974a). In 1985, the ozone hole was discovered by Farman et al. (1985). A year later, Paul – along with Frank Arnold – showed that the formation of stratospheric particles (well above the temperature threshold for ice formation) and the nitric acid uptake into these particles are crucial aspects of ozone hole chemistry (Crutzen and Arnold1986). Heterogeneous chemistry (Solomon et al.1986) and an ozone loss cycle specific for ozone hole conditions (Molina and Molina1987) turned out to be further key processes explaining the chemical processes responsible for the formation of the ozone hole. Furthermore, Paul suggested that carbonyl sulfide (COS) constitutes the major non-volcanic source of aqueous sulfuric acid aerosol particles in the stratosphere (Crutzen1976).

In recognition of the importance of the multi-phase chemistry on atmospheric aerosol particles (Abbatt and Ravishankara2023) and the many unknown processes regarding their microphysics, Paul initiated a junior research group in Mainz in the early 1990s. The name of the group was “Heterogene Chemie und Mikrophysik atmosphärischer Aerosolteilchen” (“Heterogeneous chemistry and microphysics of atmospheric aerosol particles” in English). An important starting point of this research was the paper by Luo et al. (1994), who reported on the homogeneous and heterogeneous freezing rates of sulfuric acid droplets under stratospheric conditions, which has implications for the theory of the formation of nitric acid trihydrate particles in the polar stratosphere. The three authors of that paper are shown in Fig. 3. This photograph was taken by Thomas Koop. At the same time, the scene was photographed by A. R. Ravishankara, who also wanted to take a picture of the authors of the Luo et al. (1994) paper.

Figure 3Paul Crutzen (right) during a summer school in 1993 with Thomas Peter (left) and Beiping Luo (middle) at Paestum, Italy (picture by Thomas Koop).

Further work of the junior research group showed the occurrence and importance of a new type of polar stratospheric cloud (Type Ib) that consisted of liquid rather than crystalline particles (Carslaw et al.1993, 1994; Koop et al.1995); other groups also investigated liquid polar stratospheric clouds (Tabazadeh et al.1994). It later became clear that these liquid clouds, and not the frozen nitric acid hydrate or ice particles, are the main hosts of heterogeneous chemical reactions responsible for chlorine activation and, thus, polar ozone depletion (e.g. Solomon1999; Kirner et al.2015). In another study (Meilinger et al.1995), the junior research group showed that the composition and freezing behaviour of the liquid particles depends on small-scale temperature fluctuations in the atmosphere. As it turned out, the smallest droplets reached higher HNO3 concentrations than larger ones, thus counterintuitively increasing the smaller droplets' likelihood to crystallise. When Paul, who was himself rather short in stature, first learnt about this result during a discussion, he commented on it with a pinch of self-irony and a big smile: “Never neglect the small ones!”.

A discussion about Paul as a scientist is not complete without talking about his role in the scientific community. Throughout his career, Paul interacted and collaborated with many important, influential scientists. These collaborations are easily noticeable upon investigation of his list of publications. However, perhaps even more impressive is the educational impact that he had. There is a very large number of outstanding scientists who had – and have – an extraordinary career that started with a PhD, a postdoc, or an early scientific interaction with Paul. The inspiration for these careers clearly came from Paul, and they started at the various institutions at which he was active.

3 Paul Crutzen and the birth of a new journal

For many years (Ehhalt and Ridley1996), Paul Crutzen has been an editor of classical journals (Tellus and the Journal of Atmospheric Chemistry). In 2000, however, Paul was also key in the pioneering work of establishing a new, unique concept of scientific publishing: public discussion of preprints and open-access publishing. Along with Ulrich Pöschl and Arne Richter, Paul helped found the journal Atmospheric Chemistry and Physics (ACP)”, published by the European Geophysical Society (EGS, which is now the European Geosciences Union – EGU). The first paper was submitted to ACP in 2001.

Scientific discussions have been documented before the invention of ACP; for example, in the Electronic Transactions in Artificial Intelligence (ETAI) and the Journal of Interactive Media in Education (JIME) (Pöschl2012, section “Comparison to earlier initiatives with two- or multi-stage open peer review”). Further, the review process in Journal of the Chemical Society, Faraday Transactions and in the Proceedings of the Combustion Institute is “open”, in the sense that these journals have a long history of meetings and their subsequent publication of the discussion. Faraday Discussions collects questions and answers through delegate discussion during meetings (rather than online or through a text forum): a discussion which is then edited and published alongside the articles in each volume. A similar procedure is followed by the Combustion Institute (see Nicovich and Ravishankara1982, for an example). The interactive open-access process (as we call it today) with a multi-stage public peer review as practised in ACP, however, had not been introduced in scientific publishing prior to the launch of ACP (Pöschl2012).

Initially, when the concept of public peer review and a public discussion of submitted manuscripts was introduced, there was some confusion in the community about the status of discussion papers. Since then, however, it has become clear that discussion papers are preprints similar to the manuscripts posted on other preprint servers like (last access: 14 December 2023) but with the additional feature of undergoing public peer review and discussion. This is also reflected on the web pages of ACP and other interactive open-access journals of the EGU. The ACP concept is now well-established among EGU journals and, over the years, many newly established journals have followed this example (and future journals will continue to do so; Ervens et al.2023).

In an e-mail on 18 September 2000, Arne Richter wrote that a “meeting of the `younger and wilder' atmospheric scientists under the lead of Ulrich Pöschl and Paul Crutzen regarding the launch of a new EGS journal on atmospheric chemistry took place on 15 September in Mainz”; this meeting was the birthplace of the new journal ACP (Dingwell et al.2011). ACP was founded in 2000 with Paul as a member of the advisory board. At that time, the development and success of ACP could hardly have been foreseen.

Today, ACP is a very well-established and highly ranked scientific journal. Starting with only 7 published papers in 2001 (34 in 2002 and 158 in 2003) the number of papers published by ACP increased steadily until 2010, when more than 800 papers were published. In recent years, more than 800 papers per year regularly appear in ACP (Pöschl2012; Ervens et al.2023). In Paul's words,

It has been an amazing journey: over a short period of merely a decade, a novel idea originating from Uli Pöschl and developed by an enthusiastic group of hundreds of scientists, created a new way of scientific publishing and communication, initially covering the fields of atmospheric chemistry and physics. The example has since been followed by many successors in other disciplines, with more to come (Dingwell et al.2011).

4 Anthropocene

With the Anthropocene concept (Crutzen2002; Crutzen and Steffen2003; Crutzen and Müller2019; Benner et al.2021), Paul expressed his insight that humanity is indeed changing the planet as a whole and should take responsibility for its development. He actively advocated this concept until recently (Fig. 4). The Anthropocene concept also led to the development of the iconic “great acceleration” figures (see e.g. Fig. 2 in Fishman et al.2023) that show increases in population, in greenhouse gases, in fertiliser consumption, and many other signatures of human impact on the Earth system since the industrial revolution (Steffen et al.2007).

In 2009, the Anthropocene Working Group (AWG; Fig. 4) was established within the Subcommission on Quaternary Stratigraphy as an interdisciplinary research group dedicated to formalising the Anthropocene as the current geologic time epoch and, more generally, to studying the Anthropocene as a geological time unit. The term Anthropocene became popular after Paul Crutzen proposed it spontaneously at a conference in 2000 to refer to the current epoch (Benner et al.2021; Müller2022; Fishman et al.2023). Today, the evaluation of the Anthropocene as a formal unit in the geological timescale continues (Ellis et al.2016; Zalasiewicz et al.2017; Luciano2022; Fishman et al.2023).

Figure 4Meeting of the Anthropocene Working Group (AWG) at the Max Planck Institute for Chemistry (MPI für Chemie) in March 2017. The people on the picture, clockwise from bottom left to bottom right, are as follows: Franz Mauelshagen, Institut für transformative Nachhaltigkeitsforschung (IASS), Potsdam; Colin Waters, University of Leicester, Leicester, and AWG; Jürgen Renn, MPI für Wissenschaftsgeschichte, Berlin; Bernd Scherer, Haus der Kulturen der Welt (HKW), Berlin; Jos Lelieveld, MPI für Chemie, Mainz; Reinhold Leinfelder, Freie Universität Berlin, Berlin, and AWG; Davor Vidas, Fridtjof Nansen Institut, Oslo, and AWG; Mark Williams, University of Leicester, Leicester, and AWG; Christoph Rosol, HKW und MPI für Wissenschaftsgeschichte, Berlin; Mark Lawrence, IASS, Potsdam; Susanne Benner, MPI für Chemie, Mainz; Jan Zalasiewicz, University of Leicester, Leicester, and AWG; Astrid Kaltenbach, MPI für Chemie, Mainz; Ulrich Pöschl, MPI für Chemie, Mainz; and Paul J. Crutzen, MPI für Chemie, Mainz, and AWG (picture by Simone Schweller, MPI für Chemie).

5 The impact of Paul Crutzen on atmospheric chemistry and physics

Paul Crutzen had very broad scientific interests and an enormous influence on science; his interests covered practically the entire atmosphere, from the ground to the mesosphere. The body of Paul's scientific work is too extensive and broad to be covered here, but some examples have been given above. At the same time, the appreciation of Paul's personality would be incomplete without acknowledging his interest and care for the private lives of the people around him, especially his family.

On top of his contribution to science, he was also a key figure in the development of an entirely new approach to scientific publishing that began with the journal Atmospheric Chemistry and Physics (ACP). When ACP was founded in 2000, it was unique in that it featured public discussion of published preprints and, furthermore, open access to finally accepted and published papers. The 20st anniversary of this journal is celebrated in this special issue. Paul's legacy is honoured in ACP in the form of the ACP Paul Crutzen Publication Award, which was created to recognise an outstanding publication in ACP in a particular year. The first prize was awarded in 2021.

Paul's work not only had a profound impact on the scientific world but also influenced the environmental politics of many countries. His scientific work will continue to provide guidance for the evolution of science. Likewise, his ideas will continue to have a strong influence on future global policies needed to halt the warming of Earth's climate and the destruction of our planet as we know it.

Data availability

No data sets were used in this article.

Author contributions

UP, TK, TP, KC, and RM all contributed to putting together the material for this paper and to writing the manuscript.

Competing interests

At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.


Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors.


First of all, we thank Terttu Crutzen for reading and commenting on the manuscript. Further, we thank Susanne Benner, John W. Birks, Guy Brasseur, Sylvia Crutzen, Barbara Ervens, Astrid Kaltenbach, A. R. Ravishankara, and Alan Robock for comments on this paper. We thank Paul's daughter, Ilona, and his grandson, Jamie Paul, for providing pictures from the family archives. Figure 2 is courtesy of Jens-Uwe Grooß.

Financial support

The article processing charges for this open-access publication were covered by the Forschungszentrum Jülich.

Review statement

This paper was edited by Barbara Ervens and Gabriele Stiller and reviewed by Alan Robock, Guy Brasseur, and one anonymous referee.


Abbatt, J. P. D. and Ravishankara, A. R.: Opinion: Atmospheric multiphase chemistry – past, present, and future, Atmos. Chem. Phys., 23, 9765–9785,, 2023. a

Aleksandrov, V. V. and Stenchikov, G. L.: On the modeling of the climatic consequences of the nuclear war, in: Proc. Applied Math., Computing Centre, USSR Academy of Sciences, Moscow, p. 21, (last access: 14 December 2023), 1983. a, b

Benner, S., Lax, G., Crutzen, P. J., Pöschl, U., Lelieveld, J., and Brauch, H. G. (Eds.): Paul J. Crutzen and the Anthropocene: A New Epoch in Earth's History, Springer, ISBN 978-3-030-82202-6, 2021. a, b, c

Birks, J. W. and Crutzen, P. J.: Atmospheric effects of a nuclear war, in: Vol. 19, Chemistry in Britain, Royal Society of Chemistry, 927–930, (last access: 14 December 2023), 1983. a, b

Carslaw, K. S., Brimblecombe, P., and Clegg, S. L.: Calculated partitioning of hydrogen chloride and nitric acid into stratospheric aqueous sulphuric acid aerosols, EOS, 74, 149, 1993. a

Carslaw, K. S., Luo, B. P., Clegg, S. L., Peter, T., Brimblecombe, P., and Crutzen, P. J.: Stratospheric aerosol growth and HNO3 gas phase depletion from coupled HNO3 and water uptake by liquid particles, Geophys. Res. Lett., 21, 2479–2482,, 1994. a

Chameides, W. and Walker, J.: A photochemical theory of tropospheric ozone, J. Geophys. Res., 78, 8751–8760,, 1973. a

Chapman, S.: A theory of upper atmospheric ozone, Mem. Roy. Soc., 3, 103–109, 1930. a

Covey, C., Thompson, S., and Schneider, S. H.: Global atmospheric effects of massive smoke injections from a nuclear war: Results from general circulation model simulations, Nature, 308, 21–25, 1984. a, b

Crutzen, P. and Ehhalt, D.: Effects of nitrogen fertilizers and combustion on the stratospheric ozone layer, Ambio, 6, 112–117, 1977. a, b

Crutzen, P. J.: The influence of nitrogen oxides on the atmospheric ozone content, Q. J. Roy. Meteorol. Soc., 96, 320–325, 1970. a, b

Crutzen, P. J.: SSTs – a threat to the earth's ozone shield, Ambio, 1, 41–51, 1972. a

Crutzen, P. J.: A discussion of the chemistry of some minor constituents in the stratosphere and troposphere, Pure Appl. Geophys., 106–108, 1385–1399, 1973. a

Crutzen, P. J.: Estimates of possible future ozone reductions from continued use of fluro-chloro-methanes (CF2Cl2, CFCl3), Geophys. Res. Lett., 1, 205–208, 1974a. a

Crutzen, P. J.: Photochemical reactions initiated by and influencing ozone in unpolluted tropospheric air, Tellus, 26, 48–57, 1974b. a

Crutzen, P. J.: The possible importance of CSO for the sulfate layer of the stratosphere, Geophys. Res. Lett., 3, 73–76,, 1976. a

Crutzen, P. J.: My Life with O3, NOx and other YZOx compounds, Angew. Chem. Intern. Ed., 35, 1747–1871, 1996.  a, b, c, d

Crutzen, P. J.: Geology of Mankind, Nature, 415, 23,, 2002. a, b

Crutzen, P. J.: Albedo enhancements by stratospheric sulfur injections: a contribution to resolve a policy dilemma? An Editorial Essay, Climatic Change, 77, 211–219, 2006. a

Crutzen, P. J. and Andreae, M. O.: Biomass burning in the tropics – Impact on atmospheric chemistry and biogeochemical cycles, Science, 250, 1669–1678, 1990. a

Crutzen, P. J. and Arnold, F.: Nitric acid cloud formation in the cold Antarctic stratosphere: A major cause for the springtime `ozone hole', Nature, 342, 651–655, 1986. a

Crutzen, P. J. and Birks, J. W.: The atmosphere after a nuclear war: Twilight at Noon, Ambio, 2–3, 114–125, 1982. a, b

Crutzen, P. J. and Müller, M. (Eds.): Das Anthropozän, Oekom, ISBN 978-3-96238-137-0, 2019. a, b

Crutzen, P. J. and Steffen, W.: How long have we been in the Anthropocene era? An Editorial Comment, Climatic Change, 61, 251–257, 2003. a, b

Crutzen, P. J. and Zimmermann, P. H.: The changing photochemistry of the troposphere, Tellus, 43, 136–151,, 1991. a

Crutzen, P. J., Heidt, L. E., Krasnec, J. P., Pollock, W. H., and Seiler, W.: Biomass burning as a source of atmospheric gases CO, H2, N2O, NO, CH3Cl and COS, Nature, 282, 253–256, 1979. a

Crutzen, P. J., Grooß, J.-U., Brühl, C., Müller, R., and Russell III, J. M.: A Reevaluation of the ozone budget with HALOE UARS data: No evidence for the ozone deficit, Science, 268, 705–708, 1995. a

Dingwell, D., Crutzen, P., Richter, A., Pöschl, U., and Rasmussen, M.: A short History of Interactive Open Access Publishing, Copernicus Publications, ISBN 978-3-942169-03-5, (last access: 14 December 2023), 2011. a, b

Ehhalt, D. H. and Ridley, B. A.: Editorial, J. Atmos. Chem., 23, 1–3,, 1996. a

Ellis, E., Maslin, M., Boivin, N., and Bauer, A.: Involve social scientists in defining the Anthropocene, Nature, 540, 192–193, 2016. a

Ervens, B., Carslaw, K., Koop, T., and Pöschl, U.: Two decades of successful community-based scientific discourse and transparent quality assurance by interactive open access publishing in the European Geosciences Union (EGU), Atmos. Chem. Phys., in preparation, 2023. a, b, c

Farman, J. C., Gardiner, B. G., and Shanklin, J. D.: Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction, Nature, 315, 207–210,, 1985. a

Fishman, J. and Crutzen, P.: The origin of ozone in the troposphere, Nature, 274, 855–858,, 1978. a, b

Fishman, J., Ramanathan, V., Crutzen, P. J., and Liu, S. C.: Tropospheric ozone and climate, Nature, 282, 818–820, 1979a. a

Fishman, J., Solomon, S., and Crutzen, P. J.: Observational and theoretical evidence in support of a significant in situ photochemical source of tropospheric ozone, Tellus, 31, 432–446, 1979b. a, b

Fishman, J., Birks, J. W., Graedel, T. E., Steffen, W., Burrows, J. P., Howard, C. J., and Wayne, R. P.: A Tribute to Paul Crutzen (1933–2021): The Pioneering Atmospheric Chemist Who Provided New Insight into the Concept of Climate Change, B. Am. Meteorol. Soc., 104, E77–E95,, 2023. a, b, c, d, e, f, g, h

Grooß, J.-U., Müller, R., Becker, G., McKenna, D. S., and Crutzen, P. J.: The upper stratospheric ozone budget: An update of calculations based on HALOE data, J. Atmos. Chem., 34, 171–183, 1999. a

Johnston, H.: Reduction of stratospheric ozone by nitrogen oxide catalysts from supersonic transport exhaust, Science, 173, 517–522, 1971. a

Kirner, O., Müller, R., Ruhnke, R., and Fischer, H.: Contribution of liquid, NAT and ice particles to chlorine activation and ozone depletion in Antarctic winter and spring, Atmos. Chem. Phys., 15, 2019–2030,, 2015. a

Koop, T., Biermann, U. M., Raber, W., Luo, B. P., Crutzen, P. J., and Peter, T.: Do stratospheric aerosol droplets freeze above the ice frost point?, Geophys. Res. Lett., 22, 917–920,, 1995. a

Lax, G.: From atmospheric chemistry to earth system science, GNT Verlag, Diepholz-Berlin, 174 pp., ISBN 978-3-86225-112-4, 2018. a

Lelieveld, J.: Paul J. Crutzen (1933–2021), Nature, 591, 29,, 2021. a

Lelieveld, J., Crutzen, P. J., Ramanathan, V., Andreae, M. O., Brenninkmeijer, C. A. M., Campos, T., Cass, G. R., Dickerson, R. R., Fischer, H., de Gouw, J. A., Hansel, A., Jefferson, A., Kley, D., de Laat, A. T. J., Lal, S., Lawrence, M. G., Lobert, J. M., Mayol-Bracero, O. L., Mitra, A. P., Novakov, T., Oltmans, S. J., Prather, K. A., Reiner, T., Rodhe, H., Scheeren, H. A., Sikka, D., and Williams, J.: The Indian Ocean Experiment: Widespread Air Pollution from South to Southeast Asia, Science, 291, 1031–1036, 2001. a

Levy, H.: Normal atmosphere: Large radical and formaldehyde concentrations predicted, Science, 173, 141–143,, 1971. a

Luciano, E.: Is `Anthropocene' a suitable chronostratigraphic term?, Anthr. Sci., 1, 29–41,, 2022. a

Luo, B., Peter, T., and Crutzen, P. J.: Freezing of stratospheric aerosol droplets, Geophys. Res. Lett., 21, 1447–1450,, 1994. a, b

Meilinger, S. K., Koop, T., Luo, B. P., Huthwelker, T., Carslaw, K. S., Krieger, U., Crutzen, P. J., and Peter, T.: Size-dependent stratospheric droplet composition in Lee wave temperature fluctuations and their potential role in PSC freezing, Geophys. Res. Lett., 22, 3031–3034,, 1995. a

Molina, L. T. and Molina, M. J.: Production of Cl2O2 from the self-reaction of the ClO radical, J. Phys. Chem., 91, 433–436, 1987. a

Molina, M. J. and Rowland, F. S.: Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone, Nature, 249, 810–812, 1974. a, b, c

Möllers, N., Schwägerl, C., and Trischler, H. (Eds.): Willkommen im Anthropozän, Deutsches Museum Verlag, ISBN 978-3-940396-48-8, 2015. a

Moortgat, G. K., Burrows, J. P., and Lammel, G.: Paul J. Crutzen (1933–2021), Nachrichten aus der Chemie, 69, 83, 2021. a

Müller, R.: The impact of the rise in atmospheric nitrous oxide on stratospheric ozone, Ambio, 50, 42–46,, 2021. a

Müller, R.: Paul Jozef Crutzen. 3 December 1933–28 January 2021, Biographical Memoirs of Fellows of the Royal Society, 73, 127–156,, 2022. a, b, c, d, e, f

Nicovich, J. M. and Ravishankara, A. R.: A study of the reaction of O(3P) with ethylene, Nineteenth Symposium (International) on Combustion/The Combustion Institute, Vol. 19, 23–30,, 1982. a

Portmann, R. W., Daniel, J. S., and Ravishankara, A. R.: Stratospheric ozone depletion due to nitrous oxide: influences of other gases, Philos. T. Roy. Soc. B, 367, 1256–1264,, 2012. a

Pöschl, U.: Interactive journal concept for improved scientific publishing and quality assurance, Learned Publishing, 17, 105–113,, 2004. a

Pöschl, U.: Multi-Stage Open Peer Review: Scientific Evaluation Integrating the Strengths of Traditional Peer Review with the Virtues of Transparency and Self-Regulation, Front. Comput. Neurosci., 6, 33,, 2012. a, b, c, d

Ramanathan, V., Crutzen, P. J., Kiehl, J. T., and Rosenfeld, D.: Aerosols, Climate, and the Hydrological Cycle, Science, 294, 2119–2124, 2001. a

Robock, A.: Snow and ice feedbacks prolong effects of nuclear winter, Nature, 310, 667–670, 1984. a, b

Robock, A., Xia, L., Harrison, C. S., Coupe, J., Toon, O. B., and Bardeen, C. G.: Opinion: How fear of nuclear winter has helped save the world, so far, Atmos. Chem. Phys., 23, 6691–6701,, 2023. a, b

Rodhe, H.: Paul Crutzen 1933–2021, Royal Swedish Academy of Sciences, Stockholm, (last access: 14 December 2023), 2021. a

Solomon, S.: Stratospheric ozone depletion: A review of concepts and history, Rev. Geophys., 37, 275–316,, 1999. a

Solomon, S.: Paul J. Crutzen (1933–2021), Science, 371, 892,, 2021. a

Solomon, S., Garcia, R. R., Rowland, F. S., and Wuebbles, D. J.: On the depletion of Antarctic ozone, Nature, 321, 755–758, 1986. a

Steffen, W., Crutzen, P. J., and McNeill, J. R.: The Anthropocene: Are humans now overwhelming the great forces of nature?, Ambio, 36, 614–621,[614:TAAHNO]2.0.CO;2, 2007. a

Tabazadeh, A., Turco, R. P., Drdla, K., Jacobson, M. Z., and Toon, O. B.: A study of type I polar stratospheric cloud formation, Geophys. Res. Lett., 21, 1619–1622, 1994. a

Turco, R. P., Toon, O. B., Ackerman, T. P., Pollack, J. B., and Sagan, C.: Nuclear winter: Global consequences of multiple nuclear explosions, Science, 222, 1283–1292,, 1983. a, b

Visioni, D., Kravitz, B., Robock, A., Tilmes, S., Haywood, J., Boucher, O., Lawrence, M., Irvine, P., Niemeier, U., Xia, L., Chiodo, G., Lennard, C., Watanabe, S., Moore, J. C., and Muri, H.: Opinion: The scientific and community-building roles of the Geoengineering Model Intercomparison Project (GeoMIP) – past, present, and future, Atmos. Chem. Phys., 23, 5149–5176,, 2023. a

Whitten, R., Borucki, W., and Turco, R.: Possible ozone depletions following nuclear explosions, Nature, 257, 38–39,, 1975. a

Zalasiewicz, J., Waters, C., and Head, M. J.: Anthropocene: its stratigraphic basis, Nature, 541, 289,, 2017. a

Zalasiewicz, J., Waters, C., and Steffen, W.: Remembering the extraordinary scientist Paul Crutzen (1933–2021), Sci. Am., (last access: 14 December 2023), 2021.  a

Zetzsch, C.: Paul Crutzen: 1933–2021, Toxicol. Environ. Chem., 103, 238–243,, 2021. a


Football is the game referred to in American English as soccer.

Executive editor
This personal tribute, authored by close colleagues and friends, is an homage to Paul Crutzen's profound and multifaceted impact in the field of atmospheric chemistry and physics. The article summarizes not only the exceptional breadth of research ranging from tropospheric ozone formation to stratospheric ozone loss, and coining the term ‘anthropocene’ but it also describes Paul Crutzen’s instrumental role in shaping the next generations of atmospheric scientists, many of whom now are leaders in the field. Furthermore, Crutzen’s legacy is manifested by his contributions to the creation of the journal Atmospheric Chemistry and Physics (ACP), that laid the foundation for EGU's pioneering open-access publication model, fostering public peer review and interactive scientific discourse.
Short summary
Paul J. Crutzen was a pioneer in atmospheric sciences and a kind-hearted, humorous person with empathy for the private lives of his colleagues and students. He made fundamental scientific contributions to a wide range of scientific topics in all parts of the atmosphere. Paul was among the founders of the journal Atmospheric Chemistry and Physics. His work will continue to be a guide for generations of scientists and environmental policymakers to come.
Final-revised paper