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| Die besten Wünsche zur Vollendung des 80. Lebensjahres an Peter Carl (Mitte). Es gratulieren Christiane Walter und Frank Wechsung - Kollegen aus der gemeinsamen Arbeit (2009-2012) im Guanting Flusseinzugsgebiet nahe Beijing. |
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We look back on 50 years research covering topics from nuclear fusion to the recent pandemic and present our recent insights about the human war on climate. The Telegraphenberg was the latest working place of Juri Svirezhev one of the scientific partners of Peter Carl in the 80ies. During the 80ies they were part of a joint effort of about 200 scientists worldwide to formalize and simulate the "Nuclear war" imitation game. Climate stood in the center of a sad game, ego shooter romantics was absent, a global sense for joint responsibility stood above all. Among others they published
- Stenchikov & Carl, 1985: Climatic consequences of nuclear war: Sensitivity against large-scale inhomogeneities in the initial atmospheric pollutions. AdW der DDR & Physikalische Gesellschaft
- Svirezhev et al., Carl, 1990: Götterdämmerung. Globale Folgen eines atomaren Konflikts. Hrsg. Carl; Akademie-Verlag Berlin
In the mid and late 90ies the scenarios became more peaceful but still addressed climate change at regional and global scale. Juri Svirezhev continued his work on integrated system analysis at the Potsdam Institute for Climate Impact Research (PIK). The founding director Sir John Schellnhuber had appointed him as a leader for the new department of Integrated Systems Analysis. At the same time Peter Carl changed topics modeling the Monsoon system
- Carl, 1994: Monsoon dynamics in a low-dimensional GCM. WCRP-84, WMO/TD No. 619 (II), Geneva
and regional consequences of climate change on river discharge. The latter work brought Peter Carl together with scientist at PIK and other institutions who analyzed and projected climate change impacts for the Elbe river basin in Central Europe and the Guanting basin north–west of Beijing in China.
- Carl, Behrendt, 2008: Regularity-based functional streamflow disaggregation: 1. Comprehensive foundation. Water Resources Res. 44
- Carl, Gerlinger, Hattermann, Krysanova, Schilling, Behrendt, 2008: Regularity-based functional streamflow disaggregation: 2. Extended demonstration. Water Resources Res. 44
- Carl, 2017: Quality assessment of SWIM-Guanting simulations. In: Wechsung, Kaden, Venohr, Hofmann, Meisel, Xu (Eds.): Sustainable water and agricultural land use in the Guanting basin under limited water resources, chap. 5. Schweizerbart
Our symposium gives room for contributions exceeding the wide spectrum of topics covered by Peter Carl during the professional part of his 80 planetary years. We like to celebrate this ‘scientific trace’ by stimulating talks and discussion and your participation. |
Peter Carls (machine translated) German Notes on his Scientific Trace:
Beginning
Searching for a topic for a diploma (at the AdW, Central Institute for Electron Physics; ZIE - Department of Plasma Physics) under the impression of campaigns with the aim of persuading science to leave its "ivory tower" and devote itself to the lowlands of practice.
- Nitrogen fixation from the air (fertilizer production) - dealing with the N2 molecule. Probably because suitable plants are already quite good at nitrogen fixation, the campaign came to nothing before the topic could be turned into a diploma thesis.
- A new approach initiated by the question from my mentor, Prof. Wallis: "Don't you want to look into relaxation phenomena?" - then led to my diploma thesis, which brought together the different approaches to the qualitative theory of dynamic systems (later called "chaos theory") that was just emerging at the time. It may have been risky to involve a graduate student in such a general topic, but in this case it established a way of thinking that later paid off several times over.
Dissertation
Again thanks to a campaign, but one that was more to the point: to contribute to the development of the electronics industry in the GDR. The topic of choice was the passivation of electronic components (capping with insulating layers), to which plasma physics unexpectedly found a constructive approach due to its experience with annoying, unwanted layer formations on the walls of the discharge vessels. The topic: polymer layer formation by means of glow discharge - i.e. plasma chemistry, at that time still a little 'occupied' field of research. The decision to model such a system also raised the question of whether the analog computing technology still in use at the time (graphic output via oscilloscope, photography of the calculated curves) was an option or whether it would be better to turn to the new digital computing technology - the Academy had been provided with computing centers equipped with the BESM-6 "supercomputer", including at the High Energy Physics department in Zeuthen and a little later also in Adlershof. The acquisition of a higher programming language (FORTRAN in this case) was not the only hurdle: as it turned out only when working on the computer, the model system (a set of ordinary differential equations) had the unpleasant property of "stiffness", which could lead to exorbitant computing times with the usual solution methods, although the curves were harmlessly smooth. Methods for stiff differential equations were not yet available, so that physics had to help to find more manageable model variants or modeling approaches, e.g. via graph theory (with an excursion into tensor calculus) and Monte Carlo simulation, i.e. direct physical modeling without a detour via a system of differential equations (which is based on a "mean-field" assumption, while the Monte Carlo approach allows for any trajectory, no matter how improbable, and therefore ultimately requires calibration as the price for dispensing with differential equations). While the work on the dissertation topic ultimately also benefited from the way of thinking established in the diploma thesis (assignment of different layer properties to dynamic regimes of the model as well as to discharge regimes, etc., i.e. to initial and boundary conditions of the system), new experiences were added here that helped to determine the scientific path in the subsequent period: modeling and digital simulation, solution methods for differential equation systems, and last but not least: software technology in the modeling of complex systems. Unfortunately, plasma physics itself was somewhat neglected, even if the threshold to the codes of nuclear fusion research, including the OLYMPUS technology developed at the center in Culham, was 'easily' overcome.
Nuclear fusion research
In addition to working on a number of smaller plasma physics tasks, which also involved working on systems of partial differential equations and the resulting need to further "cultivate" numerical methods, ZIE's entry into nuclear fusion research at the beginning of the 1980s was thus de facto prepared with regard to the major modeling tasks, even if not pre-programmed in this sense. In cooperation with the Kurchatov Institute for Atomic Energy in Moscow, their tokamak model was then completely regenerated in terms of software and made fit for coupling with other models (boundary layer and vessel wall). The coupling of fusion codes was also on the agenda in cooperation with the Moscow Computer Center of the Soviet Academy of Sciences, here in the context of laser-plasma interaction (i.e. laser fusion). In this context, a working visit to Moscow at the end of 1983 led to a "martial" encounter with climate research that was decisive for his future scientific career: the discovery of the severe climate disruption that a nuclear war would probably trigger. In the run-up to the conference "The world after a nuclear war" (Washington) between the science academies of the USA and the USSR, which then attracted a great deal of international attention, the Moscow colleagues had just completed their first publication on the subject, and so a few copies arrived in the GDR without delay.
Research into the consequences of war ("nuclear winter")
The attempt to interest meteorologists in the country in this burning topic was unsuccessful, however, which led to the decision to become scientifically active here ourselves, i.e. ultimately to switch from plasma physics to climate research via "initiative research". In the first quarter of 1985, a planned working visit to Berlin by the Moscow colleague Dr. Stenchikov was rededicated to this work and the first joint publication on the subject was produced, including the installation of the corresponding climate model at the computer center in Adlershof. The (necessary) software-technological regeneration of this model did not take place until the end of the 1980s - there was no time for it before then. In addition to the scientific work on other contributions (including to the international ENUWAR project), the topic also required a considerable amount of time for public relations work, including the publication, translation and co-authorship of a Soviet study under the German title "Götterdämmerung" (Twilight of the Gods) at the Akademie-Verlag and a three-volume work for the AdW Committee for Scientific Issues of Securing Peace and Abolition. Questions of Securing Peace and Disarmament. In 1991, unexpected scientific consequences of the regeneration of the model became apparent when the Berlin version was used for the first time not only for the assessment of hypothetical war events.
Oil well fires in Kuwait
The threat in September 1990 by the Iraqi dictator to trigger a global climate catastrophe of the "nuclear winter" variety by setting fire to Kuwait's oil wells in the event of the military liberation of Kuwait, which had been occupied in August, naturally called the community involved in the now terminated ENUWAR project to action, and a study was also drawn up in Berlin before the start of hostilities in the Gulf, which predicted unexpectedly far-reaching consequences of smoke emissions for the atmospheric water cycle. This paved the way for a new understanding of the planetary monsoon system.
Monsoon research
The monsoon dynamics realized in the Berlin model assigns this part of the global climate system a structure-determining part in today's climate events, which is characterized by a behaviour that corresponds to concepts of "chaos theory" and points to essential low-dimensional parts in the behaviour of the system. Topologically essential is the realization that the boreal summer monsoon represents a global circulation regime separated from the rest of the annual cycle by bifurcations, which is geometrically characterized by a torus segment in phase space to which the annual cycle "inflates". Low-dimensional behaviour of a nominally high-dimensional system can only be realized through internal synchronizations. It was therefore obvious - also in view of the fact that there were acceptance problems in the climate community with regard to the relatively "small" model - to search for traces of internal synchronization in the climate system in the real world. This search was successful, but required a shift in focus from climate modeling to data analysis.
Data analysis
The usual statistical methods of climate research cannot provide such evidence because there are very different forms of synchronization, especially those between the time and frequency domains. The adaptation of the "matching pursuit" method, which originates from language analysis, and the extension of its "dictionary" to frequency-modulated test signals brought the breakthrough. In the course of more intensive work on the methods of data analysis (and due to the unavoidable thematic focus on other projects), a method for component separation of discharge time series was also developed, which was published in a leading hydrological journal. It is ultimately a variant of now established approaches under the collective term "Dynamic Mode Decomposition". With this and other tools, contributions were made to PIK's Guanting project, as part of the GFZ's Mekong research, and to an IGB project (B.A.U.M) on agriculture and climate change. The study on the low-dimensionality of today's climate dynamics was published by Springer in several book chapters together with a comprehensive presentation of the model results on monsoon dynamics. It is about nothing less than the "dynamic state" of today's climate system, from which it may also be possible to derive ideas about how its further evolution could take shape with the help of concepts from "chaos theory". This work was interrupted by another global event that demanded scientific attention: the COVID pandemic.
COVID
The occurrence of epidemic waves is not yet particularly well understood, and the possible climatic influence on their emergence and course is still under discussion. Using COVID data for Berlin, the question of the extent to which intra-seasonal climatic fluctuations (based on data from the Lindenberg climate station) could have an influence is now being investigated here. Regardless of this, it was not a major task to set up an epidemic model, as the numerics for this have been available for decades, dating back to the time of the dissertation. The COVID topic is still "in the pipeline".
Text by F.Wechsung, Berlin, 26.2.2024
Publications that illustrate the scientific "track" - especially since the switch to climate research:
*** Translated with www.DeepL.com/Translator (free version) ***
Carl, 1980: OLYMPUS for a BESM-6 – The development of medium-scale programs within the OLYMPUS framework: System OLYDES. Computer Phys. Commun. 20
Stenchikov & Carl, 1985: Climatic consequences of nuclear war: Sensitivity against large-scale inhomogeneities in the initial atmospheric pollutions. AdW der DDR & Physikalische Gesellschaft
Carl, 1987/88: Kernwaffenkrieg, Klima und Umwelt – Pathologie einer Katastrophe (drei Hefte). DDR-Komitee für wiss. Fragen der Sicherung des Friedens und der Abrüstung bei der AdW der DDR.
Carl, 1988: „Self-Deterrence“: Global and regional structures of the climatic response to nuclear war scenarios, in: Ways out of the arms race. From the nuclear threat to mutual security. Eds. Hassard, Kibble, Lewis; World Scientific
Svirezhev et al., Carl, 1990: Götterdämmerung. Globale Folgen eines atomaren Konflikts. Hrsg. Carl; Akademie-Verlag Berlin, https://www.degruyter.com/document/isbn/9783112770061/html based on Svirezhev, 1985: Ecological and Demographic Consequences of a Nuclear War, Akademie-Verlag Berlin, Published by De Gruyter, https://doi.org/10.1515/9783112530146.
Carl, Svirezhev & Stenchikov, 2008: Environmental and biospheric impacts of nuclear war. Encyclopedia of ecology, vol. 2, Global ecology. Eds. Joergensen, Fath; Elsevier, Oxford
Carl, 1991: Notes on the climatic response in the Aftermath of Gulf War II.Z. Meteorol. 41
Carl, 1992: Zur dynamischen Struktur des planetaren Monsuns. Wiss. Z HU, 41
Carl, 1994: Monsoon dynamics in a low-dimensional GCM. WCRP-84, WMO/TD No. 619 (II), Geneva
Tschentscher, Worbs, Carl, 1994: Frequency drift and retreat variability of a GCM‘s monsoon oscillator. WCRP-84, WMO/TD No. 619 (II), Geneva
Carl, Worbs, Tschentscher, 1995: On a dynamic systems approach to atmospheric model intercomparison. WCRP 92, WMO/TD No. 732, Geneva
Carl, Behrendt, 2008: Regularity-based functional streamflow disaggregation: 1. Comprehensive foundation. Water Resources Res. 44
Carl, Gerlinger, Hattermann, Krysanova, Schilling, Behrendt, 2008: Regularity-based functional streamflow disaggregation: 2. Extended demonstration. Water Resources Res. 44
Carl, 2011: MP based detection of synchronized motions across the instrumental climate record. In: Proceedings IEEE statist. SSP workshop, Nice
Carl, 2013: A General Circulation Model en route to intraseasonal monsoon chaos, in: Banerjee & Rondoni (Eds) Applications of chaos and nonlinear dynamics in science and engineering, Vol. 3, Springer
Carl, 2014: Atmospheric tracers and the monsoon system: Lessons learnt from the 1991 Kuwait oil well fires. In: Banerjee & Ercentin (Eds.): Chaos, complexity and leadership 2012, Springer
Carl, 2015: Synchronous motions across the instrumental climate record. in: Banerjee & Rondoni (Eds) Applications of chaos and nonlinear dynamics in science and engineering, Vol. 4, Springer
Carl, 2017: Quality assessment of SWIM-Guanting simulations. In: Wechsung, Kaden, Venohr, Hofmann, Meisel, Xu (Eds.): Sustainable water and agricultural land use in the Guanting basin under limited water resources, chap. 5. Schweizerbart
