Encounter with a passionate scientist and a committed citizen: Vincent Courtillot, geoscientist, professor at Paris-Diderot University in Paris.

Interview by Véronique Anger-de Friberg.on September 16, 2010. Translated from French by Danielle Greenfield and updated.Science: Vincent Courtillot fell inside when he was small… Son of two physicists, graduates from the small but renowned school of “Industrial Physics and Chemistry of the City of Paris”, at an early age, he crossed the path of many of the scientists his parents interacted with and their families, and who will mark his youth: Langevin, Joliot, Perrin, to name only some of the most famous.  Standpoint of a committed scientist on the conduct of science and its place in society.
Véronique Anger:  How would you summarize the milestones of your career?  Vincent Courtillot: I am the son of two physicists; I soaked in a scientific and rational culture even though my mother who was also very literary was adamant that my education be balanced. In eighth grade, I fell in love with Greek. I studied ancient Greek for seven years and for a long time I even contemplated teaching it. This did not deter my parents from strongly encouraging me to study science… So I went through Math Elem, then to preparatory schools, applied to the “Grandes Ecoles” and was accepted at the National School of Mines.By then, it was a bit too late to go back to Greek, and I had grown fond of science. The School of Mines was unique in that it offered a geology program and, as I loved physics, I decided to study geophysics (which I assumed would be a blend of geology and physics), to increase my chances to be hired by employers who privileged graduates from “Ecole Normale Supérieure” and “Polytechnique”, both ranked higher than the the School of Mines in the collective unconscious. I then joined Stanford University where I graduated with a master’s degree in geophysics. It was a time of great excitement, the discovery of continental drift in its modern version, plate tectonics, and I was in the middle of it!   The department was staffed with some of the most prominent names associated with this intellectual revolution and they welcomed me with warmth and simplicity.  To me, they were giants who accepted to discuss with me and treat me as one of their peer. What a change from the situation the years before in France.  This is how, at age 24; I fell in love with a discipline that I had originally chosen for rational purposes. After one year in the United-states, I had to go back to France to do my military service. I was very lucky to integrate what was then referred to as “Direction de la recherche et des moyens d’essais” (in some ways the army’s scientists). In Stanford, I had been impressed by an article on continental drift written by a group of scientists, including one named Jean-Louis Le Mouël, and since I was able to choose my assignment, I picked his laboratory.After my military service was over, I had the opportunity to return to the United-States to undertake a thesis under the supervision of Allan Cox, one the great names of paleomagnetism or accept Jean-Louis Le Mouël’s offer to write my thesis in geomagnetism under his supervision. Being fond of physics and mathematics, I accepted the latter. I was afraid that I would not be able to study geomagnetism, which is more mathematical, any longer if I studied paleomagnetism first, which is more geological and experimental. After this exciting thesis, I realized that there was no paleomagnetism lab at the IPG; therefore I proposed to create one with one of my colleagues, Jean-Pierre Pozzi. The IPG has since been one of the few institutes in the world where geomagneticians (who usually work in physics departments) are in the same team as the paleomagneticians (who usually share offices with the geologists).
VA: In your book, Nouveau voyage au centre de la Terre (ed. Odile Jacob), you encourage: "interdisciplinarity”, a notion that is overused yet essential.   Can one be a scientist today without engaging in multidisciplinary research? VC:While some researchers choose to focus on a single topic that they will develop throughout their career, I am even more interested in exploring disciplines. While I enjoy delving into depth onto some subjects, I also like observing the interdependencies between different disciplines. However, I realize that being more interested in an interdisciplinary approach also means that I cannot be as sharp as some colleagues who become “super-specialists”. Both kinds of scientists need to work together: team work is therefore essential.
VA: How does one go from one field of expertise to other disciplines?  VC: There are two factors, chance and interdisciplinarity. In my opinion, chance is a key factor in scientific discoveries for both types of profiles I just described. Of course one must be in a frame of mind and have a general culture that will allow this chance to be seized rather than missed. When faced with questions in the discipline I was specializing in, I often discovered that some questions might find a quicker or better answer in other disciplines that I did not master. For instance in the research on “geomagnetic secular variation impulses” (called “jerks” by the Anglo-Saxons), one of the significant research projects I undertook with Jean-Louis LeMouël, I felt comfortable observing the magnetic field, isolating the effect and proving its existence. However, understanding and interpreting the phenomenon would require some knowledge in magnetohydrodynamics, a very complex field blending the complex, non linear equations of magnetism and fluid dynamics, a field which I was not a specialist in.Another example: in the 1980s’ I participated with Claude Allègre and Paul Tapponnier in a series of expeditions in Tibet to understand a major problem related of plate tectonics: the collision between India and Asia. With my first two thesis students, José Achache and Jean Besse, I tried to measure by how much and exactly when India collided with Asia to form the Himalayan Chain and the Tibetan plateau.  This required knowing the position of each continent in each geological period to calculate at what speed they moved one towards the other. We started with Tibet, we measured samples from red beds and lava flows back in our laboratory in Paris, assessed the latitudes current Tibet crossed (which was not yet High Tibet) over a period of 100 million years.  In order to understand how much of earth's crust had been absorbed to form the Himalaya and Tibet we had to explore the other side, i.e.  India. There, we studied a large expanse of lava, the Deccan traps, which had been thought to have formed over tens of millions of years. Much to our amazement, we discovered through magnetic dating that they must have erupted in a far shorter time on the order of one million years! But magnetism alone could not complete the dating process.We thus tried to understand why; it compelled the magnetician that I was to discuss with geochemists who were experts in dating. I successively joined forces with three teams (I helped the latest, headed by my friend Pierre-Yves Gillot, a prominent specialist of geochronology, to find the resources to create a laboratory for isotopic dating at the University of Orsay that I co-directed for a while) and we realized that the resulting date corresponded to the date when dinosaurs became extinct.  We were therefore confronted with the problem of mass extinction of species which, this time, required the joint assistance of paleontologists, biologists and climatologists, to be able to understand how volcanism could have altered the climate and more generally the whole biosphere, and how this climate change could have complicated the life of the dinosaurs (and actually 65% of all species then alive).A last example: I have recently come back to my previous passion, geomagnetism and in particular recent magnetic variation. Together with Jean-Louis Le Mouël and some Russian colleagues, we have shown that some specific features of the magnetic field were remarkably well correlated with some variations in the sun’s activity - which in itself was not surprising - but the fact that it also correlated with the mean global temperature of the lower atmosphere came to us as a real surprise. This is how I started to get interested in climatology at the decadal to centennial time scale, an area which is not my specialty, though I had already encountered climatologists at the million year time scale with the Indian volcanism. These are three examples of paths guided by a question, and in some cases heavily influenced by chance findings.  In research, there is indeed often something unexpected that leads one on a different track.
VA: How do you reconcile your work as a field investigator and director of the “Institut de Physique du globe de Paris”? VC: It is a key issue. I am passionate about research and at the same time, I was always aware of the opportunity that the French system offers: to be paid to do something so wonderful …I believe that it is also very hard to refuse to undertake an assignment for the common good. However, it does not mean that you cannot insist on some conditions such as not to take up important functions and heavy administrative duties for more than 4 or 5 years in a row. I always followed this rule. Although the function would force me to curtail a number of my activities, namely teaching and research, I have always managed to free two days a week, usually Friday and Saturday, to do research; a compromise which has always allowed me not to «drop out» of active research. My most recent stint has been as director of the IPG, an exceptional institution that I have prized since I joined it some 38 years ago, for the past 6 years a bit longer than any previous segment of my career, because I had to supervise construction of a whole new building that we have just moved in) and I must say that I have found this job very exciting. But I believe it is time to move on and to hand over the position to a younger person, with different ideas. I am 62 years old and I am lucky - as an academician – to be able to continue working as "Emeritus" (and therefore keep bothering my younger colleagues forever…). I am not considering retirement for the moment and I would like to spend what has to be the last segment of my career conducting research.
VA: Is ‘Institut de Physique du globe” also a University? VC: The IPG is a «graduate university” offering a number of master’s and doctorate programs, but no bachelor program (which is done by our companion university Paris-Diderot where I am also a professor). We are a small yet rather well funded institution, i.e. smaller but better funded than most larger universities. IPG has three missions, two of which are common to all universities: research and training. The third more unusual mission, observation, represents one third of the Institute’s activity. The IPG has the duty by statute to monitor natural phenomena generated in the solid earth. It is responsible for the surveillance of the three active volcanoes located on French territory (Montagne Pelée in Martinique, Soufrière in Guadeloupe and Piton de la Fournaise in Reunion) and a global seismic network to characterize large earthquakes, understand their source geometry and dynamics and model the tsunami they sometimes generate. The Institute is also responsible for a worldwide network of magnetic observatories. This is an ever more significant activity with the development of what is known as space weather. Indeed, it is becoming imperative to understand what is happening in real time to be able when possible to predict satellite failures related to solar magnetic disturbances (because they are very expensive) or major power breakdowns of entire large cities such as happened in Canada a few years ago. Our mission consists in operating these three observatory networks continuously at the best level and in the long term.  We have staff, equipments, students and permanent links between the Mainland and overseas departments to carry out this routine monitoring.This Surveillance can only be effective and meaningful if performed at the highest level. And it can be such only if linked to research. It is the reason why doctoral training, research and routine observations are essential in continuously nourishing the search for truth in the field. A ceaseless and very rich interexchange (between observation, field work, theory and modeling) is fundamental.
VA: As a scientist, researcher and director of the IPG, what is your perception of the crisis of science in France? VC: In more than 30 years, it seems to me that bureaucracy has unfortunately become heavier and financing harder. Wages for entry level researchers is a real issue because it deters many bright young minds from considering a scientific career. In Europe, the cultural level, knowledge, education should represent real opportunities for young careers and yet…. Another example, my political views bear to the left and for eight years I have served governments with a socialist majority I think that what these governments were proposing in terms of higher education and research was interesting, and I think we did quite a lot of good work (for most of our better reforms most people have forgotten when and by whom they were achieved…). But some long standing, cultural biases remain. France suffers from a number of what I call schizophrenias: I regret the disconnection between the universities and the “Grandes Ecoles”, between fundamental and applied research, between the academic and the industrial world. As a consequence today, an engineer from a “Grande Ecole” with5 years of education after high school (BAC+5) will be more readily recruited (and at a higher wage) than someone holding a PhD with 8 years of education after high school (BAC+8), including three years experience and a real understanding of what innovation is about, that is so needed. Most of our business leaders have never submitted a thesis and are not PhDs; they are unfamiliar with the university system and therefore tend to be suspicious of it. Some large research organizations attempt to take over research activities from the hands of universities. Unlike the NSF in the US for instance, the CEA (Atomic Energy Commission) or the CNRS (National Center for Scientific Research) are not only funding agencies for research, as may exist in other countries, but are decision makers who allocate staff and resources based on their own decisions (yet crucial for our laboratories),... They are key partners, but in recent years they have tended to intervene a little too much.  A new balance of power has to be redefined; this is the reason why I am in favor of increased autonomy of the universities. The CNRS has recently taken a far more open position as an agency that should primarily support public research in universities. A few years ago I wrote a “free opinion” article in Le Monde entitled “Pour la Confiance” (“For trust”) in which I condemned the culture of distrust and finicky a priori control with no evidence. I think we should trust and substitute judgment ex ante without any evidence by quality assessment ex post.  Resources should be made readily available while a genuine evaluation system developed and implemented.  In the various positions I occupied during two separate 4-year stints as director in the ministry in charge of higher education and research or advisor to the minister, we were pioneers of the implementation of a national assessment policy for the universities. We need to establish a genuine culture of trust and move closer to the Anglo-Saxon system, while remaining in line with the French system and culture. Universities should be at the heart of the higher education system and research.  Organizations for research and new agencies should support universities by providing calls for tenders (CNRS or the new ANR - National Research Agency) and external evaluations (AERES : Agency for Evaluation of Research and Higher Education). The University cannot be managed externally and therefore everything that increases autonomy of the universities brings us on the right track.
VA: You define yourself as "a Geoscientist trying to sort out truth from falsehood", a "disentangler". To get as close as possible to the truth, is it not, in principle, the vocation of all scientists? What are in your opinion, the role and the place of scientists in society? VC: This brings us to the most recent part of my research career where, together with a small group of colleagues and under the leadership of my friend Jean-Louis Le Mouël, we have dared to (unwittingly or unwillingly?) enter the domain of climate research. In the specific case of climate research I found myself at the heart of a debate where not only scientists were involved, but also politicians, journalists, and actually the whole of society. It utterly changed the scope of the debate and my vision of the role of scientists in society. Originally, I believed that all scientists were passionate about science and only science … I grew up in the culture of progress developed by the  rationalists of the 1930s – now a bit outdated - Today, I no longer believe that progress is guaranteed by scientific developments, but I am still convinced that fundamental scientific developments are essential to humanity, and remain most exciting.  Each generation then delivers applications that can go in the direction of the good or evil and citizens have to raise moral and ethical issues. But it is critical to differentiate the field of science from the field of ethics. And it is not scientists who are responsible for the use made of their discoveries, but the whole of mankind. As a passionate scientist, I believe science is an essential element of the progress of society. European countries have only limited natural resources; their true resources lay in the wealth of cultures, education and the ability to train bright young brains who will launch innovative products and ideas, and make our countries competitive by creating wealth and employment for young Europeans. Like many scientists of my generation, it seemed normal to devote some of my time to a society that allowed me to practice a profession that fascinated me throughout my life. A scientist - and a scholar in general– masters several trades: teaching and research, which are obvious occupations, but also administration, innovation, outreach, industrialization and commercialization of a product that he/she may have invented... Ten different potential trades! One must be able to switch from one to the other throughout the course of his life. The scientist has no choice but to be engaged in the debates of society. His duty is also to advise society and democratic political authorities of the country in which he resides (if lucky enough to live in a democratic country…). Heading a structure (whether it is a laboratory, a University, a Department, an administration...) is compatible with a political commitment (in the profound meaning of the words) provided of course that this commitment remains clearly separate from and respectful of science, technology and higher education, and provided decisions relevant to the structure are not tainted by “politician’s” considerations.
I've participated in many discussions between scientists that were quite technical and animated but always respectful. For instance discovering and understanding why the earth’s magnetic field undergoes impulses or why dinosaurs have disappeared is of interest to specialists or an interested public, but this has little impact on society. The debate on climate has a distinct character. For the first time, the debate about climate involved everyone, not only our colleagues but journalists, politicians, the general public: all have an opinion. It has changed everything. I first used the concept of "disentangler" in a television interview.  I was trying to explain in a simple way that scientists have to answer questions by saying whether something is true or false whereas citizens want to know if it is good or bad, ethic or unethical. I believe that the danger with the current debate is to confuse the questions: "Is it good or bad", "is it good or evil?" with the question: "is this true or false? » When we talk about global warming, we can say whether it is true or false (depending on our own understanding of this gigantic and very complex problem, and often with great uncertainty) unfortunately this answer is immediately translated by: "it is good” or “it is bad", and actually “you are good” or “you are bad”. This error is fundamental, and this is what I wish to sort out and separate. I can say what I understand about the causes or the reality of global warming as a scientist, but to say whether global warming – and its possible causes – is a good thing or a bad thing is an issue for citizens. If I say I do not believe the majority doxa in terms of science, many people will immediately conclude that I am either good or bad, a perverse combination of moral and science which is very dangerous if it is not disentangled.
VA: About the precautionary principle, do you think that scientists are instrumental in the making of politically risky or unpopular decisions? VC: The concept of precaution is essential. However, there is no such a thing as a “precaution principle”.  The notion of principle has a particular meaning for a scientist, especially for a physicist. Precaution is not a principle verifiable by laws such as it is the case for principles of physics, this term is excessive, actually outright misleading. The inclusion of such a notion in the Constitution as France has done it is an aberration insofar as a judge has no way of verifying its validity. How do you prove that someone has contravened the precautionary principle? How can it be established and measured? This is tantamount to opening a Pandora's Box! Precaution is something indeed very important, which you learn as part of your education, in the family or at school.It is clear that oil, gas and coal resources will eventually be depleted someday and to be reasonably cautious about decreasing consumption is a necessity.  It does not need to be related to a legal precautionary principle. Finally, behind the precautionary principle, lies the notion of risk which is a probabilistic concept. Zero probability does not exist; it is possible to mathematically prove that it is infinitely complex and pricey to try to achieve zero risk. Beside the fact that Humanity has evolved and adapted to a series of risks, if the absurd concept of zero risk had been applied all the time, no significant discovery would have been possible and we would still be at the age of cavemen…Both the notions of zero risk and precautionary principle are signs of an aging civilization, culture, and population, ready to open a huge umbrella to protect themselves at all times. This is certainly not a sign of a young and dynamic population. So, yes to precaution; not to the precautionary principle and risk zero seen dogmatically as a new religion, which in my opinion, leads us to economic regression, to intellectual stagnation and the loss of much of what makes the salt of our lives and gives hope of improvement to the following generations.
VA: You defend the idea that volcanism rather than a meteorite is the main cause for the extinction of the dinosaurs and that each species’ mass extinction in the geological past has been associated with a volcanic eruption. Is this theory now accepted by your peers as the dominant theory? VC: In Europe, the theory of volcanism is accepted as an alternative thesis and even in several places as the dominant thesis. I remind you that I do not deny the fall of the asteroid; I say that most of the time, species extinctions are mainly due to volcanism. This explanation has been widely accepted for several years in Europe and has more recently made its way in the United States. In October 2009, I was invited to a conference opening at the annual meeting of the Geological Society of America in Oregon on this topic. It was the second time that a large American geoscientific association dared invite me (I had been invited by the American Geophysical Union a few years before), indicating that an increasing number of colleagues there think that the theory I have been defending might actually be right...If you had interviewed me six months ago, I would have replied that I thought that the volcanic theory was for the most part accepted, but a new event occurred a few months ago. Science magazine published an article co-signed by some 40 authors claiming, with an extraordinary degree of certainty, that only the asteroid was responsible for the end of the dinosaurs and thus the Alvarez theory was proven! I do not understand how such an article, fraught with serious oversights, could have been accepted! Instantly, several American and French journalists wrote that the thesis of the asteroid had been established, without the slightest criticism and without interviewing laboratories that had a different opinion.  This Article sparked a wave of protests and the Science had to publish three different critical comments refuting most of the arguments of this article. Although the controversy has not apparently ended yet, in many geoscientific environments it is now accepted that most mass extinctions are associated with an episode of major volcanism. It is true that the Cretaceous-Tertiary boundary has witnessed both; an episode of volcanism and the fall of an asteroid, and I do not deny that the two have occurred at the same time. The question is now to define the respective impact of each. For all other extinctions, there is no definitive evidence of asteroid impact. The general cause of mass extinctions is massive episodes of volcanism as I explained in New journey to the center of the Earth. My additional arguments are, on the one hand, the discovery of significant impacts that are linked to no extinction, and, on the other hand, new results we have obtained in our laboratory and recently published. We have imagined a new way of estimating the durations of ancient volcanic outpourings and we thus have shown that, in the case of India, huge flows, over 1,000 times larger than the largest flows that have occurred in the past 1.000 years on the surface of the Earth, could have erupted in just 10 years! While it was thought that volcanism was spread quite evenly over a million years, we realize now that it was in fact made up of extremely irregular «pulses» some of which very brief and gigantic.
Moreover, by calculating the amount of carbon dioxide and sulphurous gas injected into the atmosphere, we realized then that the consequences of the asteroid impact on the atmosphere must have been similar to that of “only” a very large flow. But there are dozens of flows! So the impact may have contributed only to part of the extinctions. Even a full sequence of flows the size of the Deccan traps may not result in a mass extinction. As my latest book shows, the eruption sequence must have a certain time signature to lead to the mass extinction of species living on Earth; a disaster hard to imagine. Therefore, in recent years, we have reached the conclusion that major geological disasters can occur at time scales that could be catastrophic, even at the scale of human life. The last one occurred well over 10 million years ago. There will be a next one but it is likely millions of years away in the future…
VA: Last March you have published in Geophysical Research Letters, with Jean-Louis Le Mouël and, Elena Blanter and Mikhail Shnirman, two Russian colleagues, an article explaining that sunspot cycles and cosmic rays are apparently reflected in variations of the speed of rotation of our planet, which would confirm the potential direct or indirect link between solar activity and climate on the planet. How is it possible that cosmic rays have such an influence on the speed of rotation of the Earth? VC: As a matter of fact, in this recent scientific paper ⁽¹⁾ published under the direction of Jean-Louis Le Mouël (who is the main facilitator of our research program on climate) we are somehow going back to geophysics.  We have analyzed the speed of the Earth’s rotation or- what is equivalent – the length of day (LOD). Everyone knows that the Earth rotates about itself in 86400 seconds. But actually, the exact length of day can vary by fractions of seconds. There is for instance a well-known oscillation with a period of six months and an amplitude of 0.0003 second, which of course we cannot feel, but which has been precisely monitored for the past 40 years with modern instruments. These variations are due to the fact that the Earth is not fully solid, and changes of the length of day are due to fluid motions: at the decadal to centennial scale it is motions in the Earth’s liquid core. But at the shorter time scales, say shorter than a year, the variations are due to changes in atmospheric motions, i.e. winds.From 1960 to 2000, the amplitude of the six-month variation of LOD follows four solar cycles (the famous cycles of sunspots, monitored since they were discovered by Galileo, whose period is approximately eleven years). Changes in the speed of the solid Earth’s rotation actually reflect changes in the angular momentum of the atmosphere (applied mechanics tell us that the angular momentum of an isolated body must remain constant: the sum of the angular momentum of the atmosphere and the solid Earth must remain constant). In other words, and in somewhat simplifying, the average speed of zonal winds, following parallels geographic latitude, is modulated by the solar cycles. And this variation is not small since it reaches 30% of the 0.0003 second value of the 6-month period: actually, the flow of cosmic rays, which is strongly modulated by the activity of the Sun, correlates well ("in phase") with the variations in the semi-annual component of the Earth's rotation.Although the mechanism is far from being fully understood, some authors have proposed that cosmic rays or electrical currents of the upper atmosphere could alter cloud microphysics, and therefore cloud cover and the amount of solar energy reflected by these clouds back to space. Therefore, one can imagine a modulation of climate variations linked to the way solar activity influences cloud cover. The observation that we were able to realize is quite telling, but the suggested causal chain is not proven and there is a lot of remaining work to do!! The debate is therefore still open! In this whole business of the public discussion on climate change, the most regrettable and actually damaging point has been an apparent intention by some (many?) to claim that all had been solved and the debate closed. In a complex problem such as climate change, one should always have a warning light blinking when such a statement is made.
⁽¹⁾ Abstract: “We study the evolution of the amplitude A of the semi-annual variation of the length-of-day (lod) from 1962 to 2009. We show that A is strongly modulated (up to 30%) by the 11-yr cycle monitored by the sunspot number WN. A and WN are anticorrelated, WN leading A by 1-yr. A is therefore directly correlated with galactic cosmic ray intensity. The main part of the semi-annual variation in lod is due to the variation in mean zonal winds. We conclude that variations in mean zonal winds are modulated by the solar activity cycle through variations in irradiance, solar wind or cosmic ray intensity.».______________________
Vincent Courtillot, résumé… Geophysicist, specialist in paleomagnetism, Member of the Academy of Sciences since 2003 in the sciences of the Universe section (and also of Academia Europaea and the Chinese Academy of Sciences), Vincent Courtillot is a graduate of Ecole des Mines, Doctor of science, a graduate of Stanford University, California, a Professor of geophysics at the University Paris-Diderot and the Director of Institut de Physique du Globe in Paris, both institutions being founding members of the new pole for higher education and research (PRES) called Sorbonne Paris Cité. He has taught at Standford University, Santa Barbara and the California Institute of Technology (Caltech) and was Director of Research and Doctoral studies for the Ministry of National Education, Special Advisor to the Minister of National Education, Research and Technology (1997-1998). Then Director of Research (1998-2001). He was president of the Scientific Council of the city of Paris from 2002 to 2009.Internationally renowned scientist, he has published over 200 articles in major international scientific journals on geomagnetism (discovery of "jerks"), paleomagnetism (collision of India and Asia, and the formation of Tibet), plate tectonics in Tibet and in Afar (propagation of continental tears to form rifts), hot spots and their consequences on continental rifting and mass extinctions of biological species. He belongs to the list of highly cited scientists published by the ISI.He is also the co-author, with Jean-Louis Le Mouël, of some nine scientific publications in the past five years on climate that have passed the standard filter of scientific publications in international peer-reviewed journals (see: the most representative publications on the site of the Academy of Sciences). The recent work of his team demonstrates the magnitude of the eruptions in the Deccan traps 65 million years ago (Cretaceous-Tertiary crisis), with the extinction of the dinosaurs: lava flows of approximately 10,000 km³ could occur in a few decades, polluting the atmosphere with sulphurous gas. He has published several books for the general public ; the most recent (in French) is: Nouveau voyage au centre de la Terre (New journey to the center of the Earth ; Odile Jacob, 2009). The previous one has been published in English (Evolutionary Catastrophes: The Science of Mass Extinctions, Cambridge University Press, 1999).
To go further: -   Biography of Vincent Courtillot (by the Academy of Sciences) -   Institut de Physique du Globe de Paris-    University Denis-Diderot in Paris -    Solar forcing of the semi-annual variation of length-of-day . Geophysical Research Letters (GRL, 2010). Jean-Louis Le Mouël, Elena Blanter, Mikhail Shnirman, Vincent Courtillot. -   Vincent Courtillot, Jean-Louis Le Mouël and two fellows Russians Discover that sunspot cycles modulate the speed of rotation of our planet. Scientific publication in GRL: possible links between solar activity and climate? Read also the article by News of Tomorrow (March 2010) Original source: Pensée Unique). -   Video presentation of the book Nouveau voyage au centre de la terre  (Odile Jacob, 2009). See also the article on the site of the Editions Odile Jacob -   The spirit of adventure and the principle of precaution in science and arts I: consensus, risk and truth... an example of recent climate changes - Vincent Courtillot. In the latter part of this presentation, Vincent Courtillot explains his work published last March in GRL. (International symposium on 15-18 September 2010.) (Royal Academy of Sciences, letters and fine arts of Belgium) -   The Evolution of the species is not a long quiet river (April 2010) -   On global warming. Presentation by Vincent Courtillot (scientific days of the University of Nantes September 2009) - Volcanism or the cause of mass extinctions. Interview with Vincent Courtillot for the Radio France Culture (August 5, 2006) -   Volcanic eruptions and the evolution of species. Interview with Vincent Courtillot Canal Academy (March 2006) -   Volcanic eruptions, global climate change and the evolution of species: dinosaurs, their disappearance and our future on this planet. Video of the lecture by Vincent Courtillot of cycle "Science of the 21st century challenges" in partnership with CNRS/ccsd-IN2P3 (17 January 2006) (The scientific challenges of the twenty-first century) and http://www.academie-sciences.fr/conferences/seances_publiques/html/defis21_17_01_06.htm -   The GIEC is not the guarantor of the scientific truth (Le Figaro 2 April 2010.) (Marc Mennessier) -   Warming: when Sun is getting involved (Le Figaro 3 April 2010.) (Marc Mennessier).
Credit photos: portrait and photo coverage, Editions Odile Jacob. Vincent Courtillot standing: Jock Robey, excerpt from the book by Vincent Courtillot, new journey to the center of the Earth (Odile Jacob). Caption: "Vincent Courtillot, one foot on old 2,600 million years old 300 million years, another former pedestal glacial sediments".