The main topics of his research are:
1. From celestial mechanics to climate modelling
A. Berger is particularly known for his research on the astronomical theory of paleoclimates, the so-called Milankovitch theory (1,2). It is as early as in the late 1960s that he
approached this problem along three directions: the accuracy of the astronomical solution of
the planetary system, the calculation of the insolation (incoming solar radiation) available at
the top of the atmosphere and the modelling of climatic variations. He is one of the few
scientists to have been able to master the full multidisciplinary aspect of such a global
approach.
2. A new solution for long-term variations of the astronomical parameters
The long-term variations of the astronomical parameters of insolation that he calculated
in the early 1970s (3,5) has rapidly been internationally used, being given the accuracy
requested for paleoclimatic studies over the last one million years (the quality of this
solution allows its use worldwide since more than 35 years). The improvements that he has
introduced in the 80s (6) have extended its validity over the last few millions of years and
have stimulated new research and developments. Solutions elaborated by astronomers in
France and Canada in the early 1990s and valid over tens of millions of years have confirmed
the accuracy of the Berger's calculation (7).
3. Theoretical spectra of astronomical parameters and the double precession period
The theoretical work of André Berger led him to build original analytical developments of
both the astronomical parameters (eccentricity, obliquity and climatic precession) and the
insolation (8). These developments provide for the paleoclimatologists an easy and accurate
way to compute the numerical values requested for either the calibration of their time scale
or modelling the climate variations over the Quaternary. Moreover, they gave, for the first
time in the 1970s, the list of all the frequencies which characterize the long-term behaviour
of the astronomical parameters and their origin, both necessary to understand the spectrum
of the geological data and the results of paleoclimate simulations. In addition to the known
periods of 40 ka for obliquity and 21 ka for climatic precession, André Berger has shown off
2
the existence of periods of 400 ka, 125 ka, 95 ka and 100 ka for eccentricity, 54 ka for
obliquity and 23 ka and 19 ka for precession (4). He has indeed demonstrated the splitting of
the 21 ka precessional period into periods close to 23 ka and 19 ka. It is precisely the
existence of these two frequency components, found also in the geological data by Hays,
Imbrie and Shackleton in 1975, which according to John Imbrie has constituted "the first
most delicate and impressive of all tests for the astronomical theory".
4. Spectra of geological records and the astronomical clock
The astronomical frequencies predicted by André Berger (4) were more and more found
in paleoclimate data (9,10). These findings and the accuracy of the astronomical parameters
help to calibrate the time scale of geological records, to improve its accuracy and refine it
significantly. It is such astronomical solution which has led Shackleton et al. (11) and Hilgen
et al. (12) in the early 90s to age the currently adopted dates for the paleomagnetic polarity
reversals over the last few millions of years, this new time scale having been confirmed by
independent dating using radiometric techniques.
5. Origin and instability of the astronomical periods
The series expansions have allowed André Berger to demonstrate the links between the
periods of the three parameters (13); for example, the 19 ka and the 23 ka periods lead to all
the eccentricity periods close to 400 ka and 100 ka. A detailed analysis of the instability of
the main astronomical periods (14) and of the frequency and amplitude modulations of their
variations (15) has allowed, in particular, to trace the origin of the astronomical 100 ka
periods (16) and to show:
(i) for the eccentricity, the alternation of the predominance of the 400 ka and of the 100
ka periods with time, the weakening of the 100 ka period at the beginning of the last one
million years at a time where it becomes important in the geological record, the shortening,
at the transition between two 400 ka periods, of the 100 ka period with a weak amplitude,
and the presence of periods longer than one million years;
(ii) for the climatic precession, a weak amplitude with a short period at the 400 ka time
scale of eccentricity and of a longer period in the spectral band of 100 ka;
(iii) for obliquity, a large amplitude with a short period in the 1.3 Ma period and a longer
period in the 170 ka cycle.
3
6. Geological calibration of the astronomical solution
Contrary to the calibration of the geological time scale from the astronomical one over
the last few millions of years, climatic variations over the last tens of millions of years are
used now to improve the calculation of the astronomical parameters. This approach, already
recommended by André Berger, André Deprit and Pierre Bretagnon in 1982 at the
symposium organised at the Lamont Doherty Geological Observatory, has been used by
Nicholas Shackleton and Fred Hilgen in the early 1990s.
7. Pre-Quaternary astronomical frequencies
This astronomical theory is not only valid for the Quaternary, but also for more remote
times of the past (tens to hundreds of millions of years). This is why André Berger and his
colleagues (17,18) have calculated the impact of the very long-term variation of the
elements of the Earth-Moon system and of the Earth's rotation on the frequencies,
amplitudes and phases of the astronomical parameters. The shortening of the periods that
they have predicted has been confirmed by Alfred Fisher from paleoclimate data of the
Cretaceous.
8. Daily insolation
In addition to improving the accuracy of the astronomical elements, he has also extended
the Milankovitch theory. Trained in meteorology, he was aware of the importance of the
daily irradiation for simulating climate with models based on first principles. He introduced
and computed the long-term variations of daily, monthly and seasonal insolations (8) which
he has provided the users with easy manageable formula (all his calculations became public
domain which is undoubtedly affecting his citation index).
He showed that contrary to the caloric season insolations (19) of Milankovitch, (i) daily
insolation varies with a much larger amplitude reaching, for example, 20 % over 10,000 years
at 65°N in June 115,000 years ago (8) and (ii) that the spectral structure of his insolation
parameters is much more diverse (21).
4
He has also demonstrated taht cycles of 100 ka, 11 ka and 5.5 ka are really present in the
equatorial insolation in response to the double culmination of the Sun over a year in these
regions (22). He has also calculated rigorously the total irradiation available over any given
period during the year (23) allowing an easy and accurate way to compute the energy
received from the Sun, including in high polar latitudes where the Milankovitch
developments are not convergent
9. One of the very first EMICs
Aware of the importance of a rigorous and adequate modeling for better understanding
climatic variations, André Berger has created in the 80s a multi-disciplinary modeling group.
Their LLN coupled atmosphere-ocean-sea ice-inlandsis-carbon cycle model (24) has allowed
them to make the first simulation, ever succeeded, of the transient response of the climate
system to the astronomical forcing over the last glacial-interglacial cycles (25,26) based on
first principles and in agreement with the geological records
This model was particularly successful in simulating the entrance into glaciation around
2.7 Myr BP (27), the late Pliocene-early Pleistocene 41-kyr cycle and its transition towards
the 100-kyr cycle around 900 kyr BP (28,29), the glacial-interglacial cycles of the middle and
late Pleistocene (30) and the necessity of a high greenhouse gas concentration to make the
climates of 400 ka ago (isotopic stage 11) and of to-day (Holocene) full interglacials (31). .
This type of models – presently popularised as Earth System Models of Intermediate
Complexity by Martin Claussen and colleagues (32) – is now recognized to be a key link
between the general circulation models and the more simple models for understanding the
long-term climatic variations. This LLN model was also used as an instrument for training
scientists and is at the origin of the development of more complex general circulation
models in Louvain-la-Neuve.
10. Our exceptionally long interglacial
André Berger was the first to claim that our interglacial might be much longer than
the others (contrary to what was generally thought) because of the atypical almost circular
shape that the Earth’s orbit is approaching now (33). Climate modelling experiments that he
made with his team confirms that our climate would remain interglacial for the next tens of
thousands of years before entering the next ice age. This is particularly critical because the
atmospheric CO2 concentration is presently exceptionally high as compared to the past
(more than 1.5 times the average of the last 400,000 years). These results lead him to
5
forebode that the impact of man’s activities on climate might interfere with the climatic
evolution at the geological time scale (34,35). The potential that André Berger’s work offers
for analysing the range of such possible future climates is acknowledged, in particular in
assessments of the climatic stability at the repository sites for nuclear wastes produced in
atomic power plants, a study that André Berger has launched with a few others at the
international scale, of the possible origin of human impacts on climate well before the last
century (William Ruddiman hypothesis) and of the birth of the Anthropocene of Paul
Crutzen.
11. Feedbacks and non-linearities in paleoclimate models
The LLN model, being a compromise between scientific complexity and practical
manageability, allows easily to test the sensitivity of the climate system to the different
forcings. They have shown:
- the importance of the long-term variations of insolation which alone can generate glacialinterglacial cycles (37) confirming that the variations of the astronomical parameters are a
pacemaker of the Ice Ages. Such simulations using different constant atmospheric CO 2
concentrations lead them to suggest that there might be thresholds in the CO 2 values
around which the sensitivity of climate to CO2 could be totally different,
- that their model cannot generate any glacial-interglacial cycle in the ice volume using only
a variable CO2 (38),
- that non-linearities in the climate system are fundamental to generate, in response to
insolation, the 100 ka (39) and other periods shorter than 10 ka (40),
- the significant amplification by water vapour of the response of the climate system to both
the astronomical and greenhouse gas forcings during the last glacial-interglacial cycle (41).
- the fundamental role of the feedbacks between albedo and temperature (42), land surface
cover and snow field albedo (43), sea-level and ice volume (44), isostatic rebound and
inlandsis (45), continentality and altitude effects of the ice sheets and of snow properties
(46). – the lag between insolation, ice volume and sea-surface temperature (47).
They have also analysed:
- the impact of the high frequency variations in insolation (48,49),
6
- the response of the climate system to the insolation forcing and to volcanic, solar and
human activities over the last millennium (50,51) and the Holocene (52)
- the climate evolution during the last deglaciation (53),
- the importance of the 400 ka cycle, already pointed out by André Berger in 1989 during the
IPCC meeting of Working Group I in Bath, for the isotopic stage 11 (34), the isotopic stage 19
(54), the present interglacial (55) and its future (56).
Since 2005, André Berger has started with Qiuzhen Yin investigating:
- the isotopic stage13 where they have shown a possible strengthening of the East Asian
Summer monsoon by a wave train generated by the Eurasian ice sheet (57,58),
- the interglacials of the last 800 ka, stressing the relative impact of insolation and
greenhouse gas (54) and the role plaid by insolation in the explanation of the diversity of the
interglacials.
12. Other works
André Berger has also worked on air pollution modelling, data analysis and persistence
theory. He published reviewer papers on nuclear winter (59), desertification, deforestation,
human impacts on climate (60,61) and climate variations over the Earth history (62).
13. Training and diffusion of knowledge
André Berger contributes also significantly to the training of research scientists, to the
stimulation of a multi- and inter-disciplinary approach of the environmental problems, to
international collaboration and to the diffusion of environmental science through the public
at large. He is deeply convinced that one of the actions towards improving the environment
protection and insuring a sustainable development is teaching and education in
environmental sciences from primary schools to the University. Media and cultural
associations appreciate his syntheses and critical reviews of environmental issues, as well as
of the history and evolution of climate that he explains in clear but responsible terms.
7
REFERENCES
1.
BERGER, A., 1988. Milankovitch Theory and Climate. Review of Geophysics, 26(4), pp.
624-657.
2.
BERGER, A., 1989. Théorie astronomique des paléoclimats (en chinois). Chinese
Translation, Bulletin of Glaciology and Geocryology, 6(2), pp. 79-80.
3.
BERGER, A., 1976. Obliquity and general precession for the last 5 000 000 years,
Astronomy and Astrophysics, 51, 127-135.
4.
BERGER, A., 1977. Support for the astronomical theory of climatic change. Nature,
268, 44-45.
5.
BERGER, A., 1977. Long-term variations of the ecliptical elements. Celestial echanics,
15, 53-74.
6.
BERGER A., LOUTRE M.F., 1991. Insolation values for the climate of the last 10 million
years. Quaternary Science Reviews, 10 n°4, pp. 297-317.
7.
BERGER A., LOUTRE M.F., 1992. Astronomical solutions for paleoclimate studies over
the last 3 million years. Earth and Planetary Science Letters, 111, pp. 369-382.
8.
BERGER, A., 1978. Long-term variations of daily insolation and Quaternary Climatic
Changes. Journal of Atmospheric Science, 35(12), 2362-2367.
9.
BERGER, A., 1989. Pleistocene climatic variability at astronomical frequencies.
Quaternary International, 2, pp. 1-14.
10. HOOGHIEMSTRA H., MELICE J.L., BERGER A., SHACKLETON N.J., 1993. Frequency
spectra and paleoclimatic variability of the high resolution 30-1450 kyr FUNZA 1
pollen record (eastern Cordillera, Colombia). Quaternary Science Reviews, 12 n°2, pp.
141-156.
11. SHACKLETON N.J., BERGER A., PELTIER W.R., 1990. An alternative astronomical
calibration of the lower Pleistocene time scale based on ODP site 677. Phil.
Transactions of the Royal Society of Edinburgh: Earth Sciences, vol. 81 part 4, pp. 251261.
12. HILGEN, F.J., LOURENS L.J., BERGER A., LOUTRE M.F., 1993. Evaluation of the
astronomically calibrated time scale for the late Pliocene-Earliest Pleistocene.
Paleoceanogoraphy, 8(5), pp. 549-565.
13. BERGER A., LOUTRE M.F., 1990. Origine des fréquences des éléments astronomiques
intervenant dans le calcul de l'insolation. Bulletin Sciences, 1-3/90, pp. 45-106, Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique.
14. BERGER A., LOUTRE M.F. and J.L. MELICE, 1998. Instability of the astronomical periods
from 1.5 Myr BP to 0.5 Myr AP. Paleoclimates Data and Modelling, 2(4), pp. 239-280.
15. MELICE J.L., CORON A. and A. BERGER, 2001. Amplitude and frequency modulations of
the Earth’s obliquity for the last million years. Journal of Climate, 14(6), pp. 1043-1054.
8
16. BERGER A., MELICE J.L. and M.F. LOUTRE, 2005. On the origin of the 100-kyr cycles in
the
astronomical
forcing.
Paleoceanography,
20(4),
PA4019,
DOI:
10.1029/2005PA001173.
17. BERGER, A., LOUTRE, M.F., DEHANT, V., 1989. Pre-Quaternary Milankovitch
frequencies. Nature, 342, p. 133.
18. BERGER A., LOUTRE M.F., LASKAR J., 1992. Stability of the astronomical frequencies
over the Earth's history for paleoclimate studies. Science, 255, pp. 560-566.
19. BERGER, A., 1978. Long-term variations of caloric insolation resulting from the Earth's
orbital elements. Quaternary Research, 9, 139-167.
20. BERGER, A., 1976. Long term variations of daily and monthly insolation during the Last
Ice Age. EOS, 57(4), p.254.
21. BERGER A., LOUTRE M.F., and TRICOT Ch., 1993. Insolation and Earth's orbital periods.
J. Geophys. Research, 98 n° D6, pp. 10,341-10,362.
22. BERGER A., LOUTRE M.F. and J.L. MELICE, 2006. Equatorial insolation: from precession
harmonics to eccentricity frequencies. Climate of the Past, 2, pp. 131-136.
23. BERGER A., LOUTRE M.F. and Q.Z. YIN, 2010. Total irradiation during the interval of the
year using elliptical integrals. Quaternary Science Reviews. 29, 1968-1982
24. GALLEE, H., van YPERSELE, J.P., FICHEFET, Th., TRICOT, Ch., BERGER, A., 1991.
Simulation of the last glacial cycle by a coupled sectorially averaged climate - ice-sheet
model. I. The Climate Model. J. Geophys. Res., 96, pp. 13,139-13,161
25. BERGER, A., GALLEE, H., FICHEFET, Th., MARSIAT, I., TRICOT, Ch., 1990. Testing the
astronomical theory with a coupled climate-ice sheet model. in : L.D. Labeyrie and C.
Jeandel (Eds), Geochemical variability in the Oceans, Ice and Sediments. Palaeogr.,
Palaeoclimatol., Palaeoecol., 89(1/2), Global and Planetary Change Section, 3(1/2), pp.
125-141.
26. GALLEE, H., van YPERSELE, J.P., FICHEFET, Th., MARSIAT, I., TRICOT, Ch., BERGER, A.,
1992. Simulation of the last glacial cycle by a coupled, sectorially averaged climate ice-sheet model. II. Response to insolation and CO2 variation. J. Geophys. Res., 97
n°D14, pp. 15,713-15,740.
27. LI X.S., BERGER A., LOUTRE M.F., MASLIN M.A., HAUG G.H., and R. TIEDEMANN, 1998.
Simulating late Pliocene Northern Hemisphere climate with the LLN 2-D model.
Geophysical Research Letters, 25(6), pp. 915-918.
28. MASLIN M.A., LI X.S., LOUTRE M.F., and A. BERGER, 1998. The contribution of orbital
forcing to the progressive intensification of Northern Hemisphere glaciation. Quat. Sci.
Rev., 17, pp. 411-426.
29. BERGER A., LI X.S. and M.F. LOUTRE, 1999. Modelling northern hemisphere ice volume
over the last 3 Ma. Quaternary Science Reviews, 18, pp. 1-11.
30. BERGER, A., FICHEFET, Th., GALLEE, H., TRICOT, Ch., van YPERSELE, J.P., 1992. Entering
the glaciations with a 2-D coupled climate model. Quaternary Science Reviews, vol. 11
n°4, pp. 481-493.
31. LI X.S., BERGER A., and M.F. LOUTRE, 1998. CO2 and Northern Hemisphere ice volume
variations over the middle and late Quaternary. Climate Dynamics, 14, pp. 537-544.
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32. CLAUSSEN M., MYSAK L.A., WEAVER A.J., CRUCIFIX M., FICHEFET T., LOUTRE M.F.,
WEBER S.L., ALCAMO J., ALEXEEV V.A., BERGER A., CALOV R., GANOPOLSKI A., GOOSSE
H., LOHMAN G., LUNKEIT F., MOKHOV I.I., PETOUKHOV V., STONE P., WANG Z., 2002.
Earth system models of intermediate complexity : closing the gap in the spectrum of
climate system models. Climate Dynamics, 18, pp. 579-586; DOI 10.1007/s00382-0010200-1.
33. BERGER A. and M.F. LOUTRE, 1996. Modeling the climate response to the
astronomical and CO2 forcings. Comptes Rendus de l’Académie des Sciences de Paris,
t. 323, série II a, pp. 1-16.
34. BERGER A. And M.F. LOUTRE, 2002. An Exceptionally long Interglacial Ahead ?
Science, 297, pp. 1287-1288.
35. BERGER A., LOUTRE M.F. and M. CRUCIFIX, 2003. The Earth’s climate in the next
hundred thousand years (100 kyr). Surveys in Geophysics, 24, pp. 117-138.
36. CRUCIFIX M. and A. BERGER, 2006. How long will our interglacial be?
Transactions, AGU, 87(35), pp. 352-353.
EOS,
37. BERGER A., LOUTRE M.F., and H. GALLEE, 1998. Sensitivity of the LLN climate model to
the astronomical and CO2 forcings over the last 200 kyr. Climate Dynamics, 14, pp. 615629.
38. LOUTRE M.F. and A. BERGER, 2000. No glacial-interglacial cycle in the ice volume
simulated under a constant astronomical forcing and a variable CO2. Geophysical
Research Letters, 27(6), pp. 783-786.
39. IMBRIE J., BERGER A., BOYLE E.A., CLEMENS S.C., DUFFY A., HOWARD W.R., KUKLA G.,
KUTZBACH J., MARTINSON D.G., McINTYRE A., MIX A.C., MOLFINO B., MORLEY J.J,
PETERSON L.C., PISIAS N.G., PRELL W.L., RAYMO M.E., SHACKLETON N.J., and J.R.
TOGGWEILER, 1993. On the structure and origin of major glaciation cycles. 2. The
100,000-year cycle. Paleoceanography, 8(6), pp. 699-735.
40. PESTIAUX, P., DUPLESSY, J.Cl., VAN DER MERSCH, I., BERGER, A., 1988. Paleoclimatic
variability at frequencies ranging from 1 cycle per 10,000 years to 1 cycle per 1,000
years : evidence for nonlinear behavior of the climate system. Climatic Change, 12(1),
pp. 9-37.
41. BERGER A., TRICOT C., GALLEE H., and M.F. LOUTRE, 1993. Water vapour, CO2 and
insolation over the last glacial-interglacial cycles. Philosophical Transactions of the
Royal Society, London, B, 341, pp. 253-261.
42. BERGER, A., GALLEE, H., TRICOT, Ch., 1993. Glaciation and deglaciation mechanisms in
a coupled 2-D climate - ice sheet model. J. of Glaciology, 39 n° 131, pp. 45-49.
43. BERGER A., 2001. The role of CO2, sea-level and vegetation during the Milankovitchforced glacial-interglacial cycles. In : « Geosphere-Biosphere Interactions and
Climate », Lennart O. Bengtsson and Claus U. Hammer (eds), pp. 119-146, Cambridge
University Press, New York.
44. MARSIAT, I., BERGER, A., 1990. On the relationship between ice volume and sea level
over the last glacial cycle. Climate Dynamics, 4(2), 81-84.
45. CRUCIFIX M., LOUTRE M.F., LAMBECK K. and A. BERGER, 2001. Effect of isostatic
rebound on modelled ice volume variations during the last 200 kyr. Earth and Planetary
Science Letters, 184, pp. 623-633.
10
46. BERGER, A., FICHEFET, Th., GALLEE, H., MARSIAT, I., TRICOT, Ch., van Ypersele J.P.,
1990. Physical interactions within a coupled climate model over the last glacialinterglacial cycle. Phil. Transactions of the Royal Society of Edinburgh : Earth Sciences,
vol. 81 part 4, pp. 357-369.
47. BERGER, A., GALLEE, H., LI, X.S., DUTRIEUX, A., and M.F. LOUTRE, 1996. Ice-sheet
growth and high latitudes sea-surface temperature. Climate Dynamics, 12, pp. 441-448.
48. LOUTRE M.F., BERGER A., BRETAGNON P., BLANC P.L., 1992. Astronomical frequencies
for climate research at the decadal to century time scale. Climate Dynamics, 7, pp. 181194.
49. BERTRAND C., LOUTRE M.F. and A. BERGER, 2002. High frequency variations of the
Earth's orbital parameters and climate change. Geophysical Research Letters, 29(18),
1893; DOI 10.1029/2002GL015622.
50. BERTRAND C., LOUTRE M.F., CRUCIFIX M. and A. BERGER, 2002. Climate of the Last
Millenium : A sensitivity study. Tellus, 54A, pp. 221-244.
51. BERTRAND C., van YPERSELE J.P., and A. BERGER, 2002. Are natural climate forcings
able to counteract the projected anthropogenic global warming ? Climatic Change,
55(4), pp. 413-427.
52. CRUCIFIX M., LOUTRE M.F., TULKENS Ph., FICHEFET T. and A. BERGER, 2002. Climate
evolution during the Holocene : A study with an Earth system model of intermediate
complexity. Climate Dynamics, 19, pp. 43-60; DOI 10.1007/s00382-001-0208-6.
53. CRUCIFIX M. and A. BERGER, 2002. Simulation of ocean-ice sheets interactions during
the deglaciation. Paleoceanography, 17(4), 1054, DOI: 10.1029/2001PA000702
54. YIN Q.Z. and A. BERGER, 2010. Insolation and CO2 contribution to the interglacials before
and after the Mid-Brunhes Event. Nature Geoscience, 3(4), pp. 243-246.
55. LOUTRE M.F. and A. BERGER, 2003. Marine Isotope Stage 11 as an analogue for the
present interglacial. Global and Planetary Change, 36, pp. 209-217. DOI:
10.1016/S0921-8181(02)00186-8.
56. BERGER A. and M.F. LOUTRE, 2003. Climate 400,000 years ago, a key to the future ? In :
Earth’s Climate and Orbital Eccentricity: The Marine Isotope Stage 11 Question.
Geophysical Monograph 137, A. Droxler, L. Burckle and R. Poore (eds), American
Geophysical Union, pp. 17-26.
57. BERGER A., 2009. Monsoon and general circulation system. Chinese Science Bulletin,
54(7), pp. 1111-1112.
58. YIN Q.Z., BERGER A., and M. CRUCIFIX, 2009. Individual and combined effects of ice
sheets and precession on MIS-13 climate. Climate of the Past, 5, pp. 229-243.
59. BERGER, A., 1986. Nuclear winter or nuclear fall ? EOS, 67(32), pp. 617-621
60. BERGER A., 2005. Le réchauffement du climat au XXIe siècle : causes et
conséquences. Bulletin de la Classe des Sciences, 6e série, Tome XVI, 7-12, Académie
royale de Belgique, pp. 323-339.
61. BERGER A., 2009. Changement climatique, état des lieux. In: “Ethique et Changement
Climatique”, O. Abel, E. Bard, A. Berger, J.M. Besnier, R. Guesnerie, M. Serres (eds),
Le Pommier, Paris, pp. 17-57.
11
62. BERGER A., 2001. Le climat et ses variations depuis l’origine de la Terre. Une
composante à l’évolution de la vie. In : L’Environnement de la Terre Primitive, M.
Gargaud, D. Despois, J.P. Parisot (eds), pp. 131-162, Presses universitaires de Bordeaux,
Pessac, France.