Where Astronomy Meets Geology:
From Ice Ages to Global Warming
André Berger
Université catholique de Louvain
Institut d’Astronomie et de Géophysique G. Lemâitre
2 Chemin du Cyclotron
1348 Louvain-la-Neuve
1. One of the greatest challenges in climate research remains today the explanation
of the glacial-interglacial cycles during the Ice Ages. About 3 Ma ago, the Earth
entered into the Quaternary Ice Age. During such Ice Age the climate is not only
globally cooler, but it oscillates also between two extremes, the glacials and
interglacials, with an average periodicity of  100 ka. The Last Glacial Maximum
occurred 20 ka ago and was characterized by huge ice sheets, 1 to 2 km thick,
mainly in the northern hemisphere amounting to about 50 10 6 km3 of ice more than
now. Sea level was  120 meters below present day and the global average air
temperature at the surface was only 5°C lower than now in spite of such a
difference in the land surface cover. Analysis of the chemical composition of air
bubbles trapped in the ice sheets show also that the atmospheric mean
concentration of CO2 was  200 ppmv (it is presently 370). Such an icy situation
took about 90 ka to be created, but it took only about 10 ka to melt all this
exceeding ice. About 8 ka ago, the melting of the Eurasian ice sheet was
completed totally and a few thousands of years later it was the case for the
Northern American ice sheets. The climate at the so-called Climatic Optimum (6-7
ka BP) was quite similar to the present-day climate (out of the impact of man’s
activities): slightly warmer globally, a sea level a few meters more, and a CO 2
concentration of  280 ppmv.
2
2. Owing to the CLIMAP programme in the 1970’s and 80’s (Climate Long Range
Investigation, Mapping and Prediction) under the leadership of John Imbrie from
Rhode Island University in Providence, climate started to be reconstructed
worldwide. On this photograph you might recognize from left to right, Jim Hays
from Lamont Doherty Geological Observatory (Columbia University, new York),
Vasko Milankovitch and John Imbrie.
3. This programme reconstructed in particular the ice and sea-surface temperature
conditions prevailing at the Last Glacial maximum.
4. These sea-surface temperatures, particularly in the tropics, are now being revisited
by the EPILOG programme (Environmental processes of the ice age, land, oceans
and glaciers), whereas the continental data have been summarized recently under
the initiative of Nicole Petit-Maire within the framework of the Commission for the
geological map of the world.
5. At this last Glacial maximum, climate must have been rough up to southern France
as indicated by the paintings of our ancestors, in the Lascaux cave for example.
6. In the 1980’s CLIMAP was followed by SPECMAP which intended to produce time
series reconstructions of past climate and their spectral properties, instead of time
slices. This led to a stacked curve constructed from different deep-sea core proxy
records. Its radiometrically controlled time scale was progressively orbitally tuned
in an iterative process. For the last 200 ka, variations in the 18O proxy data for the
ice volume show clearly the saw-tooth shape of the last glacial-interglacial cycle
going from isotopic stage 5 (with 5e being the previous interglacial, called Eemian
in Europe and Sangamonian in North America) to 1(our present-day Holocene
interglacial).
7. This curve has been extended to 800 ka BP and shown for the first time at the
Milankovitch symposium in 1982. Its time scale has been refined over the last
decades, in particular by aging the Brunhes-Matuyama boundary.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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8. The photograph with all the participants ( 100) shows that this was (and is still) a
hot and very popular topic. On this photograph you may recognize Vasko
Milankovitch, John Imbrie, Suky Manabe, Steve Schneider, Jim Hays, the late
John Murray Mitchell, Nick Shackleton, Bill Sellers and Michael Ghil among many
other scientists who were already famous or became since then.
9. But this kind of long-term changes is also found in other very well known data, like
those recorded in the Vostok ice core.
CO2 and CH4 concentrations and
temperature above Antarctica over the last 400 ka display also a very clear 100 ka
signal on which high frequencies are superimposed.
10. Spectral analyses of the SPECMAP curve in particular show an overall red noise
shape of the spectrum on which very significant peaks are superimposed at
periods of 100 ka, 41 ka, 23 and 19 ka.
Actually, these periods are characteristic of the long-term changes of 3
astronomical parameters which altogether determine the distribution in latitudes
and seasons of the energy that the Earth receives from the Sun.
This observation is at the basis of the astronomical theory of paleoclimates,
which most popular version is due to Milutin Milankovitch.
11. Milutin Milankovitch was a serbian mathematican who specialised in astronomy
and geophysics. He was born on 28th May 1879 in DaIj, Slavonia (part of AustroHungary until 1919; then part of Jugoslavia and now in Croatia). He died in
Belgrade on 12th December 1958. He graduated as a doctor of technical
sciences on 17th December 1904 from the Technical High School of Vienna. On
the 1st October 1909, he was elected professor at the University of Belgrade
where he lectured on Rational Mechanics, Theoretical Physics and Celestial
Mechanics, until his retirement 46 years later. He was a member of the Serbian
Academy of Sciences, Jugoslav Academy of Sciences and Arts, German
Academy of Naturalists, Leopoldine Halle and Italian Institute of Paleontology.
12. Milutin Milankovitch was a contemporary of Alfred Wegener (1880-1930) with
whom he became acquainted through Vladimir Köppen (1846-1940), Wegener’s
father in law.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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13. It is roughly between 1915 and 1940 that M. Milankovitch put the astronomical
theory of the Pleistocene ice ages on a firm mathematical basis. His first book,
written in French, dates from 1920, but his massive Special Publication of the
Royal Serbian Academy of Sciences on Kanon der Erdbestrahlung was
published in German in 1941
14. and was translated into English in 1969 and reprinted in 1998.
15. Milutin Milankovitch wrote some 70 books and papers, including some on popular
astronomy. He was involved in the reform of the Julian calendar, became even a
writer and wrote his memoirs: “not because I thought I was such an important
person, but because I have lived in an historically interesting and turbulent
period, and I described these events as a trustworthy witness. My work spanning
some 30 years, has been closely connected with the work of other scientists who
have used my results in their respective fields. The mutual collaboration has
been documented with more than 600 letters and 100 publications. Therefore,
these memoirs are, for a good part, the history of a branch of the sciences called
“Astronomical Theory of Climatic Changes”.”
16. These memoirs were the basis of the unique biography written in English on
Milutin Milankovitch by his son Vasko Milankovitch (1995).
17. Milankovitch’s main contribution was to explore the solar irradiance at different
latitudes and seasons in great detail, to compute its long-term variations from the
orbital parameters and to relate them in turn with climate.
18. His theoretical investigation provided the basis for the core of his argument that
“under those astronomical conditions in which the heat budget around the
summer solstice falls below average, so will summer melt, with uncompensated
glacial advance being the result”.
19. The essential product of the Milankovitch theory is therefore his curve
demonstrating how the intensity of summer sunlight varied over the past 600,000
years. This curve was used to identify the European ice ages reconstructed by
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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Albrecht Penck and Eduard Bruckner, from which he concluded that these
geological data constituted a verification of his theory.
Up to the 1960’s, the Milankovitch theory was disputed as a result of discussions
based on fragmentary geological records and because the climate was
considered too resilient to react to “such small changes” as observed in the
caloric summer insolation. Milankovitch was little disturbed by these different
opinions believing firmly that his theory was correct. In the late 1960’s a
systematic approach and use of modern techniques led to major discoveries
which progressively supported his essential concept, namely that orbital
variations exert a significant influence on climate.
20. But MM was not the only one who came with the idea of relating celestial
mechanics to paleoclimates. There were a few before him. An extensive list is
given in my 1988 paper in Review of Geophysics and a historical perspective is
given in John and Katherine Imbrie 1979 book. In the early nineteenth century
Herschel, Adhemar, Croll, Murphy came with different ideas stressing the winter
or the summer season and putting more emphasis on one astronomical
parameter or the other. This continued into the second-half of the XXth century
up to the time that better geological records and time scale and numerical models
became available to test the reliability of such hypotheses. These discussions
continue and many hypotheses are still presented today.
21. This introduction aimed to show the multi-and inter-disciplinarity of such
astronomical theories of past climatic changes. They actually involve 3
fundamental sciences: astronomy and celestial mechanics, mathematics and
geometry of the insolation, and climate modeling including the verification of the
results using geological reconstructions. Moreover, if such a theory works for the
past, it is tempting to use it for the future and to analyse whether the impacts of
man’s activities during the early 3d millennium can interact with the
astronomically-induced climatic variations.
22. What are these 3 parameters. The eccentricity, e , is a measure of the shape of
the elliptical orbit. Larger it is, more distant is the Earth away from the Sun at the
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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aphelion. Its present-day value is 0.016. As the difference between the distances
at aphelion and perihelion is proportional to 2 e , the differences between the
energy is proportional to 4 e . For example, at present-day the Earth receives
6.4% more energy at the perihelion than at the aphelion.
Moreover the average energy received by the Earth over one year is inversely
proportional to
1  e2 . It means that on an elongated orbit the Earth receives
annually more energy than on a circular one, the difference being of the order of
per mil.
The obliquity,
 , is the tilt of the Earth orbit on the equatorial plane. When the
obliquity increases the latitudes of the summer hemisphere receive more energy.
For 1° of obliquity increase, the total energy received by the summer hemisphere
increases by  1%.
23. Another interesting consequence of the obliquity change is the equatorward
motion of the tropical circles and the poleward motion of the polar circles, when it
decreases, for example. Presently, it is  1.4 km/century as
 decreases at a
rate of –46.85”/century.
24. The climatic precession is a more difficult parameter to understand: it is a
measure of the Earth – Sun distance at a particular season. It is however
straightforward to see that the energy received increases everywhere over the
Earth in summer (seasons refer to the local seasons of the Northern
Hemisphere) when the summer solstice occurs at perihelion as compared to
aphelion, the reverse being true for the winter.
25. As a consequence of the astronomical precession, the North Pole pointed to the
Dragon 5000 years ago (3000 B.C.) and will point to
 -Cepheid within 5000
years (7000 A.D.). Also some 2000 years ago, the Sun was entering the Pisces
constellation at the beginning of Spring, whereas it is now entering Aries.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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26. Le Verrier in France, Miskovitch in Russia and later Milankovitch have calculated
the long-term variations of these astronomical parameters. They are obtained by
solving the set of equations which govern the motion of the planets around the
Sun and the motion of the Earth axis due to the attraction of the Moon and the
Sun on the equatorial buldge of the Earth. Their accuracy depend upon the
accuracy of the planetary masses, of the initial values of the different parameters,
and with which the perturbation function.
I have recalculated these values in the 70’s based upon the theories of
Bretagnon in France and Sharaf and Budnikova in Russia. Besides a better
accuracy, my formulation also provides an easy way for computing the numerical
values and a direct spectrum of these parameters. Expansion show easily that
obliquity is varying with an average periodicity of 41 ka which corresponds to the
largest amplitudes term of the series. In precession, there are actually four main
frequencies grouped around two principal periods of  23 ka and 19 ka, leading
to an average period of 21 ka. It is actually the discovery of this double
periodicity, found independently both in the geological data and in the
astronomical solution, which was one of the first delicate and most impressive
tests of the Milankovitch theory. For eccentricity, the series is slowly convergent;
400 ka corresponds definitely to the largest amplitude but the number of terms
which periods are very close to 100 ka explains why its average period of
variation is  100 ka.
27. With this formula, curves can be easily drawn.
For the present day, we see:
-
eccentricity is small and will reach almost zero within the next 20 to 30
thousands of years;
-
this will make e sin  almost not varying anymore, its amplitude becoming
extremely small.
At the present summer occurs at aphelion, but will at perihelion within 10 000
years.
-
Obliquity is at intermediate value and decreasing
10 ka ago, e was maximum, but weak, summer solstice occurred at perihelion
and
 was maximum, all conditions leading to high insolation in northern high
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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latitudes in summer and being most probably at the origin of the Holocene
interglacial.
28. Mathematics of insolation shows that the long-term variations of the daily
insolation values are controlled mainly by precession except for the latitudes
close to the polar night. Obliquity, however, plays a more important role in high
than in low latitudes. This explains why the amplitude of the insolation variation at
65°N in June for example will remain small over the next tens of thousands of
years, a behaviour totally different from the Eemian times. At least from a pure
astronomical point of view, the Eemian is not a good analogue for the future and
we must go 400 000 years back in time to find the first astronomical analogue to
our present and future insolation.
29. This is not only true for 65°N but for all latitudes as shown on this figure.
30. As a consequence, the Milankovitch insolation requirement can now be
 must be low, summer must occur
at aphelion which must be as far away from the Sun as possible ( e large).
transformed into 3 conditions: for a glacial,
31. However, Milankovitch himself was among the very firsts to claim that modeling
the response of the climate system to the astronomical forcing was the only way
to test the theory.
32. As it is a time dependent problem, the cause and effect relationship can only be
analysed using long-term transient simulations. This is a complementary
approach to the equilibrium simulations which aim to provide a snapshot view of
the climate in equilibrium with the boundary conditions. This important topic
requires 3-D general circulation models. However, because of their high level of
complexity, these models can not, at the present, be integrated for periods more
than 1000 years, especially when they include the atmosphere, the oceans and
the cryosphere in a coupled mode.
This is why in the late 70’s, I have initiated the construction of a model of
intermediate complexity. Others, in particular Michel Ghil and his colleagues,
have concentrated their effort on more focussed processes or on non-linear
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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system dynamics where the climate system can be considered as a internally
driven system where the oscillations are, or not, phase-locked by external
forcing.
Our model is a 2.5-D sectorial model. It is a latitude-altitude model where each
zonal belt is subdivided into at least 7 sectors. The atmosphere, hydrosphere,
cryosphere and lithosphere are coupled together. The version used here
comprises only the Northern Hemisphere with a parameterization of the Hadley
cell to avoid an equatorial wall and of the meridional transfert of heat by the
ocean in order to compensate for using only an upper oceanic mixed layer. The 3
ice sheets (Eurasian, Greenland and North American) are reconstructed through
a predictive equation for the altitude of their crest in each zonal belt and a double
parabolic shape for their longitudinal extent. The isostatic rebound is calculated
using a time dependent diffusive equation of the asthenosphere along latitude.
Sensitivity analysis of this model have clearly shown that a series of processesfeedbacks are of primary importance for simulating the gross climatic features
with a pretty good confidence.
33. These are the feedbacks between albedo and temperature, water vapor and
temperature, snow/albedo and land cover, sea level and ice volume, ice sheet,
lithosphere
and
climate
(including
continentality
and
altitude
effects).
Experiments show that all of them are necessary and that their synergism might
be as important as the processes themselves.
34. The first simulation that was completed in the 80’s concerned the last 125 000
years. Comparison to the ice volume proxy record shows that the model
reproduces quite well the low frequency part of the climatic variations over the
last glacial-interglacial cycle, with room for improvement.
35. The timing of the deglaciation was also pretty well simulated with the Eurasian ice
sheet disappearing totally 8 ka BP, followed by the North American one 3000
years later.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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36. The spectral characteristics are in perfect agreement with those of geological
data, in particular SPECMAP. The 100 ka, 41, 23 and 19 ka periods appear with
the right amplitude.
37. This kind of simulation is important to understand the mechanisms acting in the
climate system and the sensitivity of the climate system to external forcings in
particular. As the model does not include yet an interactive CO 2-cycle, the
atmospheric CO2 concentration from Vostok is used also as an external forcing,
although it is a feedback in the real world.
Using the separation factors technique (by Stein and Alpert), it is shown that the
4.5°C cooling at the Last Glacial Maximum results from the response to the
astronomical forcing and the ice-albedo feedback (AA) for 1.8°C, to the CO2
forcing for 0.9°C and from the water vapour feedback (associated to AA for 1.2°C
and associated to CO2 for 0.6°C). It is interesting to know that the sensitivity of
our model to a doubling of pre-industrial CO2 is about 2°C.
38. If the model is forced over the last hundreds of thousands of years, the 100 ka
cycle is sustained, although the ice sheets in the Northern Hemisphere melt too
often during the interglacials. If the astronomical forcing is used with a constant
CO2 concentration, the 100 ka cycle can only be sustained for CO 2 value below
230 ppmv which is about the average value over the last 400,000 years. For
concentrations larger than 270 ppmv, the ice sheets melt most of the time.
Moreover, the response of the model shows that there are threshold levels of
CO2 around which the sensitivity of the climate system is different in response to
the state of the ice cover.
On the contrary if CO2 is the only varying external forcing, the 100 ka cycle never
appears in the simulated ice volume. For a cool/cold orbit, a huge amount of ice
is formed which never melts; for a warm/hot orbit, ice sheets never appear.
39. Another key test for the reliability of the model is to show whether or not it is
capable to simulate the transition at around 900 ka BP between the dominant 41
ka cycle and a dominant 100 ka cycle which is seen in the geological record.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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40. Climate was therefore simulated starting 4 Ma years ago using the astronomical
forcing and a CO2 atmospheric concentration decreasing linearly from 450 to 200
ppmv at the LGM. Although the agreement in the spectral domain is not perfect,
the 100 ka signal appears around 900 kyr and strengthens during the whole
middle to late Pleistocene.
Finally this simulation reproduces quite well the entrance into glaciation around
2.8 Ma BP (CO2 being less than 370 ppmv in these early times).
41. Let us now concentrate to the future remembering that for the next tens of
thousands of years, insolation will not change much.
42. As I told already, the model has not yet a coupled CO 2-cycle included. Therefore
scenari of CO2 had to be built. In particular it is assumed here that the CO 2 of the
last 125 000 years will repeat itself in the future. Although it is a questionable and
rough scenario, sensitivity analyses have shown that the response of our climate
model is quite robust. Although CO2 is decreasing steadily after 30 ka AP, the
climate remains interglacial up to 50 ka AP, a behavior totally different from the
Eemian times. The next glacial maximum is not foreseen before 100 ka AP.
These results are largely different from what was claimed in the early 80’s when it
was predicted that the climate could enter the next ice age within a few
thousands of years. This difference comes primarily from the fact that, at these
times, CO2 was supposed to be constant in all simulations. Under such
hypothesis, the model shows indeed that this forecast remains untouched.
43. But what about the possibility of an interaction between man’s impact on climate
during the early part of this 3d millennium and the long-term natural climatic
changes at the astronomical time scale ?
This question results from the present-day observed global warming and the
predictions for the XXIst century. Apparently our decades are already the
warmest of the last millenia and CO2 has already reached values unequalled
over the last few millions of years. More important, the extrapolation for the future
range from 450 to 1000 ppmv for CO2 and from 1.5 to 6°C above the 1990
temperature for the global warming.
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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Considering these values, our scenario is quite conservative. It was indeed
assumed that the CO2 concentration will reached 750 ppmv over the XXI and
XXII centuries and that it will return then progressively back to the natural
scenario values over the rest of the millennium. The result is a melting of the
Greenland ice sheet completed after 10 ka and its re-appearance after 20 ka
A.P., an evolution similar to the natural one being reached only at 50 ka A.P.
Whether this is plausible or not remains to be proven, in particular by a better
investigation of stage 11 and just before.
44. Who is going to win: ice age or global irreversible warming ?
45. Whether I am right or not ? Who knows ?
46. But it remains critical to know whether we will enter soon into an ice age or man’s
activities will make our climate jumping into a superinterglacial for long
(irreversible process ?). Maybe the Anthropocene of Paul Crutzen will be the link
between the Quaternary Ice Age and a Quinternary Warm Period similar to the
Cretaceous warm times.
47. But are the glacial-interglacial cycles really of astronomical origin ?
What about the explanation offered by the Indians of the Canadian Rockies:
HOW THE WATER SPIRIT
CARVED THE MOUNTAINS
As soon as Water received her power,
created more beautiful, Sun
she went laughing and dancing
became jealous and turned his
through the hills,
face away from the earth.
carrying pieces of land off to the
sea until the landscape was filled
Deprived of Sun’s warmth,
with canyons of Water’s making.
Water froze, her power locked in
Seeing that the rugged,
icen chains. Being very sly,
mountainous terrain Water
Water allowed her icy form to
sculpted made the world he
build up in the high mountains,
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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until slowly, slowly, the ice
smoothing out the canyons into
moved down the valleys, tearing
broad valleys. Seeing that Water
the earth as it went. In this way,
had once more outwitted him,
Water put the finishing touches
Sun relented and smiled again
on her mountain landscape,
upon the earth.
Some references
1. Books
BERGER A. (Ed.), Climatic Variations and Variability : Facts and Theories, NATO
ASI, D. Reidel Publishing Company, Dordrecht, Holland, 795pp., 1981.
BERGER A., IMBRIE J., HAYS J., KUKLA G. and SALTZMAN B. (Eds), Milankovitch
and Climate. Understanding the Response to orbital Forcing. NATO ASI
Series C vol. 126, Reidel Publ. Company, Holland, 895pp., 1984.
BERGER A., DICKINSON R., KIDSON J. (Eds), 1989. Understanding Climate
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Union, Washington D.C., 187pp.
BERGER A., SCHNEIDER S., DUPLESSY J.Cl. (Eds), 1989. Climate and GeoSciences, a Challenge for Science and Modern Society in the 21 st Century.
NATO ASI Series C : Mathematical and Physical Sciences, vol. 285, Kluwer
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BERGER A., 1992. Le Climat de la Terre, un passé pour quel avenir. De Boeck
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2. Articles
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Paleoclimatic variability at frequencies ranging from 1 cycle per 10,000 years to
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
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1 cycle per 1,000 years : evidence for nonlinear behavior of the climate system.
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GALLEE, H., van YPERSELE, J.P., FICHEFET, Th., MARSIAT, I., TRICOT, Ch.,
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BERGER A., TRICOT C., GALLEE H., and M.F. LOUTRE, 1993. Water vapour, CO2
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Philosophical
Transactions of the Royal Society, London, B, 341, pp. 253-261.
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.,
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BERGER A. and M.F. LOUTRE, 1997. Comments to the paper by McIntyre-Molfino
Intertropical latitudes, precession and half precession cycles. Science,
278(5342), pp. 1476-1478.
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. 615-629.
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.
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.
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.
LOUTRE M.F. and A. BERGER, 2000. Future climatic changes: are we entering an
exceptionally long interglacial ? Climatic Change, 46(1-2), pp. 61-90.
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.
In press :
BERGER A., 2001. The role of CO2, sea-level and vegetation during the
Milankovitch-forced glacial-interglacial cycles. In : Proceedings « GeosphereBiosphere Interactions and Climate », Lennart O. Bengtsson and Claus U.
Hammer (eds), New York : Cambridge University Press.
BERGER A. & M.F. LOUTRE, 2001. Climate 400,000 years ago, a key to the future ?
In : Marine Isotope Stage 11 : An Extreme Interglacial, A. Droxler, L. Burckle
and R. Poore (eds), American Geophysical Union Monograph. (invited paper)
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
16
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
17
Milutin Milankovic
1879 1958
-
From his autobiography
with comments by his son, Vasko
and a preface by André Berger
181p., 51 figures, 12 facsimile
1995
European Geophysical Society
Max Planck Str. 13
D-37191 Katlenburg-Lindau
Federal Republik Germany
35 USD - Egs@copernicus.org
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001
18
Louis Slichter lectureship, Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, April 2001