# Preface "Climate change: from the geological past to the uncertain future – a symposium honouring André Berger"

M. Crucifix, M. Claussen, G. Ganssen, Joel Guiot, Z. Guo, T. Kiefer, M. -F.

Loutre, D. -D. Rousseau, E. Wolff

► To cite this version:

M. Crucifix, M. Claussen, G. Ganssen, Joel Guiot, Z. Guo, et al. Preface "Climate change: from the geological past to the uncertain future – a symposium honouring André Berger". Climate of the Past, 2009, 5 (4), pp.707-711. 10.5194/cp-5-707-2009. hal-01457764

HAL Id: hal-01457764

https://hal.science/hal-01457764

Submitted on 26 Aug 2020

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Preface

Climate change: from the geological past to the uncertain future –
a symposium honouring André Berger

M. Crucifix<fnref n="1" />, M. Claussen<fnref n="2" />, G. Ganssen<fnref n="3" />, J. Guiot<fnref n="4" />, Z. Guo<fnref n="5" />, T. Kiefer<fnref n="6" />, M.-F. Loutre<fnref n="1" />, D.-D. Rousseau<fnref n="7" />, and E. Wolff<fnref n="8" />

André Berger – many of us have heard of or met this lively figure of the climate scientific community in person. In May 2008 a workshop was organised in Louvain-la-Neuve, Belgium, for the occasion of his “official” retirement – of course André will never retire: he was recently awarded an Advanced Research Grant by the European Research Council too pursue his research. More than one hundred scientists were present with a spectrum ranging from friends since the beginnings of modern climate research to current PhD students. A huge concentration of talents, a healthy mix of generation and nationality; a wonderful testimony to a professor about whom the youngest of us can only suspect the breadth of his commitment to the scientific community and public education, the depth of his scientific insight and his faith into what mankind can accomplish.

The present special issue includes 17 papers presented
during the workshop. Here, the generation mix is present
again: while three authors are recipients of the Milankovitch
medal (initiated by André) of the EGU, one author is the
PhD student of a former PhD student of a former PhD stu-
dent of André. All authors share a common point: the
work they present somehow relies on the impulse given by
André Berger to climate and palaeoclimate science through-
out his career, either through his contribution to the astro-
nomical theories of palaeoclimates, his vision of the multi-
disciplinary character of palaeoclimate and climate sciences,
the promotion of climate modelling, or his action as a leader
at the service of the scientific community as a whole.

Milankovitch theory and Berger cycles

The idea about the influence of Earth's orbital parameters
on climate dates back to the nineteenth century mostly with
J. A. Adhémar (1860) in France, J. Herschel and J. Murphy
(1876) in Great Britain, J. Croll (1875) in Scotland, L. Pil-
grim (1904) in Germany as pioneers of the astronomical the-
ory of palaeoclimate (cf. Berger, 1988 for a historical ac-
count). It is usually referred though as Milankovitch the-
ory (1941) because of the large contribution of Milutin Mi-
lankovitch, a Serbian engineer and mathematician. He was
indeed the first to complete a full astronomical theory of the
Pleistocene ice ages, using computations of the orbital ele-
ments by Le Verrier (1855) and Stockwell (1873) to estimate
changes in the energy balance of the Earth and the resulting
climate variations, and give quantitative support to the view
that ice ages are caused by changes in Earth's orbit.

However, the theory remained the Milankovitch hypothe-
sis in the literature until the mid-1970s when Hays, Imbrie
and Shackleton (1976) published their now classical “pace-
maker” paper. They analysed a number of marine records
and found spectral power concentrated near periods of 100,
42, 23 thousand years (kyr) and, in two records, 19 kyr. At
that time there was reason to think that orbital variations,
with periods near 40 kyr (obliquity, “tilt” of earth’s axis) and
23 kyr (precession) could influence climate change. There
was however no reason to expect that the period of 19 kyr
could also dominate precession.

<figure><img src="image_2.png" /></figure>

Correspondence to: M. Crucifix
(michel.crucifix@uclouvain.be)

<footnote n="1">¹Institut d'Astronomie et de Géophysique G. Lemaître, Université catholique de Louvain, Belgium</footnote>

<footnote n="2">²Max-Planck-Institut für Meteorologie, Hamburg, Germany</footnote>

<footnote n="3">³Free University of Amsterdam, Institute of Earth Sciences, The Netherlands</footnote>

<footnote n="4">⁴CNRS, CEREGE, France</footnote>

<footnote n="5">⁵Institute of Earth Environment, Chinese Academy of Sciences, China</footnote>

<footnote n="6">⁶PAGES International Project Office, Bern, Switzerland</footnote>

<footnote n="7">⁷CNRS-ENS, Laboratoire de Météorologie Dynamique, France</footnote>

<footnote n="8">⁸British Antarctic Survey, Cambridge, UK</footnote>
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** About 110 scientists were present to honour André Berger in May 2008 at a symposium entitled “Climate change: from the geological past to the uncertain future – a tribute to André Berger” in Louvain-la-Neuve, Belgium.</figcaption></figure>

By the mid-seventies the secular variations of the orbital elements of the principal planets were known with a reasonably high accuracy, notably due to the works of Brouwer and van Woerkom (1950), Sharaf and Boutnikova (1967), Anolik et al. (1969) and Bretagnon (1974) who based themselves on the foundations laid by J. L. Lagrange (1781), U. Leverrier (1855), J. Stockwell (1873), and G. Hill (1897). However most of the time they were expressed in a sidereal framework, that is, with respect to the stars and not with respect to the seasons. Investigators interested in the problem of ice ages, such as L. Pilgrim (1904), M. Milankovitch (1941) and, later, Sharaf et al. (1967) and A. Vernekar (1972) computed time-series of elements expressed relative to the vernal equinox and the ecliptic plane, hence more relevant for climatic theories. However, the characteristic periods of these elements were not known, and there was no extensive assessment of their accuracy. In particular, there was nothing like a “double” precession peak in the orbital frequencies known at the time.

This is where André Berger comes into play. During his PhD thesis (Berger, 1973) he first delivered an up-to-date numerical solution for obliquity and the longitude of perihelion relative to the equinox (Berger 1976b), based on the solutions of Bretagnon (1974) for the planetary system, and Sharaf and Budnikova (1967) for the luni-solar precession. He next compared the accuracy of this solution with those previously available (Berger, 1977a). The breakthrough was then his finding of an analytical expression for the *climatic* astronomical elements, under the form a sum of sines and cosines (Berger 1978b). In this way, the periods characterising them could be listed in tables for the first time, and insolation could be computed at very little numerical cost. This very patient and obstinate work yielded the demonstra-

tion that the spectrum of climatic precession is dominated by three periods of 19, 22 and 24 kyr, that of obliquity, by a period 41 kyr, and that of eccentricity has periods of 400 kyr, 125 kyr and 96 kyr (the Berger periods). The origin of the 19 and 23 kyr peaks in the Hays et al. spectra was thus elucidated (Berger, 1977b). According to John Imbrie, this result constituted the most delicate proof that orbital elements have a sizable effect on the slow evolution of climate (Imbrie and Imbrie, 1979). Berger's solution, named BER78, was later used by Shackleton et al. (1990) to correct the then-adopted age of the Brunhes-Matuyama magnetic reversals, soon confirmed by radiometric methods.

After this milestone, Berger and coworkers also delivered a trigonomical expansion of the orbital elements valid for several million years (Berger and Loutre, 1991) built up from a numerical solution of the planetary system (Laskar, 1988). They explored the astronomical origins of the 100-kyr cycles, as well as the frequency and amplitude modulations of the astronomical parameters and their instability (Berger and Loutre, 1990, Berger et al., 1998, 2005; Mélice et al., 2001). Berger was also the first to introduce and compute the long-term variations of daily, monthly and seasonal insolation and demonstrated the large amplitude of daily insolation changes (Berger, 1976a), which is now used in all climate models. His prediction in the early 1990s about the shortening of astronomical periods back in remote times (Berger et al., 1989, 1992) has been confirmed by palaeoclimate data of Cretaceous ages, and constitutes thus an important validation and development of the Milankovitch theory for Pre-Quaternary climates.
## EMICS before their time

Berger's scientific carrier is also highlighted by his very first efforts in the 1980s to develop what might be considered today as the first Earth system model of intermediate complexity (which he called at that time a 2.5D model), even if the phrase *EMIC* would be coined much later by Martin Claussen in 2000 and popularized in Claussen et al. (2002). The *LLN-2D* model included simplified ice-sheet, atmosphere and even ocean mixed-layer dynamics, and proved to be able to reproduce the transient response of the climate system to the astronomical forcing over the last glacial-interglacial cycle (Berger et al., 1990; Gallée et al., 1991). This approach has now been recognized as a key to understand long-term climate variations and constitutes another important contribution to the development of astronomical theories of palaeoclimates. In the recent years, together with his team, he has been applying these lines of knowledge to understand the behaviour of the Earth's climate system at key time intervals, such as the climate during the marine isotope stages (MIS) 11 (Loutre and Berger, 2003), MIS-13 (Yin et al., 2008), the Holocene (Crucifix et al., 2002; Bertrand et al., 2002) and the future (Berger and Loutre, 2002; Berger et al., 2003). These results are not only important for our theoretical understanding of past climates, but they are also of huge value for climate prediction. Indeed, when in the 1970's the succession of glacial and interglacial episodes became correctly dated, palaeoclimatologists shared the opinion that the present interglacial would last about 10 000 years just like the previous ones. The statement is not without political implications: why should one care about greenhouse-gas emissions if our destiny is to dive into glaciation? By developing the concept of insolation analogues (Berger, 1979) and promoting climate dynamics modelling André Berger substantiated the paradigm according to which glacial inception is not expected to happen for several tens of thousands of years, even in absence of human intervention (Berger and Loutre, 2002).

## Towards data-model comparison

A decisive step in the study of the climate of the last mil-
lennium was the first International Workshop on Dendrocli-
matology in 1974. It was organised by the Laboratory of
Tree-Ring Research of Tucson, and in particular H. Fritts, the
pioneer of this discipline. This workshop with André Berger
as participant and contributor was the start of an impressive
network of tree-ring data and of the International Tree-Ring
 DataBase (ITRDB). The foundation of the ITRDB meant that
most of the active practitioners around the world shared a
minimum set of criteria for the development and recording
of dendroclimatic data. This database laid the foundation
for the famous millennial climate reconstructions by Mann
et al. (1998) and many others in their wake.

André Berger was convinced of the robustness of the tech-
niques developed by the Tucson's school and came back
enthusiastic to Belgium. "Collect proxy data, share them
with colleagues and work in an interdisciplinary way: this
is the way to go" he said. This moment marks the begin-
ning of collaborations between climatologists and palaeoe-
cologists in Belgium, France and Italy (at least). The enter-
prise demanded the development of quantitative methods to
deal with tree-ring data, a task he assigned to himself with
success: significant progress was achieved when the Climate
Research Unit in Norwich (1980) organised a second work-
shop (specifically with Moroccan cedar data: Berger et al.,
1979; Munaut et al., 1979). The reference book published af-
ter this workshop proved that the team built by André Berger
had reached visibility (Guiot et al., 1982a, b).

His vision was contagious and, with the book edited by
Flohn and Fantechi (1984), he appeared to be one of those
who inspired the environmental research program of the Eu-
ropean Union (Berger et al., 1984): Several EU- and NATO-
funded projects, schools and workshops (launched or simply
supported by André) gathered continental palaeoclimatolo-
gists, palaeoceanographers, glaciologists and climate mod-
ellers to better understand the climate mechanisms governing
the last climatic cycle, e.g. EPOCH project (1988–1992), the
Palaeoclimate Modelling Intercomparison Project (PMIP),
which is still active today, and other summer schools (Du-
plessy et al., 1991, 1994)

## Teaching new generations

Berger also contributed significantly to the training of re-
search scientists and students, stimulated a multi- and inter-
disciplinary approach to Earth system problems, and fos-
tered international collaborations in order to strengthen the
relationships between geophysics, geochemistry and geo-
sciences in general. Today, many senior climatologists re-
member well the “Erice” summer school that he organised
in 1980, and where he gathered the most famous scientists
of a period where global change was not yet that trendy:
R. Barry, B. Bolin, W. Broecker, W. Dansgaard, J. C. Dup-
lessy, H. Flohn, H. Fritts, W. Gates, M. Ghil, K. Hasselmann,
W. Kellog, G. Kukla, J. Imbrie, N. Shackleton, J. Smagorin-
sky. One product of this school is a reference book edited
by Berger (1981). For sure this summer school gave the mo-
tivation and scientific bases to several climatologists today
active in the Intergovernmental Panel on Climatic Change
(K. Briffa, J. Guiot, A. Henderson-Sellers, M. Hughes,
P. Huybrechts, J. Jouzel, H. Oerlemans, J. P. van Ypersele).
Later, his book for a wider audience (Berger, 1992) inspired
generations of French-speaking climate students.

André Berger continued to promote geosciences (Berger
et al., 1984, 1989, 2005) and became the president of the
European Geophysics Society (EGS). He set the merging of
EGS and the European Union of Geosciences (EUG), which
resulted in the foundations of the present European Geo-
sciences Union (EGU), of which he is the honorary presi-
dent.

At last, a tribute to André Berger would not be complete
without mentioning his profound commitment to the civil so-
ciety. We all know that there is no point in being a skilful and
esteemed scientist if you do not somehow communicate your
passion and knowledge. André always put this into practice.
Early in the eighties he warned policy-makers and the media
about the urgency of climate change and its implications for
the development of the society, especially regarding energy
choices. Still nowadays he devotes a large amount of his time
sharing his vision of climate and human society to the pub-
lic. It is therefore no surprise that besides the recognition he
gained among his peers, André Berger became a known and
respected figure in Belgium and well beyond.

*Acknowledgements.* The present special issue was supported by the EGU in recognition of the exceptional services of André Berger. The meeting held 26–29 May 2008 in Louvain-la-Neuve was co-funded by the Belgian Agency for Radioactive Waste and Enriched Fossil materials, the IGBP Past Global Changes (PAGES) programme, the Belgian National Fund of Scientific Research, the Belgian Federal Science Policy Office, the French Institut National des Sciences de l’Univers, the French Commissariat à l’Énergie atomique, the Vinçotte company and the Science Faculty of the Université catholique de Louvain.

References

Adhémar, J.: Révolutions de la mer: déluges périodiques, Lacroix-Comon, Hachette et Cie, Dalmont et Dunod, Paris, 2Nd edition, 1860.

Anolik, M. V., Krasinsky, G. A., and Pius, L. J.: The trigonomet-
rical theory of secular perturbations of major planets, Trudy As-
tronomicheskoj Observatorii Leningrad, 14, 3–47, 1969.

Berger, A.: Théorie astronomique des paléoclimats. Dissertation
doctorale (2 vol.), Université catholique de Louvain, Louvain-
La-Neuve, Belgique, 1973.

Berger, A.: Long term variations of daily and monthly insolation during the Last Ice Age, EOS, 57, p. 254, 1976a.

Berger, A.: Obliquity and general precession for the last 5,000,000 years, Astron. Astrophys., 51, 127-135, 1976b.

Berger, A.: Long-term variations of the ecliptical elements, Celestial Mech., 15, 53–74, 1977a.

Berger, A.: Support for the astronomical theory of climatic change, Nature, 268, 44–45, 1977b.

Berger, A.: Long-term variations of caloric insolation resulting
from the Earth's orbital elements, Quaternary Res., 9, 139–167,
1978a.

Berger, A.: Long-term variations of daily insolation and Quaternary climatic changes, J. Atmos. Sci., 35, 2362–2367, 1978b.

Berger, A.: Insolation signatures of Quaternary climatic changes, *II Nuovo Cimento*, 2C(1), 63–87, 1979.

Berger, A. L., Guiot, J., Mathieu, L., and Munaut, A. V.: Cedar tree-ring and climate in Morocco, Tree-Ring Bulletin, 39, 61–75, 1979.

Berger, A. (Ed.): Climatic Variations and Variability: Facts and Theories, NATO ASI, D. Reidel Publishing Company, Dordrecht, Holland, 795 pp., 1981.

Berger, A., Imbrie, J., Hays, J., Kukla, G., and Saltzman, B. (Eds.): Milankovitch and Climate. Understanding the Response to orbital forcing, Vol. 126, Reidel Publ. Company, Holland, 895 pp., 1984.

Berger, A.: Milankovitch theory and climate, Rev. Geophys., 26, 624–657, 1988.

Berger, A., Schneider, S., and Duplessy, J. Cl. (Eds): Climate and Geo-Sciences, a challenge for Science and Society in the 21st Century, NATO ASI Series C, Vol. 285, Kluwer Academic Publishers, Dordrecht, 1989.

Berger, A., Loutre, M. F., and Dehant, V.: Pre-Quaternary Milankovitch frequencies, Nature, 342, p. 133, 1989.

Berger, A. and Loutre, M. F.: Origine des fréquences des éléments astronomiques intervenant dans le calcul de l'insolation, Bulletin Sciences, 1-3/90, 45-106, 1990, Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique.

Berger, A., Gallée, H., Fichefet, Th., Marsiat, I., and Tricot, Ch.: Testing the astronomical theory with a coupled climate-ice sheet model, Palaeogr. Palaeoclimatol. Palaeoecol., 89, 125-141, 1990.

Berger, A. and Loutre, M. F.: Insolation values for the climate of the last 10 million years, Quaternary Sci. Rev., 10, 297-317, 1991.

Berger, A.: Le Climat de la Terre, un passé pour quel avenir, De Boeck Université, Bruxelles, 479 pp., 1992.

Berger, A., Loutre, M. F., and Laskar, J.: Stability of the astronomical frequencies over the Earth's history for paleoclimate studies, Science, 255, 560–566, 1992.

Berger, A., Loutre, M. F., and Mélice, J. L.: Instability of the astro-
nomical periods from 1.5 Myr BP to 0.5 Myr AP, Paleoclimates
Data and Modelling, 2, 239–280, 1998.

Berger, A. and Loutre, M. F. An exceptionally long interglacial
ahead?, Science, 297, 1287–1288, 2002.

Bertrand, C., Loutre, M. F., and Berger, A.: High frequency varia-
tions of the Earth's orbital parameters and climate change, Geo-
phys. Res. Lett., 29, 1893, doi:10.1029/2002GL015622, 2002.

Berger, A., Loutre, M. F., and Crucifix, M.: The Earth's climate in the next hundred thousand years (100 kyr), Surv. Geophys., 24, 117–138, 2003.

Berger, A., Mélice, J. L., and Loutre, M. F.: On the origin of the 100-kyr cycles in the astronomical forcing, Paleooceanography, 20, PA4019, doi:10.1029/2005PA001173, 2005.

Berger, A., Ercegovac, M., and Mesinger, F.: Paleoclimate and the Earth Climate System, Serbian Academy of Sciences and Arts, Scientific Meetings volume CX, Department of Mathematics, Physics and Geo-Sciences Book 4, Belgrade, 2005.

Bretagnon, P.: Termes à longues périodes dans le système solaire, Astron. Astroph., 30, 141–154, 1974.

Brouwer, D. and van Woerkom, A. J. J.: The secular variations of the orbital elements of the principal planets, Astronomical papers American Ephemeris and Nautical Almanac, Vol. XIII Part II, 81–107, 1950.

Claussen, M., Mysak, L., Weaver, A., Crucifix, M., Fichefet, T., Loutre, M. F., Weber, S., Alcamo, J., Alexeev, V., Berger, A., Calov, R., Ganopolski, A., Goosse, H., Lohmann, G., Lunkeit, F., Mokhov, I., Petoukhov, V., Stone, P., and Wang, Z.: Earth system models of intermediate complexity: closing the gap in
the spectrum of climate system models, Clim. Dynam., 18(7),
579–586, 2002.

Croll, J.: Climate and time in their geological relations: a theory of secular changes of the Earth's climate, Appleton, New York, 1875.

Crucifix, M., Loutre, M. F., Tulkens, Ph., Fichefet, T., and Berger, A.: Climate evolution during the Holocene: A study with an Earth system model of intermediate complexity, Clim. Dynam., 19, 43–60, doi:10.1007/s00382-001-0208-6, 2002.

Duplessy, J. C., Pons, A., and Fantechi, R. (Eds.): Climate and Global Change, European Communities, Luxemburg, 1991.

Duplessy, J. C. and Spyridakis, M. Th. (Eds.): Long Term Climatic Variations, Data and Modeling, NATO ASI Series I: Global Environmental Change, Vol. 22, Springer Verlag, Berlin, 1994.

Flohn, H. and Fanteshi, R. (Eds.): The Climate of Europe: Past, Present and Future. Natural and Man-Induced Climatic Changes: A European Perspective, Atmospheric Sc. Library, Reidel Publ. Company, Holland, 1984.

Gallée, H., van Ypersele, J. P., Fichefet, Th., Tricot, Ch., and Berger, A.: Simulation of the last glacial cycle by a coupled sectorially averaged climate – ice-sheet model. I. The Climate Model, J. Geophys. Res., 96, 13139–13161, 1991.

Guiot, J., Berger, A. L., and Munaut, A. V.: An illustration of alternative transfer function methods in Switzerland. Climate from Tree-Rings, edited by: Hughes, M. K., Kelly, P. M., Pilcher, J. R., and LaMarche Jr., V. C., Cambridge University Press, 160–163, 1982.

Guiot, J., Berger, A. L., and Munaut, A. V.: Response functions. Climate from Tree-Rings, edited by: Hughes, M. K., Kelly, P. M., Pilcher, J. R., and LaMarche Jr., V. C., Cambridge University Press, 38–45, 1982.

Hays, J. D., Imbrie, J., and Shackleton, N. J.: Variations in the Earth's Orbit: Pacemaker of the Ice Ages, Science, 194, 1121–1132, 1976.

Hill, G. W.: On the values of the eccentricities and longitudes of the perihelia of Jupiter and Saturn for distant epochs, Astron. J., 17, 81–87, February 1897.

Imbrie, J. and Imbrie, K. P.: Ice ages, solving the mystery, Enslow, 1979.

Lagrange, J. L.: Théorie des variations séculaires des éléments des planètes 1. In Nouveaux mémoires de l'Académie Royale des Sciences et Belles-lettres, 199–276, Berlin, 1781.

Laskar, J.: Secular evolution of the solar system over 10 millions
years, Astron. Astroph., 198, 341–362, 1988.

Leverrier, U.: Recherches astronomiques, Annales de l'Observatoire Royal de Paris, Tome II, 1855.

Loutre, M. F. and Berger, A.: Marine Isotope Stage 11 as an analogue for the present interglacial, Global Planet. Change, 36, 209–217, doi:10.1016/S0921-8181(02)00186-8, 2003.

Mann, M. E., Bradley, R. S., and Hughes, M. K.: Global-scale temperature patterns and climate forcing over the past six centuries, Nature, 392, 779–787, 1998.

Mélice, J. L., Coron, A., and Berger, A.: Amplitude and frequency modulations of the Earth's obliquity for the last million years, J. Climate, 14, 1043–1054, 2001.

Murphy, J. J.: The glacial climate and the polar ice-cap, Q. J. Geol. Soc. London, 32, 400–406, 1876.

Milankovitch, M.: Canon of insolation and the ice-age problem, Narodna biblioteka Srbije, Beograd, 1998, English translation of the original version of 1941.

Munaut, A. V., Berger, A. L., Guiot, J., and Mathieu, L.: Den-droclimatological studies on cedars in Morocco, Colloque Inter-national du C.N.E.S.: Evolution des Atmosphères Planétaires et Climatologie de la Terre, Nice 1978, Ed. CNES Toulouse, 373–379, 1979.

Pilgrim, L.: Versuch einer rechnerischen Behandlung des Eiszeit-
enproblems (Essay on a Mathematical Treatment of the Problem
of the Glacial Period), Jahreshefte für vaterländische Naturkunde
in Württenberg, Vol. 60, 1904.

Shackleton, N. J., Berger, A., and Peltier, W. R.: An alternative as-
tronomical calibration of the lower Pleistocene time scale based
on ODP site 677, Phil. Transactions of the Royal Society of Ed-
inburgh, Earth Sciences, 81, 251–261, 1990.

Sharaf, S. G. and Boudnikova, N. A.: Secular variations of elements of the Earth's orbit which influences the climates of the geological past, Tr. Inst. Theor. Astron. Leningrad, 11, 231–261, 1967.

Stockwell, J. N.: Memoir on the Secular Variations of the Elements of the Eight Principal Planets, Smith. Contr. Knowledge, 18(3), Washington, 1873.

Vernekar, A. D.: Long-term global variations of incoming solar ra-
diation, Meteor. Monogr., 34, 21 pp. and tables, 1972.

Qiuzhen Yin, , Berger, A., Driesschaert, E., Goosse, H., Loutre, M. F., and Crucifix, M.: The Eurasian ice sheet reinforces the East Asian summer monsoon during the interglacial 500 000 years ago, Clim. Past, 4, 79–90, 2008,
http://www.clim-past.net/4/79/2008/.