The analysis of stable isotopes and natural radioactive elements makes it possible to approach the study of major biogeochemical cycles in an original way and to reconstruct changes in the Earth's climate and environment by applying current principles.
[5] Jean-Claude Duplessy initially focused on the concretions of the caves and demonstrated that they were good recorders of the hydrological cycle and air temperature at the time they were formed.
[17][18] Chronology plays an essential role in understanding the evolution of climates and the links with astronomical theory initiated by Dr. Milankovitch and developed by André Berger in Louvain-La-Neuve and John Imbrie at Brown University.
[20] While developing this research and a group of marine paleoclimatology, he has endeavoured to bring to light in France the study of biogeochemical cycles within the surface envelopes of our planet.
This programme would bring together the actions of biologists, chemists and geochemists by highlighting the fundamental role of the coupling between biology and geochemistry, which led to the now recognized notion of biogeochemistry.
At the request of COFUSI (Comité français des unions scientifiques internationales),[22] Duplessy chaired the French scientific committee of the International Geosphere-Biosphere Programme.
This research program initiated the study of the variability of the coupled geosphere-biosphere system, giving high priority to palaeoclimatic and palaeo-environmental reconstructions over geological time.
The last interglacial period of 120,000 years, often taken as an analogue of a significantly warmer climate than today, reflects major changes in global ocean temperature and circulation that have contributed to destabilizing the West Antarctic ice cap.