He is best known for his significant contribution to the renaissance and further development of the astronomical theory of paleoclimates and as a cited pioneer of the interdisciplinary study of climate dynamics and history.

He has renewed this theory and improved the accuracy of the long term variations of the astronomical parameters used for calculating of the incoming solar radiation (insolation) over the last and next millions of years.

He became known in 1977 for his paper in Nature and later in the Journal of Atmospheric and Terrestrial Physics (1978), delivering all the spectral components of the long term variations of orbital eccentricity, obliquity (axial tilt) and climatic precession.

[14] Based on such climate models, he showed the importance of the long-term variations of insolation to simulate the glacial-interglacial cycles,[15][16] the possible exceptional length of our interglacial[17][18] the importance of the 400-ka period in searching for analogues of our present-day and future climate,[19] the relative role of the multiple feedbacks involved in the explanation of the glacial-interglacial cycles, water vapour in particular.

[20] More recently he initiated research on the origin of the east Asian summer monsoon in China[21] and started to work on the diversity of climate over the last nine interglacials.

He is a voting member of the BAEF (Belgian American Educational Foundation, Herbert Hoover Commission for Relief in Belgium) which he was fellow in 1970–1971.

He has organised and chaired international meetings, among which are the First International School of Climatology on Climatic Variations and Variability, Facts and Theories at the Ettore Majorana Center of Erice in Sicily, from 9 to 21 March 1980,[22] the symposium Milankovitch and Climate (with J. Imbrie) at the Lamont Doherty Geological Observatory from 30 November to 3 December 1982,[23] the tenth general assembly of the European Geophysical Society in Louvain-la-Neuve from 30 July to 4 August 1984, the IUGG symposium Contribution of Geophysical Sciences to Climate Change Studies in Vancouver in August 1987,[24] the symposium Climate and Geo-Sciences, a Challenge for Science and Society for the 21st Century in Louvain-la-Neuve in May 1988,[25] the symposium Climate and Ozone at the Dawn of the third Millennium in honour of Paul Crutzen, Nobel Prize 1995, of Willi Dansgaard and Nicholas Shackleton, Crafoord Prize 1995 and, with Claude Lorius, Tyler Prize for Environment 1996, the Milutin Milankovitch anniversary symposia in Belgrade in 2004 [26] and 2009, the first Colloque à l'étranger du Collège de France at the Palais des Académies in Bruxelles on 8–9 May 2006 (with J. Reisse and Jean-Pierre Changeux), the Third von Humboldt International Conference on East Asian Monsoon, Past, Present and Future, at the Chinese Academy of Sciences in Beijing from 24 to 30 August 2007 (with Z. Ding) .