France

Claude Lorius

2001 Balzan Prize for Climatology

For his outstanding activities and innovative in-depth results in the field of polar paleoclimatology.

Claude Lorius was born in Besançon in 1932  (†2023). Research Fellow and later Director at CNRS, in Grenoble, a member of the Académie des sciences, Lorius has taken part in a great number of polar campaigns, mostly in Antarctica. He owes his fame in climatology mainly to his research on ice. His is the intuition that air bubbles, trapped in ice for millennia, may disclose the composition of atmosphere in the past. His is also the discovery that the isotopic composition of ice may indicate the temperature at the time of precipitation. He has also demonstrated how, through special analytical methods, it is possible to determine atmospheric pressure at the time of ice formation. Such data have not only played a crucial role in the reconstruction of climate changes over past millennia, but also helped us understand how close the relation is between climate and the concentration of greenhouse gases in the atmosphere and how dependent it is on human activities. Lorius was one of the first scientists to sound the alarm bell on the dangers posed by the current warming of the planet.

Laudatio

Claude Lorius is one of the pioneers in the development and implementation of new methods to determine historical climate conditions from ice cores. Isotopic analysis of the oxygen-18 and deuterium contents of the ice cores allowed him to estimate air temperature. Air bubbles in the ice provided information about the content of “greenhouse gases” such as carbon dioxide and methane or chlorofluorocarbons, in the atmosphere.

The investigation of ice cores from Antarctica and Greenland demonstrated not only that the composition of the Earth’s atmosphere had undergone large, well defined variations but that these variations were correlated with drastic climatic changes between warm and glacial epochs.

Professor Lorius was the driving force behind the Antarctic ice core work, a Franco-Russian collaboration. From the Vostok station about 2100 m of ice core was extracted in 1982, covering about 140,000 years. In 1999, 3623 m were extracted, providing data for 420,000 years, containing four transitions between such warm and glacial epochs at about 18,000, 135,000, 245,000 and 335,000 years BP. This supports the idea that changes in the orbital parameters of the Earth cause variations in the intensity of solar radiation which in turn trigger natural climatic changes.

Among the important results of immediate interest deriving from Lorius’ work are the following: our present warm, “interglacial”, epoch is of extremely long duration and quite stable compared to others. In the past there have been repeated, sudden, drastic changes in temperature occurring on a time scale of decades. Finally the current greenhouse gas concentration is much higher than at any time during the last 400,000 years. This is difficult to explain without taking into consideration human activities over the last two hundred years.

Lorius was and is in the forefront of these globally important research activities, a participant in 22 polar expeditions, an excellent organizer of multidisciplinary teamwork and international scientific collaboration, by which he has become the father of a new generation of scientists in this field.