The Crafoord Prize 1995

The Royal Swedish Academy of Sciences awards The 1995 Crafoord Prize for pioneering contributions that have increased our knowledge of climatic changes during the Quaternary period, i.e. during the past 2,5 million years. Professor Willi Dansgaard, University of Copenhagen (b. 1922) and Professor Nicholas Shackleton, University of Cambridge (b. 1937) are awarded the prize for fundamental work on developing and applying isotope geological analysis methods for the study of climatic variations during the Quaternary period.

The value of the Crafoord Prize is SEK 2.8 million. It is devided equally between the two prizewinners who will receive their prize at a ceremony at the Academy on September 28th 1995.

Today´s climate read in the long-term archives of the world´s inland ice and deep-sea sediments

Today´s climate can only be interpreted and possible future changes predicted if enough is known about how and why the climate changed in the past. Inland ice and deep-sea sediment represent unique archives where the swings between colder and warmer periods can be followed, chiefly through variations in oxygen isotopes. In small air bubbles in the ace it has also been possible to record how the carbon-dioxide content of the atmosphere has varied. Chemical substances in the ice and plankton remains in the sediment also afford valuable information.

Willi Dansgaard has contributed greatly to out knowledge of climatic change during the past 160 000 years by developing methods of analyzing the stable oxygen isotope 18O in drill core samples from inland ice. The information, which is quantitative, continual and well dated, has markedly altered our view of changes in the climate.

Nicholas Shackleton has been rewarded for his fundamental analyses of deep-sea sediments for the connection between oxygen isotope variations and climatic variations, which has provided us with a global time scale and a global picture of variations in climate over the past 2.5 million years.

Dansgaard early reached down to ice that was about 100 000 years old. This enabled him to determine temperature variations during and after the most recent ice age. Shackleton traced more than twenty oscillations between colder and warmer periods during the whole Quaternary period. Drilling has since been carried out in Antarctica, where ice as old as 200 000 years has been studied. Drill cores from many basins of the deep oceans have substantially widened the time perspective.

These unique series of data have in their turn stimulated researchers to carry out detailed theoretical studies to elucidate the causes of climate changes in the past. Studies of this type during the past few decades have become increasingly important, since knowledge of earlier changes is a precondition for understanding whether and how man is affecting the climate. It is conceivable, for example, that the climate changed relatively rapidly during the most recent ice age, and the same was probably true during the preceding interglacial period between ice age some 120 000 years ago. Yet the climate appears to have been considerably more stable during the period since the last ice age, with the important exception about 11 000 years ago, during the period which is termed the Younger Dryas period. Researchers are now asking themselves whether such rapid changes can also occur in our time.

Climate researchers can now test their models of climatic variation against data of the type that Dansgaard and Shackleton displayed almost thirty years ago. This has proved to be of fundamental importance in trying to understand the fascinating picture of the climate of the past, which we have today.