The 2003 Milutin Milankovic Medal is awarded to John Imbrie for his leadership in the systematic examination of the response of the global climate system to forcing by changes in the Earth-Sun orbital geometry.
Throughout his career, John Imbrie has applied quantitative methods to solve geological problems. In the late 1960’s he turned his attention to Pleistocene marine sediments and developed a transfer-function approach to the estimation of past sea-surface temperatures. The method was first applied to fossil foraminifer populations and subsequently to many other fossil groups. He then set up the CLIMAP project that made a synoptic reconstruction of the sea-surface temperature of the global ocean at the height of the last ice age. This paved the way for general circulation modeling of climates in the geological past and for using the geological past as a test of models designed to forecast future climates. Within that project, John Imbrie was a member of the team that vindicated the work of Milutin Milankovic by demonstrating that changes in the geometry of the Earth-Sun system did indeed pace the glacial cycles of the Pleistocene. He then set up a team that systematically examined how the climate system actually operated, and demonstrated that the system can be better understood by examining separately the response to different components in the forcing. As a generous colleague, John Imbrie has promoted the notion that all data and numerical methods should be freely shared with the international community, and he has ensured that the palaeoceanographic community are leaders in the free exchange of data.