Bette L. Otto-Bliesner

The 2023 Milutin Milanković Medal is awarded to Bette L. Otto-Bliesner for her exceptionally outstanding contribution to modelling the earth system from deep-time to glacials and interglacials, and leading pioneering work to use palaeoclimate for better future projection.

Bette Otto-Bliesner started her career by studying Meteorology at the University of Wisconsin. She developed a then state-of-the-art atmospheric general circulation model (GCM), which took into account seasonal cycles, in her PhD study. The model was used in pioneering studies by John Kutzbach and herself, who revealed how the earth’s Monsoon system 9000 years ago was paced by orbital forcing. This early work not only lay the foundation for all subsequent modelling of palaeo-monsoon in Africa, India and Asia, but was also among the first applications of GCMs to modelling palaeoclimate in general. She further expanded her modelling work at the National Center for Atmospheric Research (NCAR) to understand the role of orbital forcing as well as greenhouse forcings over multiple geological time intervals from regional to global scales with her colleagues and collaborators around the world.

A series of papers in the 1990’s and early 2000’s helped solve enigmas by addressing the role of vegetation, cloud, weathering, and mountains in climate change under very different boundary conditions during the Cretaceous and older geological periods. Her 2006 Science paper was a landmark in using models to simulate the warmer climate and higher sea levels during the last interglacial period, which further stimulated the scientific community to investigate the tipping points of sea ice and ice sheets in our climate system. She has also made several significant contributions to understanding the climate of the last millennium. She set the standard of running model multiple ensembles (Last Millennium Ensemble), which has become a mainstay and a unique aspect of the palaeoclimate community. In addition to examining warm climates, Bette Otto-Bliesner addressed key questions of the Ice Age climate, including the climate and ocean of the Last Glacial Maximum and the role of freshwater forcing in causing abrupt climate changes. In this area, Bette Otto-Bliesner and her collaborators made a truly pioneering scientific breakthrough where, using a state-of-the-art GCM, they completed the first successful simulation of the continuous evolution of the global ocean-atmosphere over the last 21,000 years. This project “Transient Climate Evolution (TraCE)” led to fundamental new insights into our understanding of deglaciation dynamics, the climate-CO2 relationship, hydrological change and abrupt climate changes.

Recently, Bette Otto-Bliesner and her team have used the latest National Center for Atmospheric Research (NCAR) model (CESM2), which was developed for future projection in the latest Intergovernmental Panel on Climate Change (IPCC) report AR6, to show that the model climate sensitivity was too high because of cloud-related temperature feedback by analyzing the past climate (Eocene) observation and simulation. They highlighted the importance of palaeoclimate perspectives for future climate projection by developing for the first time a calibrated model which performs well both under modern and palaeo conditions.

Bette Otto-Bliesner has been a tireless leader in the palaeoclimate modelling community and served many organisations where she coordinated scientific research with much passion and patience. This includes her key role in various activities of the Palaeoclimate Modelling Intercomparison Project (PMIP) and PAGES (Past Global Changes) Working Groups. Her expertise and reputation led to her being selected as a Lead Author for the Palaeoclimate chapters of the fourth and fifth reports of the IPCC. Her groundbreaking and influential contributions to the understanding of the Earth’s climate system in the past, her outstanding and selfless leadership in the climate modeling community, and her devoted service to bridge the gap between the palaeoclimate and future climate communities, make Bette Otto-Bliesner exceptionally deserving of the Milutin Milankovic Medal.