The 2022 Milutin Milankovic Medal is awarded to Hai Cheng for pivotal contributions in speleothem palaeoclimatology, uranium series dating, and the understanding of Earth’s orbital variations in tropical climates.
Hai Cheng received his PhD in geochemistry from Nanjing University, China, 1988. Throughout his career he has conducted research at the Academica Sinica in Beijing, the Kyoto University, the Macquarie University, the University of Minnesota, and since 2010 at the Xi’an Jiaotong University.
Over the past three decades, Hai Cheng has been at the leading edge in the technical developments of U-series dating and geochemistry to address fundamental questions in long- term climate change research.
His primary contribution has been the refinement and application of U/Th series disequilibrium dating to speleothems. He was instrumental in developing a world standard radiogenic isotope laboratory for dating speleothems at the University of Minnesota. His contributions in the 230Th dating technique, its use in calibrating the radiocarbon timescale, and its application to cave speleothem isotopic climate records were key in the study of millennial climate variability over hundreds of thousands of years.
Hai Cheng and collaborators produced iconic climate data sets from speleothems in China and South America, such as the famous record from Hulu Cave. The incomparable climate information contained in these Chinese speleothem records provided the most accurate absolute age control for climate variability from pole to pole.
Hai Cheng and colleagues extended the Chinese speleothem records back 640,000 years, thereby revolutionizing knowledge of how the monsoon system has varied on regional to global scales, and according to Milankovic cycles. They demonstrate that the primary forcing of changes in monsoon rainfall is precession of the equinoxes; that insolation sets the pace of millennial-scale events, including those associated with terminations and ‘unfinished terminations’; that millennial variability first found in Greenland ice cores is mirrored in the tropics; that northern and southern hemisphere monsoon systems are antiphase to each other at both orbital and millennial timescales; and have accurately shown the timing and structure of glacial terminations. Thus, Hai Cheng and colleagues have been the leading proponents of the concept of a ‘global paleomonsoon’.
In addition to his outstanding scientific contribution, Hai Cheng is also a leader recognized for his wise and effective mentoring of students; his unequivocal support to early career scientists; his generosity and collaborative spirit; and his dedication to maintaining a large network of collaborators.
Owing to his essential breakthrough in accurately dating speleothem records and making them vital templates against which most other paleoclimate records are calibrated, Hai Cheng represents our community particularly well and a worthy recipient of the Milankovic Medal.