Slowlyvarying incoming solar radiation associated with Earth’s orbit can directly drive abrupt temperature change by more than10 degrees Celsius within a few decades in Greenland, as indicated by scientists from China, Germany, UK and Australia. This new study is the first in a complex climate model to confirm that abrupt climate variability can be directly driven by change in Earth orbital parameters. These abrupt changes, referred to as Dansgaard-Oeschger events, have been observed in ice cores collected in Greenland. The results of the study have just been released in the journal Nature Geoscience.

　　Late Pleistocene glacial periods were characterised by abrupt climate variability in the high latitudes of the Northern Hemisphere. For the cause of these abrupt events, previous studies mainly focus on internalforcing factors to climate system, while roles of externals, such as incoming solar radiation, remain unclear.

　　“To answer this question, we performed a transient climate experiment in a fully coupled model by only applying orbital changes under otherwise stable glacial conditions”, said by Prof. ZHANG Xu, from Institute of Tibetan Plateau Research  Chinese Academy of Sciences and Lanzhou University, the first author of this study, “this experiment reproduce several Dansgaard-Oeschger events consistent with reconstructions, confirming that gradual changes in Earth’s orbit alone can trigger rapid climate change”.    

　　Earth’s orbit consists of three parameters – eccentricity, obliquity and precession – of which periodicities are 100kyr and 400kyr, 40kyr and ~21kyr, respectively and which exert different effects on the temporospatial distribution of incoming solar radiation across the Earth.

　　“Changes in either eccentricity-modulated precession or obliquity can stimulate these abrupt changes, but by different governing dynamics” said by Prof Dr ZHANG, “that is, precession via modulating tropical Atlantic-to-Pacific moisture export, while obliquity by influencing sea surface temperature and sea ice in the subpolar North Atlantic.”

　　These findings – direct influence by orbital change on abrupt climate variability – complement the classic Milankovitch theory that indicates orbital-scale glacial-interglacial cycles are driven by changes in Earth’s orbit, deepening our understanding of millennial-scale climate variability through the Pleistocene.

　　This work was supported by the National Natural Science Foundation of China.