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 internal forcing factors to climate system, while roles of externals, such as incoming solar radiation, remain unclear.  

To answer this question, researchers from China, Germany, the UK and Australia conducted a transient climate experiment in a fully coupled model by only applying orbital changes under otherwise stable glacial conditions.

This complex climate model confirmed 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.

Their study was published in Nature Geoscience on Nov. 1.

"We find that slowly varying incoming solar radiation associated with Earth's orbit can directly drive abrupt temperature change by more than 10 degrees Celsius within a few decades in Greenland," said Prof. ZHANG Xu from the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences and Lanzhou University, the first author of this study.    

Earth's orbit consists of three parameters – eccentricity, obliquity and precession. They 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 Prof. ZHANG. "Precession modulates tropical Atlantic-to-Pacific moisture export, while obliquity influences sea surface temperature and sea ice in the subpolar North Atlantic."

Furthermore, contrasting insolation effects over the tropical versus subpolar North Atlantic, exerted by obliquity or precession, result in an oscillatory climate regime, even within an otherwise stable climate.

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