The climate response to the astronomical forcing and greenhouse gases in East Asia during the Last Interglacial based on HadCM3 simulations

Orbital parameters and Greenhouse gases (GHG) are two crucial factors influencing the climate at global and regional scales. How climate responds to different configurations of astronomical parameters and GHG is not yet fully understood in East Asia with relatively complex climate and orographic conditions. In this study, we study the separate effects of insolation and GHG on the temperature and precipitation in six sub-regions within East Asia during the last interglacial. We performed a series of snapshot simulations every 2 ka with HadCM3 which covered the last interglacial. Boundary conditions comprise astronomical parameters and GHG concentrations, and other forcings are kept as pre-industrial values. The results show that the summer surface air temperature can largely be explained by the direct effect of summer insolation and is positively related to GHG. Temperature shows a consistent and good relationship with precession, obliquity and CO₂ concentrations among different sub-regions. However, summer precipitation shows a relatively heterogeneous pattern. In East Asia summer monsoon regions, precipitation is strongly controlled by insolation, and the monsoon intensity can be explained by land-sea pressure gradient and thermal contrast. In South China Sea, summer precipitation is less directly related to insolation and internal feedbacks are more important. The relative effects of precession, obliquity and GHG on precipitation are different between sub-regions, partly explaining the regional diversity within East Asia. The modeled climate are consistent with the proxy-based reconstruction in general.