| Summary: | The individual contributions of insolation and greenhouse gases (GHG) to the interglacial climates of the past 800,000 years, as well as their combined effects and synergism, are quantified through simulations with an Earth system model of intermediate complexity and using the factor separation technique. The interglacials are compared in terms of their forcings and climate response. Our results show that MIS-9 is the warmest interglacial and MIS-13 the coolest. GHG are responsible for a large part of the difference between the global annual mean temperatures of the interglacials as a direct result of the greenhouse effect. However, insolation plays a significant role through its seasonal and regional impacts, particularly during the local summer of both hemispheres. Analysis of the individual effects of insolation and GHG shows that their relative importance on the interglacial intensity varies from one interglacial to another. MIS-9 is the warmest GHG-induced interglacial and MIS-17 the coolest. MIS-9 is also the warmest insolation-induced interglacial and MIS-7 the coolest, the insolation-induced cooling of MIS-7 beating its GHG-induced warming and making it one of the cool interglacials. In the explanation of the generally warmer post-MBE interglacials, boreal winter - or equivalently austral summer - is a key season and the Southern Hemisphere plays a more important role than the Northern Hemisphere as it warms significantly during both seasons (Yin and Berger, 2010). Our simulations also show that the variations in the global tree fraction and desert fraction are mainly controlled by insolation, being almost independent of the GHG concentration changes. This is due to the fact that, being given the warm interglacial conditions, the tree fraction is not sensitive to temperature change but sensitive to precipitation change which, at the regional scale, is mainly controlled by insolation. The response of the sea ice in the Arctic is different from that in the Southern Ocean. In the Arctic, the winter sea-ice ...
|
|---|