Individual contribution of insolation and CO2 to the interglacialclimates of the past 800,000 years
Qiu Zhen Yin AndréBerger
Abstract The individual contributions of insolation andgreenhouse gases (GHG) to the interglacial climates of thepast 800,000 years are quantified through simulations with amodel of intermediate complexity LOVECLIM and usingthe factor separation technique. The interglacials are comparedin terms of their forcings and responses of surface airtemperature, vegetation and sea ice. The results show that therelative magnitude of the simulated interglacials is in reasonableagreement with proxy data. GHG plays a dominantrole on the variations of the annual mean temperature of boththe Globe and the southern high latitudes, whereas, insolationplays a dominant role on the variations of tree fraction,precipitation and of the northern high latitude temperatureand sea ice. The Mid-Brunhes Event (MBE) appears to besignificant only in GHG and climate variables dominated byit. The results also show that the relative importance of GHGand insolation on the warmth intensity varies from oneinterglacial to another. For the warmest (MIS-9 and MIS-5)and coolest (MIS-17 and MIS-13) interglacials, GHG andinsolation reinforce each other. MIS-11 (MIS-15) is a warm(cool) interglacial due to its high (low) GHG concentration,its insolation contributing to a cooling (warming). MIS-7,although with high GHG concentrations, can not be classifiedas a warm interglacial due to it large insolation-inducedcooling. Related to these two forcings, MIS-19 appears to bethe best analogue for MIS-1. In the response to insolation,the annual mean temperatures averaged over the globe andover southern high latitudes are highly linearly correlatedwith obliquity. However, precession becomes important inthe temperature of the northern high latitudes and controlsthe tree fraction globally. Over the polar oceans, the responseduring the local winters, although the available energy issmall, is larger than during the local summers due to thesummer remnant effect. The sensitivity to double CO2 is the highest for the coolest interglacial.
Keywords Interglacials, Astronomical theory, Insolation, CO2 , Factor separation, Paleo climate modeling
PUBLISHED BY: Climate Dynamics, 2012, Vol 38, Issue 3-4, 709-724, DOI 10.1007/s00382-011-1013-5
SOURCE: http://link.springer.com/article/10.1007/s00382-011-1013-5/fulltext.html