| Summary: | To understand better our current interglacial and its future, we have investigated the response of the climate system to insolation and GHG during the warm intervals (Climatic Optimum) of the interglacials over the past 800,000 years using both LOVECLIM (Yin and Berger, 2010, 2012; Yin, 2013) and CCSM3 (Herold et al., 2012; Nikolova et al., 2013). A particular attention is paid to the 5 warmest interglacials MIS-1, -5, -9, -11 and -19. If we identify the peaks of the interglacials with NH summer at perihelion, MIS-1, MIS-11 and MIS-19 show a pretty similar latitudinal and seasonal distribution of the incoming solar radiation. When compared to the average of the last 9 interglacials, they are under-insolated over the whole globe during boreal summer and are over-insolated during boreal winter with a maximum at the South Pole. This insolation distribution leads to a cooling over all the continents in boreal summer and to a warming over the whole Earth, except the Arctic, in boreal winter. A warming over the Southern Ocean in austral winter occurs during MIS-1 and MIS-19 due to the summer remnant effect of insolation. However, this does not happen in MIS11 because the large global cooling during this season is dominating the remnant effect of the austral summer. This leads to MIS-11 being a cool insolation-induced interglacials and thus not as good an analogue of MIS-1 as MIS-19, at least as far as insolation is concerned. The CO2e of MIS-1 and MIS-19 is also practically the same (265 ppmv) but is larger for MIS-11 (286 ppmv). This pretty low value for MIS-1 and MIS-19 cools the Earth, reinforcing the insolation-induced cooling during boreal summer and moderating the warming during boreal winter. The reverse happens for MIS-11 for which its higher value allows it to be finally classified among the warm interglacials. The best analogue to MIS-1 depends therefore upon the criteria used to select such an analogue. If the interglacial peaks are considered, their global annual mean temperatures are slightly lower than ...
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