| Summary: | Numerous interglacials have been espoused as Marine Isotopic Stage (MIS) 1 analogues or windows into the future of Holocene climate based on their astronomical characteristics, seasonal insolation patterns or their similarity to predicted anthropogenic warming. However, to date there has been little quantitative study of the climate of these interglacials within a physically robust framework. Here we examine the climate response to peak interglacial forcing during MIS1, 5, 9, 11 and 19 using the Community Climate System Model 3. We determine which interglacial provides the closest analogue to peak MIS1 conditions as well as the mechanisms that dominate the surface climate responses of these interglacials. Considering the differences in astronomical parameters and greenhouse gases we discount MIS5 and 9 as analogues of peak MIS1 conditions due to their significantly stronger seasonal climate responses. Conversely, based on seasonal and hemispheric averages of surface temperature, precipitation and sea-ice cover, MIS11 and 19 are most similar to MIS1, with MIS11 actually exhibiting a higher affinity particularly during boreal summer. This is attributed to a greater similarity in the seasonal and latitudinal distribution of insolation over middle latitude Eurasia and North America, which are the regions most sensitive to insolation change given the absence of ice-sheet dynamics in our model. Global ocean overturning circulation is also closer to MIS1 during MIS11 than MIS19, due predominantly to differences in Weddell Sea bottom water formation. Thus, under the assumption of present-day ice-sheets MIS11 appears to be the better climatic analogue to peak MIS1 climate. Surface temperature variations between the interglacials are primarily due to sensitivity of the relatively large northern hemisphere landmasses to insolation, sea-level pressure changes in the North Pacific and Southern Oceans, cooling in the Nordic Seas and the summer-remnant effect (winter warming due to increased sea-ice melt during more intensely ...
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