AO represents the pure contribution of the ocean ,4V represents the pure contribution of the vegetation AO V represents the synergism between the ocean and vegetation AO V gives the sum of all contributions: A + AO 4- AV + AO V

AO V — AO = AV + AO V gives what we would conclude from a classical sensitiv ity experiment for the contribution of vegetation changes (control case: fixed vegetation) NH Northern Hemisphere; NH|, Northern Hemisphere lands; XAfrj. North African lands SH Southern I lemisphere

The difference between the ice volumes simulated in the control, V\\y and in the reference, experiments is actually the sum of the individual contributions of the vegetation and the sea level feedbacks and of their synergism (see Equation 1). Most of the time, V\\ is smaller than Vqq, the combined effect of both the vegetation-snow albedo and the sea level feedbacks reducing progressively the amount of ice stored in the ice sheets of f-fo. After one full glacial-interglacial cycle, this reduction amounts to 20 x 106 km1 of ice. It is only at stage 5d that the difference V\\ — ^oo is slightly positive, the vegetation and sea level mechanisms contributing to increase the amount of ice during this abortive glaciation. At stage 4 and a little after the LGM of stage 2, their global contribution is negligible and V\\ = ifo. But the detailed explanation is not as

simple nor as straightforward, and the calculation of Fjo, J oi, and IH is necessary (Figure 8.6).

During the whole stage 5, from 122 to 70 kvr BP, it is essentially the vegetation-

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