Since the development of general circulation models in the 1970s, the numerical simulation of ancient climates has been a major issue, both to test the codes under extreme conditions and to understand the mechanisms behind the climate changes that have marked the history of the globe as testified by various proxies.

The modeling of ancient climates has explored the consequences of major shifts in the forcing of climate dynamics on all time scales, from mountain range uplift to orbital variations to abrupt changes in greenhouse gas concentrations. Today, the study of ancient climates is more valuable than ever, as shown by its increasing share in IPCC reports but also by the strong demand for quantification of past climate changes from other disciplinary fields, notably those interested in the evolution of biodiversity.

Nevertheless, great challenges, both theoretical and technological, await paleoclimate modeling in the years to come, which may invite us to rethink our way of understanding paleoclimates.

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