What Can Glacial–Interglacial Cycles Reveal about Climate Sensitivity?

The variations in climate during the Pleistocene epoch represent some of the most dramatic examples of climate change in Earth’s history, encompassing interglacial states like the present and glacial states in which ice sheets covered the northern half of North America and substantial portions of Eurasia. These glacial-interglacial climate variations provide evidence of how climate responds to radiative forcing, and thus can yield insights about climate sensitivity. Specifically, such insights can be obtained by considering two aspects of glacial-interglacial climate variations: the transition into a glacial state and the maintenance of a glacial state. The former is particularly dependent on the sensitivity of Arctic climate, whereas the latter can provide broad constraints on global climate sensitivity. Some recent climate simulations will be evaluated in the context of their implications for global and Arctic climate sensitivity.