A Dusty Past

In light of the puniness of the climate forcing associated with Milankovitch seasonality cycles and with reorganizations of thermohaline circulation, the very large changes in global climate recorded in marine sediments and in polar ice point to the existence of a powerful amplifier. A candidate for this role is proposed here. It involves changes in the position of the polar ice front and hence in the steepness of the latitudinal thermal gradient. The steeper the gradient the higher the frequency of severe storms. The consequent greater entrainment of dust and sea spray into the atmosphere leads to increases in the Earth's albedo. In particular, the millennial-duration Dansgaard-Oeschger events are attributed to changes in the position of the sea ice front driven by the bipolar seesaw in deep water production.