We're already in an Ice Age, namely the Quaternary. The glaciers have receded somewhat, but the Earth still has a high level of glaciation compared to other geo

We're already in an Ice Age, namely the Quaternary. The glaciers have receded somewhat, but the Earth still has a high level of glaciation compared to other geological periods. One of the most important factors is the arrangement of the continents[1]. First, having a large polar continent allows ice to accumulate and increase the Earth's albedo significantly. Second, having two major oceans instead of one decreases the efficiency of heat transfer around the globe, allowing other pockets of glaciation to occur. In a scenario with no polar continents and only one major ocean a glaciation is virtually impossible regardless of where we are in the Milankovitch cycles[2], because the Earth is effectively swimming in a thermodynamic bath. Atmospheric composition is actually a relatively minor factor, it's just that human activity can't shift continents around or affect solar cycles and those both change on much longer timescales than human activity. [1] https://www.wisegeek.com/how-does-the-placement-of-the-continents-affect-global-climate.htm https://www.wisegeek.com/how-does-the-placement-of-the-conti... [2] https://en.wikipedia.org/wiki/Milankovitch_cycles https://en.wikipedia.org/wiki/Milankovitch_cycles