evidence: This happens in a multitude of ways. As ice sheets grow, sea levels change dramatically, falling around 120 meters compared to today’s levels and exposing large areas of land currently underwater and allowing growing vegetation to take up more CO2. Colder ocean water dissolves more CO2, absorbing more from the atmosphere, though this is somewhat offset by the effect of higher salinity on ocean CO2 absorption – as fresh water from snow freezes into ice sheets. [...] The fact that relatively small changes in external forcings can drive such a large planetary response during ice ages should serve as a cautionary example. This is because human emissions of CO2 and other greenhouse gases push the Earth further out of the range of climate conditions that have characterised the past few million years.