evidence: When these cycles cause the northern latitudes to get less sun in the summer, it allows ice sheets to begin to expand. These ice sheets in turn reflect more incoming sunlight back to space, resulting in a "positive feedback" that drives additional regional cooling. [...] A recent study by Dr Daniel Baggenstos at the University of Bern and colleagues examined the relative contribution of different factors during the transition from the last ice age to the current interglacial period. They found that albedo – changing reflectivity of the surface as ice sheets shrink – was the largest factor responsible for about half of the warming, while changing CO2 concentrations and other greenhouse gases was responsible for 37%, while reductions of the amount of reflective dust and other aerosols in the atmosphere made up the remaining 13%. [...] Specifically, Shakun and colleagues argue that changes in orbital cycles triggered initial melting of ice sheets in the northern hemisphere. This caused large amounts of freshwater to pour into the oceans as ice sheets melted, disrupting the Atlantic Meridional Overturning Circulation (AMOC), which, in turn, cooled the northern hemisphere and warmed the southern hemisphere.