A new study by PCC community members, Eric Steig and Brad Markle, is out in Nature. The team, led by researchers at University of Colorado, Boulder, demonstrated that climate variability in the Southern Hemisphere was forced by ice-sheet topography in the Northern Hemisphere. By using a fully-coupled climate model, the team determined the reason for the observed change in the ice core. They demonstrate that the retreat of the Laurentide–Cordilleran ice-sheets fundamentally altered the circulation of the ocean and atmosphere by reducing the strength of interactions between the tropical Pacific and high southern latitudes. Their results show that interannual and decadal variability in West Antarctica was reduced by nearly half during this retreat.