Temperatures in the Arctic are currently climbing two to three times faster than the global average. The result – and, thanks to feedback effects, also the cause – is dwindling sea ice. In a study published in the actual volume of Nature Communications, geo- and climate researchers at the Alfred-Wegener Institute, Helmholtz Centre for Polar- and Marine Research (AWI) show that, in the course of our planet’s history, summertime sea ice was to be found in the central Arctic in periods characterised by higher global temperatures – but less CO2 – than today.