The concentration of carbon dioxide (CO2) in the atmosphere determines whether the Earth is in greenhouse or ice age state. Before humans began to have an impact on the amount of CO2 in the air, it depended solely on the interplay of geological and biological processes, the global carbon cycle. A recent study, headed by the GFZ German Research Centre for Geosciences in Potsdam, Germany, shows that the break-up of continents—also known as rifting—contributed significantly to higher CO2 concentrations in the atmosphere.