Controlling atmospheric carbon dioxide

Paleoclimate The atmospheric concentration of carbon dioxide (CO2) has varied substantially over the past million years in tandem with the glacial cycle. Although it is widely agreed that upwelling of Southern Ocean water is a key factor, the finer details about what caused these CO2 variations are of great importance for understanding climate. Ai et al. identified three modes of change in Southern Ocean upwelling, adding a third to two previously recognized ones. This new mode can help explain better the relative timing of the glacial and CO2 cycles. Science , this issue p. [1348][1] [1]: /lookup/doi/10.1126/science.abd2115