Deglacial decoupling

摘要

Over the past million years, the Earth's climate regularly fluctuated between cold glacial and warm interglacial states. The standard explanation for these cycles holds that variations in the shape of the Earth’s orbit and the tilt of its spin axis affect the waxing and waning of glacial states, by altering the amount and distribution of solar radiation reaching the planet~1. The changes in incoming solar radiation are thought to be amplified by changes in atmospheric carbon dioxide concentrations and ocean circulation~1. Palaeoclimate reconstructions support this view, with temperature and atmospheric CO_2 concentrations (as recorded in Antarctic ice cores) varying in concert~2. Writing in Nature Geoscience, however, Landais and colleagues~3 find that the coupling between temperature and carbon dioxide concentrations broke down during the latter part of the penultimate glacial termination, suggesting that oceanic and atmospheric circulation affected the carbon cycle in an unusual way.