Climate News: Geographers in the U.S. have found a new factor in the carbon cycle, andall too ominouslya new potential source of the greenhouse gas carbon dioxide (CO2). They have identified huge deposits of fossil soils, rich in organic carbon, buried beneath the Great Plains of America. The discovery is evidence that the subterranean soils could be a rich store, or sink, for ancient atmospheric carbon. But if the soil is exposedby erosion, or by human activities such as agriculture, deforestation or miningthis...