"Climate energy scientist Steven Davis of the Carnegie Institution’s Department of Global Energy and colleagues posed a hypothetical: What would happen if the whole world suddenly stopped building new carbon dioxide emitters, from coal plants to cars, and let the existing ones die naturally of old age? Will the carbon emitters of today push us over the limit, no matter what we do next? Not just yet, Davis claims in a paper in the Sept. 10 Science. But just because we’re not doomed yet doesn’t mean we can relax. 'The currently existing infrastructure is not going to create the worst impact of climate change,' Davis said. 'The devices whose emissions will have the worst impact have yet to be built.'"