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If Earth overheats, can it be artificially cooled? Should the effort begin now? Who would decide? The very idea of "geoengineering," and the unknown risks of tweaking our climate, leaves many scientists with more questions than answers. AP Photo/Courtesy of NASA hide caption

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So far, the tobacco industry has paid more than $100 billion to state governments as part of a settlement. While smoking is down among young people and even adults in some areas, it's still unclear where much of that money has gone. Carolyn Kaster/AP hide caption

toggle caption Carolyn Kaster/AP
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