Somali refugees lead their herds of goats home for the night outside Dadaab, Kenya. A new study shows that animals in many parts of the developing world require more food — and generate more greenhouse emissions — than animals in wealthy countries. Rebecca Blackwell/AP hide caption

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We face real-world decisions now about everything from sea level rise, to energy infrastructure to what food is best for you. Karen Bleier/AFP/Getty Images hide caption

itoggle caption Karen Bleier/AFP/Getty Images

The Larsen B ice shelf on the Antarctic Peninsula, which is among the places where such ice has been breaking off. Mariano Caravaca /Reuters/Landov hide caption

itoggle caption Mariano Caravaca /Reuters/Landov

A police officer guards Cambodia's famed temple of Angkor Wat. The powerful city-state collapsed in 1431 after suffering through two decades of droughts. Heng Sinith/AP hide caption

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Two Iberian lynxes at a nature reserve in northern Spain. (February 2006 file photo.) Victor Fraile /Reuters /Landov hide caption

itoggle caption Victor Fraile /Reuters /Landov

World War Z is just the latest pop-culture incarnation of the Zombie Apocalypse. Adam Frank says the zombies keep coming because they're trying to tell us something. MPC/Paramount Pictures hide caption

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The Capitol dome is seen behind the Capitol Power Plant, which provides power to buildings in the Capitol complex in Washington, D.C. Carolyn Kaster/AP hide caption

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Crew members unload a catch of sockeye salmon at Craig, Alaska, in 2005. Researchers say fish are being found in new areas because of changing ocean temperatures. Melissa Farlow/National Geographic/Getty Images hide caption

itoggle caption Melissa Farlow/National Geographic/Getty Images