People survey the damage on Scenic Highway in Pensacola, Fla., after part of it collapsed following heavy rains and flash flooding on April 30. Marianna Massey/Getty Images hide caption

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The world must cut its greenhouse gas emissions to meet its goals, climate experts said Sunday. Members of the Intergovernmental Panel on Climate Change (left to right) Youba Sakona, Ramon Pichs Madruga, Ottmar Edenhofer and Rajendra Pachauri hold copies of their new report in Berlin. John MacDougall/AFP/Getty Images hide caption

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Farmers participate in a CGIAR climate training workshop on how to interpret seasonal rainfall forecasts in Kaffrine, Senegal. Courtesy of J. Hansen/CGIAR Climate hide caption

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The U.N. Intergovernmental Panel on Climate Change's report. ipcc.ch hide caption

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A tall, rubbery weed with golden flowers Dalmatian toadflax is encroaching on grasslands in 32 U.S. states. pverdonk/Flickr hide caption

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Cattle graze at a Brazilian Agricultural Research experimental farm in Planaltina in Goias state. To reduce emissions from deforestation, the Brazilian government is experimenting with grazing on integrated forest and pasture lands. Evaristo Sa/AFP/Getty Images hide caption

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The jet stream that circles Earth's north pole travels west to east. But when the jet stream interacts with a Rossby wave, as shown here, the winds can wander far north and south, bringing frigid air to normally mild southern states. NASA/GSFC hide caption

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