Climate scientists who scrutinized the U.N. accord are urging citizens to keep a sharp eye on each nation's leaders to make sure they follow through on pledges to reduce emissions. Simone Golob/Corbis hide caption

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U.S. Rep. Lamar Smith, R-Texas, and Kathryn Sullivan, director of the National Oceanic and Atmospheric Administration, have been tangling for months over the legitimacy of a climate study NOAA scientists published in Science. Drew Angerer/AP; Mark Wilson/Getty Images hide caption

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President Obama attended the plenary session of the international climate conference Monday, just outside Paris. By using regulations instead of treaties, Obama hopes to continue to cut U.S. emissions of greenhouse gases. Eric Feferberg/AFP/Getty Images hide caption

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Climate models project 21st century global temperatures. NASA's Scientific Visualization Studio and NASA Center for Climate Simulation hide caption

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A man walks through hundreds of pairs of shoes displayed in Paris as part of a rally called "Paris sets off for climate" on Sunday, Nov. 29. More than 140 world leaders are gathering around Paris for high-stakes climate talks this week. Laurent Cipriani/AP hide caption

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Delegates from about 170 countries gathered in Kyoto in December 1997 during the United Nations Framework Convention on Climate Change. This year in Paris, the stakes are even higher, negotiators say. AFP/Getty Images hide caption

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A field near harvest time at Meyers Farm in Bethel, Alaska, can now grow crops like cabbage outside in the ground, due to rising temperatures. Daysha Eaton/KYUK hide caption

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Zach Whitener, research associate at the Gulf of Maine Research Institute, holds a cod while collecting samples for a study. Gulf of Maine Research Institute hide caption

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This image shows Hurricane Patricia, a Category 5 storm, blasting toward southwestern Mexico on Friday. The photo was taken from the International Space Station. Scott Kelly/AP hide caption

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Imagine a bar without the booze. Delegates wrangling in Bonn, Germany, this week have to figure out soon how to cover the world's climate bill. Oliver Berg/DPA/Landov hide caption

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Bull trout are running out of time in Montana as their traditional waters heat up, biologists say. By moving more than 100 fish to higher elevations, fisheries scientists hope to save the species by seeding a new population in waters that will stay cooler longer. Jim Mogen/USFWS hide caption

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New Mexico's largest electric provider — the coal-fired San Juan Generating Station near Farmington — has been defending a plan to replace part of an aging coal-fired power plant with a mix of more coal, natural gas, nuclear and solar power. Susan Montoya Bryan/AP hide caption

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The Antarctic ice sheet stores more than half of Earth's fresh water. Scientists wondered how much of it would melt if people burned all the fossil fuels on the planet. UPI /Landov hide caption

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The Two-Way

What Would Happen If We Burned Up All Of Earth's Fossil Fuels?

Scientists used an estimate of how much fossil fuel is left in the ground to do computer simulations and come up with a worst-case scenario.

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President Obama makes his way across the tarmac Monday to greet well-wishers upon arrival at Elmendorf Air Force Base in Anchorage, Alaska. Mandel Ngan/AFP/Getty Images hide caption

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Floodwaters from rising sea levels have submerged and killed trees in Bedono village in Demak, Central Java, Indonesia. As oceans warm, they expand and erode the shore. Residents of Java's coastal villages have been hit hard by rising sea levels in recent years. Ulet Ifansasti/Getty Images hide caption

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Pope Francis prays during his general audience in Saint Peter's Square at the Vatican on June 3. The pope has made statements supporting the idea that climate change is man-made, and his upcoming encyclical on the environment and poverty is highly anticipated. Vincenzo Pinto/AFP/Getty Images hide caption

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A fully loaded container ship sails along the coast. Historically, ships have taken most of the sea measurements that go into the estimate of Earth's average surface temperature. iStockphoto hide caption

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