Crew members pull an oyster dredge in Tangier Sound of the Chesapeake Bay near Deal Island, Md., in 2013. A study found that the Chesapeake Bay shellfishery is a "hot zone" for ocean acidification. Patrick Semansky/AP hide caption

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Robert Davies (standing) and the quartet during a performance of "The Crossroads Project." Musicians include (left to right) Robert Waters, Rebecca McFaul, Anne Francis Bayless and Bradley Ottesen. Andrew McCallister /Courtesy of The Crossroads Project hide caption

itoggle caption Andrew McCallister /Courtesy of The Crossroads Project

To put their probes into the Arctic Ice, researchers hitched a ride on a South Korean icebreaker. Courtesy of Craig M. Lee/University of Washington hide caption

itoggle caption Courtesy of Craig M. Lee/University of Washington

The eruption of Mount Pinatubo in the Philippines in 1991 spewed almost 20 million tons of sulfur dioxide into the atmosphere, causing worldwide temperatures to drop half a degree on average. Arlan Naeg/AFP/Getty Images hide caption

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An unmanned aerial vehicle films vineyards in France. Drones like this one are also being used in Califiornia, as part of a broader "precision farming" movement designed to lower greenhouse gas emissions. Sami Sarkis/Ocean/Corbis hide caption

itoggle caption Sami Sarkis/Ocean/Corbis

Marina owner Mitzi Richards carries her granddaughter in September as they walk on their boat dock at the dried up lake bed of Huntington Lake in California, which was at only 30 percent capacity as a severe drought continued. The state was in the grip of its third year of severe drought, the worst in decades. Mark Ralston/AFP/Getty Images hide caption

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Country representatives listen to opening remarks at the start of the United Nations' Conference of the Parties on Climate Change in Lima, Peru. Cris Bouroncle/AFP/Getty Images hide caption

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Lightning strikes near Ben Hill Griffin Stadium at Florida Field in Gainesville, Fla., in August. A new study says a rise in average global temperatures due to climate change will increase the frequency of lightning strikes. Phil Sandlin/AP hide caption

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Chinese President Xi Jinping and President Obama, seen here during a ceremony at the Great Hall of the People in Beijing, announced pledges to reduce greenhouse gases. HUANG JINGWEN/Xinhua /Landov hide caption

itoggle caption HUANG JINGWEN/Xinhua /Landov

U.S. President Barack Obama, right, smiles after a group of children waved flags and flowers to cheer him during a welcome ceremony Wednesday with Chinese President Xi Jinping at the Great Hall of the People in Beijing. In a surprise agreement late Tuesday, China agreed to a first-ever target for capping its carbon emissions, while the United States pledge to cut faster than previously planned. Andy Wong/AP hide caption

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Oil, carried here by the Trans-Alaska Pipeline, is fundamental to the state's economy. But Alaskans also face the effects of climate change in their daily lives. Al Grillo/AP hide caption

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Manuel Pulgar-Vidal, Peru's Minister of Environment, U.N. Secretary-General Ban Ki-moon, Intergovernmental Panel on Climate Change (IPCC) Chairman Rajendra Pachauri and Renate Christ, Secretary of the IPCC present the Synthesis Report during a news conference in Copenhagen on Sunday. Scanpix Denmark/Reuters/Landov hide caption

itoggle caption Scanpix Denmark/Reuters/Landov

A Haitian woman holds cherries from a coffee tree. Haiti's coffee trade was once a flourishing industry, but it has been crippled by decades of deforestation, political chaos and now, climate change. Patrick Farrell /MCT /Landov hide caption

itoggle caption Patrick Farrell /MCT /Landov