Workers at Los Alamos National Laboratory used organic cat litter to clean up nuclear waste. The litter triggered chemical reactions that later caused a drum to burst. Department of Energy/Flickr hide caption

itoggle caption Department of Energy/Flickr

A 2008 view of the leading edge of the Larsen B ice shelf, extending into the northwest part of the Weddell Sea. Huge, floating ice shelves that line the Antarctic coast help hold back sheets of ice that cover land. Mariano Caravaca /Reuters/Landov hide caption

itoggle caption Mariano Caravaca /Reuters/Landov

Interior Secretary Sally Jewell speaks in Anchorage, Alaska. The Obama administration is requiring companies that drill for oil and natural gas on federal lands to disclose chemicals used in hydraulic fracturing operations. Dan Joling/AP hide caption

itoggle caption Dan Joling/AP

Bayway Refinery in Linden, N.J., is one of two refineries that are involved in the settlement. It's no longer owned by Exxon, but they are on the hook for the cleanup. Joel Rose/NPR hide caption

itoggle caption Joel Rose/NPR

The abandoned Cherokee Clay and Brick Mine in Lee County, N.C., may become a landfill for coal ash. Dave DeWitt/WUNC hide caption

itoggle caption Dave DeWitt/WUNC

A platform owned by Mexico's state-run oil company Pemex is seen off the Bay of Campeche in the Gulf of Mexico. The country has recently opened up its energy sector to foreign investors. Victor Ruiz/Reuters/Landov hide caption

itoggle caption Victor Ruiz/Reuters/Landov

Tybee Island, Ga., site of an annual sand arts festival, is a popular tourist destination. Local officials worry about a federal proposal to open areas off the coast to oil and gas development. Stephen Morton/Savannah College of Art and Design/AP hide caption

itoggle caption Stephen Morton/Savannah College of Art and Design/AP

Renewable energy sources — such as the Eolo wind park about 75 miles south of the Nicaraguan capital, Managua — generate about half of the country's electricity. Officials predict that figure could rise to 80 percent within years. Inti Ocon/AFP/Getty Images hide caption

itoggle caption Inti Ocon/AFP/Getty Images

Climate skeptic Willie Soon has argued in the past that too much ice is bad for polar bears. An investigation into Soon's funding found he took money from the fossil fuel industry and did not always disclose that source. iStockphoto hide caption

itoggle caption iStockphoto