Andres Quiroz, an installer for Stellar Solar, carries a solar panel during installation at a home in Encinitas, Calif. Sam Hodgson/Bloomberg via Getty Images hide caption

itoggle caption Sam Hodgson/Bloomberg via Getty Images

The building at 120 East 81st Street is among those converting from an oil- to natural-gas-burning furnace. Jeff Brady/NPR hide caption

itoggle caption Jeff Brady/NPR

A vote to ban fracking in Broomfield, a suburb of Denver, headed to a recount this month after the measure failed by just 13 votes. Broomfield was one of four Front Range towns considering limits or bans on the drilling procedure some fear may not be safe. Kristen Wyatt/AP hide caption

itoggle caption Kristen Wyatt/AP

The chimneys of the Kolaghat Thermal Power Station loom above a field flooded for rice farming near Mecheda, West Bengal, India, in July 2011. Dibyangshu Sarkar/AFP/Getty Images hide caption

itoggle caption Dibyangshu Sarkar/AFP/Getty Images

The EPA tries to keep track of all sorts of methane producers — including herds of methane-belching cattle. Emmett Tullos/Flickr hide caption

itoggle caption Emmett Tullos/Flickr

Saltwater wetlands that include marshes and shoals on Virginia's Atlantic coast. U.S. coastal wetlands losses were 25 percent greater from 2004-2009, according to a recent federal study. U.S. Fish and Wildlife Service hide caption

itoggle caption U.S. Fish and Wildlife Service

University of California, Davis food safety field scientists Michele Jay-Russell, Paula Kahn-Rivadeneira, Anna Zwieniecka, Navreen Pandher and Peiman Aminabadi celebrate the first day of their experiment testing E. coli survival in soil. Courtesy of Fhon Saharuetai hide caption

itoggle caption Courtesy of Fhon Saharuetai