A plume of steam billows from the coal-fired Merrimack Station in Bow, N.H. in January 2015. Jim Cole/AP hide caption

itoggle caption Jim Cole/AP

One of the 20 GPS sensors deployed on Greenland's Helheim Glacier to track its movement. Alistair Everett/Swansea University hide caption

itoggle caption Alistair Everett/Swansea University

A bathtub ring marks the high-water line on Nevada's Lake Mead, which is on the Colorado River, in 2013. Julie Jacobson/AP hide caption

itoggle caption Julie Jacobson/AP

Dennis van Berkel, an attorney with the Dutch environmental group Urgenda, stands on an earthen berm on the outskirts of Amsterdam. The water is higher than the land on the other side of the berm. A Dutch court ruled in favor of Urgenda on Wednesday, saying the Dutch government must cut carbon emissions by 25 percent. Environmental groups in other countries were closely watching the case. Ari Shapiro/NPR hide caption

itoggle caption Ari Shapiro/NPR

AquaBounty's salmon (background) has been genetically modified to grow bigger and faster than a conventional Atlantic salmon of the same age (foreground.) Courtesy of AquaBounty Technologies, Inc. hide caption

itoggle caption Courtesy of AquaBounty Technologies, Inc.

The Smuttynose Towle Farm brewery in Hampton, N.H., has an invisible but tight envelope that keeps the interior temperature consistently cool or warm, prevents energy loss and ultimately saves money. Courtesy of Smuttynose Brewing Company hide caption

itoggle caption Courtesy of Smuttynose Brewing Company

Bill Pentak of Panda Power Funds (left), Plant Manager John Martin (center) and Construction Manager Rob Risher (right) stand in front of the construction site for the new Panda Liberty gas power plant in Towanda, Penn. The plant, expected to come online in early 2016, was deliberately sited on top of the Marcellus Shale to take advantage of the cheap, abundant gas. Marie Cusick/WITF hide caption

itoggle caption Marie Cusick/WITF

Farmer Efi Cohen inspects almond trees on a kibbutz south of Jerusalem. The Israeli government says it's safe to use treated sewage water to irrigate tree fruit, but not all crops. Emily Harris/NPR hide caption

itoggle caption Emily Harris/NPR