Cardinals follow a news conference to present Pope Francis' encyclical "Laudato Si," or "Praise Be," at the Vatican on Thursday. The far-reaching papal letter addressed climate change and the poor. Andrew Medichini/AP hide caption

itoggle caption Andrew Medichini/AP

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

itoggle caption Vincenzo Pinto/AFP/Getty Images

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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Gustav Dejert/Ikon Images/Getty Images

Plankton collected in the Pacific Ocean with a 0.1mm mesh net. Seen here is a mix of multicellular organisms — small zooplanktonic animals, larvae and single protists (diatoms, dinoflagellates, radiolarians) — the nearly invisible universe at the bottom of the marine food chain. Christian Sardet/CNRS/Tara Expeditions hide caption

itoggle caption Christian Sardet/CNRS/Tara Expeditions

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

ADP Co-chairs Daniel Reifsnyder (left) and Ahmed Djoghlaf (center) say their negotiation work is difficult but worth it. "We only have one planet, you know," Reifsnyder says. "We have to protect it." Courtesy of IISD/ENB hide caption

itoggle caption Courtesy of IISD/ENB

Much of the Netherlands is below sea level, including Amsterdam. Urgenda argues that any rise in the sea level could have a huge impact on the country. Ari Shapiro/NPR hide caption

itoggle caption Ari Shapiro/NPR

President Obama, seen here inspecting solar panels on the roof of the Department of Energy, has submitted a U.S. pledge to reduce greenhouse gases. Kevin Lamarque/Reuters/Landov hide caption

itoggle caption Kevin Lamarque/Reuters/Landov

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

These beans, grown on test plots at the International Center for Tropical Agriculture in Colombia, can thrive in temperatures that cripple most conventional beans. Courtesy of CIAT/Neil Palmer hide caption

itoggle caption Courtesy of CIAT/Neil Palmer

Staghorn coral planted by scientists in the Florida Keys. Researchers hope to give the same sort of boost to the world's shrinking population of pillar coral, now that they can raise the creatures in a laboratory. Joe Berg/Way Down Video/Mote hide caption

itoggle caption Joe Berg/Way Down Video/Mote