Largest Climate Rally Ever Calls for Obama to Reject Keystone Pipeline (photos)

An estimated 40,000 activists gathered on Feb. 17 in the shadow of the Washington Monument in what has been described as the largest U.S. climate rally ever. The rally preceded a march to the White House to urge President Obama to reject the proposed Keystone XL Pipeline. The event was headlined by Bill McKibben, founder of 350.org, and Michael Brune, the executive dIrector of the Sierra Club. In addition to derailing the pipeline, organizers called for the president to limit greenhouse gas emissions and work for cleaner, renewable energy.

350.org takes its name from the atmospheric concentration of carbon dioxide, in parts per million, which climate scientists and activists say is a safe upper limit for preventing significant climate change. The year 2012 was the hottest year on record. Many scientists believe that the continued burning of greenhouse gasses will raise global temperatures further and increase the likelihood of extreme weather events. In his recent State of the Union address, the president seemed to agree, but gave few specifics on how to combat climate change.

View our photos of the rally and march by clicking on the photo icons below.