Despite frigid temperatures, members of UT's SPEAK club marched around the National Mall in Washington, D.C., on Sunday to voice their concerns about the threat of climate change.

They were not alone; more than 35,000 other demonstrators joined them in what organizers called the largest climate-change protest in U.S. history.

SPEAK, or Students Promoting Environmental Action in Knoxville, is a student group that aims to bring about environmental awareness and action to UT's campus and the Knoxville community. Traveling to the nation's capital for Sunday's climate rally was a way for the club to be a part of the climate change conservation movement on a more national level. Organized by the environmental groups 350.org and Sierra Club, the march was focused specifically on demonstrators' opposition to the proposed construction of the Keystone XL Pipeline, an oil pipeline that would run from Canada to Texas and collect oil from tar sands. Bipartisan supporters in the Senate are pushing for approval of the $5.3 billion pipeline, hoping to create more jobs for the downtrodden economy and make progress toward energy independence.

Opponents of the proposal, however, cite the risk of an oil spill from the pipeline as well as its potentially dangerous extraction methods as reasons for dismissal.

Known as "fracking," the process of the oil's extraction is widely thought to emit more greenhouse gases than traditional methods of oil production. Many protestors fear underground contamination in areas surrounding the extraction points. High levels of water pollution have been reported. The crowds urged President Obama, who has already delayed the proposal, to exercise his executive veto on the bill. Speakers at the event said the decision he makes will be a key part of his legacy.

Eric McAnly, co-president of SPEAK and a senior in chemistry, has attended the event each of its three years of existence. The original protest in 2011 involved fewer than 5,000 people, and McAnly noted the march's growth.

"I thought the rally went rather well for the weather conditions and for the amount of people who were there," said McAnly. "I think there were more people there than they ever expected."

He drew parallels between Martin Luther King Jr.'s march on Washington 50 years ago and the environmental march held on Sunday.

"I think it was great (of organizers) to connect that social justice issue from back in the '60s with what we are now facing, this injustice upon the climate," he said. "This is really a historical moment."

Kelsey Campbell, an undecided freshman and a member of SPEAK, was also impressed with the movement.

"I couldn't believe the turnout and the positive, peaceful feel of the demonstration," she said. "I hope the scale of the event will encourage people to do their own research on the Keystone pipeline and climate change instead on dismissing it as a radical cause."

Environmental activists are cautiously hopeful and eager to hear a decision from the president. For more information about this movement visit 350.org.