Greens question Hillary's climate chops

A number of climate activists who rallied on Sunday in New York City for the largest climate change march to date, said they aren't convinced Hillary ClintonHillary Rodham ClintonSessions says he doesn't regret recusing himself from Russia probe Judiciary Committee Republicans want a second special counsel: report Fusion GPS: White House trying to smear us on Russia MORE is their candidate if she runs for president.

Founder of the prominent activist group 350.org, Bill McKibben, told MSNBC that the former secretary of State has a lot to prove.

“I think Hillary Clinton has an awful lot to demonstrate to environmentalists and people who care about climate change,” said McKibben, whose group helped organize Sunday's march.

“She oversaw the complete fiasco that was the Copenhagen Conference as secretary of State. That was the biggest foreign policy failure since Munich. It’s not a proud record," he added.

In a recent renewable energy speech in Las Vegas, however, a majority of Clinton's speech was dedicated to sounding the alarm on climate change.

In her book, "Hard Choices," the likely democratic front-runner in 2016, made the 2009 Copenhagen meeting the focus of one of the chapters, touting her work with President Obama to get critical conversations flowing between the U.S. and China.

Still, actor Mark Ruffalo isn't sure Clinton will get support from greens, a critical faction of the base that has helped Obama.

Clinton's problem is her stance on fracking for natural gas, a significant element of the U.S. energy boom, which Obama supports as well.

"Unless she changes that, the climate change voters, the people who take this very seriously, are not going to be able to get behind her,” Ruffalo told MSNBC.

“If someone can offer up another way forward, [climate voters] are going to get behind that person. Just like Obama, they got behind him,” Ruffalo added, suggesting Sens. Elizabeth WarrenElizabeth WarrenSenate heading for late night ahead of ObamaCare repeal showdown Dem senators 'seek assurances' Icahn not swaying regulators on AIG: report Maryland Dem considering bid to take on Trump MORE (D-Mass.) or Bernie SandersBernie SandersLive Coverage: Senate votes down 'skinny' ObamaCare repeal Sanders: Senate healthcare fight 'totally bananas' Overnight Defense: Military won't lift transgender ban until Trump sends directions | House passes national security spending | Russian sanctions bill heads to Trump MORE (I-Vt.) as possible alternatives, according to MSNBC.
“These are people who get this, who are not beholden to this 100-year-old fossil fuel stranglehold on leaders like Hillary Clinton," Ruffalo said.