By Nadia Prupis.

Whatever Bernie Sanders thinks of Hillary Clinton's presidential qualifications, the former secretary of state is "uniquely unsuited" to the task of stopping climate change, author and activist Naomi Klein writes in a new op-ed for The Nation .

Combating climate change "requires a willingness to go head-to-head with the two most powerful industries on the planet—fossil fuel companies and the banks that finance them," she writes. "Hillary Clinton is uniquely unsuited to this task."

Among all the uncertainties in the presidential race this year, one thing is certain, Klein says: "The Clinton camp really doesn't like talking about fossil fuel money."

Following her viral face-off with a Greenpeace campaigner last week, Clinton was asked by another climate activist at a Pittsburgh rally on Thursday night if she would reject money from fracking lobbyists—to which Clinton laughed and said, "Read the articles," likely referring to recent reporting by the New York Times and the Washington Post which seemed to debunk the idea that Clinton had taken campaign contributions from oil and gas companies.

"We've done our research," the activist, Sage Lincoln, responded. Watch:

[Insert caption here]

Greenpeace has previously reported that Clinton took more than $300,000 from people working for fossil fuel companies and an additional $1.4 million in "bundled and direct donations" from registered fossil fuel lobbyists.

Lincoln, a Pittsburgh native, told the climate group 350 Action on Thursday that she was particularly concerned over Clinton's ties to fossil fuels because "despite having no family history of asthma, me and two of my siblings have developed it."

"One of the reasons for the bad air quality is clear: there is fracking occurring everywhere in Southwestern Pennsylvania," Lincoln said. "It's in our country parks, our backyards, and even within a stone's throw of the nearby Mars School District. Climate change is dramatically impacting us globally and locally, and we must do everything in our power to curb emissions."

And, as Klein explains at The Nation, that's exactly where Clinton falls short.

Klein writes:

While Clinton is great at warring with Republicans, taking on powerful corporations goes against her entire worldview, against everything she's built, and everything she stands for. The real issue, in other words, isn't Clinton's corporate cash, it's her deeply pro-corporate ideology: one that makes taking money from lobbyists and accepting exorbitant speech fees from banks seem so natural that the candidate is openly struggling to see why any of this has blown up at all.

Days after world leaders at the COP21 climate conference in December finalized a deal to curb worldwide greenhouse gas emissions, Clinton vowed to look into the donations to her campaign.

However, 350 notes, she has yet to follow through—and voters have noticed.

"While Clinton laughs this off, voters who care about our climate and the influence of money in politics are still really disturbed by her continued acceptance of these industry donations," said Yong Jung Cho, spokesperson for 350 Action. "If Clinton wants to prove she is a climate leader that will keep fossil fuels in the ground, she needs to pledge to refuse these donations, and she needs to do it now."

Yet as Klein writes, Clinton's historically "pro-corporate ideology" speaks for itself.

Luckily, the primary "isn't over," she continues, "and Democratic voters need and deserve to know all they can before they make a choice we will all have to live with for a very long time."