Exxon Mobil spokesman Alan Jeffers says whatever the environmental arguments, the bottom line is "there is simply no viable alternative" to carbon-based energy, and that the "symbolic villainization" of Exxon by movements like Fossil Free is counterproductive. (Chevron and coal giant Peabody did not return calls for comment.)
(Read More: Daniel Yergin on the Globalization of Energy Demand)
The movement faces a mighty Goliath. The endowments of the top 50 richest schools in the U.S. total about $269 billion. Say 5 percent of their portfolios are in the targeted fossil fuel companies, and say the campaign was so wildly successful that half of those schools chose divestment. That would put some $6.7 billion in play.
That would surely get attention, but consider that the seven companies named at the top of this story have a combined market cap of $3.8 trillion. The $6.7 billion amounts to less than one-fifth of 1 percent of that.
What's more, currently, none of the wealthiest schools have divested—although many have students agitating for it.
At Harvard, which has one of the largest endowments at more than $30 billion, Chloe Maxmin helped get a referendum urging divestment on the student government election ballot, and 71 percent of students voted in favor.
The university trustees are as yet unpersuaded, saying research and education are the proper routes to addressing climate change, not divestment.
Maxmin, a 21-year-old junior studying social studies and environmental science, is undaunted by the outsize wealth of Big Oil and its cohorts, and admits the economic damage the movement can inflict is limited.
She said the purpose of divestment is twofold: "Making a pariah" of fossil fuel companies and establishing their "rogue status" and building a movement that will alter and lend urgency to public discourse on climate change.
It's early in the going, Henn said, but in the six months since the movement got started in earnest, five small schools have divested. The first on board was Hampshire College, which was also the first to divest in South Africa during the anti-apartheid campaign of the 1980s—an inspiration for Fossil Free.
The first big fish they're hoping to reel in, Henn said, is Brown, which is endowed at about $2.5 billion. "They've already taken some steps," he said.
Tactics vary across campuses, Maxmin said, citing a 200-person rally on her campus in Cambridge, Mass., the staging of a shantytown for "climate refugees" at Brandeis and a sit-in at the office of the president at the Rhode Island School of Design.
In addition, hundreds of churches and 13 cities have committed to divestment, including San Francisco, whose board of supervisors voted unanimously in April to urge the retirement board to divest $583 million, Henn said.