On Monday, the Rockefeller Brothers Fund, which controls $860 million in assets and is presided over by heirs of famed oil tycoon John D. Rockefeller, decided to sell its assets tied to fossil fuel companies and to invest in clean energy alternatives. The pronouncement made plenty of headlines but will hardly hurt the industry's bottom line.

Fifty foundations in total have shown enthusiasm for the global fossil fuel divestment movement ahead of a climate change summit at the United Nations on Tuesday and after a climate change march in New York that drew about 600,000 activists. Fossil fuel companies will soon watch $50 billion in assets change hands as philanthropies, institutions, local governments and individuals follow through on pledges to divest from oil and gas in favor of clean-energy alternatives, but those divestments amount to a penny for every dollar in the centuries-old industry valued at nearly $4.7 trillion.

"It's all wishful thinking," said Fadel Gheit, an oil and gas analyst for Oppenheimer. "Oil is still the easiest, most convenient, best solution so far. I tell people, 'Don't throw out your old furniture before you get new furniture or you’ll be sitting on the floor.'"

According to a report by Arabella Advisors, which aims to help philanthropies and individuals give effectively to their causes, about 180 institutions and local governments and more than 650 individuals representing $50 billion in assets have pledged to divest from fossil fuels. Since January, the number of such pledges has more than doubled, the report said.

But the commitments to divest are still miniscule in comparison to the mammoth fossil fuel industry. The nearly 1,500 exchange-listed oil and gas companies are together valued at $4.65 trillion, according to a recent paper by Bloomberg New Energy Finance.

"Fossil fuels are investor favorites for a reason," the BNEF report said. "Few sectors offer the scale, liquidity, growth and yield of these century-old businesses vital to today's economy…. Oil and gas companies are too large and too widely held for divestment to be easy or fast."

The shares dumped by those in the divestment movement won't likely have trouble finding new buyers.

"People don’t see any practical, realistic substitute for oil for decades to come," Gheit said. 

Advocates for the divesture movement know that they're up against a huge industry and say that their aim is to move finances from oil, gas and coal to renewable energy projects; through that momentum, they hope to influence legislation to, in turn, squeeze more finances out of oil and gas into renewables.

"This is a movement to start a political discussion. We never expected Harvard to divest overnight," said Jamie Henn, director of strategy and communications for 350.org, an environmental group involved in the divestment movement that began on college campuses. Stanford University has decided not to invest in coal mining companies, but others with big endowments such as the University of California, Yale University and Harvard University have declined activists' calls to divest from fossil fuels. 

Henn, however, still sees the movement making an impact. Sitting in a café in Manhattan, he described a Flood Wall Street activist passing by the window protesting carbon assets. "The discussion of carbon is very real on Wall Street now. And all of that has happened in the last 18 months. We're just getting started."