The Rockefeller Brothers Fund, built with profits from their great-grandfather’s Standard Oil Co., is selling investments in the fossil fuel industry in a move to pressure companies that are adding to climate change, Bloomberg said Sept. 22.

On that day, the New York City-based fund joined a group of institutions and individuals announcing they will abandon companies reliant on coal and tar sands. Total divested funds reached $50 billion this week, and advocates on Sept. 22 pledged to triple the total by next December.

“We are immediately divesting from coal and tar sands, the most carbon-intensive fuels,” Stephen Heintz, president of the Rockefeller Brothers Fund, said that day. The fund, created in 1940, also will assess how to cut other fossil fuel investments while boosting renewable energy companies, he said.

Students and activist investors are backing the divestment effort spearheaded by the environmental group 350.org to persuade foundations, corporations, universities and others to divest from the 200 companies with the largest share of coal and oil resources, including Exxon Mobil Corp. (NYSE: XOM).

With the Rockefeller Brothers Fund, managing assets of about $860 million and separate from the larger Rockefeller Foundation, set to pull out of coal and oil sands, and to look at phasing out investments in oil and natural gas, the effort will get a symbolic boost.

“It’s not a huge economic lever, but it does begin to send financial signals and it brings visibility to the issue,” Heintz said in an interview. “This is like a snowball, and it’s going to get more and more mass as it rolls forward.”

Heintz said John D. Rockefeller, the founder of Standard Oil at the end of the 19th century who helped develop the domestic petroleum industry, would be prepared to move away from the oil business.

“We are quite convinced that if he were alive today, as an astute businessman looking out to the future, he would be moving out of fossil fuels and investing in clean, renewable energy,” Heintz said in a statement.

South African cleric Desmond Tutu, who helped spur calls for divestment that led to the end of apartheid in his home nation in the 1980s, on Sept. 22 endorsed the divestment drive.

“Climate change has become the human rights challenge of our time,” Tutu told advocates via video message that day. “We can no longer continue feeding our addiction to fossil fuels as if there is no tomorrow, for there will be no tomorrow.”

Asked about Exxon being targeted by the divestment effort, a company spokesman referred to a report it released earlier this year.

“Energy use and mix evolve slowly due to the vast size of the global energy system,” the Exxon report said. “We believe the transition to lower-carbon energy sources will also take time, despite rapid growth rates for such sources.”