NEW YORK (Bloomberg) -- The Rockefeller Brothers Fund, built with profits from Standard Oil Co., is selling investments in coal and tar sands producers in a move to pressure companies that are contributing to climate change.

The fund, founded in 1940 and based in New York City, today joined a group of 800 institutions and individuals announcing they will divest from fossil-fuel companies. Total funds making that pledge reached $50 billion this week, and advocates today vowed 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 today. Given the source of the fortune, “it’s a very important signal to the market.”

The Rockefeller Brothers Fund, which has assets of $860 million and is separate from the larger Rockefeller Foundation, will now 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. and India Coal Ltd.

Activists said the turnout of 310,000 people to march in Manhattan yesterday, along with the latest surge in divestment, showed producers of non-renewable fuels are starting to lose ground with investors and the public.

Heintz said John D. Rockefeller, the founder of Standard Oil more than a century ago, was developing cutting edge fuels when he began investing in oil production at the end of the 19th century to displace whale oil.

“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.

The Rockefeller family fund will keep shares of Exxon, the main successor to Standard Oil after the government-ordered breakup, in part to press the oil and gas producer to account for its carbon assets, he said.

“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.”