The Rockefellers, who made their vast fortune on oil, will on Monday join and other philanthropies and high-wealth individuals in a pledge to sell and get out of a total of $50 billion US worth of fossil fuel assets.

The Global Divest-Invest coalition will announce Monday that the Rockefeller family and others have joined the global movement to divest fossil fuel investments, a day before 120 heads of state address the United Nations to discuss what efforts their countries are making to address a marked long-term increase in greenhouse gas emissions.

Stephen Heintz, president of Rockefeller Brothers Fund, says of John D. Rockefeller: "We are quite convinced that if he were alive today … he would be moving out of fossil fuels and investing in clean, renewable energy." (Spencer Platt/Getty Images)

Since the movement began in 2011, some 650 individuals and 180 institutions which together own $50 billion in assets have pledged to divest from fossil fuels over five years using a variety of approaches.

One of the signatories is the Rockefeller Brothers Fund, Stephen Heintz, an heir of Standard Oil tycoon John D. Rockefeller, said the move to divest away from fossil fuels would be in line with his wishes.

"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.

At the end of July, the fund had $860 million in assets, although it is not known how much of that is specifically invested in fossil fuels.

The fund has committed to invest 10 per cent of its assets in what it deems sustainable development since 2010. Monday's announcement takes that commitment one step further.

Since January 2014, commitments by campuses, churches, cities, states, hospitals, pension funds, and others in the United States and abroad doubled, from 74 to 180, according to philanthropic giving consultancy Arabella Advisors.

One of the higher profile education institution divestments came in May, when Stanford University said it will no longer use any of its $18.7 billion endowment to invest in coal mining companies.

South African Archbishop Desmond Tutu will call for a freeze on all new fossil fuel exploration. (CBC)

While some smaller liberal colleges have made divestment announcements, some larger institutions have been reluctant.

The University of California voted last week to maintain its investments in fossil fuels, frustrating a student-led effort to divest its portfolio in oil, natural gas and coal.

South African Archbishop Desmond Tutu, an anti-Apartheid figure who has been a strong voice on the need for economic divestments, will add to Monday's announcements in a recorded video announcement in which he will call for a freeze on all new fossil fuel exploration.

"We can no longer continue feeding our addiction to fossil fuels as if there is no tomorrow, for there will be no tomorrow," he said.