There is a rift forming among energy investors in some of the world's largest energy companies over a global campaign aiming to make fossil fuels as unpopular as tobacco, to better combat climate change. Over the past seven months, investors including the likes of the heirs to the Rockefeller Standard Oil fortune and the board of trustees at California's Stanford University have decided not to invest in coal companies. And the ramifications are significant.

Some church groups and others, such as the University of Glasgow, are taking this a step further; saying they will shun all fossil fuel investments through a grassroots campaign, much like the one used to end apartheid in South Africa. In total, the institutions and individuals total at least $50 billion of investment, and have said that they will sell some or all of their fossil fuel holdings in protest.

Other investors, however, do not agree with this method.  They believe hanging on to shares in oil and gas companies such as Royal Dutch Shell and ExxonMobil, or coal groups like Peabody Energy, is the best way to engage directly with the companies and encourage them to adopt more climate-friendly strategies.

"The idea that shaming an industry will somehow reduce greenhouse gas emissions is not correct," managing director of Light Green Advisors, a New York asset management firm that specializes in environmental sustainability investing, Jonathan Naimon says. "It isn't like divestors are bringing any solutions to the table."

"It's actually projects and technologies that reduce emissions and the people developing them are in energy supply companies as well as energy-using companies."

Harvard University has also been under pressure from students and faculty to sell its fossil fuel holdings, but has repeatedly rejected this pressure with president Drew Faust saying it would not be "warranted or wise."

Bill McKibben, US environmental activist and writer who co-founded the 350.org climate campaign pushing the divestment policy, says engagement strategies only work with some companies.

"If we have a problem with Apple paying Chinese workers bad wages you don't need to throw away your iPhone and boycott Apple stock" McKibben says. "You need to put pressure on them so they pay people better and the price of an iPhone goes up a dollar and everyone's happy."

But he argues that fossil fuel extraction companies are a very different case, particularly because their value is so dependent on their reserves of oil, gas and coal.

"There's no way that engagement can persuade them to get out of this business as long as it remains a profitable business," McKibben says. "The idea that anyone else is going to merrily persuade Chevron or BP that they want to be in the renewables business or something is nuts." He argues this would only happen with government pressure and that in turn would require the dilution of energy companies' political power by efforts such as the divestment movement.

Churches have also become involved, and have become an arena for debate over global warming issues worldwide.  The World Council of Churches, which represents approximately 560 million Christians, has adopted the divestment strategy.

"The use of fossil fuels must be significantly reduced and by not investing in those companies we want to show a direction we need to follow as a human family to address climate changes properly," said Rev Dr Olav Fykse Tveit, WCC general secretary.

It seems, at least for now, that investors are split on their investment policy and strategy, as it comes to fossil fuels. And this debate is likely to continue as climate change and environmental issues consistently rank as some of the most hotly contested issues of society today.