About US$8 trillion of known coal reserves lie beneath the earth's surface. The companies planning to mine and burn them are being targeted by the growing ranks of investors concerned with the greenhouse gases that will be made.
Storebrand ASA, which manages US$74 billion of assets from Norway, sold out of 24 coal and oil-sands companies between July and November including Peabody Energy, the largest US coal producer, citing a desire to cut fossil-fuel industry holdings.
Norway's opposition Labour Party has proposed banning the country's US$800 billion sovereign wealth fund from making coal investments.
"Maybe we've hit some kind of nerve in the debate," said Christine Torklep Meisingset, Storebrand's head of sustainable investments in Oslo. "Hopefully, other investors will be acting along the same lines. There could be an interesting parallel to tobacco."
The movement is an offshoot of a campaign by more than 70 investors to pressure all fossil-fuel industries on climate change.
It harks to the 1990s anti-tobacco push and is gaining help from unlikely partners. The International Energy Agency, a 28-nation group promoting energy security, is lobbying increasingly to limit the release of heat-trapping gases.
Coal, whose burning spews about twice the greenhouse gases as natural gas, is not in retreat. In 2011, coal was used to generate 30.3 per cent of the world's primary energy, the highest level since 1969, according to the World Coal Association, an industry trade group. That share slipped only to 29.9 per cent last year.
Future curbs on carbon emissions beyond 2020 may cut valuations on coal assets by as much as 44 per cent, according to HSBC.
"There is the beginnings of divestment out of pure-play coal by some investors," said Nick Robins, head of HSBC's climate change office in London. "There's been a very marked rise in concern about this issue. There's a recognition that as you move to a low-carbon economy that coal is potentially most vulnerable."
Coal remained a "good story" with demand from China and India estimated to grow almost 4 per cent a year to 2020, Godfrey Gomwe, chief executive of Anglo American's thermal coal unit, said.
Ivan Glasenberg, chief executive of Glencore Xstrata, wrote in the company's sustainability report last month: "We believe that fossil fuels will continue to play a significant role in the global energy mix."
Globally, share prices of thermal coal producers have slid over the past two years on declining demand for the fuel and fears of oversupply. Patriot Coal filed for bankruptcy last year while fellow United States producer Arch Coal has dropped 71 per cent and Peabody 44 per cent. China Shenhua Energy, the nation's top producer, is down 27 per cent over the same period while Indonesia's biggest exporter Bumi Resources is off about 80 per cent.
"There's a pretty plausible case that this is the beginning of the end," said Craig Mackenzie, investment director and head of sustainability at Scottish Widows Investment Partnership. Scottish Widows divested from pure-play coal producers last year on the prospect that demand for the fuel will continue to wane amid a booming US natural gas market.
A group of 70 investors including California's two largest public pension funds and F&C Management, holding more than US$3 trillion in combined assets, wrote to the world's top 40 oil, gas, coal and electric power companies in September urging them to assess the risks climate change poses to their business.
International Energy Agency executive director Maria van der Hoeven has described coal as the "biggest elephant in the room" in the debate about how to shift away from fossil fuels to help manage climate risks. Coal-fired power stations remained the cheapest form of energy for developing nations, she said. The agency has said coal demand would need to fall by 3.5 per cent a year in the 2020s to meet a United Nations target for temperature gains to be kept below 2 degrees Celsius by 2100.
Total production rose 2.9 per cent to an estimated record 7.8 billion tonnes last year. There's about one trillion tonnes of reserves left, equivalent to 132 years of global output at the 2012 rate, according to the coal association.
Greenhouse gas emissions from the energy industry are forecast to rise 20 per cent above 2011 levels by 2035, according to a report by the IEA. This means that global temperatures could rise an average of 3.6 degrees above pre-industrial levels by mid-century, far above the internationally agreed-to target of 2 degrees.
UN scientists said in September that humans have now emitted more than half the carbon permissible to remain within the 2-degree limit. To meet that target, about two-thirds of proven fossil-fuel reserves must remain in the ground, mostly coal, according to the IEA.
"There's potential risk here that could be very material to companies involved in coal production resulting from a potential future in which coal demand declines more quickly than companies are currently anticipating," said Vicki Bakhshi, head of governance and sustainable investment at F&C Investments.