From the carbon bubble to 'dirty energy'
Leaving the "dirty stuff" in the ground is fast becoming the mantra of environmentalists, with the global campaign to move money out of fossil fuels gaining momentum. There is pressure to divest from oil and gas companies on the basis that they represent a "carbon bubble" of overvalued assets, but the industry says this stance is "simply naive". Here are some of the key questions.
Where does the idea of divestment come from?
Rewind 30 years to the 1980s, when divestment meant ditching shares in South Africa during the apartheid era. Academics argue that divestment increased public visibility of the injustices of South Africa's apartheid government and contributed to its decline. Since then, similar movements have targeted a host of issues, such as sweatshop labour, use of landmines, and tobacco advertising. The fossil fuel divestment campaign is based on encouraging people to move their money away from fossil fuels and invest in sustainable energy.
Who is leading the way in getting out of fossil fuels?
The campaign started in the US and has spread around the world. Hundreds of institutions controlling about £30bn of assets have now pledged not to invest in companies seen to fuel global warming. Among those in the UK who have signed up are universities and organisations such as Glasgow University and the British Medical Association. The Church of England, which has an investment portfolio of £9bn, has warned it could withdraw its investments from oil giants BP and Shell unless they do more to tackle climate change. There are also consumer campaigns, such as Move Your Money, which wants customers to put pressure on their banks to cut ties with "dirty energy".
What does the science say?
Scientific studies show that existing fossil fuel reserves are several times greater than can be burned if the world's governments are to fulfil their pledge to keep global warming below the limit of 2C regarded as the threshold of dangerous climate change.
What are the pros and cons?
Some charities, such as the Wellcome Trust, say it is better to work with the energy companies involved to become more environmentally friendly rather than sell out on them. Others, including some scientists, take the view that expensive technologies such as carbon capture and storage could be a solution to the problem of carbon emissions and will need financial investment from industry as well as government. Many oil companies accept that some reserves will have to remain in the ground to tackle global warming. The practical approach is to burn the fossil fuels that are most cost-efficient and least "dirty". But some environmentalists say fossil fuel companies will never play a leading role in any move towards a low-carbon economy.
What happens next?
One view is that the recent drop in oil prices presents a once-in-a-lifetime opportunity for governments to get rid of fossil fuel subsidies and introduce a price on carbon. This generally goes against government thinking and concern over job losses in the oil and gas industry. With the divestment campaign gathering pace - and momentum building for the Paris climate talks in December - there is renewed hope among campaigners. But with environmental policies getting little attention in the UK election, and coal, oil and gas companies continuing to spend billions on exploration, NGOs are already upping their rhetoric in calling for renewed government efforts over climate change.