Last year the UN Intergovernmental Panel on Climate Change warned that unless the world's mean temperature is stabilised - prevented from rising by more than 2C - we risk runaway climate change. That meant 80 per cent of known coal, oil and natural gas reserves must be kept in the ground as "stranded" assets, worth nothing. The fossil fuel industry has ignored this threat; those undeveloped assets are a huge part of its market wealth.
The Westpac protesters came from two groups, 350 Aotearoa and the Coal Action Network Aotearoa. As the energy industry drills, fracks and mines around the globe, the US parent of one of those organisations - 350.org - has emerged as its nemesis, wielding a potent weapon: divestment.
Protesters want investors to withdraw support from 200 fossil fuel companies, including huge players such as ExxonMobil and Chevron. It's a war in which Westpac suddenly found itself cast as a bad guy by the emerging divestment movement.
While divestment is an economic strategy, the campaign is pitched as a moral crusade aimed at universities, pension funds and other big investors. The Kiwi end of the campaign has held divestment forums, sent letters to institutions asking them to sell fossil fuel stocks, and staged flash mob events at Westpac branches.
"Protesters went to Westpac's Cuba St branch in Wellington and symbolically withdrew $1 from their accounts," says Ashlee Gross, 350 Aotearoa's national co-ordinator. "To remind them we are customers and have the power to remove our money."
A dollar is a piffling amount, but the symbolism is significant; fossil fuel divestment is already under way in New Zealand. The Anglican Church has divested. The Church sees divestment as a moral issue because climate change in our region would harm people who are least responsible for rising temperatures: Pacific Islanders faced with rising seas.
While state-owned funds, notably the NZ Superannuation Fund, with $440 million (2.3 per cent of its capital) invested in fossil fuels, according to a World Wildlife Fund report last year, and the Accident Compensation Corporation, with $626.8 million invested (3.4 per cent), have shown willingness to stop investing in the nuclear industry, they seem less likely to follow the Church's example when it comes to fossil fuels.
Westpac said it "provides banking services to Bathurst Resources, but has not been involved in financing Bathurst's Denniston Escarpment Mine Project".
Which is arguably disingenuous, as a loan was made in 2012 to Bathurst's Cascade Mine on the edge of the Denniston plateau, the beachhead for Bathurst, which is gearing up for larger-scale mining on the plateau.
"We're not trying to shut down the Cascade Mine," says Gross. "We made it clear to Westpac [at a November meeting] we understood the loan wasn't specifically for Denniston. But that doesn't mean it didn't enable the funding of Denniston ... there's no financial separation between Bathurst mines. It's not like they are different corporations or different subsidiaries. And Bathurst made it clear to their stakeholders, in putting that information out publicly, that the profit they were making from Cascade was going into Denniston."
However, Hamish Bohannan, Bathurst's chief executive, says Westpac's earlier support is "totally unrelated" to present developments, that the company is "almost debt free" and present work is funded from equity. While acknowledging the need to "step away from fossil fuels" because of climate change, he says the 350 campaign is "sleight of hand", as on the West Coast Bathurst mines high-quality metallurgical coking coal, used in steel production, and there is no alternative fuel. He points out that steel is used as a raw material in many renewable-energy industries, "and we wouldn't have the tools to get alternative power without coal in the first place. It is a journey".
The company says it will provide 400 direct jobs, 200 of them on the West Coast, and generate $1 billion for the New Zealand economy. This is a selling point for Bathurst and a stick with which to bash critics. "It's the most difficult part of campaigning to stop a coal mine," says Gross. "I'm intensely aware it would have a short-term, direct impact on people. I wish that wasn't so. But we know coalmining is not a sustainable industry. It's not realistic. You're pulling the wool over people's eyes in a sense, claiming it is. Coal's not going to last."
The 350.org global divestment campaign was started by American environmentalist Bill McKibben, with a call to arms titled "Global Warming's Terrifying New Math", published by Rolling Stone magazine.
The organisation's name comes from the idea that the highest concentration of CO2 the atmosphere can stand, without triggering catastrophic climate change, is 350 parts per million.
McKibben said that to keep global warming below 2C, humans can produce another 565 gigatons of CO2, something that is expected to take until 2028. But the fossil fuel business has known reserves of 2795 gigatons of carbon, five times more than McKibben's limit, and is keen to exploit this bounty.
Those reserves are factored into share prices, creating assets which companies can borrow against. The reserves also give the industry political clout. No wonder Big Oil has fought tooth and nail against CO2 regulation - the dreaded carbon tax. Stranded assets could doom the industry. The subprime mortgage debacle that triggered the 2008 financial meltdown would be tame in comparison.
"The basic problem fossil fuel companies face," McKibben tells the Herald, speaking from Vermont via Skype, "is that they can't deny the math we've laid out. Their business plans make clear they are going to break the planet. That they're going to raise the temperature of the earth 3 or 4 degrees Celsius this century. A small group of rich people. And that math is their weakness. They no longer have any intellectual case to make. All they have now is their power."
Fossil fuel gets a free pollution ride, says McKibben. It does not have to pay for the huge downstream costs - a warming planet and acid oceans - resulting from its main waste product, CO2. A carbon price would stop that.
McKibben believes we have the technology to change - he cites Germany's steady shift to solar energy - but lack the will. And, of course, the fossil fuel business often enjoys cosy relations with government.
Everyone enjoys the benefits of cheap fossil fuels, so "tackling climate change is like trying to build a movement against yourself", McKibben has written.
So far, change has been incremental, too slow given the imminent threat posed by climate change. Divestment is aimed at the industry's heart and has spread like wildfire across US college campuses and primed a global protest network. To date, 63 US institutions, including the cities of Seattle and San Francisco, have divested stocks, says 350, as has Storebrand, a giant Norwegian life insurance and pension company which manages about US$74 billion. "Young people get this completely," says McKibben.
So does divestment work? A study last year from Oxford University's Smith School of Enterprise and the Environment, titled "Stranded assets and the fossil fuel divestment campaign", looks at campaigns against gaming, tobacco and pornography "sin stocks", and against South Africa's apartheid regime. It says those campaigns went through three stages: core investors sold holdings in the target industry, creating public awareness; universities, cities and religious bodies followed suit; the campaign went global as big investors jumped ship.
It usually took a decade.
The fossil fuel campaign has reached second base in about two years. "It's not mainstream," says Ben Caldecott, who co-authored the Oxford University study, but "it's moving up the agenda very quickly". He believes social networking has been instrumental in helping pick up the divestment pace.
The study suggests divestment will probably have a limited impact on the entire fossil fuel industry, as any shares divested might be bought by less idealistic investors. But "less liquid" coal stocks could suffer.
"The coal market is smaller relative to the oil and gas markets," says Caldecott. "There are fewer numbers of investors in coal than there are in oil and gas and so it's easier to target and influence coal investors." Coal is the industry's low-hanging fruit.
The key to divestment having an impact on fossil fuel companies is stigmatisation, finding scapegoats and damaging their reputation. Vilified firms can find themselves barred from public tenders or licences - putting off shareholders, who may demand management changes or the appointment of new board members, in a cascade effect which is exactly what protesters seek.
"The outcome of the stigmatisation process, which the fossil fuel divestment campaign has now triggered, poses the most far-reaching threat to fossil fuel companies and the vast energy value chain," says the Oxford University study.
"When we looked at divestment campaigns," says Caldecott, "one of the things that was surprising is that all had been successful in changing regulations in one way or another." He points out that in small economies with few investors - say coal in New Zealand - "it's not clear how you ignore public opinion or completely avoid stigmatisation. It is likely to affect you in one way or another. The way in which it's most likely to affect companies in this space is by fewer banks willing to lend them money or, if they do, wanting a higher cost of capital."
There are signs that coal is vulnerable. The World Bank and the European Union have stopped loans for most new coal fired power plants, as has the US. Norway's US$800 billion sovereign wealth fund has also been pressured to end its investments in coal. Then there's that carbon bubble. Another 2013 report, from the Carbon Tracker think tank, backed by Lord Stern at the London School of Economics, says oil, gas and coal reserves held by the fossil fuel industry are overvalued. Any moratorium that keeps them in the ground would probably hammer the industry's market value.
The Oxford study found that if divestment meant exchange-traded funds could not put money into fossil fuel firms, "the effect on the stock price could be substantial".
Still, even stigmatisation is not guaranteed to directly bring down fossil fuels. The ultimate impact of divestment may be structural change across the energy industry, with natural gas tipped as a transitional, or bridging, fuel to a low-carbon future.
"I think we will see a decadal transition," says Caldecott. "The fossil fuel industry is not going to go away quickly. The challenge for campaigners is how do you stop certain environmental limits from being breached? One is the 2 degree limit. Is it possible to prevent that being breached? It looks unlikely."
But "frontier oil", from remote, challenging locations, is more vulnerable due to the high costs involved, especially given the advent of cheap natural gas.
Last month Royal Dutch Shell, concerned about tougher US environmental regulations, abandoned its 2014 drilling programme in the Chukchi Sea, between Alaska and Siberia, after spending US$5 billion since 2003 without drilling a single well. Other costly ventures, including those off New Zealand, may give investors pause.
The tipping point, from fossil fuels to renewables, has yet to arrive. The divestment campaign, and threats of stigmatisation, may hasten its arrival.
