This month, the Obama administration announced new rules aimed at cutting carbon pollution from power stations by 30% from 2005 levels by 2030. Never before has a US president attempted to regulate carbon dioxide emissions from power stations and the move has been hailed by scientists and policymakers as an important step towards a global economy powered by clean energy.
The urgent need to move away from energy produced by fossil fuels - such as coal, oil and gas - had been made abundantly clear earlier this year when the UN's Intergovernmental Panel on Climate Change published a report that said the world needed to make a "massive shift" to renewable energy in order to curb climate change.
Yet, according to the International Energy Agency's latest figures, 82% of the world's energy is still produced by fossil fuels (pdf). So how can this "massive shift" to a renewables-based economy be achieved?
That question was at the centre of a roundtable debate, organised by the Guardian and sponsored by WWF. To begin the discussion, David Nussbaum, WWF UK's chief executive, told participants that his organisation had "spent over 50 years safeguarding the natural world", but climate change threatened to undermine that work.
WWF had therefore produced a report that looked at whether the world could go fully renewable by 2050. "The report said you could get extremely close", said Nussbaum, but it will require "an awful lot of investment and an awful lot of change in the systems that countries use for their energy".
Coal, oil and gas would obviously have to be phased out of the global energy mix and made as unappealing as possible for investors. Fortunately, he added, WWF was not alone in campaigning to stop money being invested in fossil fuels.
Participants heard how the Fossil Free divestment movement, which aims to put pressure on public institutions to divest from fossil fuels, had been a remarkable success. "A good number of institutional investors now have this on their agenda," said Ben Caldecott, programme director at the University of Oxford's Smith School of Enterprise and the Environment.
The work of organisations such as the Carbon Tracker Initiative, which aims to highlight the financial risk associated with holding carbon-based assets that could become "stranded" due to policy changes designed to tackle climate change, was also held up as an example of momentum gathering behind the move to a clean energy economy.
Shell (pdf) and ExxonMobil have even had to issue statements denying their assets will become stranded, participants heard. "We've now got to the point where the FTSE is looking at a fossil-free index," said Nussbaum.
Ian Temperton, head of advisory at Climate Change Capital, highlighted the current state of the renewables industry, pointing to figures from Bloomberg New Energy Finance that showed global investment in clean energy stood at $254bn (£150bn) last year, down from $286.2bn in 2012 and the record $317.9bn of 2011. This reduction was partly because "the kit got cheaper", he said, adding that solar, in particular, was becoming more affordable.
To put those figures into context, it is estimated that $3tn are pumped into fossil fuels each year, once subsidies are taken into account. It is thought a further $1.2tn is being spent every year dealing with the effects of climate change - and that figure will continue to rise.
Renewable energy is "a growth market", said Dimitri Zenghelis, senior visiting fellow at the Grantham Research Institute at the LSE. "But we haven't reached that takeoff stage, that critical mass where everybody says: 'This is inevitable.'"
So what is holding back that critical mass?
Vivian Nicoli, investment director at Eiser, told delegates that her firm had recently canvassed key investors to find out if they would be interested in a specific renewables fund. Their answer, she said, was for the most part "no".
Investors are very cautious because regulators often change renewable energy subsidies and tariffs, she said, which doesn't give investors the stability they are looking for. For example, governments often agree to pay more for electricity produced by renewables in order to encourage long-term investment in the industry, however, that price can often be reviewed or even scrapped when the political landscape changes. "A more cohesive strategy at the national level would help," Nicoli added.
Stephanie Pfeifer, chief executive of the Institutional Investors Group on Climate Change, agreed policy changes were harming the investment landscape. "Retroactive changes have been the most-damaging thing to the market ... they damage sentiment everywhere," she said.
Yet, despite uncertainty over tariffs and subsidies, all delegates agreed that the global political consensus was moving broadly away from fossil fuels to renewables. In Africa and Asia, this was being driven by a need to produce more electricity, often in remote areas where solar power was the best option. In China, the motive was to improve air quality and in western Europe, security of supply was an issue, the roundtable heard.
Would these factors not encourage the big energy companies to hedge against policy shifts detrimental to their business model and start focusing on renewables? Scott McGregor, CEO at Camco Clean Energy, thought not.
"Big energy companies are tankers -they only know how to do one thing," he said. "The renewable sector has a different supply chain and management profile ... even big utilities don't know how to do renewables, let alone the oil companies."
Templeton agreed: "Oil companies should be good oil companies until we don't need them anymore."
If the big energy companies were not going to lead the transition to a clean economy, then who would and how could this be achieved? For many delegates, it was important to create renewable investment vehicles that had the scale of a Shell or BP. Pension fund managers with enormous sums invested in these giants of the FTSE currently had no viable renewable-based alternative to transfer their funds into. As Templeton pointed out, when it comes to investments, renewables still sit in the "alternative, alternative, alternative" pot.
Pfeifer suggested that governments and development banks had a role to play here helping to build scale in the renewables industry so companies become bigger and more attractive to institutional investors.
"You need to mainstream these asset classes," agreed Oliver Griffiths, head of government affairs and policy at the Green Investment Bank. "You need institutional investors to think [renewables] are much more mainstream than they are seen to be at the moment."
Nicoli also thought that government-backed institutions, such as the Green Investment Bank, could unblock investment. There are a lot of projects that are "stuck" and can't get over the line, she said. "We're looking at the Green Investment Bank to get us over the line."
McGregor didn't think the initial focus should be on institutional investors, who, he said, were not "first movers". The renewables market is tiny, he added. "The pension funds will be there when the industry is ready, but the industry needs to scale up." Until the industry develops, other sources of finance, such as venture capital funding, would be sufficient, he said. "The money is not the issue, it's the product."
The finance to invest in renewable infrastructure projects is there, agreed Nicholas Pincott, a partner at legal firm Norton Rose Fulbright, but more work needed to be done to create the right environments for these projects to succeed. For example, delegates suggested community-owned energy projects similar to those in Germany, where communities generate their own energy from renewable sources, could be replicated in other countries to help bring the industry up to scale.
Zenghelis aired concerns that a possible side effect of the move to renewables would be the price of coal coming down in countries with less stringent environmental policies in place.
For many delegates, the only way to counter this was through a global carbon price, although there was disagreement around the table about how this could work in practice, given that Russia and the "Stan" states were still likely to dig these resources up. "You need to find a way to prevent that stuff being burnt," Zenghelis said.
However, he added a note of optimism saying that if China and the US move heavily on renewables, "it's game over" for fossil fuels.
But perhaps Nicoli summed up the mood of participants best, likening the world's transition to a clean economy to an unstoppable train that has already left the station. "It's going to happen," she said, "because it makes economic sense."
At the table
Katie Allen (Chair) Economics reporter, the Guardian
David Nussbaum Chief executive, WWF UK
Ben Caldecott Director, stranded assets programme, Uni. of Oxford's Smith School of Enterprise and Environment
Oliver Griffiths Head of government affairs and policy, Green Investment Bank
Scott McGregor Chief executive, Camco Clean Energy
Vivian Nicoli Investment director, Eiser Infrastructure Partners LLP
Stephanie Pfeifer Chief executive, Institutional Investors Group on Climate Change
Nicholas Pincott Partner, Norton Rose Fulbright
Ian Temperton Head of advisory at Climate Change Capital
Dimitri Zenghelis Senior visiting fellow at the Grantham Research Institute at the London School of Economics
This content has been sponsored by WWF, whose brand it displays. All content is editorially independent. Contact Rachel Joy on 020 3353 2688020 3353 2688 020 3353 2688020 3353 2688 (email@example.com). For information on roundtables visit: theguardian.com/sponsored-content