World leaders have a self-imposed deadline to agree a new global climate deal by the end of 2015.

The last time politicians met under such a spotlight was in Copenhagen in 2009, and the headlines following it were heavy with adjectives like “failure”, “setback” and “disaster”. So the next 13 months are being touted as crucial preparation for next year’s crunch talks in Paris.

This week, representatives from business, government and civil society mulled over past mistakes and future obstacles at international affairs thinktank Chatham House’s annual climate change conference – a kind of high-level get-together for climate.

Carbon Brief was there, and while the conference’s famous Chatham House Rule means we can’t say who said what, we can give you an idea of what the attendees say needs to be done to get to an agreement in Paris.

Reconnecting

Outside the meeting, protesters waved banners complaining about Shell’s sponsorship of the event. That was presumably music to the ears of those inside the room, who were talking up the need for more public engagement on climate change in the build up to 2015.

There are signs public interest is reemerging. A number of references were made to the climate march in New York this year, where an estimated 400,000 people turned out, calling for politicians to take immediate action to cut emissions. The march was the largest climate protest in history, organisers claim.

The campaign to get high-profile institutions to stop investing in fossil fuel companies, known as divestment, was also cited as an example of a campaign that draws on a groundswell of public opinion. In the UK, Glasgow University became the first academic institution in Europe to divest earlier this year, following a number of US universities’ example.

But is that really going to make a difference? Arguably public engagement with climate change was never higher than in the months leading up to the 2009 conference. It’s tempting to suggest that if such pressure failed to catalyse a deal five years ago, not much is going to change this time around.

But, some speakers argued, it was public pressure that subsequently made Copenhagen’s failings so obvious. Public scrutiny of the Paris talks will be key to ensuring the agreement is more than tokenistic, the speakers said.

If that’s the case, campaigners have a little over a year to generate enough support to hold negotiators to account.

Political leadership

Public pressure won’t be enough to secure a new global deal, however. Political leadership will also be key.

The US, in particular, is expected to set the tone for a 2015 deal. In 2009, President Obama made an eleventh hour appearance to try and add impetus to the talks. Leaders eventually agreed the Copenhagen Accord, a weak political agreement deferring almost all the major decisions.

This time, the US is arguably in a much stronger position to lead, thanks to President Obama’s climate action plan. But the rest of the world will need to be convinced the US will continue to take action once Obama’s gone if they are going to put pen to paper in Paris, the speakers said.

Presidential elections are due to take place in early November. Whoever wins won’t be in office in time to have a direct impact on the Paris talks, and President Obama might make climate change a big issue in his final days in office and push for action. But if he’s set to be replaced by a more conservative and less climate-friendly president, his actions could be almost immediately undone.

Perhaps more important is whether the US Congress is onside. That would be a lot easier if there was a Democrat majority in Senate, as it holds the power to set the budget for key departments like the Environmental Protection Agency and keep Obama’s plan alive. But the Republicans have just won a majority in the Senate, and will be in control for at least the next two years.

So it looks like the US’s domestic politics will once again dictate the parameters of any new global deal. The main difference this time is that the US now has something resembling a national climate policy in place.

Economics

Possibly the easiest way to get politicians on board is to show that climate policies can also be good for the economy.

In 2009, the world had 250 gigawatts of wind, solar and biomass electricity generation capacity. By the end of 2013, that had risen to 560 gigawatts, according to thinktank REN21. That shows the speed at which low carbon technologies can progress and help cut emissions, speakers argued.

Costs have fallen as reneawble energy technology matures and becomes more widespread. But not enough to make renewables an obviously cheaper source of electricity than fossil fuels.

If renewables were to displace fossil fuels as the cheapest way to get power, all other aspects of a global deal will fall into place, one speaker argued.

They said a research and development budget of £150 billion should be enough to make that happen. The IPCC estimates that global investment in low carbon energy sources will need to increase by $147 billion a year if the world is going to cut emissions enough to prevent warming of more than two degrees.

So while renewables look like a more viable energy technology than five years ago, there’s a long way to go before they’re providing enough power to significantly dent energy sector emissions.

End game

So the world needs to develop a massive public movement on climate change, elect politicians willing to upset the status quo, and undergo a technological revolution if Paris 2015 is going to avoid the fate of Copenhagen 2009.

That may seem like a lot to ask – but perhaps only if people repeat the mistake of thinking climate policymaking starts and ends in a conference hall in a foreign land.

While the Paris meeting is an obvious moment for campaigners, businesses, and politicians to focus on, it’s not the be all and end all of climate change policymaking, the speakers argued.

There simply needs to be sufficient public interest, political will and technological progress to secure a framework agreement by the end of 2015, they said. Once a deal is in place, its ambition and the extent to which countries seek to cut their emissions can be tweaked.

In that way, Paris could be the start of a process that leads to countries around the world addressing climate change, rather than another false start.