The offices of the UN’s climate change body in Bonn have glorious views over a pretty stretch of the Rhine river, looking out on grasslands and splendid old and new buildings. Just a short distance away is the historic campus most famous for being where the Marshall plan was signed after the second world war.

That plan, which channelled billions in American aid to rebuild European economies, was instrumental in creating modern Europe, and redrawing the global economy. Instead of the punitive measures and reparations inflicted on Germany in the Versailles treaty, the Marshall plan offered healing and financial support – a message of hope, not fear.

Christiana Figueres, the UN’s climate change chief, has a task just as great as the architects of that plan. She is in charge of the world’s response to global warming, a threat potentially more catastrophic than any disaster yet seen, but one which is so slow-burning that governments and the public have been able largely to ignore it for more than three decades since scientists began to prove incontrovertibly the dangers that greenhouse gas emissions pose to our planet’s stability.

On Monday, governments will meet in Paris at a make-or-break conference in an attempt to forge a new global treaty, hopefully as effective and far-reaching as the Marshall plan, that would limit future carbon emissions and bring financial assistance to the poor who will be worst-hit by the effects of warming.

High stakes but little historical progress

The stakes could scarcely be higher. It is now more than 20 years since governments made their first joint attempts at controlling emissions and dealing with climate change. Since then emissions have continued to rise strongly in nearly every year, the exception being those scarred by financial crisis. In 1992, when the UN Framework Convention on Climate Change (UNFCCC) was signed, binding countries to avoid dangerous levels of warming, the carbon content of our atmosphere was about 356 parts per million (ppm), most of that poured into the air since the Industrial Revolution. Now, it stands at 398ppm – not far short of the 450ppm that scientists estimate as the threshold beyond which our climate will change drastically and irrevocably, bringing extremes of weather, floods, droughts, heatwaves, and rendering swaths of the globe virtually uninhabitable.

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The history of international efforts on climate change has so far been one of ineffectual and ignored treaties, unseemly wranglings over which nations should bear the greatest “burden” – as if saving the only planet we have can be so described – and political grandstanding laced with vicious recriminations. Progress, if measured in carbon output, has been nil.

Figueres is deeply aware of all this. Born into a politically well-connected Costa Rican family, she is the daughter of the man who led his country’s transition to democracy and served three times as its president, and after training as an anthropologist has spent her life in public service. As a member of the Costa Rican climate negotiating team from 1995, she helped write the Kyoto protocol and subsequent agreements.

Asked why she chose to work on climate change, she tells a story about the once common golden toad that went extinct in Costa Rica in 1989. Figueres has illustrations of the toad on the wall of her office.

“I saw this species when I was a little girl, but when I had my two little girls the species no longer existed,” she said. “It had just a huge impact because I realised that I was turning over to my daughters – who were very, very young, they were born in 1988 and 1989 – a planet that had been diminished, by our carelessness, by our recklessness.” It was this realisation that led her to work on the climate problem.

The golden toad was once abundant in a small, high-altitude region of Costa Rica. The last sighting was on 15 May 1989, and it has since been classified as extinct by the IUCN. Photograph: USFWS

Figueres cuts a compact figure, businesslike and direct, though with moments of fire. She answers every question immediately, with punch, hard facts and rapid conclusions, and sometimes humour. On the platform of climate talks, she is intense and focused, whatever chaos may be happening around her.

But this time she does not expect chaos. “We haven’t questioned whether we’re going to get an agreement [in Paris] for many, many months,” she says. “Now the question is how ambitious is the agreement going to be. At the beginning of this year when I started talking about how we are going to get an agreement, people were quizzical. Now I think everybody has accepted that as a fact: we are going to get an agreement, because there is enough political will, increasing political will. It makes fundamental economic sense. It is in countries’ national interests to really spur up this transformation [to a low-carbon economy].”

The impact of Paris attacks will be felt

If the UN negotiations are to succeed this year, Figueres will play the pivotal role. She has three main tasks: to ensure countries stick to stringent targets on emissions; to provide developing countries with financial support from the rich world to develop green energy and adapt to global warming; and to produce the draft text that can be signed into a watertight legal instrument.

But a deep shadow now hangs over the Paris talks. The attacks that killed 130 people and left scores more critically injured have scarred France, and Europe. For many French people, the long-term problem of climate change may be seen as an irrelevance to their present danger. Former president Nicolas Sarkozy called for the talks to be postponed, but François Hollande was adamant they must go ahead. Security will be stepped up, especially for the more than 130 world leaders expected to attend, including Barack Obama, Xi Jinping, Narendra Modi, Angela Merkel and David Cameron. A march through Paris planned by civil society groups has been prevented from going ahead and other demonstrations will be muted.

Figueres was quick to respond to the atrocity. “In deep pain. Standing in solidarity with Paris and the whole of France,” she wrote on Twitter. It has been her only public pronouncement.

The Guardian’s interviews took place before the events, and she declined the offer to comment further for this piece. Behind the scenes, her officials have been working closely with the French government, on security and on how to handle delegations differently.

What will be the impact on the talks? World leaders will inevitably be asked about terrorism before global warming, and it may dominate some of their private meetings. But the rawness of the horrific events will change the atmosphere, to one more sombre, respectful and hard-working. Delegates will be under greater pressure than ever to forge an agreement, and to forgo the kinds of political grandstanding and theatrics that have coloured previous talks.

The lead-up talks this year have been held up by wrangling over fine wording, the placement of a few phrases, details of language and intent. These will seem trivial in a bloodstained, grieving city, and few governments will want to be seen as taking a selfish or histrionic stand, or depriving France of a measure of hope and success. Solidarity forged in tragedy may yet carry the day.

French foreign minister, Laurent Fabius (second left), with Figueres in Paris earlier this year. Photograph: Miguel Medina/AFP/Getty Images

The omens are good for an agreement: careful planning by Figueres and the French hosts have ensured that most of the key obstacles have been removed long in advance. The key number to remember is 2C – the scientifically agreed warming threshold from pre-industrial temperatures for dangerous climate change. On current trends, if no action was taken at Paris, the world would be in for warming of as much as 5C this century. If this does not sound like much, recall that the last ice age was only about 5C colder than average temperatures today.

For Figueres, the 2C target is now within striking distance. Governments representing more than 90% of global emissions have submitted plans to the UN that, if followed, would lead to warming of about 2.7C to 3C, according to various analyses. Figueres endorsed these findings, saying: “The [pledges - known as Intended Nationally Determined Contributions] have the capability of limiting the forecast temperature rise to around 2.7C by 2100, by no means enough but a lot lower than the estimated four, five or more degrees of warming projected by many prior to the INDCs.”

Making progress now is crucial though. “The investments that we’re going to make globally over the next five, 10, maximum 15 years, but certainly the ones within the next five years, will determine the quality of life of future generations,” she says, “as simple as that.”

Crucially, a Paris agreement would also contain a mechanism for reviewing national emissions plans every five years, allowing the pledges to be ratcheted up regularly.

On finance, progress has been substantial. At the Copenhagen summit in 2009, rich countries pledged that the developing world would receive financial assistance of $100bn a year by 2020, to help countries cut greenhouse gas emissions and cope with the effects of climate change. The OECD found in a report this autumn that about 60% of those finance flows are already happening, with money coming from rich country governments, development banks such as the World Bank, and the private sector. A report from the World Resources Institute found that the remainder is likely to be made up by 2020, from increasing funds from public institutions and private sources.

There will still be arguments over the legal form – will it be a treaty, a protocol or “an agreed outcome with legal force”, as stipulated at previous talks? The latter is arguably the weakest, but still would represent a binding legal agreement, the holy grail of climate talks.

The legacy of Copenhagen’s chaos

What can go wrong? At the Copenhagen climate summit in 2009, where nations were supposed to sign a legally binding agreement that would govern the world’s response to climate change for decades to come, the signs were also good. In advance of the meeting, for the first time, both developed and developing nations had jointly agreed on curbs to their greenhouse gas emissions. For rich countries, this meant absolute cuts to their carbon output. For the poor world, it meant limits on future emissions.

But Copenhagen ended in scenes of chaos, and bitter recriminations among countries. A fully binding legal agreement was beyond reach, though the major developed and developing economies did sign a “political declaration” enshrining their emissions targets to 2020, which is still in force today. In Figueres’ words, it was “the most successful failure we’ve ever had”.

Part of what went wrong at Copenhagen was that world leaders arrived at the last minute, intending to sign a deal that was not yet written. When they flew in, their negotiators were still in the throes of detailed talks on a text, arguing over the placement of commas and delicate phrasing. While emissions targets had been agreed by the biggest countries, there was no commitment on financial assistance to the poor, and developing countries could not go home without that. Many world leaders used their moment on the world stage, in the glare of global media, as an opportunity to air long-held grievances that had little to do with climate change. These theatrics ensured that, although a deal was reached, the scenes of discord and diplomatic upsets were what people remembered.

Protesters take part in a rally dubbed ‘climate shame’ during the last day of the UN climate summit in Copenhagen in December 2009. Photograph: Kristian Buus/AFP/Getty Images

Figueres has worked hard to avoid that this time, and most countries will be wary, in the tragic circumstances of the Paris talks, of histrionics. This time, civil society groups have been brought in at an early stage, and the world leaders will arrive at the start, in order to iron out differences and instruct their officials to come to an equitable agreement as soon as possible.

Figueres’ role in this has been central. While we are talking, she has to break off to take some calls. One is from the office of the Prince of Wales, who will be coming to Paris in an attempt to bring together businesses, NGOs and governments, using his unique convening power. “A fantastic climate crusader, a lighthouse of action,” Figueres calls him. This sort of “soft” diplomacy, involving hours of personal contact from Figueres with all of the major figures expected to shape the talks, has been essential to creating an atmosphere in which leaders feel able to come to a deal.

If Paris succeeds, Figueres will be entitled to the lion’s share of the credit. She has learned the lessons of Copenhagen, and worked closely with the French hosts on an unprecedented diplomatic push around the world. She also cites “changes in the real economy – fundamentals that have changed” – the cost of renewable energy has plummeted (solar power is 70% cheaper than in 2009); investment in clean fuels has increased; and now most of the world’s big economies have legislation on greenhouse gas emissions. “At Copenhagen, we tried to take a big huge cathedral dome and drop it down on to the absence of any pillars. Where were the pillars for that? Well, obviously the dome falls and crashes. This time, we have very strong pillars,” she says.

But Figueres has also benefitted from a sea-change in climate geopolitics that has taken place since Copenhagen – the reversal of China’s stance on international cooperation on global warming.

Determination won out in Durban

Paris was not made in France. It was made at Durban, in South Africa, in 2011, when what was expected to be another routine annual meeting of the UNFCCC turned into the most extraordinary climate conference ever seen, profoundly changing the course of the 20-year talks.

One person came with a plan. Connie Hedegaard, the EU’s top climate official, had been Denmark’s environment minister at the Copenhagen talks and was determined to correct the “nightmare” that Copenhagen had become. She wanted to persuade other governments to set a new deadline for agreeing commitments on emissions to take over from when the Copenhagen commitments ran out, in 2020.

During the two weeks of talks in Durban, she assembled a “coalition of ambition”, made up mainly of the poorest countries who would suffer most from climate change. By the final day, she had more than 130 countries on her side. But two governments stood opposed: China and India.

What followed was an astonishing test of strength. With talks scheduled to end at 6pm on the second Friday of the meeting, the hosts wanted to wrap up and go home. Hedegaard refused. Finally, in the early hours of Sunday morning, as dawn broke over Durban, the hold-outs relented and she had her way.

China and India, seeing they were isolated and their traditional allies would not stand with them, agreed to a timetable for talks on a post-2020 agreement. That timetable was for Paris, in 2015.

South African international relations minister, Maite Nkoana-Mashabane (right), receives a standing ovation from Figueres and hundreds of delegates at the closing session of the Durban climate talks in December 2011. Photograph: Rajesh Jantilal/AFP/Getty Images

Since that moment, China’s position has swung remarkably. China’s top officials were soon drafted into formatting a new position, one that would require limits to greenhouse gas emissions that would also benefit its citizens, suffering from the appalling air quality resulting from untrammelled coal-fired power stations and dirty industry, with new regulations forcing higher standards on all. Last year, China agreed for the first time to peak its emissions – a key building block for a Paris deal.

Figueres has been the beneficiary of Hedegaard’s toughness, and the political changes that have followed. She is determined to capitalise on that. “Humans don’t have a stronger guiding force than my own self-interest. True for you, true for me, but it’s also true at the national level. There is no stronger guiding force than a national interest. So now we have very strong forces that we are working with.”

For Figueres, Paris also marks a personal legacy. When the summit is completed and, the UN hopes, a new process of future talks under way, she will step down from her post. Her future plans, she shrugs, are up in the air. By then, she hopes to have achieved what no one before her has done: a legal and binding agreement that will be enough to cut emissions in line with scientific advice, and that will be adhered to by governments around the world for the next decade and beyond.

Normally quick to respond to questions, the only time in our conversations that she hesitates is when asked about the fate of poor countries if the Paris talks fail. “I hope we don’t fail,” she eventually says. “They will be the ones that suffer.”

She looks away. There are tears in her eyes.