2C - it’s become shorthand for a safe, equitable climate deal. But the science and the UN’s position is unequivocal that if the world warms 2C above the pre-industrial age by 2100, many countries will face unbearable devastation.

Of the 195 countries present at the UN climate conference in Paris, 106 of the poorest have said a target of 1.5C is the only acceptable pathway for humankind. The head of the UN’s climate process, Christiana Figueres, has also backed this goal.

Despite the vast majority of media reporting, which suggests the overarching aim of the UN climate process is to reach a 2C target, the question is still very much alive. Negotiators in Paris met in a spin-off group on Monday night to discuss changing the long term goal to 1.5C.

This consensus-driven group is likely to deliver a final position by Friday. It is expected that wealthy countries will prevail in keeping the 2C target. A source close to the negotiations told the Guardian that on Tuesday a Saudi Arabian official had objected to the debate, saying: “I don’t think there is any scientific finding supporting 1.5C.”

However a 2014 World Bank report, found the 1.5C target was “technically and economically feasible”. One of the co-authors of that report was Dr Bill Hare, founder and CEO of Climate Analytics. He said meeting this goal would require all action to be brought forward by a decade. This would cost roughly 50% more to achieve than 2C, but would save significantly more by averting some climate-related disasters.

Hare said the cuts to emissions required by this goal necessitated a revolution in the economy and particularly investment in disruptive technologies.

Such technologies, he said, are embodied by Tesla’s rapidly improving electric vehicles and batteries and the use of biofuels for aviation. If visionary engineering projects outstrip expectations (as solar has, something even Barack Obama noted on Tuesday), they could overthrow the current models. Very quickly the impossible becomes just very hard. Or, as the Guardian overheard one Paris observer put it: “If the low hanging fruit is out of reach, cut the bloody tree down.”

The other overwhelmingly important step on the way to a 1.5C target is the load it will place on those countries who are set to emit the most over the coming decades – among those are India, Brazil and China. This has lead to divides in place of the traditional unity between developing nations.

“You will see some resistance on the idea of 1.5 degrees [from China],” said Li Shuo, a campaigner with Greenpeace China, as the cuts required happen earlier and go deeper than the government is willing to concede. However Li said even the world’s biggest emitter was showing signs that it could turn on a fivepence.

“Just two years ago if you asked anyone in Beijing whether they believed China’s coal consumption can decline this year, nobody would believe that,” he said. “It will decline further this year. So I think that created a lot of space for a very rapid U-turn of China’s emissions profile as well.”

Some academics say that Hare’s reading of the models is overly optimistic and relies too heavily on technological solutions that do not yet exist. Bob Ward, policy and communications director of the Grantham Research Institute on Climate Change in the UK, co-authored a paper as early as 2012 which concluded the 1.5C goal was already out of reach.



“There may be theoretical pathways that involve steep emissions cuts and large negative emissions but they do not really seem feasible,” he said.



Negative emissions rely on us sucking the carbon out of the atmosphere. One of the great hopes for this potentially game-changing technology is the capture and storage of carbon emissions from fuels derived from plants. This leads to a net loss of carbon from the atmosphere. The technology for this is still very much in a developmental phase, with no guarantee of long term viability.

Professor Kevin Anderson, deputy director of the Tyndall Centre for Climate Change Research, said negative emissions were being unwisely treated as a get out of jail free card.

“There’s a lot of naive optimism around these negative emissions. To be thinking about the world just assuming it works is incredibly dangerous. And that’s what we’ve done now. We have normalised this technology that does not work, that we do not know about,” he said.

Yet the debate persists. French president François Hollande said in his opening address to the conference that delegates should aim for “1.5C if possible”. At a press conference in Paris on Tuesday Obama said: “We want to get to 2C or even lower than that.”

Adnan Amin, director-general of the International Renewable Energy Agency, said staying at 1.5C was technologically feasible, although “very hard”.

“If we factor all the other elements like reforestation, it may be possible,” he said. “But it’s something that will require a level of political will that is currently non-existent.”

This is the crux of the problem. Academics are interpreting models that are based, in part, on assumptions about the climate policies of 195 countries. This is where the scientists split into two entirely unscientific camps – optimists and pessimists.

“I am perfectly happy to concede that one is entitled to be pessimistic. But that’s not a scientific statement,” said Hare. “The ultimate question is whether the politics is able to swing these shifts and right now no one really knows the answer to that.”

Anderson concedes that the politics of the 1.5C target are still live and even backs the aspiration of the poorest nations to make it the target of the climate talks.



“From a political point of view, one and a half is a really important dialogue and needs to be hammered home. Even though scientifically it’s not viable,” he said.

But Hare said scientists also had a responsibility because pessimism would be self-fulfilling. “The more observers say it can’t be done, the less likely it is to be done. So scientists have an impact on the policy debate,” he said.



The next two weeks in Paris are likely to give a degree of clarity about the biggest unknown – the politics. A target will probably be clarified. Although the open-ended nature of the proposed deal, which seeks countries to commit more in the coming years, will mean this wrangle will go on for a few years yet.