With increasing appreciation that limiting global temperature rises to 2°C amounts to folly, is 1.5°C attainable? Is 2°C the best remaining scenario on offer?

For the Bonn UNFCCC climate talks in June a report was presented from 70 scientists gathered together in a process called the “structured expert dialogue”. It warned that even current levels of global warming of around 0.85°C are already intolerable in some parts of the world:

“Some experts warned that current levels of warming are already causing impacts beyond the current adaptive capacity of many people, and that there would be significant residual impacts even with 1.5C of warming (e.g. for sub-Saharan farmers), emphasising that reducing the limit to 1.5C would be nonetheless preferable.”

Sophie Yeo at The Carbon Brief took a look at the scientists’ report and the political feasibility of a 1.5°C limit.

They say that we have to understand that the 2°C limit, chosen at Cancun in 2010, was political rather than scientific.

It is often painted as a scientific threshold, but the decision was, ultimately, a political one. For some of the most vulnerable nations, it was a compromise. Scientists say that a 2C world will severely impact agriculture, sea levels, coral reefs and Arctic ice, with the world’s poorest people hit first and hardest.

Yeo says the UNFCCC report states that the differences between 1.5 and 2°C were likely to be “meaningful”, with 2°C increasing the chance of extreme events and passing irreversible tipping points in the climate system. The world would be distinctly safer with 1.5°C.

The technology required for 1.5°C would be the same as for 2°C, but deployed faster and hence more expensive. Negative greenhouse emissions, that is taking CO2 from the atmosphere, is already part of the deal towards the end of the century.

No resolution was reached on the issue of targets at Bonn. Negotiators agreed to keep talking, and essentially kicked the can down the road to Paris.

The Paris meeting is the so-called annual Conference of Parties, where a new post-Kyoto international agreement is supposed to be struck. Countries have been asked to volunteer their mitigation plans prior to the meeting, so that they can be analysed to give negotiators a clear view of their adequacy in the light of the science.

With almost complete certainty, the combined plans will be short of the mark and probably indicate a potential warming of 3°C by the end of the century. Matters will come to a crunch point between two groups.

On the one side there will be a powerful group led by China, India and the Saudis. The Saudis with around 50% of their GDP coming from its oil and gas sector will not want more ambitious targets. China and India want the right to keep increasing emissions until around 2030 when they may manage to peak. They say the developed countries should reduce enough to make space for them.

The science indicates that carbon dioxide emissions can continue on current levels for just six more years before the carbon budget associated with keeping temperatures below 1.5°C is blown.

On the other side is a group of small, poor states, including the island states which see the matter as one of life and death.

One of the big problems is that whatever is decided in December 2015 is not due for implementation until 2020. Pretty much by design the possibility of ramping up targets before 2025 does not presently exist.

How this matter is to be resolved should be exercising everyone’s mind, but 1.5°C looks politically beyond us.