More then 150 world leaders will today kickstart talks that could lead to a historic climate deal. Prime Minister David Cameron and US President Barack Obama will be among those attending the opening day of the United Nations summit in Paris.
The talks take place amid unprecedented security in Paris, whereprotesters clashed with riot police after a climate march was banned following the terror attacks in the city.
The gathering of so many heads of state is intended as a clear signal to negotiators that they must reach a significant agreement.
Mr Cameron will call for “global action to deal with a global problem”. The last major climate conference five years ago in Copenhagen failed to secure sign-up to a universal target for reducing emissions.
But in advance of the Paris talks 183 nations have submitted individual commitments, large or small, to slow global warming. The EU has pledged to cut greenhouse gases by at least 40% by 2030 while China has vowed that its emissions will peak by 2030.
ScreenGrab Paris protests ahead of climate talks These “differentiated responsibilities” allow the world to share an overall goal of limiting emissions by 40-70% by 2050 and 100% by 2100, according to the UN.
Lead negotiator for the UN, Christiana Figueres, said the pledges covered 95% of carbon emissions and would limit the rise in global temperature this century.
“We are no longer (heading for) 4,5 or 6 degrees,” she said. “We are now in the bandwidth of 2.7 to 3.5 degrees. Is that enough? No, because we have to stay under 2 degrees.”
The 2C threshold is seen as the safe limit for temperature rise, beyond which the climate becomes dangerously unstable.
“The Paris agreement needs to bend the curve of emissions and also chart the path of continued decrease of emissions until we get the task done,” said Ms Figueres.
But there are still major issues that need to be resolved. The EU wants any deal to be legally enforceable, but that is being resisted by the US.
And poorer countries that are most vulnerable to climate change want richer nations to pay into a fund to help them adapt to a warmer world.
Mr Cameron said: “We must include a five-yearly review mechanism to increase ambition in the future. “Whilst emissions reductions should always be pledged country by country, we must review our ambition regularly if we are to hit our final 2 degree goal.”