Hope of COP21 deal, but hurdles remain: EU

There is strong hope of a deal at the United Nations climate summit in Paris but hurdles still remain, the European Union's Commissioner for Climate Action and Energy told CNBC on Thursday.

"I am sure we (will) have a deal, I am not able to give assurances that it will be by Friday evening, but the challenge is so important, that if we need additional time it shouldn't be a problem," Miguel Arias Cañete told CNBC.

"The important thing is to get out of Paris with a powerful instrument fit for purpose, and the purpose is to limit global warming below two degrees, far below two degrees," he added.

For almost two weeks the summit, known as COP21, has seen the world's leaders, scientists, pressure groups and UN agencies attempt to thrash out a new international agreement on the climate with the aim of keeping global warming below 2 degrees Celsius.

Some of the obstacles that still need to be breached include an agreement on a long-term goal.

"There are many parties who want 1.5 (degrees) to be also part of the final agreement: how to go from 2 degrees to 1.5 and… the language we have to find," Cañete said. "We are still not there yet," he added.

Cañete also said that a "dynamic process of stock-taking" was needed every five years, and that progress was needed, "to make sure that this dynamic process starts in 2018-19, and that in 2021 we can prepare new commitments… because with the actual commitments we are on track only for three degrees and not to 2 degrees."

Cañete's comments come after the head of the Organization of Economic Cooperation and Development (OECD) told CNBC that there there are still "serious and contentious" issues to resolve.

Angel Gurria, the secretary-general of the OECD, told CNBC Thursday that "there's been a lot of progress" but more work needed to be done ahead of a deadline for world leaders to come up with a global agreement on limiting greenhouse gas and temperature rises by Friday.

"Now we're really down to the nitty-gritty which is going to be the defining of the ambition (the carbon reduction targets), the resetting mechanism over the timeframe, the measuring, verification and reporting system and obviously the finance is going to be critical so these issues are coming back."

--CNBC's Holly Ellyatt contributed to this report