Every country will also be expected to "overachieve" its own targets in a joint effort to keep global temperature rise below two degrees, which is the scientific threshold when impacts of climate change become extremely pronounced.

France's chief climate diplomat Laurence Tubiana recently shared with a group of Indian journalists how the negotiations in Paris ought to be long-term, "not just ten years", and how countries will have to "unilaterally" enhance their commitments to prevent dangerous impacts of climate change.

This is because most big polluters have said they are not willing to reopen discussions or set higher targets than what they have already presented in their Intended Nationally Determined Contributions (INDC). INDC contains details of what actions each country will voluntarily take under a new international climate agreement. But even INDCs put together may not be able to meet the two degree Celsius target.

"I understand that China has been very clear, and many others as well, that they would not reopen discussions on their contributions formally. But what could be possible, and through cooperation, is that countries begin to act unilaterally on their contributions even if these are conditional to flow of finance," Tubiana said. In brief, the cost of reducing CO2 emissions will reduce enormously over the years making it easy for countries to meet and perhaps "overachieve" their targets. This could be embedded in the agreement itself.

For instance, the EU is targeting at least 40% reduction in CO2 emissions by 2030 from 1990 levels. "The fact that it is at least or minimum of what they will do is important," she said. Such a move becomes crucial because research organizations believe that the current state of INDCs may not add up to limit the 2 degree Celsius rise. China, for instance, recently released its INDC, saying the country will peak emissions by 2030, carbon intensity of the economy will reduce up to 65% by 2030 on 2005 levels. But these are modest and perhaps far from achieving the two-degree target, climate research organizations have observed.

Tubiana said there will be a "transparency mechanism" to track how countries are implementing their targets. Less developed countries may be exempted from it. "Again, it is not intrusive and it is facilitative."

There are also talks of putting forward long term scenarios for 2050 which US and China have agreed to where targets will be indicative and aspirational in nature. "It's to respond collectively to how the world economy will look like if we were serious about climate change. What would be the system, the sectors, the technology, the behavior," she said. An interesting element in this will be "lifestyles". "It's not there in the discussions but we will like to see that. Already on the food aspect where lots of people going for a more vegetarian food base, and I think... bicycles. It could start from sort of small ideas like bicycle society. But I think it is important." She said.

"So, the concept is to deliver in Paris what was promised in Copenhagen, a clear pathway for the USD 100 billion fund by 2020 per year, but we could think further on what could be the financial mechanism to really facilitate this transition." The fund is what the industrialised countries, about 24 of them will provide for climate change mitigation efforts each year.

Tubiana reiterated "We would like to avoid at all cost a messy adoption of the agreement in Paris. The benchmark is No Copenhagen anymore...You can't write a legal text overnight. That is not possible. So, we insist that parties stick to a very transparent negotiating process and not a last minute closed door process."

COP21 is a crucial climate conference where an international climate agreement is likely to be made to keep global temperature rise below 2 degrees.

A similar important climate conference was held in Copenhagen in 2009 which was to have an agreement but failed.

196 countries party to the negotiations have agreed to publicly outline what post-2020 climate actions they intend to take under a new international agreement, known as their Intended Nationally Determined Contributions (INDCs)

The INDCs will largely determine whether the world achieves an agreement in 2015 where dangerous impacts of climate change can be avoided.