After years of halting progress, this year's United Nations Climate Change Conference looks set to finally nail down a global deal to combat rising temperatures. But if it fails, will the UN framework take a back seat to a raft of agreements between individual nations?
Brasvell's Glacier in Svalbard, Norway, calving Photo: AFP / Sylvain Cordier / Biosphoto
Listen to Insight - Climate Summit - Talkfest or Opportunity?
The alarming speed with which the planet is warming adds impetus to the looming talks in Paris, known as COP21.
The United Kingdom's Met Office recently announced that its data for 2015 so far showed the mean temperature of the Earth's surface would reach 1° above pre-industrial levels this year.
This is half-way to the 2° target agreed to by 196 countries which are signed up to the United Nations Framework Convention on Climate Change.
The 2° target is seen by many as a tipping point beyond which many irreversible effects of climate change could occur, including the melting of the Greenland icesheet and large releases of greenhouse gases from thawing permafrost.
The UN framework was agreed in 1992 at the Earth Summit in Rio de Janeiro, and five years later the Kyoto Protocol was signed.
But the agreement has failed to slow the emissions of greenhouse gases or the rate of warming, mostly because it has not have broad enough buy-in.
In 2009, a global deal looked likely but, for a range of reasons, talks all but collapsed, before being salvaged by the United States and a group known as the BASIC countries (China, India, South Africa and Brazil), who nutted out the Copenhagen Accord. It wasn't adopted by the UN, but it at least meant the whole process wasn't pointless.
Since then talks have been back on track, and now the Paris meeting has been tasked with finalising a new agreement.
This time there is momentum and political agreement in the lead up to the conference, so it is hoped a global deal will finally get over the line.
But even if it does, it's possible that while there may be a binding agreement to reduce emissions, the emissions reduction targets may not be binding.
It's that point that environmentalists say could mean the deal looks good but only on paper.
Late last year, the US President Barack Obama and Chinese President Xi Jinping made a joint announcement that they would take action on climate change. They both announced their own domestic targets and outlined the steps they would take to reach them.
In September this year, they made another joint statement reiterating their commitments and adding their voices to calls for a successful climate agreement in Paris, but interestingly the statement also talked about "a new era of multilateral climate diplomacy."
Is it possible that agreements like the US-China one could take on a greater importance than one agreed by the United Nations?
New Zealand's Climate Change Minister, Tim Groser, said UN and multilateral deals should not be seen as alternatives.
"I think the UN system itself is central to it because we have to have broad-based participation - this is completely different to my other area of expertise, trade, where actually you don't need to have other countries, but we all understand that climate change is completely different."
"The broad UN framework is the right framework, but it's not the only show in town."
The head of the OECD's Environment Directorate, Simon Upton, also supported that view.
"There's no question that the UN is the only body that can deal with this - this is a truly global problem, it's not regional, it's not local, it's absolutely global so it needs to be dealt with at the global level.
"There's a global public good at risk so we need the UN, it's the only entity which can have conversations at that level."
Victoria University Professor of Climate Change, Dave Frame Photo: RNZ / Chris Bramwell
Victoria University Professor of Climate Change, Dave Frame, also highlights how important country-to-country deals might be.
"The US and China have the predominant hands now, but India and other countries that accumulate around India in these [UN] negotiations will be a really important determinant of whether we get anywhere near 2°, because those countries will need to participate in order to keep under 2°.
"But at the moment they are showing very few signs of wanting to play, at least within this UN framing, it may be the case that bilateral or multi-lateral deals offline from the UN may be more fruitful for their participation."
But how vital is that 2° target?
The deputy director of the New Zealand agricultural greenhouse gas research centre, Andy Reisinger, said while it was important to have a target, it was not known whether there was a dramatic change in the consequences of climate change between 1.9 and 2.2°.
"Two degrees is often presented as a threshold, but there is no singular threshold that is located at 2° that you can identify scientifically, it's much more a political target.
"A politically set target of 2° is really important to provide a benchmark for providing mitigation objectives, but in a way, thankfully, there is nothing that says the world is fine at 1.9° but goes to hell in a handbasket at 2.1°.
"But it is also important to recognise that the world isn't fine at 1.9° - there's a lot of damages that we're seeing already that that will escalate further."
