Negotiators are working frantically at the COP26 climate summit to get an agreement on international carbon markets which has failed time and again.
Photo: 123RF
Reports out of Glasgow are that the "Article Six" talks could finally get over the line.
The talks are crucially important but fiendishly complicated, trying to finally hash out the rules for how international carbon markets will work.
Countries which have done better than expected in cutting emissions will be able to sell reduction credits to others struggling to meet their commitments.
Since Paris in 2015, negotiations have never reached a resolution.
The major hurdles? How to prove reductions are real.
Another issue New Zealand is pushing back hard against is double counting - that if a country sells an emission reduction it can't also count it in its own pledges.
Former International Energy Agency Climate Change Unit head Dr Christina Hood is an Article Six expert and a COP old hand.
She said double counting was cheating.
"The idea that you could count an emission reduction more than once is just not negotiable, the whole thing falls apart if you let that happen."
New Zealand has to buy two thirds of its reductions offshore to meet our recently strengthened pledge to halve net emissions by 2030.
The government intends to develop relationships with Asia Pacific countries, for example paying them to plant trees, or providing money for renewable power projects.
The argument is the atmosphere does not care where the CO2 comes from, and you get more bang for your buck in developing countries.
Hood said a functioning international carbon market was critical for New Zealand to be able to keep its reduction promises.
"To negotiate things from scratch, including all of the detail, takes a huge amount of time and resource and we will be in a much, much better position if this ruleset is in place."
Some countries and many environmentalists totally reject carbon trading - saying there is no evidence it will lower emissions.
Samoan New Zealander Marco De Jong - who is at COP26 - studies the history of Pacific climate change diplomacy at Oxford.
Pacific nations' survival hinged on keeping warming below catastrophic levels, he said.
"The Pacific has a lot to lose if Article Six goes badly.
"Really this was an opportunity [for New Zealand] to make good on the kind of Pacific reset or step up that's been touted but I'm not sure that's the case at the moment."
New Zealand has said one of its top three priorities at COP26 is helping to make sure the world hears the Pacific's perspective.
But De Jong said Pacific civil society groups have struggled to meet with New Zealand negotiators or learn their bottom lines.
"They're not forthcoming really about their position at all so we're kind of left in the dark and you certainly can't tell the chef what to cook from the kids table."
Other fishhooks in the Article Six talks are that developing countries want a portion of money from trades on the international market to go towards funding their climate adaptation efforts.
They argue rich countries caused the warming so should pay for the damage.
And New Zealand will also be pushing hard to stop four billion gigatonnes of leftover Kyoto carbon credits from being allowed to be used, as that will push the world further away from hitting reduction goals.
University of Cambridge climate researcher Dr Natalie Jones said New Zealand has been trying in the negotiating rooms to stop efforts to set a limit on the amount a country can offset its emission by buying offshore.
Any agreement would come down to the wire, she said.
"There are still major divisions and I would say it will come down to a deal in the last hours of this week so it's a matter of just waiting at this point and seeing what happens."
If negotiations fail they will be picked up again in Egypt next year.