Climate Change Minister Tim Groser says New Zealand faces "a big challenge" in making new commitments to cut emissions, following a global agreement in Peru at the weekend.
Mr Groser said the Lima agreement, signed on Sunday night, laid the groundwork for a comprehensive deal in Paris next December, where world leaders plan to set binding emissions targets for all major countries for the first time.
He said there was still a lot of work to do but it was positive that the "mess" witnessed at Copenhagen talks in 2009 had so far been avoided.
Negotiators from 190 countries at the Lima conference agreed on a plan to fight global warming that would include all countries.
Those countries, including New Zealand, must now report back in March, or soon after, with national plans for reducing emissions.
The Lima deal requires bigger commitments from countries than their pre-2020 pledges. New Zealand has an emissions reduction target of 5 per cent below 1990 levels by 2020.
Mr Groser said making a greater commitment up to 2030 would be "a big challenge" for New Zealand because 80 per cent of its electricity already came from renewable sources.
"Once you're that high it's difficult to find low-hanging fruit," he said.
There were other obstacles.
No solutions had yet been found by New Zealand researchers into reducing the emissions produced by agriculture.
And forests in New Zealand, which captured carbon, would be harvested in the late 2020s and early 2030s, making it more difficult to cut carbon emissions which contributed to a warming atmosphere.
"There's a lot of work to do but we'll come up with something and have a good story to tell," Mr Groser said.
The minister said it was also difficult to set a target because the Lima deal had not established a legal framework for reducing emissions.
Climate Change Minister Tim Groser. Photo / NZME.
Green Party climate spokesman Kennedy Graham rejected Mr Groser's claim that there was no "low-hanging fruit", saying that similar agriculture-based countries had reduced their dairy herds.
"That's an option, but you almost get shot in the temple if you say that in New Zealand because of the milk-to-China syndrome."
What was the United Nations conference in Lima about?
Negotiators from nearly 200 countries were meeting to discuss how to limit carbon emissions and take other steps to prevent harmful climate change. Current agreements for limiting emissions expire in 2020, and new, binding targets for all countries will be set at a meeting in France next year.
What was agreed?
Negotiators agreed on a plan to fight global warming which would include all countries for the first time. Rich countries such as the US and developing economies such as China and India were expected to share the burden of cutting greenhouse gas emissions.
How does it affect New Zealand?
New Zealand, like all countries, will have to come up in the next few months with a new emissions target for the post-2020 period. The target must progress beyond its current target, which is cutting emissions by 5 per cent of 1990 levels by 2020.