New Zealand has fast-tracked ratification of the Paris Agreement, getting in just before the threshold which brings the historic climate change agreement into force.
New Zealand's ambassador in New York, Gerard van Bohemen, was to take the formal step to ratify the agreement at the United Nations overnight.
Climate Change Minister Paula Bennett said it was earlier than anticipated but had been fast-tracked with support of Opposition parties.
That was done to beat the European Union and ensure New Zealand was one of the countries to ratify before the threshold at which the agreement will come into force.
To come into force, at least 55 countries accounting for at least 55 per cent of total global greenhouse gas emissions have to ratify it.
Bennett said the European Union was initially not expected to ratify until next year, but had now moved to do so within the next week.
The EU's entry would push it over the 55 per cent of emissions required.
As a result New Zealand moved its own date forward from November when it had aimed to ratify in time for the next major climate change summit in Marrakesh.
"That means we are part of the first tranche. It is as much symbolic as anything else, to be part of that first tranche. But there have been noises that the '55-club' may be able to sit in different committees that are deciding accounting processes round forestry and international trading and that sort of thing."
As of Tuesday night, 62 of the 191 countries to have signed the Paris Agreement had ratified, accounting for 51.89 per cent of total global greenhouse gas emissions.
They included major emitting countries such as China, the United States, India and Brazil.
New Zealand's targets under the agreement are to reduce greenhouse gases to 30 per cent below 2005 levels by 2030 - a target that will apply from 2021.
It is the equivalent of an 11 per cent reduction below 1990 levels - and Opposition parties have argued New Zealand should be more ambitious and aim for up to 40 per cent below 1990 levels.
In a minority view in the Foreign Affairs Select Committee report on the Paris Agreement, Labour and the Green Party said they believed the agreement should be ratified as early as possible, and a more ambitious target was needed.
They also described the decision to use 2005 rather than 1990 as the baseline as a "political chicanery".
"It seeks to assuage the public by wiping the global mitigation failures of the first 15 years from public gaze."
Bennett signed the agreement for New Zealand in April this year.
The Paris Agreement covers emissions obligations after 2020 and commits all countries to limiting global temperature rise to 1.5C this century.