The government has pledged to halve its net emissions by the end of the decade, a big increase on its previous pledge of 30 percent.
The target is New Zealand's contribution to the international Paris Agreement to limit global warming to 1.5 degrees Celsius.
Prime Minister Jacinda Ardern said the boost means the country is now pulling its weight, with the pledge bringing it into line with the recommendations of the Climate Change Commission.
Climate Minister James Shaw said the announcement meant the amount of climate pollution New Zealand was responsible for in 2030 would be half what it was today.
But New Zealand cannot get there with domestic reductions alone, Shaw said - in fact, a full two-thirds will have to be purchased from other countries at a cost of about a billion dollars a year.
Shaw said the preference was to work with developing countries in the Asia Pacific region to, for example, plant trees, but as the decision was only made by Cabinet in past week all of the details were still to come.
He said he would love the country to go further, but the balance had to be struck as to what is feasible without considerable economic and social disruption.
There currently is no agreed mechanism on trading international carbon credits, which would be another option for New Zealand to buy credits.
The issue will be discussed at COP26, but Shaw said a trading scheme must have environmental integrity, and if it ended up anything like a previous version he would not touch it with a barge pole.
He said bilateral agreements with countries were more likely to be more transparent and lead to real reductions.
He cited Switzerland as a country which has signed agreements with countries like Peru over the past year as a model New Zealand would be looking towards.
Shaw said the new Nationally Determined Contribution (NDC) moved New Zealand from the back to the middle of the OECD pack, roughly in line with the EU.
He said Cabinet decided cutting domestic emissions was the the top priority - it voted to make the targets more ambitious than the option officials first brought to them - but that decades of inaction means to get there it has to have agreements with other countries until at least 2030.
The government's comprehensive plan to cut domestic emissions will be released in May next year.
'This decade is make or break for the planet' - James Shaw
"New Zealand's enhanced contribution to the global effort to fight climate change now represents our fair share, and is in line with what's needed if we are to avoid the worst impacts of global warming on New Zealand," Ardern said in a statement.
"Climate change is a priority for the government because it's a threat to our economy, our environment and our everyday lives. Lifting our commitment is an investment in a stable climate that will benefit us all in the future."
The announcement comes ahead of the massive UN COP26 climate summit in Glasgow which officially kicks off tomorrow evening New Zealand time.
"This decade is make or break for the planet," Shaw said in a statement.
"To stand a chance of limiting global warming to 1.5C, the science shows we now have about eight years left to almost halve global greenhouse gas emissions.
"That's eight years for countries to make the necessary plans, put in place policies, implement them, and ultimately deliver the cuts.
"I am confident we can do it and in doing so open the door to a thriving world that is cleaner, healthier, and more equitable," Shaw said.
Mixed reactions to announcement
A climate expert said the government's updated emission reduction target is close, but not close enough.
Bronwyn Hayward from the University of Canterbury said New Zealand will be judged by its actions.
"With this commitment, we start to move from being rated highly insufficient to at least getting in the game of being able to match our rhetoric with other countries.
"The real problem is that we actually need to have action now that supports our emissions."
"Late as we are, we have got a new ambitious target, now we have to meet it with actions, and that's what really matters
"So where are we going to make those emissions, how are we going to do it? Are we simply going to buy overseas carbon credits, or are we going to be able to make some realistic cuts across all our economy?"
Hayward also said it is disappointing that the Prime Minister will not be at the Glasgow conference.
Greenpeace Aotearoa agriculture campaigner Christine Rose said that the new target playing fast and loose with the numbers.
Equating gross emissions with net emissions didn't stack up - or address the biggest source - agricultural emissions.
She said the new targets are too little, too late and action is needed to tackle agricultural emissions now.
But Council of Trade Unions president Richard Wagstaff said the enhanced target was a positive step.
Wagstaff said unions support ambitious global climate action and government, businesses, and unions needed to work together.
Change to measures
The government has changed the way it it expresses the new NDC to a 'point in time' target to bring it into line with how many other countries do it.
It states the reduction to net emissions as 50 percent below gross 2005 levels by 2030.
However, this equates to a 41 percent reduction in 2005 level using a 'emissions budget' approach which averages out reductions across the 2021-30 emissions budget period.
Shaw said only a small number of counties use the emissions budget approach but the method means they are actually more accountable for all their emissions.