Government are introducing the long-awaited proposed changes on how it will attempt to tackle climate change to Parliament today.
The Climate Change Response (Zero Carbon) Amendment Bill sets out a 10 per cent reduction target of biological methane emissions by 2030, and "aims" for a 24-47 per cent reduction by 2050.
It proposes limiting global warming no more than 1.5 degrees Celsius.
"The Bill also creates a legal obligation on the Government to plan for how it will support New Zealand towns and cities, business, farmers and Iwi to adapt to the increasingly severe storms, floods, fires and droughts we are experiencing as a result of climate change," Climate Change Minister James Shaw said.
"The critical thing is to do everything we can over the next 30 years to limit global warming to no more than 1.5 degrees Celsius and the Zero Carbon Bill makes that a legally binding objective.
"Carbon dioxide is the most important thing we need to tackle, that's why we've taken a net zero carbon approach."
The original timeline had anticipated the Act to be in force by April 2019, however the new timeline predicts late 2020.
"We've built a practical consensus across Government that creates a plan for the next 30 years, which provides the certainty industries need to get in front of this challenge," Prime Minister Jacinda Ardern said.
The Bill creates a Climate Change Commission, which is intended to give "advice, guidance and regular five-yearly 'emission budgets'", Mr Shaw said.
The Bill takes a split gases approach, with 'long-live gases and short-live".
Opposition leader Simon Bridges said the Commission found "common ground" with National, he had serious reservations about the methane reductions.
"We are not convinced that the proposed 24-47 per cent reduction for methane meets our test in terms of science, economic impact or global response. This target goes beyond credible scientific recommendations.
"We have signalled to the Government in earlier discussions that it is exactly the sort of decision a newly formed Climate Commission should advise Parliament on, rather than politicians cherry picking numbers. Waiting five years to finally assess whether it's fit for purpose is not acceptable."
It has also drawn criticism from Greenpeace, describing it as "toothless" and that it has "no ability to enforce its climate change targets".
Dr Russel Norman said the bill "sends some good signals, until you get to the section at the end that negates everything else you've just read".
"This section states there is no remedy or relief for failure to meet the 2050 target, meaning there’s no legal compulsion for anyone to take any notice. The most anyone can do is get a court to make a 'declaration' that the Government isn't achieving its climate goals, but this declaration doesn’t make the Government actually do anything."
ACT leader David Seymour intends to oppose the Bill, saying it is about "a global audience than good policymaking".
"New Zealand's actions are not going to change the climate. We account for just 0.17 per cent of global emissions," Mr Seymour said.
"New Zealand will not prosper if we are forced to make significantly deeper emissions cuts than our trading partners. We will simply impoverish ourselves and push economic activity to other countries."
NZ Beef and Lamb called the proposed methane reduction target as "deeply" concerning.
"The proposed methane reduction targets of between 24-47 percent by 2050 significantly exceed both New Zealand and global scientific advice and the government is asking more of agriculture than fossil fuel emitters elsewhere in the economy," chair Andrew Morrison said.
Mr Shaw said the agriculture sector "is incredibly important to New Zealand, but it also needs to be part of the solution".
"That is why we have listened to the science and also heard the industry and created a specific target for biogenic methane."
"The split gases approach we’ve agreed on is consistent with that commitment."