Climate Change Minister Nick Smith said setting a long-term target provided certainty about domestic climate change policy.
Speaking at the New Zealand Climate Change Research Institute Forum in Wellington, Dr Smith said feedback from a recent public consultation supported setting a long-term emissions reduction target.
"We believe a 50 percent reduction in greenhouse gas emissions from 1990 levels by 2050 . . . strikes the right balance. It has New Zealand doing our fair share and is comparable with the targets set by our major trading partners."
The move would require major changes in the next 40 years.
"The Government's existing programme includes the emissions trading scheme, support for home insulation, solar water heating systems, biofuels, electric cars and electrification of Auckland rail, and major research initiatives such as the Global Research Alliance on Agricultural Greenhouse Gas Research."
Also an advisory group on green growth established in January would identify additional programmes to help achieve the reductions.
"This target will need to be regularly reviewed to take into account the latest science, development of new technologies, and progress by other countries. New Zealand's contribution to global emissions is very small and our objective should be neither to lead nor lag but do our fair share."
Environmental lobby group WWF said the target was ''totally inadequate''.
WWF-New Zealand climate change programme manager Peter Hardstaff said emissions needed to be reduced by at least 80 percent.
"Based on evidence collected up to 2005, the Intergovernmental Panel on Climate Change (IPCC) - the world's foremost scientific body on climate change - showed that to avoid runaway climate change, by 2050 industrialised countries need to cut emissions 80 percent below 1990 levels (the standard base-year used in climate negotiations)," he said.
"Rich countries such as New Zealand have a responsibility to act on the science and take action to cut emissions."
He said many government policies were going in the wrong direction; for instance, allowing state owned enterprise Solid Energy to proceed with plans to convert inefficient lignite coal into liquid fuel while measures adopted internationally such as vehicle fuel economy standards had not been adopted.
"Cutting global CO2 emissions, including New Zealand's, to safe levels is achievable. But it requires action from us all: individuals, businesses and government. And the quicker we act the better."
