Adaptation itself, the group's report explained, could be split into four categories: Avoiding places exposed to climate change impacts; retreating from those places over time; accommodating changes; and protecting against them through hard engineering.
Elsewhere, there was a need for more investment in science and research, a new "centralised service" to give expert advice, more climate-focused capability across public and private sectors, and funding structures that would hold up over the long term.
In the shorter term, the group said, the Government should make adaptation a priority - for itself, councils and the public - and build in some of the bigger "foundational" recommendations into its proposed Zero Carbon Act.
That act, which has a goal of driving New Zealand's net greenhouse gas emissions to zero by 2050, is one of two projects that form the centrepiece of new climate action by the Government.
The other is an independent Climate Change Commission, whose first duties are to look at how the methane-heavy agriculture industry might be brought into the Emissions Trading Scheme, and how the country can transition to 100 per cent renewable energy by 2035.
The working group's new report follows increasingly bleak estimates around climate change's risk to New Zealand, where more than $200 billion of public assets and infrastructure is under threat from rising seas and storm surges.
Most of New Zealand's major urban centres and population are located on the coast or on floodplains of major rivers.
Even the mid-range projected sea-level rise over the next 50 years, 30cm, was enough to affect all seaside areas to a varying extent.
Under this scenario, in Wellington a one-in-100-year flood would become an annual event, in Dunedin this would become a one-in-two-year event, and in Auckland a one-in-four-year event.
That meant the once-in-a-century January 2011 storm that put much of the Northwestern Motorway underwater would happen once every four years, and a 40cm sea-level rise would make it a two-year occurrence.
A 70cm rise would make it a monthly event.
The working group's co-chair, Victoria University senior researcher Dr Judy Lawrence, said even if the world stopped all greenhouse gas emissions today, our climate would still change for centuries.
"Previous emissions take time to show their impact and are long lasting," she said.
"We are already seeing the effects of climate change with sea-level rise, more floods and hotter temperatures and we can expect further losses and damage.
"We need robust data to assess our risks and see where and who is most vulnerable and exposed. This will enable us to put a national plan into action which is independently monitored and reported on.
"Adaptation needs to be funded so that there are incentives for people and organisations to take adaptive action," Lawrence said.
"All of this work needs to be supported by strong leadership. The group has conveyed its expectation that the Government will put in place a co-ordinated set of measures.
"These will enable New Zealand to reduce its exposure and vulnerability to the changing climate."
Climate Change Minister James Shaw said new money allocated in the Budget - that included $8.9 million over four years for policy work and $2.2m to get the new commission up and running - had been put toward those priorities.
"Taking early action in the right areas is likely to avoid the need for more abrupt action later," he said.
"I see risk assessment as a priority and I intend to bring options to Cabinet soon for a decision on how and when to do a risk assessment.
"In the coming weeks we will be asking New Zealanders how they see New Zealand adapting to the effects of climate change as part of the Zero Carbon Bill consultation."
