The Climate Change Commission's just-released draft advice came with some fresh insights that should give New Zealand hope in meeting ambitious greenhouse gas targets. Science reporter Jamie Morton looked at five of them.
Our road fleet can be decarbonised
Given roughly 98 per cent of our light vehicles run on fossil fuels, clearing New Zealand's highways of gas-guzzlers might appear an impossible feat right now.
Yet the commission found it was entirely possible to nearly decarbonise our fleet - from small cars to large trucks - by 2050.
It required an increase in electric vehicle (EV) sales so rapid that nearly all vehicles entering the country's fleet would be electric by 2035.
That switch, while ambitious, would ultimately deliver "significant" cost savings, the commission said, while reducing pollution and replacing imported fuels with local renewable electricity.
Today, light vehicles like the cars, utes and SUVs we drive are a major source of our emissions, accounting for nearly 11 megatonnes (Mt) of carbon dioxide equivalent (CO2-e).
While EV is ownership is on the rise, numbers are still far too low, with just 24,092 on the road as at last month.
The commission listed the many reasons why people didn't buy them, such as higher up-front costs, lack of choice, charging network access, range anxiety and New Zealand's limited leverage for accessing future supplies.
That needed to change as quickly as possible.
To meet the proposed emissions budgets it set out, and to be on track for 2050, at least 50 per cent of all light vehicle and motorbike imports should be electric - either battery EV and plug-in hybrid - by 2027.
The commission said the Government should place a time limit - as early as 2030 but no later than 2035 - on light vehicles with internal combustion engines entering, being manufactured, or assembled here.
It should also introduce a package of measures to ensure there were enough EVs entering the country - and slash their upfront cost until they were cost competitive with their petrol-powered equivalents.
At the same time, New Zealand could take bold steps to no longer be a dumping ground for high-polluting cars - namely by introducing an emissions target of 105 grams CO2 per kilometre, as soon as 2028.
While government efforts to date have lagged, last week brought a step in the right direction.
That was a renewed commitment to pass a clean car import standard this year, to only buy zero-emissions public transport buses from 2025, and mandate a lower-emitting biofuel blend across the sector.
Transport Minister Michael Wood said the new standard, beginning next year, would see the 105 grams CO2/km target phased in through annual targets that grew progressively lower, to give importers time to adjust.
"The Import Standard will prevent up to 3 million tonnes of emissions by 2040, mean more climate-friendly cars are available, and will give families average lifetime fuel savings of nearly $7,000 per vehicle."
We can also electrify more of our energy use
The electrification of energy use was an essential part of New Zealand's "just transition" - but it would require a major expansion of the electricity system.
It was possible for wind, geothermal and solar power to meet the expected growth in demand from electrifying transport and heat to 2050, while keeping electricity affordable.
Even with this growth, the emissions from the generation of electricity could reduce considerably relative to today.
To shoulder that shift, however, the energy industry would need to build more low emissions generation capacity - and quickly.
That could come with complications.
Big changes in demand or supply - like the Tiwai Point Aluminium Smelter closing, which the commission said should happen in 2026 - could stoke uncertainty in the market, in turn resulting in generators delaying investment in new renewable generation.
"Barriers to rapid electrification will need to be systematically addressed," the commission found.
"For consumers and industry to invest and convert to electrification, they need to have confidence that electricity will be available, affordable and reliable."
The NZ Battery project would deliver advice on potential solutions to the challenge of "dry year" energy security, when not enough could be generated through hydro.
"While a solution to this challenge could enable Aotearoa to reach 100 per cent renewable electricity, it could cost taxpayers billions of dollars," the commission said.
It suggested other options for reducing emissions should be considered, as other actions may have a larger impact for the same cost.
"Arriving at 100 per cent renewable electricity is the desired endpoint, but the timing and sequencing of the transition is important."
Ultimately, it said the Government should have in place, by mid-2023, a renewable energy target of at least 60 per cent by the end of 2035, along with milestones to hit by 2025 and 2030.
Along with that, it had to set a deadline to retire electricity generation assets, decide how to address the "dry year" problem and bring in measures, like a disclosure regime, to wholesale electricity market uncertainty over the 2020s.
Factories can swap coal boilers for clean heat
The advice suggested low and medium temperature heat in industry and buildings could be decarbonised by 2050, through a switch away from coal, diesel and gas to electricity and biomass.
Its analysis indicated these costs could range up to $250 per tonne CO2-e reduced - but would be less than this where heat pumps or biomass can be used.
"Energy efficiency and behaviour changes that reduce energy demand will play an important role in many areas," the commission said.
"These can help to cut emissions sooner and in hard-to-abate sectors. They can also contribute cost reductions and co-benefits."
But the commission acknowledged some activities - notably industrial processes that use high-temperature heat - would be hard to electrify.
Nonetheless, slashing pollution from process heat - making up a third of our energy-related emissions - would be "critical" for meeting the 2050 target.
The commission's budgets required the use of coal in boilers to come down by around 1.4PJ a year - roughly the equivalent to the energy used by one very large dairy processing factory.
By 2035, under the commission's suggested budgets, emissions would ultimately have to come down by 2Mt of CO2-e - with the bulk of those cuts required by the decade's end.
"To get on a low emissions pathway Aotearoa needs to take urgent action to avoid locking in new fossil fuel process heat assets, and focus on converting boilers to low emissions sources of energy."
Current barriers to doing that included the time required to convert plants and establish or expand fuel supply chains, as well as to upgrade grid infrastructure and build new renewable electricity generation.
The Government has moved on the issue by opening a new $70m fund for companies to make the switch - and do so quickly.
The challenge also spelt out the need for a range of new cleaner energy sources.
While bioenergy and hydrogen both held promise, New Zealand first needed to understand how best to make use of their potential.
"Our analysis indicates that these fuels have significant potential for reducing emissions in transport, process heat and industrial processes," the commission found.
"However, more work is needed to support establishing supply chains and infrastructure and making them more cost-competitive."
A long-touted "bioeconomy" could only be realised if the Government provided direction on the priority uses of bioenergy, signalled the optimal scale of a system, helped overcome barriers, and offered investment and procurement support.
We can plant more forest
The commission was blunt in telling the Government it could no longer plant its way out of bringing down CO2 levels.
While forestry pulled about 9.5Mt of carbon dioxide out of the atmosphere today - our emissions would be 14 per cent higher without it - that total needed to be ratcheted up to 15.5 Mt.
"Our path for gross emissions requires at least 16,000 hectares of new native forests per year by 2025, and 25,000 hectares per year by 2030 until at least 2050," the commission said.
"It also requires 25,000ha per year of exotic afforestation out to 2030, reducing down to no new exotic afforestation for carbon removals by 2050."
In total, around 380,000ha of new exotic forestry would be established by 2035.
There was also an important place for new native forests, which could also be planted on less productive land.
With a sustained high rate of planting through to 2050, new native forests could provide a long-term carbon sink of more than 4 MtCO2 per year.
"Further reliance on forestry as a carbon sink could divert action away from reducing gross emissions in other sectors, and make maintaining net zero emissions after 2050 challenging," the commission said.
"However, new permanent native forests could provide an enduring carbon sink to help offset residual long-lived emissions over the long term."
Importantly, while permanent native forests sucked carbon at slower rates than exotic planted forests, they continued to do so for hundreds of years.
"Native forests also offer other benefits, such as long-term erosion control, improved biodiversity and recreational benefits.
"There is an estimated 1.15 to 1.4 million hectares of erosion-prone land, much of which would not be suitable for production forestry but could be suitable for converting to permanent forest."
One Manaaki Whenua-Landcare Research estimate indicated around 740,000ha of marginal land not suitable for commercial forests could naturally regenerate if pests were managed, and some of this land was Government-owned.
However, there were currently limited incentives for landowners to change less-productive farmland to permanent native forests – either through planting or by letting it revert.
Production forests, meanwhile, could play multiple roles in the transition to low emissions.
That included providing a carbon sink in the short to medium term, offering low emissions wood products to replace higher emissions alternatives, and by substituting bioenergy for fossil fuel use.
"However, production forests only contribute towards meeting the country's emissions budgets and targets up until they reach their long-term average stock – which is around 20 years for Pinus radiata."
Production forests planted over the next decade would continue to contribute towards emissions budgets until about 2050, while forests planted beyond 2030 would contribute to removals in the longer term.
The commission noted that current settings under the New Zealand Emissions Trading Scheme might incentivise more large-scale pine plantations than was actually desired to meet 2050 targets - and this could lead to forestry displacing gross emissions reductions.
"Any option to limit planting exotic forests for carbon removals, including amendments to the NZ ETS, would need to be carefully explored and analysed."
We can meet contentious methane targets
How to bring down levels of biogenic methane largely stemming from livestock - and responsible for a third of our greenhouse gas emissions - is perhaps the most debated area of New Zealand climate policy.
But the commission found the current target range set under the Zero Carbon Act - a reduction of 24 to 47 per cent by 2050 - couldn't achieved under status quo measures that would actually only see levels drop by just 12 per cent below 2017 levels.
The good news was that New Zealand could indeed achieve what the commission recommended: a 16 per cent drop, from 1.32Mt CH4 to 1.11 Mt, by 2035.
Particularly, the 1.2Mt CH4 of biogenic methane and 8.3Mt CO2-e of long-lived gases currently emitted by agriculture would need to fall by 0.97 Mt CH4 and 6.9 Mt CO2-e respectively.
Under an optimistic, so-called "tailwinds" scenario, major technology and behaviour changes would mean biogenic methane could fall as far as 59 per cent below 2017 levels by 2050.
And even under its tougher "headwinds" scenario, slower changes in technology and behaviour still allowed biogenic methane to fall to a quarter below 2017 levels by 2050.
Here, changing certain farm management practices would help.
That included adjusting stocking rates and supplementary feed and nitrogen inputs for emissions efficiency, as well as breeding low emissions sheep into the national flock, and using low nitrogen feeds.
Specifically, dairy and sheep and beef animal numbers would need to be brought down by around 15 per cent by 2030, compared with an eight to 10 per cent reduction under current policies.
"Many of these changes will be driven by freshwater policy, so farmers may already be taking actions to reduce their emissions," the commission said of its suggestions.
"Achieving emissions reductions of the scale required will rely on highly skilled farm management and high-quality data to support decision making."
The Government's Biological Emissions Reference Group had already found these emissions reductions could be achieved without reducing profitability.
Other promising options currently being researched and developed include a methane inhibitor that would be compatible with the pastoral farming system, and a methane vaccine.
The commission also noted the Government was working with industry through the He Waka Eke Noa Partnership to develop a farm level pricing system outside the ETS.
"The partnership is also developing the information and support needed to manage farms in a low emissions way, including training, extension, and farm and forestry advisory services," it said.
"It will be important that these tools can deliver emissions reductions consistent with emission budgets and targets, and that they endure beyond 2025."
What's the report?
Last year, the recently-formed, independent Climate Change Commission was asked to review whether New Zealand's commitments were ambitious enough to help the world keep warming within 1.5C of pre-industrial levels.
What are those commitments?
New Zealand has pledged to slash emissions by 30 per cent below 2005 levels, and 11 per cent below 1990 levels, by 2030. Under its Zero Carbon Act it separately aims to bring down carbon dioxide to net zero by 2050 - and reduce methane levels by somewhere between 24 to 47 per cent.
Is that enough?
Absolutely not, if New Zealand wants to aim for that 1.5C mark. The commission says all greenhouse gas levels need to drop by around a third by 2035. That means a halt on petrol car imports after 2032, slashing livestock numbers by 15 per cent by 2030, and planting 380,000 hectares of new exotic forestry would be established by 2035.
So what happens now?
The Government, which is currently drawing up its first three five-year sets of emissions budgets out to 2035, will consider that advice. It's unclear how much of it the Government will adopt, but Climate Change Minister James Shaw pointed out the pathway set by the commission was realistically achievable - even with today's technology.
How can I have my say?
Anyone is welcome to make a submission on the Commission's advice at haveyoursay.climatecommission.govt.nz. Consultation runs until March 14 and the commission will finalise its advice by the end of May.