Climate policy increasingly relies on sophisticated modelling to estimate future emissions and guide public policy. But every model is built on assumptions. This report explores why those assumptions matter—and why understanding them is just as important as understanding the headline figures.
eLocal Report: Based on reporting by Newsroom.
The Reporting
A detailed Newsroom investigation has raised questions about whether New Zealand's official projections for agricultural methane emissions accurately reflect the likely impact of current government policy. The report centres on criticism from the independent Climate Change Commission, climate policy experts and even sections of the agricultural sector, who argue that the Government's latest emissions modelling may rely upon assumptions that are difficult to justify under existing policy settings. :contentReference[oaicite:0]{index=0}
At the heart of the investigation lies a simple but important question.
If the Government removed one of its major emissions reduction policies—the planned pricing of agricultural emissions—how can long-term emissions projections remain almost unchanged?
As Newsroom notes:
"Last year, officials projected methane emissions from livestock and waste would fall by a quarter by 2050... However, between the two sets of calculations, the Government made a major policy decision, ruling out a price on agricultural emissions." :contentReference[oaicite:1]{index=1}
The article reports that, despite abandoning agricultural emissions pricing, official projections still anticipate methane emissions falling by almost the same amount by 2050 as previously forecast. That has prompted questions about what assumptions have changed inside the Government's modelling. :contentReference[oaicite:2]{index=2}
Climate Change Commission Chief Executive Jo Hendy told Newsroom that confidence in public policy depends upon robust projections.
"Good policy decisions need to be made on robust projections that are the best estimate of what current policy will achieve." :contentReference[oaicite:3]{index=3}
She warned that overly optimistic assumptions could delay necessary policy responses.
"If we overestimate what we're on track for, then we're going to discover down the track when it's too late to act that we're not going to make it." :contentReference[oaicite:4]{index=4}
The Ministry for Primary Industries disputes that criticism.
Strategy Director Chris Kerr defended the updated methodology, telling Newsroom:
"The use of scenarios was a deliberate decision to improve our approach to projections to ensure they are fit for purpose in the face of rapidly increasing uncertainty..." :contentReference[oaicite:5]{index=5}
Climate Change Minister Simon Watts likewise defended the projections, stating:
"The Government has confidence in the approach taken to develop projections... All forecasts are inherently uncertain, but are based on the best information we have..."
Emissions Pricing
One of the central issues examined by Newsroom concerns the role that emissions pricing was originally expected to play.
The Government's 2024 Emissions Reduction Plan assumed that pricing methane emissions from livestock would encourage farmers to adopt new technologies capable of reducing emissions. Officials estimated that pricing would significantly improve uptake of methane inhibitors and other mitigation technologies that farmers would otherwise have little commercial incentive to adopt.
A price on emissions was expected to improve the commercial case for new technology.
Image: Lynn Grieveson via Newsroom.
The investigation explains that officials originally projected almost 70 percent of dairy farmers would eventually adopt methane inhibitors if an emissions price existed. Without pricing, uptake was expected to remain minimal.
Yet following the Government's decision to abandon agricultural emissions pricing altogether, the revised modelling still projects methane emissions falling by almost exactly the same amount by 2050. Newsroom reports that this outcome depends upon substantially greater voluntary uptake of new technologies together with assumptions that those technologies will prove more effective than previously estimated.
Comparison of projected agricultural methane emissions under different modelling assumptions.
Chart: Newsroom / Flourish.
Projected emissions reductions under successive modelling approaches.
Chart: Newsroom / Flourish.
One of the strongest observations highlighted by Newsroom comes from former Ministry for the Environment chief executive James Palmer, who later described the assumptions underpinning the revised modelling as:
"It's a pretty arbitrary set of assumptions at the moment."
Fonterra has set targets to cut emissions from its farmers.
Image: Lynn Grieveson via Newsroom.
Newsroom reports that concerns about the Government's modelling are not limited to the Climate Change Commission.
Parliamentary Commissioner for the Environment Simon Upton questioned what he described as the "heroic" assumptions underpinning the projections, particularly around technologies that are either still under development or have yet to achieve widespread commercial adoption.
As he told the Dairy Leaders Forum:
"Now the Government's latest baseline emissions projections assume that by 2030, '37 percent of dairy cattle are vaccinated with a methane vaccine that reduces enteric methane emissions by 10 percent'. I personally find this assumption heroic." — Simon Upton
He continued by questioning the practical incentives available to farmers following the removal of methane pricing.
"Government projections appear to be relying on farmers acting out of the goodness of their hearts... What incentives will there be to take up new technologies?"
Newsroom also reports that DairyNZ urged caution over "ambitious assumptions on technology uptake", while independent climate policy experts questioned whether similar emissions outcomes could realistically be achieved after removing the principal policy mechanism previously expected to drive adoption.
Former Climate Change Commission adviser Paul Young summarised the concern:
"At face value, it is odd for the latest emissions projections to assume greater uptake of agricultural emissions technologies after the scrapping of the policy instrument previously assumed to drive their adoption."
Scenario-Based Modelling
The Ministry for Primary Industries says the apparent contradiction stems from a change in methodology rather than political interference.
Rather than modelling the effect of individual government policies, officials now use a scenario-based approach that attempts to estimate what may occur under a range of possible future conditions.
Chris Kerr from the Ministry explained:
"We have confidence in the scenario approach we've taken because they use the latest available information while taking into account the uncertainty we face over the next 25 years."
Officials argue that rapid changes in technology, international markets, consumer expectations and scientific developments mean historical trends are becoming less reliable indicators of future behaviour.
Critics disagree.
Climate Foundation adviser Christina Hood told Newsroom the methodology effectively assumes its own conclusion.
"It's just hypothetical assumptions. You draw a conclusion that says that 24 percent reductions are possible if we assume that technology uptake gives us 24 percent reductions. That doesn't tell us anything at all. It's just a circular kind of an argument."
The Bigger Picture
Viewed through the Editorial Intelligence framework, this story is not fundamentally about methane.
Nor is it primarily about dairy farming.
It is about predictive modelling.
Governments increasingly rely on sophisticated models when making decisions involving climate policy, infrastructure, healthcare, transport, migration, housing and economic planning.
These models are valuable decision-making tools.
However, every model is built upon assumptions.
Those assumptions may relate to technology, economics, demographics, consumer behaviour, regulation or international markets.
Change one assumption and the projected outcome can change significantly.
That does not necessarily mean a model is wrong.
It simply means its conclusions should always be considered alongside the assumptions that produced them.
Understanding those assumptions is an essential part of understanding public policy.
What Does This Mean for New Zealand?
This story extends well beyond agricultural emissions.
Successive governments rely upon predictive modelling when making decisions involving billions of dollars of public expenditure and regulation.
- Climate policy...
- Infrastructure investment...
- Healthcare planning...
- Transport...
- Housing...
- Economic forecasting...
All depend upon models attempting to estimate future outcomes.
For New Zealanders, the important lesson is that public confidence depends not only on the sophistication of those models but also on transparency.
Citizens should be able to understand:
- what assumptions are being made;
- what evidence supports those assumptions;
- what uncertainties remain; and
- how projections change as new evidence emerges.
Understanding the assumptions behind major policy decisions allows citizens to better understand how governments arrive at those decisions.
National Interest Test
The broader principle illustrated by this story is that assumptions matter.
Every predictive model is only as reliable as the evidence supporting the assumptions built into it.
That applies not only to climate policy but across almost every area of modern government.
For New Zealand, the National Interest Test therefore asks a broader question.
Are major public policy decisions being based upon modelling that is transparent, evidence-based and regularly tested against real-world outcomes?
Strong public policy is built upon robust science.
It is strengthened further when the assumptions behind that science are openly explained, independently scrutinised and updated as better evidence becomes available.
An informed democracy requires citizens to understand not only the conclusions presented in official reports but also the assumptions that produced those conclusions.
Understanding how governments model the future is ultimately part of understanding how governments make decisions.
Source
Original reporting:
Newsroom — NZ cows set to emit far more climate pollution than Govt projected
By Marc Daalder
eLocal note: This eLocal Report draws upon the original Newsroom reporting while applying independent editorial analysis, New Zealand context and the National Interest Test. Readers are encouraged to read the original article alongside this report and draw their own conclusions.