The executive director of a climate lobby group says she fears the government's methane review will be used to present politics as scientific fact, bypassing the Climate Change Commission because it was not giving the answers the government wanted.
The government appointed an independent science panel to look at whether New Zealand's 2050 climate target was consistent with achieving "no added warming" from methane.
Its report was due to go to Cabinet ministers last Friday but has not been publicly released yet.
However the panel was banned from looking at whether "no added warming" was a good target for the government to adopt - and ministers have previously given conflicting answers on whether the government will adopt it.
Lawyers for Climate Action's Jessica Palairet said the panel was asked a narrow question and did not look at whether 'no added warming' was fair or appropriate.
"Our concern here is that we see the government potentially looking to change our methane target, claiming that a change is required because there's been a significant change in science but actually there's been a change in politics," she said.
"The terms of reference for the methane review panel frame 'no additional warming' as a scientific principle but it's actually a political choice," she said.
Several major farming groups support a goal of 'no added warming' from methane, which would likely result in a lower 2050 target than the current one of 24-47 percent cuts. Earlier calculations put the required range at around 10-25 percent by 2050 depending on various assumptions.
Reviewing the country's methane target for consistency with "no added warming" was part of the National-NZ First coalition deal.
However, by law, the Climate Change Commission is also required to review New Zealand's 2050 targets across all greenhouse gases every five years, and advise the government whether anything significant has changed that could justify changing the target.
Like the methane panel's report, the commission's report to the government is due to be made public in the coming days.
Jessica Palairet said her group was concerned the panel's findings would be used to side-step the commission's role.
Lawyers for Climate Action has successfully overturned government climate decisions before.
"Our concern is that the government looks like it might bypass the Climate Change Commission's 2050 target review replacing it with its own independent panel, when the (Climate Change Response) Act contemplates that the target should only be changed if the Climate Change Commission recommends it should be changed," she said.
Early indications were that the commission would not support lowering the methane target. Its initial discussion document said its preliminary view was that there was "no justification" for reducing New Zealand's overall 2050 target, and that there might be grounds for it being tougher.
The discussion document noted that if the government wanted to weaken the methane part of the target, but maintain its overall ambition, other kinds of businesses and households would have to do more to cut more off their carbon dioxide emissions, which it said would impose "significant" costs on other groups.
Lowering methane target risks damaging NZ's reputation, Lawyers for Climate Action says
Lawyers for Climate Action released its own report looking at fairness and trade issues, by climate researcher and economist Kristen Green of Kāpiti Climate Insights.
Green's report found switching to a target of "no added warming" from methane would be "self serving to New Zealand" and "unfair to others" - and could make it harder for New Zealand farmers to win export contracts.
She concluded that aiming for no additional warming above 2017 levels for farming's methane (as opposed to lowering the impacts) "would effectively allow New Zealand to maintain its current share of warming from methane into the future, rather than seeking the deep reductions in emissions that the Intergovernmental Panel on Climate Change has made clear are needed now."
Green said keeping heating at 2017 levels was arbitrary, and it would shift the burden of cutting greenhouse gas emissions on to other sectors of the New Zealand economy, and other countries.
If countries like New Zealand with large, developed farming industries adopted 'no additional warming' targets, it would "privilege countries with developed agricultural sectors and penalise low-income nations who are still developing their food systems", she said.
That was because those poorer countries would not be able to increase the heating coming from their animals, while New Zealand's high per-capita heating levels could stay the same.
Green said lowering New Zealand's methane target would also "risk disrupting trade arrangements (including the NZ/EU FTA), and damaging New Zealand's reputation for sustainable agricultural exports".
"We would be the first country in the world to adopt such a principle - and it may ultimately backfire as an agricultural
protection measure as it will harm New Zealand's brand and disadvantage exporters competing ... for contracts where climate requirements are part of terms of supply.
"Our methane target matters because methane is responsible for around 48 percent of our total emissions and two-thirds of our warming to date, and methane is a powerful greenhouse gas with 80 times the heating power of carbon dioxide over its first 20 years," Green said.
'No added warming' fairer goal farming groups say
Farming groups say 'no added warming' is a fairer goal, because lessening the heating from methane is the equivalent of pulling carbon dioxide out of the air. They say carbon emitters are not being asked to do this, so farmers producing methane should not have to, either.
Methane passes through the atmosphere much faster than carbon dioxide, meaning its heating impact can be turned up or down more quickly.
All paths to keeping the planet within 1.5C to 2C of heating require some cuts to methane from farm animals, according to the IPCC - but countries are allowed to set their own targets for different gases, consistent with the overall goal of stopping climate change.
Buyers of New Zealand dairy products such as Mars and Danone are pressuring suppliers to help the meet ambitious targets to lower their climate impacts, of which a big part is their ingredients.
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