A group of 26 prominent climate scientists has challenged New Zealand and Ireland over their climate reporting practices, accusing both governments of using flawed methane accounting to mask ongoing emissions. In an open letter published by the Financial Times, the group warned that the GWP metric risks undermining global climate action.
Explain What GWP Is and Why It’s Controversial
The Global Warming Potential star (GWP) method differs from the traditional GWP100 approach, which compares the warming effect of methane to carbon dioxide over a 100-year period. Proponents of GWP claim it better reflects methane’s short-lived impact in the atmosphere. Critics, however, say it is being misused to justify “no additional warming” targets that permit emissions to remain flat rather than decrease.
“It’s like saying ‘I’m pouring 100 barrels of pollution into this river, and it’s killing life. If I then go and pour just 90 barrels, then I should get credited for that’,” said Paul Behrens, professor of environmental change at Oxford University.
Drew Shindell of Duke University added that this method “lets you off the hook, and ‘grandfathers in’ any emissions that are already going on.”
Highlight Agricultural Methane Emissions in NZ and Ireland
New Zealand and Ireland are among the world’s highest per capita emitters of agricultural methane due to their intensive livestock industries. Agriculture accounts for nearly half of all greenhouse gas emissions in New Zealand, while the dairy sector is the largest contributor in Ireland, with dairy cows producing particularly high methane levels.
Herd sizes in Ireland have grown over the past 15 years, bucking trends seen elsewhere in the European Union. “Exactly the opposite of what’s needed,” said Paul Price of Dublin City University, pointing to the urgency of methane reductions in line with the Paris Agreement.
Warn of a Potential Global Precedent Being Set
The open letter warns that the use of GWP by these two nations could encourage other countries to adopt similarly lenient approaches, threatening global climate pledges. These include the 2015 Paris Agreement and the Global Methane Pledge launched in 2021.
“If you’re a rich farmer that happens to have a lot of cows, then you can keep those cows forever,” said Shindell, who noted that such an approach would disadvantage low-emitting nations and developing farmers working to feed growing populations.
Present the Scientific Debate on Methane Metrics
Myles Allen, a key figure behind GWP, defends its use and argues that it is up to governments—not scientists—to decide how to address past warming caused by herd growth.
“Governments and not scientists must decide whether farmers should undo past warming from herd growth,” Allen said. He described the traditional GWP100 as “a dodgy speedometer” that distorts the real-time impact of methane.
Review Policy Developments and Remaining Questions
New Zealand is expected to finalise its methane targets later this year. A recent government review proposed a 14–24% reduction in methane emissions by 2050 under a “no additional warming” framework which is significantly lower than the 35–47% cuts recommended by the country’s independent Climate Change Commission. The governments of both New Zealand and Ireland declined to comment on the scientists’ letter.