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BARRY BRILL: What Will We Do About .... the Mammoth Methane Mistake

For over 30 years, New Zealanders have believed that they produce relatively high emissions of greenhouse gases; and that our farmers are responsible for nearly half of all those emissions.

No longer. Science moves on.

We now find that all our climate change calculations have been based on a simple but fundamental error.

Several leading climate scientists identified this mistake as long ago as 2017. Their peer-reviewed research paper (Allen et al 2018) showed that the global warming potential (GWP) of livestock methane had been over-stated by some 400%. The old (1991) opinion that methane was 28 times more potent than CO2 was based on demonstrable errors.

This research was widely accepted around the world and was mentioned with approval in the 2019 Special Report of the UN’s Intergovernmental Panel on Climate Change (IPCC) Report on 1.5°C. No rebuttals or countervailing arguments appeared in the formal scientific literature.

Oxford Professor Myles Allen – one of the world’s best known climate scientists and dubbed by the BBC as ‘the physicist behind net zero’ – had no doubt at all that the correct multiple is about 7: “That this formula is vastly more accurate than the traditional accounting rule is indisputable.”

But some New Zealand authorities have been understandably reluctant to accept such a consequential change after so many years of beating the same drum. Thousands of farmer meetings had been assured that “the science is settled”.

All of New Zealand’s published greenhouse gas inventories relied on the out-dated GWP figure – as did our calculations for the Kyoto Protocol, the Paris Agreement and every annual COP for two decades. The computer modelling for the Zero Carbon Bill was based on the discredited GWP as were all the carbon budgets and other work by the Climate Change Commission; along with the Government’s consequent Emissions Reduction Plan and even its First Risk assessment.

New Zealand’s first Climate Change Ambassador, Adjunct Professor Adrian Macey, stresses the importance of reporting accurately if the Paris Agreement is to achieve its goals. He expresses dismay that the Ministry and the Climate Change Commission (CCC) initially misunderstood the flaws of the old GWP. He points out that the error is disproportionately affecting New Zealand among other OECD countries.

The GWP of methane did not matter too much to other developed countries, whose main emissions worry was CO2. But New Zealand was different. As livestock methane made up almost 40% of all the country’s projected warming, it's true GWP was highly material to every calculation and every policy.

The Minister has been playing for time. A small number of European academics were questioning the metrics and undertaking further research. But that all came to nothing and no scientific articles or papers were ever published to support the languishing GWP. However, until the next formal assessment report by the IPCC, no viewpoint could claim to be finally set in concrete.

Then came another peer-reviewed journal paper. Lynch & Garnet (2021), which again highlighted the “special characteristics” and “nuances” of livestock methane and warned against “heavy-handed policy interventions”. The two articles in the Nature journal “Climate and Atmosphere Science” were highly influential and both are now in the 99th percentile for measured impact.

But the Green Party Minister continued to kick for touch. The hope now was that New Zealand farming leaders would volunteer to a compromise figure under the long-running He Waka Eke Noa negotiations. The actual science had lost its relevance.

Then the Sixth Assessment Report (AR6) of the IPCC landed like a mortar shell on those negotiations. AR6, which has been tabled progressively over 2022-23. Working Group 1 (“The Physical Science”) squarely addressed the methane GWP issue at page 1016 of Chapter 7:

“…expressing methane emissions as CO2 equivalent of 28, overstates the effect on global surface temperature by a factor of 3-4”

That is the final word. With a level of infallibility to rival the Pope, the “gold standard” of climate science has left the New Zealand authorities with nowhere to hide. If there was ever a debate, it is now over. The use of a GWP of 28 for agricultural methane is simply a dead parrot.

About these momentous events, the Minister has had nothing to say. Although the IPCC’s decision is clearly the news of a lifetime for all of New Zealand’s copious subsidised climate change reporters, they too have been strangely silent. A hush has settled over He Waka Ika Noa.

Perhaps bureaucrats are working overtime in the background to rewrite all the Government’s policies? Or perhaps diplomatic pathways are being cleared for revised climate pledges? Maybe the Minister intends to challenge the scientific authority of the IPCC? Perhaps the National Party will emerge blinking into the sunlight and share its opinion?

Whatever the justifications, this cone of silence cannot last much longer. An election is pending. Watch this space .....

Barry Brill OBE JP LL.M(Hons) M.ComLaw is a former MP and Minister of Energy, Petrocorp director, and chair of the Gas Council, Power NZ, ESANZ, and EMCO. He is presently the Chairman of the New Zealand Climate Science Coalition.

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