Scientists accuse Ireland and New Zealand of methane ‘accounting trick'

Irish Examiner

17-06-2025

A group of 26 climate scientists from around the world have penned an open letter to New Zealand and Ireland criticising how the methane greenhouse gas is measured.
In Ireland's case, it may be a reaction to the programme for government 2025 commitment to "recognise the distinct characteristics of biogenic methane, as described by the Intergovernmental Panel on Climate Change, and advocate for the accounting of this greenhouse gas to be re-classified at EU and international level".
The 26 scientists, in an open letter shared with the London-based Financial Times newspaper, said governments with large livestock sectors, including those of Ireland and New Zealand, are increasingly using a new method for calculating methane's effect on climate change which estimates its contribution to warming based on how emissions are changing relative to a baseline.
They specifically accused politicians in New Zealand and Ireland of using an 'accounting trick' to back their sheep and cattle industries. It is believed they are referring to GWP*, a version of the Global Warming Potential formula devised by the Intergovernmental Panel on Climate Change.
Other climate researchers, at the University of Oxford, came up with GWP* about six years ago, as a better way for governments to set emissions targets for different greenhouse gases.
They said the original GWP100 method did not reliably account for the different impacts of long-lived (such as carbon dioxide) and short-lived (such as methane) gases.
They said different lifespans of emissions were crucial to understanding their potential to warm the earth's atmosphere. Carbon dioxide accumulates in the atmosphere, and even if its emissions ceases, the warming they caused would continues for centuries. But methane does not accumulate, being relatively rapidly removed naturally from the atmosphere. But GWP100 does not allow for this, according to the GWP* camp.
Now, a different scientist at the University of Oxford, Paul Behrens, global professor of environmental change at the university, is one of the 26 whose open letter to the Financial Times warned some governments are misapplying GWP*, to justify allowing emissions to remain flat rather than decline.
They warned this could set a precedent, allowing other countries to justify minimal reductions in methane emissions, and jeopardising commitments under the 2015 Paris Agreement as well as the Global Methane Pledge launched in 2021.
Myles Allen, professor of geosystem science at Oxford University's physics department, and one of the scientists behind GWP*, said governments, not scientists, must decide whether farmers should undo past warming from herd growth.
He still supports separate targets for methane and carbon dioxide, saying GWP100 overstates the warming impact of constant methane emissions, and is slow to reflect the impact of emission changes.
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