Summarised by Centrist
An Australian report argues that the standard method used to measure livestock methane exaggerates the additional warming caused by stable cattle and sheep populations.
Methane researcher Alan Lauder says the problem lies with GWP100, the metric governments use to convert different greenhouse gases into carbon dioxide equivalents.
“Methane is not a stock gas like CO2 – it is a flow gas,” the report says.
Carbon dioxide accumulates in the atmosphere and can remain there for centuries. Methane breaks down after about 12 years.
Lauder argues that because Australian cattle and sheep numbers have remained broadly stable since the mid-1970s, methane released today is largely replacing methane that is already breaking down.
Under those conditions, he says livestock methane continues to maintain existing warming but does not add warming in the same way as a growing source of carbon dioxide.
The report says GWP100 can therefore overstate the warming effect of stable or falling methane emissions, while understating the effect of rapidly rising methane.
Lauder points to an alternative metric known as GWP*, which places greater emphasis on whether methane emissions are increasing, stable or declining.
He says Australia could publish supplementary reporting using another metric alongside GWP100, but currently chooses not to do so.
The report does not argue that livestock methane should be ignored.
It says reducing methane from a stable herd would lower atmospheric concentrations and produce a cooling effect.
Lauder warns that inaccurate accounting could affect farming regulations, bank lending, supply-chain targets and land values.
He argues that forcing herd reductions on the basis of an unsuitable metric could reduce agricultural exports, regional employment and government revenue without accurately reflecting the sector’s effect on global temperatures.
