A panel led by former climate change commissioner, academic and farmer, Nicola Shadbolt, was recently tasked with outlining the latest science on methane in New Zealand, and what level of biogenic methane emissions would be needed in 2050 to ensure that no additional warming would come from livestock methane emissions relative to 2017.
The report found that biogenic methane sources are ‘current’ carbon, the result of bacteria in anaerobic environments breaking down plant matter recently formed through photosynthesis.
In contrast, methane sourced from fossil fuel production, when it is broken down by atmospheric chemistry, adds ‘new’ carbon to the atmosphere, carbon that had been locked up for millions of years underground.
New Zealand, since 2019, has been operating a “split gas” target, with biogenic methane, a short-lived gas, being treated separately to other greenhouse gases.
This has drawn a rebuke from a group of 26 scientists, including David Styles of Galway University, DCU’s Barry McMullin and climate change researcher Paul Price, who have warned that the “no additional warming” target for methane “could jeopardise New Zealand’s commitments under the Paris Agreement”.
The letter highlights that nearly half of New Zealand’s greenhouse gas emissions come from agriculture – primarily the livestock sector.
In part, New Zealand is drawing on the work of Myles Allen, a member of the International Panel on Climate Change. Methane has a bigger warming effect than other greenhouse gases, but stays in the environment for a much shorter period. This is allowed for in an assessment system known as GWP*.
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