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Methane emission cuts of one-fifth required to meet Paris climate targets: new research

Thursday 30th August 2018

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New Zealand needs to cut its methane emissions by about one-fifth from 2016 levels if it's to meet the Paris climate change commitments, according to new research prepared for the Parliamentary Commissioner for the Environment.

With 86 percent of New Zealand's methane emissions coming from farm animals - mainly cows - the research puts a scientific lens on the political question of how quickly the country should cut emissions of methane, a short-lived climate change-inducing gas, from pastoral agriculture.

That's especially because New Zealand is "well ahead of most other countries" in how to treat emissions from livestock methane, commissioner Simon Upton says in a note produced ahead of a full report due later this year. Upton made the modelling available early to contribute to policy work underway now on the Net Zero Carbon Bill, due in Parliament by December for passage next year.

The bill could see methane treated differently from other greenhouse gases, so what New Zealand does is likely to be "closely scrutinised," says Upton, who noted the rationale behind the government's proposed 'split gas' target was missing. 

"The government has provided no indication of the level at which methane emissions might be stabilised under this option, or the amount of warming that might follow from stabilisation."

According to Ministry for the Environment advice on June 26 to Climate Change Minister James Shaw, released to Carbon News under the Official Information Act, there is "no consensus" about what "sustainable" means in the government's commitment to "stabilised short-lived gases". The target to cut emissions of long-lived gases, such as carbon dioxide, to "net zero" by 2050 is accepted.

Research undertaken for the PCE by Dr Andy Reisinger at the New Zealand Agricultural Greenhouse Gas Research Centre suggests methane cuts of 22 percent from 2016 levels would be required to bring emissions below 2016 levels by 2050. Further reductions of 20-to-27 percent would be needed by 2100 to allow the warming impact from those emissions to peak and slowly stop contributing to warming global temperatures.

If the world didn't try as hard, New Zealand might cut its methane emissions 10 percent and make a proportionate contribution to reducing GHG emissions and associated warming, Resinger's report found.

A 22 percent by 2050 cut was "seen as achievable by some in the agricultural sector," Acting Climate Change Minister Eugenie Sage said in a statement, "given that methane output per unit of production has been in decline by about 1 percent per year for the last few decades, and given some leaders in the sector believe they can reduce methane output by as much as 30 percent using existing technology and best practice". 

The PCE note said modelling of the same "deep initial reductions" in methane emissions of 20 percent by 2030 to support the 'more global action scenario', "proved to be a particularly stringent constraint". 

In an appendix to his research, Reisinger says such a target may not be a realistic because it would require deep reductions in the immediate future.

"A more gradual trajectory would lead to some additional warming in the near term requiring deeper emissions reductions later."

Conversely, most of the future total warming from methane will be caused by future methane emissions, says Reisinger. "Reducing future methane emissions as far as possible (rather than only to a level where they do not cause additional warming), could therefore substantially reduce New Zealand’s overall contribution to future climate change – provided this is done in addition to, rather than instead of, reducing carbon dioxide to zero."

The country's greenhouse gas (GHG) emissions profile is unusual for a developed economy because so much of its total emissions come from agriculture rather than the production of carbon dioxide - the most prevalent and a long-lived GHG. Most of those emissions come from fossil fuels burnt for industrial processes and transport.

Reisinger warns his analysis is limited by the fact it does not model other GHG emissions, such as nitrous oxide or the potential impact of land use changes and the contribution of forestry planting to meeting New Zealand's Paris accord commitments.

The modelling "can therefore only give an indicative answer regarding the importance of future methane emissions for New Zealand's overall future contribution to climate change."

The PCE note comes ahead of next Tuesday's publication of the Productivity Commission's final report on achieving a low-carbon economy.

That report, ordered by the previous National-led government, is expected to call for urgent decisions on how New Zealand will meet both its Paris commitments, which include reducing GHG emissions by 30 percent from 2005 levels by 2030. Climate Change Minister James Shaw expects to introduce the Zero Carbon Bill to Parliament before year-end.

The MfE advice published today says the definition of 'sustainable' is "not a scientific question – it depends on political, economic and social choices, as well as technological developments and progress on reducing long-lived gases”.


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