Agricultural Greenhouse Gas Research Centre deputy-director Dr Andy Reisinger was commissioned by Parliamentary Commissioner for the Environment Simon Upton to research the impact methane from livestock has on NZ’s contribution to global warming.
His work modelled what changes are needed for methane cuts to play a role in NZ’s efforts to move towards a zero-carbon economy by 2050.
The report’s release came amid a swirl of claims about methane’s role in NZ’s greenhouse gas profile and how it should be treated.
Methane has a 12-year life in the atmosphere compared to hundreds for carbon dioxide and nitrous oxide.
However, the gas also has a global warming effect 25 times greater than carbon dioxide.
Reisinger’s work found holding NZ’s methane emissions steady at current levels will not be enough to avoid extra warming.
Taking a business-as-usual approach to methane emissions will mean the warming it causes will continue to increase gradually for centuries, long after the methane itself has levelled off.
Upton said methane emissions might be short-lived but are by no means benign.
Even reducing methane emissions by 10-22% below 2016 levels by 2050 will only maintain existing warming levels.
Upton has been at pains to emphasise he is not endorsing a specific target level for methane from livestock but wants to use the research to open up wider policy discussions grounded in underlying science.
“This work only provides a reference point as to where you have to go if you do not want more warming – you could go up in terms of reduction requirements or you could go down,” Reisinger said.
The report got a generally favourable response from the pastoral sector.
Federated Farmers climate change spokesman Andrew Hoggard said it shows cuts to methane emissions to ensure no further warming occurs are greater than other estimated cuts suggested but the research has a strong scientific grounding for its estimates.
That is unlike claims by some campaigners that reducing methane emissions to zero is the only acceptable path.
Beef + Lamb NZ policy general manager Dave Harrison said the body recognises for NZ to have a meaningful role in combating climate change all sectors need to play a part but there is also a need to recognise the contribution to gas emissions cuts sectors have already made since 1990.
The dry stock sector has reduced its emissions by 30% since 1990.
Reisinger said it is up to policy makers to determine where they go and one option if methane is not going to be reduced by as much could be to require greater reductions from another sector.
“This is just a science-based target for methane.
“It requires social and economic analysis and I have not done any of that here. But that analysis needs to be done before policy is put in place.”
Reisinger said dealing with methane reduction in future has to be addressed because of its contribution to future warming. It is not a legacy problem from past behaviour that is creating the future warming issues.
“Is a 20% reduction ambitious or is it weak?
“That requires a separate analysis. Similarly, who says no additional warming is enough when NZ is being asked to participate in an international effort?”
NZ is unusual because it is a developed nation grappling with a greenhouse gas profile quite different from most other developed nations.
The next step will be to feed the research into the Zero Carbon Act legislation as a targeted level.
Upton plans to release a full report later in the year on biological sources and sinks of greenhouse gases and how they might be treated in the context of climate targets and policies.
