Cutting methane emissions from farms will involve a value judgment, not just a scientific call. Photo: Getty Images

Just what is the Government’s Zero Carbon Bill target for methane based on? And is the lighter methane target preferred by farmers more scientific? A new report tries to clarify matters.

A new report says gentle methane cuts being put forward by some farming groups would raise “equity issues” for the rest of New Zealand that science cannot answer.

Politicians might still decide to go with them, but there’s no scientific reason why they need to, says the note from the New Zealand Agricultural Greenhouse Gas Research Centre. 

Federated Farmers has told its members that the “best available science” supports cutting methane by 10 percent by 2050, and that farmers should be able to plant trees to offset those emissions in lieu of making gas cuts.

The farming group’s policy is laid out in a survey it sent to members ahead of making a submission on the Government’s proposed Zero Carbon Bill.

The ZCB sets draft methane cuts at between 24-47 percent by 2050, depending on emerging technology and other developments.

National has indicated it, too, wants the 47 percent maximum methane reduction lowered, though it hasn’t said what target it would support.

All other gases will need to be reduced by a net 100 percent by the same 2050 deadline.

But while farming groups say the best science supports dropping methane by just 10 or, at most, 22 percent to stop global warming, two reports from scientific institutions have cast doubt on whether that target is laid down by science.

The source for the 10-22 percent range is calculations released by the Parliamentary Commissioner for the Environment, Simon Upton, and made by Andy Reisinger, the deputy director of the NZAGRC. They answered a narrow question: what would it take for New Zealand livestock to make no increased contribution to climate change, or, in other words, to keep creating the same amount of heating that cow and sheep burps from this country are making today?

Reisinger’s calculations found that 22 percent cuts by 2050 would be enough to maintain but not grow the slice of global warming coming specifically from New Zealand’s animal burps, if the world was on track to stay within 2 degrees C. If the world was tracking for 1.5C, 22 percent wouldn’t be enough because our methane would stand out more. Even in a 2C scenario, most of the 22 percent cuts would need to be made in the next few years to flatten the heating, making the near-term cuts in Upton’s modelling twice as steep as what the ZCB proposes.

Simon Upton

Upton clarified all this after farming groups used the 10-22 percent range to critique the ZCB targets, issuing a follow-up note and pointing out his range didn’t account for social or economic factors. His other, bigger report on farming and forestry rather spooked some fossil-emitting businesses by saying only farmers should be allowed to offset their emissions with tree-planting. But as Upton later pointed out, that second report envisaged a huge range of possible methane and nitrous oxide cuts, from 20 percent for both gases combined, to 100 percent.

Upton’s move to straighten the record prompted Winston Peters to flourish a print-out of Newsroom’s story on the topic in Parliament and urge farmers to read it.  

Now Reisinger — the researcher who helped Upton with the 10-22 percent calculations — has written a note with Sinead Leahy, also of the NZAGRC, that aims to explain where the ZCB numbers come from and sort out the science from the politics. “We hope that the information in this note helps decision-makers separate the roles of climate science and value judgments,” it begins.

A plain translation of its overall message might be that choosing a target is laden with political judgments about what is fair to different economic interest groups, what is fair between nations, and what sectors of society should bear the brunt of curbing heating.

Currently methane makes a bigger contribution to New Zealand’s impact on global warming than the cumulative impact of other two main greenhouse gases, carbon dioxide and nitrous oxide, combined, says the report. (Those figures, by the way, don’t count the carbon lost from historic deforestation). That’s despite the other two gases being much longer-lived than methane.

If New Zealand kept making the same amount of all three gases, methane would remain New Zealand’s biggest single contribution to climate change for about the next six decades, the report says, before being overtaken by carbon dioxide. If, for some reason, we never reduced emissions of any gases, carbon dioxide would gain on methane and overtake it, because it is much longer-lived and accumulates.

But if, as farming groups are suggesting, New Zealand made methane cuts of 10-22 percent to emissions from our cows and sheep, and got the long-lived gases down to net zero (to combat climate change), methane would remain New Zealand’s biggest single contribution to climate change for the forseeable future. That’s because the 10-22 percent range is designed to keep each gas’ slice of warming roughly the same size as it is today and, right now, methane is ahead in New Zealand.

The report isn’t saying that’s a bad idea, it’s saying there’s no particular reason why it’s a good one.

Fair call?

It’s a bit surprising to read that methane is responsible for more than half the warming to date, because it is commonly said that methane accounts for a little over a third of New Zealand’s greenhouse gas emissions. That’s correct too, but it’s not the same as the share of global heating that methane is causing today. That’s because commonly used figures are drawn from international emissions accounting, which averages each gas’ effects over 100 years. Scientists are increasingly abandoning that framing for methane because it discounts the short-term impact and exaggerates the long-term. Methane is potent but short-lived, which is why it gets its own separate target under the ZCB. If it was lumped in with carbon under one big target, people might use shrinking methane as replacement for shrinking carbon dioxide, which would be terrible, long-term, for the climate.

Globally, methane is normally seen as a kind of add-on, that can help hasten and deepen what will need to be radical efforts to shrink carbon dioxide to zero.

But none of that tells us what’s the best target. 

So why do farming groups say their preferred methane target of 10 percent is backed by science?

It comes down to the gnarly truth that we can’t undo the heating caused by the carbon dioxide we’ve already released.

Because carbon lasts a long time in the atmosphere, the CO2 we pumped out yesterday has already locked in future warming and we physically can’t do a thing about it.

Methane isn’t like that – any changes we make in future will help the climate fairly quickly.

But some farming groups contend that, since we can’t undo the future damage still to be caused by our past carbon emissions, it’s unfair that methane emitters should have to stop their future heating. Basically, they’re saying their cows and sheep should be allowed to keep putting the same amount of heat in the atmosphere as they are putting in today.

Since we’re not asking car drivers to suck their previous emissions back into their tail pipes (because it’s physically impossible), fairness demands that animals also be allowed to keep heating the climate as much as they are, and not reduce their impact, goes the reasoning. 

In fact, Federated Farmers told Newsroom that requiring farmers to cut methane’s heating going forward would amount to holding them responsible for their historic warming, and would be just as absurd as holding the energy sector to account for all the warming caused since the first lump of coal was burned in New Zealand. (Newsroom could not quite get its head around this particular bit of the argument).

“Surely the pragmatic approach is to look forward and concentrate on preventing future warming,” said the group.

Given the urgency of the climate problem, it might seem odd to argue that any gas, or its emitters, has a right to keep making the same amount of heating it is making today, purely on the basis that another gas’ effects (carbon dioxide’s) are irreversible. Particularly in New Zealand, where methane has an outsized impact.

But the farming groups’ reasoning has backing from two outspoken and well-qualified climate scientists, Victoria University’s David Frame, and Oxford University’s Myles Allen. Allen visited New Zealand recently and spoke to farming groups.

Frame and Allen’s work is partly what Federated Farmers means when it talks about the “best available science” – the scientists’ modelling found that 1/3 of one percent in cuts a year, or roughly 10 percent by 2050, would stop any worsening warming from methane. (Frame agrees this number only applies if the world is off-track for an ambitious temperature goal, like 1.5C. “It’s true that if the rest of the world cuts methane radically then we would need to do a bit more,” he told Newsroom.)

What the new NZAGRC note says is that this is not wrong, but that this line of reasoning doesn’t represent “the science” – it implies making a value judgment that “not worsening warming from methane” is the best and fairest goal for climate policy.

Equal warming is not the same as equal effort, the report says, and it’s a political choice to choose to go with one goal or the other. Politicians might also choose a mix of targets based on equal effort from different sectors, or based on the least cost.

And, they might decide they want to keep the planet as cool as possible, for the least cost, rather than trying to keep the heating from all gases static. It’s a values call. 

“For short-lived gases like methane, a target based on ‘not causing additional warming’ amounts to a grand-parenting approach, i.e. an entitlement to continue to emit methane in future at a level that is determined solely by past emissions regardless of abatement potential or cost,” the NZAGRC note says. “Like all grand-parenting approaches, this raises equity issues that cannot be resolved by climate science.”

It goes on: “Climate science cannot tell us how much New Zealand should reduce its emissions: the lower all emissions including methane can go, the better for the climate. The question for agriculture is what methane emission reductions are possible while still helping to sustain and support New Zealand’s economy and maintaining viable and vibrant rural communities and businesses.”

It’s a tough one, and, the NZAGRC note is saying, it can’t be answered by science alone. 

Perhaps part of the reason why it’s proving so difficult is because New Zealand is a high-per-capita methane emitter and a would-be early adopter of a ZCB. We are treading where few other countries have yet had to go.

What’s fair?

The NZAGRC report includes calculations of the effect New Zealand has had on the climate to date. It’s not big, but it’s big per-capita and per-hectare of land mass. 

“New Zealand’s total gross greenhouse gas emissions to date (fossil carbon dioxide, nitrous oxide, and biogenic methane) are estimated to have contributed a little over 0.0028°C to the observed global warming of about 1°C above pre-industrial levels. While small in absolute terms, New Zealand’s share in global warming to date is more than 4 times greater than its share of the global population and about 1.5 times greater than its share of the global land area,” says the note.

It goes on to break down methane’s share, which is the majority right now but will be overtaken by carbon in several decades’ time.

“New Zealand’s biogenic methane emissions currently make a bigger estimated contribution to global warming than cumulative emissions of fossil carbon dioxide and nitrous oxide combined. If gross emissions of those three gases continued at current rates, biogenic methane would remain New Zealand’s largest single contributor to global warming for the next six decades, despite its relatively short lifetime in the atmosphere.”

The report lays out the sources for the government’s methane targets, which come from an IPCC report on keeping the planet within 1.5C — the same report that underpins many governments’ saying carbon needs to get to net zero globally by 2050.

Unlike the PCE’s numbers, and some other suggested methane targets, the IPCC’s scenarios for how fast to cut various gases incorporate the economic costs of reductions. The IPCC takes the average of dozens of different studies modelling different paths to 1.5C, all of them based on curbing heat for the lowest cost.

Each one makes slightly different assumptions, for example, on the uptake of nuclear power, bioenergy, the pace of renewables, changing dietary choices, climate policy around the world, and other variables. But none of the scenarios assumes that some amazing new technology is invented to suddenly cut animal methane, such as an inhibitor or vaccine, says the NZAGRC. 

There are extremes in what the models project for methane, ranging from almost no cuts to over 50 percent.

The ZCB has gone with the interquartile range (roughly speaking, the middle half of the range, or the 25 to 75 percentile) giving it 24-47 percent cuts from 2010 levels in 2050.

Of course, as farming groups have already pointed out, taking the global average figures may not translate that well to New Zealand.

The NZAGRC report also acknowledges the global numbers won’t be a perfect reflection. 

But, on the other hand, for every country that chooses to go easier than the global average on methane, someone else on the planet has to curb their emissions more to keep heating on the same track.

Countries can always play with their own mix of gases – but that, too, comes with trade-offs.

For example, the NZAGRC says, if methane emissions globally were reduced by only 10 percent below current levels by 2050, the deadline for getting global carbon dioxide emissions to net zero would have to be brought forward by about 20 years to 2030 to be on track for 1.5C.

That would make a fiendishly hard task, harder.

There are more nuances on the methane question.

In a sense, the ZCB’s range is slightly gentler on animal methane overall than the IPCC range, because it doesn’t incorporate the much stricter IPCC scenarios for methane not from farming.

For example, the IPCC’s modelling had a much steeper range of cuts for methane emissions arising from the extraction and use of fossil fuels — 79- 88 percent reductions, but its animal methane targets are less because the models all assume that it is much more expensive and less feasible to make deep emission reductions in agriculture than other sectors.

When methane from all sources was combined, all the IPCC scenarios that kept temperature inside 1.5°C required 35 percent cuts or more of methane from all sources, with a median of 57 percent.

The ZCB has taken the IPCC’s range for farming methane and applied it to all biological methane sources – meaning landfills and animal burps.

That may help farmers a little because, while most of New Zealand’s methane is from animals, any cuts made to the other portion by capturing, say, landfill methane and burning it, would count towards the overall reduction total.

On the other hand, while the methane targets were a little lighter, the nitrous oxide targets in the ZCB are much more ambitious — a 100 percent net reduction, as opposed to 1-26 per cent. The IPCC modelling assumed it wouldn’t be feasible to make big changes to nitrous oxide as cheaply as it people could make changes to methane.

Farmers may argue — and already are — that the complete package of farming gas cuts needs to balanced for its overall toughness. 

Then there’s the climate. 

Say that 47 percent methane cuts could be made a reality by 2050, without bankrupting food producers, along with getting to net zero on other gases: “This would see the total warming caused by New Zealand peak around 2040 and decline thereafter…there are clear benefits, in terms of avoided climate change,” says the NZAGRC note. “How fast and how deep New Zealand can reduce its emissions is a question of economics, social and distributional impacts, not of climate science.”

There are many questions still to answer, so perhaps it’s lucky that the numbers are a range, and even that range may be up for debate and tweaking by the Climate Commission. 

One of the biggest outstanding questions when it comes to adapting the global numbers for New Zealander is how much does it cost to cut different gases here? But one of the reasons we don’t know is that we haven’t yet, really, tried to reduce them.

It would be good to know whether the cost of cutting methane in New Zealand is roughly the same as the IPCC models, for example.

But, the NZAGRC report says, we don’t know much about the real cost of abatement here because there has never been an incentive for farmers to do it. “Hence (the) limited practical experience of farmers incorporating greenhouse gas emissions into business decisions. Any emission target or target range for 2050 therefore can only be considered as an indicative starting point that must be subject to revision based on advances in mitigation technologies, possible changes in international markets and consumer demand, and actual responses of farmers to abatement incentives and the implications for rural communities.”

A lot to weigh up, and only some of it can be answered by climate science, or so says the latest note. Stay tuned for the next clarification. 

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