By cutting our high methane emissions, New Zealand could produce a cooling effect that would fight against global warming, a new scientific paper says.
The working paper could be central to lobbying efforts from the farming industry, which is seeking to lessen action on climate change.
International researchers determined the effect of the country’s goals for methane – a potent but quick-to-degrade greenhouse gas.
If the targets were achieved, the quick-degradation of the gas would mean a drop in the level of warming contributed by methane. This cooling might even offset the ongoing nitrous oxide emissions produced by agriculture and the carbon dioxide from all sectors for a couple of decades, the paper found.
Science can only explain the effect of the target – not say whether it is fair or not, the researchers told Stuff.
Farming experts said the work raises serious questions about whether Kiwi farmers are being asked to do more than their fair share.
The researchers behind the paper, Myles Allen of the University of Oxford and Michelle Cain of the Cranfield University, are leading proponents of calculations capturing the cooling effect of larger methane cuts.
Allen and Cain ran a computer model that took this effect into account, into the future where the world introduces moderate climate action.
Since the methane targets might have a cooling effect large enough to balance heating from other greenhouse gases, the overall effect could be zero warming between the 2030s and 2050, the paper said. Basically, Aotearoa would stop contributing to global warming.
The results provide a “starting point for the discussion”, Cain said.
Dominico Zapata/Stuff
When digesting grass, cows and other livestock burp up the planet-heating greenhouse gas methane.
“Reducing methane emissions is good, if it’s not having any adverse effects that are going to outweigh benefits.”
This would be similar for any country pursuing significant methane cuts.
In a media release, Dairy NZ chair Jim van der Poel said the paper “raises serious equity concerns for farmers who may be being asked to do more of the heavy lifting”.
Federated Farmers President Wayne Langford said most farmers are unhappy with the reduction target of 24-47%. “[They] have felt like they’ve been asked to go further and faster than needed – that’s why this review is so important.”
What’s the beef?
The Zero Carbon Act’s methane target of 24%-47% echoed an agriculture-specific estimate made in 2018 by the leading climate science body, when determining the action needed to limit global heating to 1.5C.
Since farms and rubbish dumps produce methane, the target applies to both industries.
Landfills can capture and burn the gas to generate electricity. The waste sector – responsible for 9% of national methane – has embraced the reduction challenge, even telling the Climate Change Commission in 2021 it could do more.
Many farms could cut methane by running more efficiently, but tools to prevent livestock from belching the gas aren’t available yet (the closest option is currently seeking regulatory approval).
David White/Stuff
On top of producing greenhouse gas, farming is exposed to climate-fuelled extremes such as drought.
Less enthusiastic about reducing methane, the agriculture sector commissioned the newly-released paper.
By the end of next year, the Climate Change Commission will review the appropriateness of the 2050 targets and could recommend an alteration if there is “significant enough change in circumstances to justify it”.
The new paper has not been peer reviewed, unlike a standard research study published in a scientific journal. The researchers said the computer model they used is peer-reviewed and produced consistent results.
Methane science is complicated.
Essentially, when the country’s methane levels were increasing – until about 2006 – the warming effect was particularly strong. Over its short life, the gas is more than 80 times more potent than carbon dioxide.
For that reason, methane is responsible for nearly 60% of New Zealand’s contribution to global warming since 1850 (this is noted in the paper, although Allen said it’s rare for historic pollution to be factored into target-setting).
Importantly, should the country ever start to produce notably less methane, the atmospheric ‘blanket’ of heat would begin to thin – effectively producing cooling.
This effect is why, in recent years, global leaders have targeted methane emissions. Two years ago, the US launched a global pact to cut methane 30% by 2030 and is setting up a deal to help Turkmenistan plug its massive methane leaks.
Allen and Cain also make the case that methane cuts are important.
“The reduction of agricultural methane is an integral part of minimising contribution to warming and therefore avoiding 1.5C,” the paper said. “The New Zealand Government should invest in mitigation of the agricultural sector as well, noting that it is the only sector with substantial potential to achieve additional cooling.”
Action on methane must be accompanied by ambitious efforts to reduce fossil fuel usage, the paper said.
Andrew swallow/Stuff
When cows urinate, the soil receives a concentrated dose of nitrogen – which produces nitrous oxide.
A new benchmark?
With assistance from graduates, the researchers also calculated what would be necessary to achieve “no additional warming”.
This is the point at which the effect on the Earth’s temperature stabilises – no extra warming, but no cooling either.
What’s put into the calculations matters.
If the world takes moderate action on emissions, New Zealand’s warming from methane should halt with a 15% cut by 2050.
Warming would then stabilise at 2020 levels – the year chosen by the researchers. A different percentage would be required for methane to stabilise at 2017 levels (the year used in the Zero Carbon Act) for example, the researchers said.
In addition, if other countries make rapid progress, national ambition on methane would need to step up as well. To stabilise at 2020 levels, methane could need to fall 27%, the paper concluded.
Allen said: “The faster the world as a whole acts, the more New Zealand’s emissions matter.”
The two results focus exclusively on methane. But it’s not the only greenhouse gas produced by agriculture.
If the sector wanted to balance the warming effect of all its emissions, that could be achieved with methane cuts of between 29%-40%, the researchers found.
Allen warned: “It’s important not to get too hung up on exact numbers”.
It wasn’t possible to “nail down the exact reduction to within a percent”, he said, and so national targets will need to be regularly revisited.
What’s fair?
Each of New Zealand’s greenhouse gas targets is in service of a larger goal: to help limit how high Earth’s temperature gets.
Unlike methane, long-lived carbon dioxide and nitrous oxide must reach net-zero to achieve no additional warming. Leading scientists warn carbon dioxide must reach this benchmark around 2050 to limit heating to 1.5C.
Global temperatures roughly 1.2C above the pre-fossil-fuel era are already driving extreme weather.
STUFF
In 2020, a part of New Zealand saw 61 days of drought in a row. For many, it was devastating.
The international accord to fight climate change, the Paris Agreement, requires countries including New Zealand to keep global temperatures “well below 2C” while aiming for 1.5C. The Zero Carbon Act enshrined 1.5C.
In another exercise – which Cain described as “almost a back-of-the-envelope calculation” and Allen warned is unusual – the researchers estimated a national methane target compatible with 1.5C.
In 2015, the world was 1.1C hotter, leaving 0.4C to play with. The researchers divided this up by population, allocating New Zealand 0.065% of the 0.4C to ‘use up’.
Then, the team made the “simplistic” assumption that carbon dioxide and nitrous oxide fall in a straight line between 2020 and 2050, Cain said. That smooths out what the Government intends to do, which is take less action in the short-term balanced by faster action from 2030.
After carbon and nitrous emissions are removed, the researchers concluded New Zealand could reduce methane by 27% and stay within its per-capita share of the remaining 0.4C.
However, under the Paris accord, New Zealand and other developed countries have agreed to “take the lead” to reduce emissions.
If gathering robust science on methane was the first stage of setting a national target, debate on what the agriculture sector could achieve and what it should contribute from a moral perspective would be the second step, Cain said.
“We were asked to do some modelling. That’s where our role ends. It’s over to you, New Zealanders.”
Gerhard Uys/Stuff
The Government is funding tools to cut methane, such as a nationwide search for low-emitting sheep.
Although the researchers approve of investment into tools to cut methane, they said “the reduction of agricultural methane emissions should not come at the expense of food production”.
In the paper, they theorise that limiting agriculture in one country would cause a corresponding rise in deforestation in others.
Kiwi farming leaders regularly express similar concerns. If New Zealand reduces its comparatively low-emitting milk or meat production, the hypothesis goes, it would be wholly replaced by milk and meat production on higher-emitting international farms – and global emissions could rise.
Asked about the inconsistent evidence of this ‘waterbed effect’ for farming, Allen said the paper raised this as an issue. “You’d have to model it.”
The funding bodies – Federated Farmers, Beef + Lamb, and DairyNZ – provided a list of questions to the research team. Some questions were rejected.
The groups received a briefing on the findings and provided feedback on areas that confused them, Allen said. “But what came out of the model was what came out of the model.”
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