Victoria University of Wellington’s Dave Frame unpacks the incorrect assertion that early action on methane buys time for mitigation of CO2.
Sometimes bad ideas just won’t die. So it is with the incorrect assertion that early action on short-lived climate pollutants such as methane buys time for mitigation of long-lived climate pollutants such as CO2.
The most recent articulation of this idea was in the final report of the Prime Minister’s former Chief Science Advisor, Professor Sir Peter Gluckman, which claimed that “while noting that methane emissions from agriculture cannot, and need not be, reduced to zero, reducing global methane emissions quickly will [reduce] the peak warming temperature and the rate at which CO2 emissions need to be reduced … The delay will allow more time to bring direct CO2 emissions to net zero”.
This is incorrect. Research several years ago showed that reductions in short-lived gases like methane do not buy time for later CO2 reductions.
In a 2013 paper called “The role of short-lived climate pollutants in meeting temperature goals” in Nature Climate Change, a group of us looked at the climate response to emissions scenarios that contained cuts to methane and black carbon, superimposed against standard emissions scenarios.
We varied the timings of the cuts to the short-lived climate pollutants (SLCPs), to see if it was true early cuts made any difference to the long-run behaviour of the climate. They did not.
From our experiments, we concluded “early SLCP reductions, compared with reductions in a future decade, do not buy time to delay reductions in CO2”.
So you can shave a little off peak temperatures, but that is all.
The following year, Professor Ray Pierrehumbert, Halley Professor of Physics at the University of Oxford in the UK, wrote a review paper that assessed competing claims, set out the relevant physics and made the following points very clearly:
“If the prime climate protection goal is to limit peak warming, then early SLCP mitigation is pointless, because in no case does early SLCP mitigation significantly reduce the peak warming. The calculation does show, however, that eventual SLCP mitigation helps trim the magnitude of the peak warming.”
The paper continues: “It is seen that any amount of substitution of SLCP abatement for CO2 abatement results in a situation in which a temporary and modest reduction in near-term temperature is bought at the expense of a permanent increase in the long-term temperature. The greater the substitution, the less the short-term climate benefits and the greater the irreversible harm.”
This research has been available for several years and the results are very clear. Findings like these are why even the Climate and Clean Air Coalition – strenuous advocates of action on SLCPs – include in their factsheets the point that “early action on SLCPs cannot ‘buy time’ for delayed mitigation of CO2”.
So if things are very clear on this, why do Sir Peter and others (here and abroad) continue to get it wrong?
As Winston Churchill observed, the velocity of an established falsehood tends to outstrip the ability of the truth first to dress and then to accelerate in pursuit. So it is with the ‘methane mitigation buys time for CO2’ myth.
The main reason for its persistence probably has to do with incentives – early SLCP action suits various groups, especially but not only states and activists that want to pretend methane mitigation matters more for the climate than it really does, and scientists whose research interests (or funding) turn on the mitigation of short-lived species.
It also suits fossil fuel companies, of course, which have a history of shrewd political spread-betting on climate change issues.
In New Zealand, there is a strong official mantra about the centrality of agricultural mitigation efforts in our research portfolio. It is claimed, repeatedly, there are great opportunities if we continue to focus much of our climate mitigation research effort there.
But are these claims about the primacy of agricultural mitigation research correct? Agricultural mitigation research in New Zealand has chewed through around $65 million over 10 years, with little to show for it in terms of deployable technologies.
I’m not saying that investment was a mistake – those researchers deserve commendations for the candour with which they discuss their prospects: they promise no magic bullets and point to no game-changing successes.
However, that money would have brought down a lot of CO2 emissions. It could have been spent on smart-meter initiatives, public transport or even doing something about the largest-point sources of CO2 emissions.
Those are things we know we have to do to stop our contribution to climate change; yet they are things that currently are not being done.
New Zealand is like a company whose ferries have been getting slower and slower (rising CO2 emissions) but whose strategy is to create some clever app to help people get back to their cars faster (agricultural mitigation investments).
Instead we continue with a Pollyanna-ish approach to CO2 – the idea we’ll just buy those technologies and adopt clever approaches as others create them, even though the attitude of leaving the problem to others is exactly what the current Government objected to in the previous administration’s position, and even though CO2 is the main and most urgent problem.
The agricultural mitigation mantra also has a misalignment between those who bear its risk and those who accrue its potential benefits, since stringent pressure on agricultural emissions coupled with a large investment in associated research leaves researchers with the benefits – generous funding – and farmers with the costs, or at least the risks, should the research continue to be unsuccessful.
The rational thing to do would be to phase targets for methane so pressure follows technological success – to apply pressure to agricultural methane emissions only as technologies to do something about them become available at reasonable cost.
So why not set a moderate policy now, with the opportunity to increase pressure later, once you have better options and once you have the main issue under control?
The positive thing is it doesn’t matter much when the scientists are successful, as long as they are eventually. As we showed in our Nature Climate Change paper, you get the same long-term temperature benefits from reducing methane emissions by a quarter in over 20 years’ time as you do from beginning that initiative now.
In that sense, the relationship between CO2 mitigation and methane mitigation is like crossing the Cook Strait on the ferry: the overall time (and success) of the trip is governed by the speed of the ferry, although you can help a bit at the far end by being organised and ready to return to your car for efficient disembarkation.
The point here is it doesn’t really matter whether you return to your car 10 minutes before disembarking or two hours before. You’ll still drive off the ship at the same time.
To extend the analogy further, New Zealand is like a company whose ferries have been getting slower and slower (rising CO2 emissions) but whose strategy is to create some clever app to help people get back to their cars faster (agricultural mitigation investments).
The app doesn’t work, the ferry keeps getting slower, but the learned bodies and Government departments keep asking us to focus on the app, not the ferry. I think we should fix the ferry.
Reducing methane emissions “helps trim the magnitude of […] peak warming”, but it doesn’t buy time; and the overall warming is determined mainly by cumulative emissions of CO2.
These govern how much the world heats up and how fast it gets there. The aim is to stop that. Limiting peak warming was what we signed up to in Paris. Let’s deliver on it.