A guest post by Sean Devine:
The Climate Change Commission, has produced its 2021 draft advice for consultation (January 2021) on managing New Zealand’s contribution to human induced global warming. But the advice is conceptually flawed, putting its long-term credibility at risk.
The critical problem is that the policy framework is based on what is called the “carbon dioxide equivalent” emissions of the different sources of greenhouse gases. The carbon equivalent of methane is 28, as a 1kg pulse of methane traps the same heat as 28 kts of carbon dioxide.
While the target for carbon dioxide is to reduce carbon dioxide emissions to net-zero by 2050, this cannot be the target for methane emissions from New Zealand’s pastoral animals such as cows and sheep, as these emission can be made net-zero by capping emissions at say, the 2017 level. Methane emissions from these animals recycles. What then is the basis of methane management?
The problem is that the policy framework, without scientific justification, is articulated in terms of the inputs – the emission equivalents carbon dioxide for each gas, not the outcome, the global temperature.
Policy should be articulated in an “input-output-outcome” framework to determine the critical parameters. Policy must focus on the causes of the increase in temperature (manage the outcome), which is driven by the output, (the actual level of gas in the atmosphere), not equivalent emissions.
Should I use a sheep or a petrol-powered mower to mow my grass, if their equivalent emissions are identical? The answer is: “the sheep”, as in terms of gas levels in the atmosphere, the methane produced by the sheep recycles, turning into carbon dioxide and then into grass. On the other hand, carbon dioxide from the mower, persists in the atmosphere with about 20% remaining in 1000 years (See Joos Figure 5). It is not the equivalent emissions that count, but the level of gas in the atmosphere.
Suppose there is a society with two communities, one of which is sustainable with only two children per couple, the other producing 10 children per couple. If the population is unsustainable, the growing population must first be reduced, not the sustainable population.
So too with methane and carbon dioxide for an economy like New Zealand. Because methane produced from a fixed number of pastoral animals is recyclable, it is sustainable. If the number of animals is capped, the methane emissions become net-zero and and no longer increase the global temperature. No matter what governments might promise, it will be extremely difficult to reduce carbon dioxide emissions to net-zero by 2050, yet pastoral methane emissions could be made zero now.
The Commission’s approach ignores the scientific fact that reducing pastoral equivalent emissions by 10%, actually lowers global temperature. In contrast, reducing carbon dioxide emissions by the equivalent amount just delays the temperature rise by 14 years over 100-year period.
Emission equivalents are no longer needed, as a recent article by Allen et al. (2018) provides a better equivalent – that of the output, the level of gas in the atmosphere. This equivalent, known as the carbon dioxide-e*, can be used to determine the actual warming due to that gas. For example, in terms of the level of gas in the atmosphere, a change of methane emissions by 1 kt per year warms as much as a one-off injection of 28 x 100 kts of carbon dioxide into the atmosphere. The output, the level of methane in the atmosphere, stabilises over the 100-year period.
But the important factor it is the change in methane emissions that changes the global temperature. If pastoral methane emissions are capped there is no consequential increase in global temperature.
A policy of reducing pastoral methane emissions in New Zealand by 30%, is equivalent to reducing carbon dioxide emissions (36 kt/yr) completely for the next 28 years. This is bizarre. On what basis should we do this? This illustrates the muddled conceptual framework. Of course, pastoral methane emissions should be reduced as far as possible, perhaps by breeding or appropriate diet. Also, other sources of methane and nitrous oxide from agriculture still need to be managed. But the inconsistent policy framework is not defensible scientifically, or in terms of equity.
Don’t just listen to the scientists, understand both the science and policy, otherwise there will be no long-term societal buy-in. Somethings have to look right, this is one that has to be right.
Allen, M.R.;Shine, K.P.; Fuglestved, J.S et al. 2018. A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation. npj Clim and Atmos Sci. 1;16. doi.org/10.1038/s41612-018-0026-8
Joos, F.; Roth R,; Fuglestvedt, J.S. et al. 2013. Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis. Atmos. Chem. Phys. 13;2793-2825. https://doi.org/10.5194/acp-13-2793-2013, 2013. Table 5.
Sean Devine was originally an infrared researcher in both New Zealand and the UK, spending 25 years in research in what was DSIR. After studying economics, Sean moved into science management. Following his role as Executive Director of the Association of Crown Research Institutes, Sean joined Victoria University as a research fellow and taught strategy for a number of years. Recently Sean from a systems’ perspective has published a new approach to economics, that sees an economy is a far from equilibrium system sustained by energy. He is no not quite retired, having had a book published on Algorithmic Information theory in 2020.
I can only agree that treating a gas that only stays in the atmosphere for 40 years the same as one that stays for 1,000 years is bizarre.