Greenhouse accounting: methods, methane and moos

10 Feb 2011

IN THE current political climate the prospects of significant reductions in greenhouse gas emissions might seem bleak. Only last year the US Senate jettisoned its emission cap-and-trade scheme legislation program. The Australian government, battered and bruised by the Copenhagen experience, had thrown the towel in a few months earlier, with a new multi-party climate change committee unlikely, in my view, to grasp the nettle.

With a carbon price and an emission cap lost in a maze of political trepidation and expediency, why now worry about the details of the accounting of greenhouse gas emissions? And why focus on methane?

The paramount reason is that only with an accurate system of emissions accounting can the Australian government and its people get a clear understanding of how and how much Australia contributes to global warming. Then, with that understanding, we can decide what policies are needed to best reduce that contribution. The reason to focus on the accounting now is that implementing measures like a cap-and-trade scheme or a carbon tax will be a hard slog, with great administrative and compliance complexities. Making an early start, including developing robust methods for accounting of emissions, will mean that when the politicians are finally ready to act then subsequent further years of teething pain will be avoided.

Methane needs focusing on because it’s been the politically ignored unsexy member of the greenhouse gas family. It makes up around a fifth of Australia’s current emissions. Most of those emissions emanate from the agriculture sector, whose activities urban Australians are not passionate about, beyond perhaps a respect for the iconic farmer. This is in contrast to carbon dioxide, which makes up around seventy-five percent of Australia’s emissions, and has the easier to relate to issues of coal power stations, cutting down of ancient forests etc.

In what follows the greenhouse gas accounting framework is introduced, a bias in the framework uncovered, the mooing cow is shown to be a lot less innocent than it looks and the need for an ally to face reality for the sake of planetary health is explained.

The framework

The methodology for reporting on greenhouse gas emissions is subject to a hierarchy of controls. At the highest level is the 1992 United Nations Framework Convention on Climate Change (UNFCCC), which has the ultimate objective of “stabilising… greenhouse gas concentrations at a level that would prevent dangerous human interference with the climate system.” The UNFCCC and the associated 1997 Kyoto protocol provide the overarching emissions-reporting obligations and guidelines for parties to those treaties.

The UNFCCC’s 93-page reporting guidelines cover estimation methodologies, reporting formats, the needs for transparency, consistency and accuracy, and requirements for reporting levels of uncertainty on published emissions data. The Kyoto protocol reporting guidelines differ slightly, mainly in relation to the treatment of land use, land use change and forestry activities.

In Australia, the National Greenhouse and Energy Reporting Act 2007, administered by the Department of Climate Change and Energy Efficiency, is the main legal instrument for meeting emissions-reporting obligations. There are also accompanying regulations and other legal instruments.

Unlike Acts, which are passed by parliament, regulations are created and modified by ministers and public servants, albeit legally constrained not to contradict the intent of the parent Act. In some respects, Acts can be thought of as building frameworks, while regulations are the interior decoration, and therein lays the potential for “devil in the detail.”

The National Greenhouse and Energy Reporting Act 2007 enforces a regime of annual emissions reporting. Emissions data for the years 1991–2008 is available on the Department of Climate Change and Energy Efficiency website.

A bias in the UNFCCC framework
The UNFCCC accounting framework is well nigh impossible to comprehend fully because of the magnitude and complexity of the underlying science. The bias in accounting for methane emissions described below was discovered serendipitously. It relates to the equivalence ratio employed in the UNFCCC framework. A CSIRO chief scientist kindly helped out with some of the science.

Equivalence ratios are analogous to currency exchange rates. They allow emissions of greenhouse gases other than carbon dioxide to be brought back to a single “currency,” the CO2 equivalent, whose sign is not the familiar $A but rather the CO2-e. The equivalence ratios are derived from the study of the global warming potential of gases relative to carbon dioxide, calculated over a specified period of time.

A period needs to be specified because some gases remain in the atmosphere for less time than others, due to various atmospheric interactions (for example, a major component in methane breakdown is its reaction with hydroxyl radicals in the tropospheric layer of the atmosphere). Short living gases have higher relative (to carbon dioxide) warming potential when compared over small periods. For longer periods, with less of the gas remaining, the relative warming potential decreases.

Typical equivalence ratio periods used in official reports are 20 years, 100 years and 500 years. As an example, methane’s 20-year period equivalence ratio value is 72. That means that over a 20-year period, a volume of methane emitted into the atmosphere causes 72 times the warming of an equivalent amount (the same molecular mass) of emitted carbon dioxide.

The International Panel on Climate Change (IPCC) is the official setter of equivalence ratio values, which it regularly reviews. Generally, reviews of significant greenhouse gases have resulted in increased equivalence ratios – in other words, advances in the science have led to an understanding that key gases are causing greater warming than previously thought. Methane’s equivalence ratios have increased as per the following table.

Methane Equivalence Ratios


Comparison Period

Year estimated by IPCC

20 years

100 years

500 years













Yet, to this day, the UNFCCC guidelines prescribe that emissions reporting apply the IPCC-1995 equivalence ratios. They also prescribe that the 100-year period be used, which as shown for methane in the table, has much smaller equivalence ratios than for the 20-year period (again because methane doesn’t stay in the atmosphere anywhere near as long as carbon dioxide).

By trawling though the UNFCCC website, one can see that the IPCC-1995 equivalence ratios were first earmarked for replacement as far back as 2004.

Australia’s position

Australia put its position on using updated equivalence ratios in a 2008 submission to the UNFCCC. Australia suggested that the IPCC-2007 equivalence ratios replace the IPCC-1995 set. However, Australia wanted the use of the 100-year period to continue for two reasons: an absence of compelling scientific or policy arguments for alternative time horizons, and the fact that a change in time frame would unnecessarily introduce complexities relating to accounting and time series consistency without any appreciable general benefit.

How greater complexity would be introduced and inconsistency added was not explained. It should be a simple enough computing exercise to re-derive previously published emissions data using 20-year or 40-year equivalence ratios. That process would create a set of consistent and comparable historical emissions data. Perhaps the Department of Climate Change and Energy Efficiency’s abacus beads get tangled with larger emission numbers?

More scientifically scary than the thought of departmental beads tangling, and implicitly assumed with the use of 100-year period equivalence ratios, is that climate policy is targeting the stabilisation of atmospheric gases over that period – that is, we have a century to get things right. However, science tells us that the first possible encounter with a climate change tipping point could happen way before another 100 years have passed. This, then, is the compelling policy reason (that the department couldn’t find) to change to a smaller period than 100-years. The whole aim of climate change policy is to avert global disaster and our greenhouse gas accounting system should be aimed at giving us the most accurate picture of how we are tracking.

In effect, Australia accepted the smaller increase caused by updating to the IPCC-2007 100-year equivalence ratio value but rejected the larger increase associated with switching to a 20-year or 40-year period. Was Australia’s position really about applying the precautionary principle on side of economic prosperity, especially that of the agriculture sector, rather than on the environmental side? There has been continuous debate about whether agriculture should be included in emission abatement schemes and if so at what stage. Underestimation of its greenhouse gas impact makes it easier to delay its inclusion.
Recently the UNFCCC decided to defer any final decision on adopting updated equivalence ratios until after the IPCC Fifth Assessment reporting in 2012, an example of how dreadfully slowly things move in UN processes.

And what about the mooing cow?

Australia’s love affair with BBQ steak and roast lamb may provide an additional explanation for the government’s fear to move away from 100-year equivalence ratios. According to the Department of Climate Change and Energy Efficiency, methane emissions made up 21 per cent of Australia’s total greenhouse gas emissions in 2008. About 60 per cent of those methane emissions were from the agricultural sector, with a good portion of those arising from the digestive processes of cattle (mainly), sheep and other ruminants.

If the department were to recalculate its emission data using 20-year equivalence ratios, then methane emissions would make up around 40 per cent of Australia’s 2008 total and the heating contribution of ruminants would approach that of coal power stations. In the grander scheme of things, Australian meat-lovers may need to change their habits as much as those so-called big polluters.

And, finally, what of the Kiwis?

New Zealand, a nation with a reliance on agricultural production, will have their emission numbers greatly inflated with the use of shorter period equivalence ratios.

Under the current greenhouse accounting methodology, agriculture already makes up almost exactly 50 per cent of New Zealand’s total emissions. Those agricultural emissions, as well as the nation’s total emissions, have been growing in recent years. If the UNFCCC were to adopt shorter period equivalence ratios, reversing that emission growth would be harder and bring extra economic hardships. World agreements will eventually demand that reversal of emission growth so this is no idle threat

Undoubtedly there are other countries in the same boat as New Zealand. Disproportionate impacts abound with climate change action, part of the reason why it’s so difficult. That doesn’t mean Australia should stick its head in the sand in the hope of avoiding economic pain for our pals or ourselves. Policy compilation and implementation must be correctly informed on how methane is contributing to global warming. Australia should now advocate for the use of shorter period equivalence ratios and the UNFCCC should adopt them. Otherwise the planet will pay a disproportionate price.
Ilan Salbe has been working as a public servant for over 20 years modelling the water supply systems of Sydney and the Murray and Murrumbidgee Valleys. In a private capacity he has researched a wide variety of topics and he is active in the NSW Blue Mountains community.

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