The concept of permanence or reversibility of emission reductions was a recurrent topic in the negotiations of the Kyoto Protocol and subsequent trading schemes, standards and reporting methods.

While the term permanence is frequently cited as an essential feature of efforts to reduce emissions none of the key UNFCCC, IPCC or ISO documents gives a satisfactory definition of this important term. Many documents refer on to other sources for clarification, but tracing the links back gives limited satisfaction.

For example, the VCS lists permanence as one of its 8 core principles, but refers readers to ISO 14064, part 2 for a definition. For its part, ISO 14062, part 2, describes permanence, somewhat vaguely as:

“…a criterion to assess whether GHG removals and emission capture and storage are long-term, considering the longevity of a GHG reservoir or carbon pool and the stability of its stocks, given the management and disturbance environment in which it occurs.”

ISO then refers those seeking further clarity to a rather obscure document recording an agreement between parties negotiating the Kyoto Protocol, so called Decision 19/CP.9 . However, the relevant paragraphs (38 to 50) of this legal style agreement provide no explanation of permanence; instead they set out a complex set of temporary crediting rules devised to address the “non-permanence” of forestry and agriculture carbon in the CDM.

At this point the trail becomes confusing. The CP.9 document refers to work carried out by the IPCC (Special Report on Land Use, Land Use Change and Forests), which repeatedly states “there is no consideration of non-permanence…. because these items are under consideration by SBSTA”.

The literature indicates that the debate over permanence has focused almost exclusively on forest and other land use related activities, designed to increase stocks of carbon held in vegetation and soils. However, without a clearer definition, an examination of the underlying processes associated with GHG emissions shows many emission reducing activities could have permanence related issues. Here is a quick overview:

1. Renewable Energy, Fuel Switching
Permanence is rarely raised, however, the physical units of carbon (molecules in the fuel that is displaced) that would have been emitted in the absence of the low carbon energy supply are unlikely to be permanently sequestered. They are much more likely to be combusted by another fuel user. So a question arises as to whether renewable / low carbon energy represents permanent avoidance of emissions or a reduced rate of combustion of fossil fuel reserves. The delay in emissions is likely to be short if renewable energy supply depresses the price of fossil fuels, and the lower price consequently leads to increased consumption of fossil fuels in other jurisdictions.

2. Energy Efficiency
Similar issues arise for energy efficiency measures. The physical units of carbon which aren’t released because of an energy efficiency programme are unlikely to remain unused – and the question then arises of how long the emissions are delayed for.

3. Destruction or Avoidance of Fugitive Gases
The destruction of fugitive gases such as coal mine and landfill methane and industrial by-products may be genuinely permanent where there are finite quantities of precursor feedstocks. (Some of these processes raise questions of additionality, which is a separate issue). However, in the case of some N2O avoidance techniques there may be questions as to whether the nitrate is transported to other ecosystems where de-nitrification could occur.

In conclusion
Permanence is wielded as a powerful term in negotiations and regulation on GHG abatement but there is poor clarity on the detail of its meaning. Without a clearer definition the concept could be applied to almost any mitigation action.


  1. Very interesting observation. It would be interesting to understand what the timeperiod of an emission delay is with a renewable energy project. I guess an eyeopener would be that when we would be able to run the whole world 1 year on renewables only, the delay would be 1 year. If we would plant sufficient forest to store the carbon of one year, the delay would be minimum 50 years.

  2. Emissions aren’t permanent either. eg a pulse injection of methane at T = 0 is all cycled out of the atmosphere well before 100 years. A pulse injection of carbon dioxide has substantially decayed over 100 years but there is still `30 – 40% left. CFCs are around for thousands of years but not fowever.
    Nonetheless I think carbon sequestration should be over geological timeframes to offset the emission of fossil carbon.
    As a start towards this I put forward the idea that a legally binding and credible commitment to sequester carbon for a MINIMUM of 100 years is a useful step towards this, such that credit is not allowed for shorter periods of guaranteed storage, but full liability remains for re-emission in perpetuity once credited. The hundred year period is chosen for consistency with the period over which the cumulative thermal forcing effects of the different greenhouse gases is quantified to calculate CO2 equivalency.

  3. Congratulations Richard. A valuable contribution. Permanence as 100 years has no basis in science. The time it takes a molecule of CO2 to cycle out of the atmosphere is variously estimated as being 5 to 55 years. Yet this communal myth of 100 years is quoted by scientists and others – including the authors of Australia’s Carbon Farming Initiative Handbook – as if it is peer-reviewed fact. What other pieces of fiction are masquerading as fact in the biosequestration debate? See

  4. Michael can you reference the peer reviewed papers estimating CO2 residence time in the atmosphere as 5 – 55 years. The IPCC uses the Berne Model which gives the time course of decay I quoted above. Have a look at the Special Report on LULUCF and the Assessment Reports. Particularly the Special Report on LULUCF (page 86 or so from memory). Cheers

  5. The 5 (about 4) reference: “The turnover time of CO2 in the atmosphere, measured as the ratio of the content to the fluxes through it, is about 4 years. This means that on average it takes only a few years before a CO2 molecule in the atmosphere is taken up by plants or dissolved in the ocean.” However, it can take far longer for the atmosphere to adjust to the new levels of CO2, up to 200 years. Watson, R.T., Rodhe, H., Oeschger, H. and Siegenthaler, U. 1990. Greenhouse gases and aerosols. In IPCC Report No 1, World Meteorological Organization and United Nations Environment Programme, Cambridge University Press.

    The 55 reference:
    “In operationalising the Absolute Global Warming Potential concept, the Kyoto Protocol sets 100 years as the reference
    time frame over which cumulative radiative forcing is to be measured. Over this 100-year period, the decay curve integral is equivalent to the forcing effect of approximately 55 tonne-years of CO2. Hence, we can infer that removing 1tCO2 from the atmosphere and storing it for 55 years counteracts the radiative forcing effect, integrated over a 100-year time horizon, of a 1 t CO2 pulse emission. Under the terms of the Kyoto Protocol, the AGWP100 of CO2 represents the radiative effect of a pulse emission which any
    sequestration-based activity is designed to counteract (or indeed, any emission reduction activity is designed to avoid
    or delay). In effect therefore, as understood by the Protocol, carbon sequestered at t=0 and stored until t=55 is directly equivalent to an avoided emission at t=0 and could be credited accordingly. Any new emission from the subsequent release of the stored carbon at t=55 would not be deemed to have caused any additional radiative forcing effects to those which characterized the start point of the
    project, measured over the 100-year reference period from the point of emission/sequestration. This timeframe of
    equivalence between sequestered and emitted CO2 is here called the ‘Equivalence Time’ (Te). The re-emission of
    sequestered carbon after its storage for t=Te does not affect this equivalence.”
    Pedro Moura Costa and Charlie Wilson, An equivalence factor between CO2 avoided emissions and sequestration – description and applications in forestry, Mitigation and Adaptation Strategies for Global Change, Volume 5, Number 1, 51-60

    I assume the first reference is peer reviewed and the second isn’t.

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