COMMENTARY
In defence of historical accountability for greenhouse gas emissions

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Abstract

This commentary argues in defence of equal per capita emissions with historical accountability as a general rule for allocating the right to emit greenhouse gases. Historical accountability takes into account historical inequalities in per capita emissions. Implicitly it gives every human being an equal share of the global resource atmosphere, independent of place or time. Three reasons are put forward to argue why historical accountability should be the guiding principle for an international agreement allocating rights of emissions. In addition, as it has been dismissed by many scholars, six arguments are given to refute objections against historical accountability.

Introduction

Allocating rights to greenhouse gas emissions will always be a most contentious issue, no matter what the total reduction rate. Indeed, the more overall reduction takes place, the more contentious will the allocation rule be. Parties to a treaty aiming for reductions of greenhouse gas emissions pay high attention to who has emission rights, as can be seen from the exhausting negotiations that took place leading to the Kyoto Protocol in late 1997 (United Nations, 1997).

There are many different general rules on how to allocate rights to emit greenhouse gases. The most prominent ones are allocation proportional to emissions in a specified base year or future business-as-usual projected emissions (a rule known as ‘grandfathering’), allocation on an equal per capita basis without historical accountability and allocation on an equal per capita basis with historical accountability — or any mixture thereof. The ‘grandfathering’ rule regards differences in base year or future projected business-as-usual per capita emissions as basically justified, as these differences are prolonged into the future. The second rule regards unequal per capita emissions as unjustified and allocates future emission rights on an equal per capita basis, but disregards historical inequalities of emissions. The third rule is different from the equal per capita rule only in that differences in historical emissions are also taken into account. It holds countries accountable for the amount of greenhouse gas emissions remaining in the atmosphere emanating from a country’s historical emissions. It demands that the major emitters of the past also undertake the major emission reductions in the future as the accumulation of greenhouse gases in the atmosphere is mostly their responsibility and the absorptive capacity of nature is equally allocated to all human beings no matter when or where they live. Historical accountability is also known under the name ‘natural debt’ and has been pioneered by Grübler and Fujii, 1991, Smith, 1991.

These allocation rules can be defined formally. Assume, for simplicity of exposition, that a treaty encompassing all countries specified a worldwide emission target for each year t over a future time period of T years (t=1,…, T). Then the rules can be defined in their most simple form as follows:xit=xibwb · wt(allocation proportional to base year emissions)xit=PopibPopwb · wt(allocation on an equal per capita basis without historical accountability)where xit is country i’s allocation of emissions for each target year t, xib are country i’s emissions in a specified base year (which might or might not be the current year), wb are base year world emissions and wt are world target emissions for the year t. Popib is country i’s base year population and Popwb is base year world population.1

The same rule, but with historical accountability, is not quite as straightforward to formalise. First of all, we have to explicate what we mean by ‘historical accountability’. Define the Historical Emission Debt (HEDi) of a country i as follows:HEDi=j=seyijPopijPopwj · ywjwhere s is the start year, e is the end year of accounting (which need not be identical to b), Popi(j) and Popw(j) are defined as above for year j, yi(j) and yw(j) are country i’s and world emissions from year j, which are still remaining in the atmosphere in the end year of accounting.

The idea behind historical accountability is that countries which have in the past emitted in excess of an equal per capita allocation should have less than their equal per capita allocation of emission rights in the future, and vice versa for countries which have in the past emitted less than their equal per capita allocation. In other words, countries with a positive HED have to compensate countries with a negative HED for their past emissions in excess of their population share up until their HED is fully compensated for. (Note that, of course, the sum of HED over all countries is equal to zero.)

There are two further complications, however. First, in addition to an agreement on s and e, i.e. the accounting period, agreement is also needed upon the time period over which this compensation takes place. This is because for many countries it would simply be impossible to compensate for their HED in one year, as their HED might well exceed their total emission permits for that year. Second, if compensation takes place over a range of years rather than in one year, then it also has to be taken into account that a country’s HED decreases over time as the stock of past emissions in the atmosphere decreases slowly according to a certain decay rate, which depends among other things on the type of greenhouse gas and the concentration of this gas in the atmosphere. Because of decay, countries with a positive HED would want this period to be long and would want compensation to occur in the later part of that time period, whereas countries with a negative HED would want a short period and compensation to occur in the early part of that time period. Assume, for simplicity, that countries agreed on N, the number of years during which compensation takes place, which need not be identical to T. Assume further, somewhat arbitrarily, that they agreed that compensation is required according to the following formula:Cin=1NHEDin(n=1,...,N)where HEDin is the HED of country i still remaining in the atmosphere in year n. Then, the rule which allocates emission rights on an equal per capita basis with historical accountability can formally be defined as follows:xit=PopibPopwb · wt−Cin(allocation on an equal per capita basis with historical accountability)

‘Grandfathering’, the first allocation rule, is in the interest of developed or Annex 1 countries.2 It allows the continuation of their unequal access to the common resource atmosphere. In addition, they are not held accountable for their historical emissions that gave rise to the problem of global warming in the first place. That emission rights should be allocated on an equal per capita basis and that historical differences in emissions should also be accounted for is, on the other hand, the shared view of almost every scholar and policy maker from the developing world (e.g. Agarwal and Narain, 1991, Hyder, 1992, Ghosh, 1993). It is the objective of this commentary to argue in defence of this view. Section 2 lists three reasons in favour of historical accountability. Maybe more importantly, the commentary also aspires to refute some of the many objections that have been raised against historical accountability in the literature (Section 3).

Section snippets

Three reasons in favour of historical accountability

First, on the most basic level, science is on the side of historical accountability. It is undisputed that global warming is a consequence of the increased concentration of greenhouse gases in the atmosphere, which is a function of emissions that accumulated over time. It is true that emissions also decay slowly over time, but that does not invalidate the fundamental insight that global warming is not caused by current emissions of any particular year, but by a history of emissions over a long

A refutation of some objections against historical accountability

Let us turn to some objections against historical accountability now and try to refute them. A first objection claims that past generations have been ignorant of the detrimental consequences of emitting greenhouse gases and that the developed countries should therefore not be held accountable for historic emissions (Grubb, 1995, p. 491). While the first warning of global warming dates back to the last century (Arrhenius, 1896), it is presumably fair to say that it was not before the mid 1980s

Conclusion

Where is the international community of nation-states standing with respect to historical accountability? The preamble to the United Nations Framework Convention on Climate Change acknowledges that ‘the largest share of historical and current global emissions of greenhouse gases has originated in developed countries’ and Article 3 speaks of ‘common but differentiated responsibilities’ for climate protection (United Nations, 1992). The Kyoto Protocol demands emission restrictions only from

Acknowledgements

This paper has benefited from discussions with Ademar Romeiro and Mauricio de Carvalho Amazonas, both from Instituto de Economia at Unicamp, Campinas, São Paulo, and both leading members of the Brazilian chapter of the International Society for Ecological Economics (ECO-ECO). I would like to thank three anonymous referees for very helpful comments. All remaining errors are mine. Financial assistance from the European Commission’s (DG XII) Marie Curie Research Scheme on Climate and Environment

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