The Climate Equity Reference Project approach to Equity Benchmarking

The Climate Equity Reference Project (CERP) approach to equity benchmarking is built upon the core equity principles of the UNFCCC. These principles have been nicely summarized[1] as follows:

  1. A precautionary approach to adequacy, referring to the collective obligations of countries to undertake and support urgent and adequate global action to prevent dangerous impacts of climate change and provide effective adaptation to unavoidable impacts, without which there can be no justice. (Article 3.3: “The Parties should take precautionary measures to anticipate, prevent and minimize the causes of climate change and mitigate its adverse effects.”)
  2. Common but differentiated responsibility and respective capability (CBDR+RC), in which obligations to take action and provide support, and rights to receive such support, are accepted as functions of both historical and current emissions, and of capability to act. (Article 3.1: “The Parties should protect the climate system for the benefit of present and future generations of humankind, on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities.”)
  3. The right to sustainable development, which we understand as the right of all countries to not just lift their people out of poverty, but also to provide their citizens with sustainable and universalizable living standards. By sustainable we mean “development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” By universalizable, we mean living standards that could be made available to the citizens of all countries. (Article 3.4: “The Parties have a right to, and should, promote sustainable development.”)

The Climate Equity Reference Calculator models the CERP approach to equity benchmarking. It allows the user to select a global mitigation pathway of a specified level of ambition, thereby determining the size of the global mitigation need – the mitigation gap – that is then taken to be fairly shared among countries according to the UNFCCC principles of equity.[2] It also allows the user to estimate the global adaptation need, which is (for the moment) taken to include the loss & damage need.

More precisely, a Calculator user selects equity-related settings relating to responsibility and capability, and other key parameters. These settings, taken together, define an “equity benchmark”. This benchmark is then used (see the discussion below) to calculate national “fair share” of the global climate-related effort. Again, this effort includes not only mitigation (though most all of our attention is necessarily focused on mitigation) but also adaptation and loss & damage.

The obvious reality is that people have different conceptions of how “fair shares” should be defined. It is precisely for this reason that a transparent framework for articulating and calculating fair shares, in terms of the stated UNFCCC principles and in a comparable manner, can be tremendously illuminating and helpful. It can increase our common understanding of what climate fairness actually means from different perspectives. It can clarify the kinds of international climate arrangements that might be widely accepted as being fair enough by a wide set of actors, and thus serve as foundations for the large-scale cooperation that will be necessary in the years ahead. And it can help us to understand the kinds of equity assessment that can help move us towards such arrangements.

Fair shares of global efforts

The CERP framework supports an infinitely gradated number of equity benchmarks, all of which, as noted above, are defined in terms of the UNFCCC’s core equity principles. Also note that, critically, these benchmarks are designed to clarify national fair shares of global needs, not national domestic efforts. Indeed, the whole point of the CERP exercise is to show how each country’s total efforts (whether undertaken at home or abroad) can be meaningfully assessed against one or another definition of its fair share.

This is illustrated by the following graphs, which show how a mitigation gap is partitioned into mitigation fair shares that are assigned to individual countries on the basis of their responsibility and capacity.


It’s also important to note that a nation’s fair share of the global mitigation effort may be quite different from its domestic mitigation potential (and here we mean both techno-economic potential and emission reductions associated with consumption and lifestyle changes). For wealthy and high emitting countries (i.e., those with high capability and responsibility), any reasonably defined national fair share will generally exceed the country’s domestic mitigation potential, and in some cases even exceed its domestic emissions. For poor and low emitting countries (i.e., those with low capability and/or responsibility), domestic emissions – which is to say the national potential for curbing global emissions – may greatly exceed the country’s fair share of the global mitigation effort. For countries with middle-range incomes and emissions, domestic mitigation potential and fair share may be more closely correlated.

What this clearly demonstrates is that international finance and technology support is absolutely critical. Otherwise, the wealthier countries will be saddled with greater mitigation obligation than they could possibly discharge, and poorer countries will be left with a great mass of unexploited mitigation options and unfunded adaptation needs. This would be an untenable situation rendering the pursuit of any ambitious global mitigation pathway quite impossible. For this reason, it only makes sense to consider fair shares in terms that include both domestic reductions and support for climate action in other countries.

Equity benchmarks

The Calculator supports a wide range of settings and parameters (any group of which defines an equity benchmark), which it uses to calculate a fair share of the total global effort (however defined) for each country. Below, as a guide to the resulting equity model, we’re going to discuss a small set of indicative benchmarks.

Note first that each benchmark is defined in terms of responsibility and capability. These core equity notions are represented in a transparent way using explicitly defined quantitative indicators: capacity is defined using indicators that reflect income, and responsibility is defined using indicators that reflect cumulative GHG emissions. Various ethical perspectives on these two underlying equity notions are possible, so the Calculator presents the user with various settings and choices relating to how to interpret responsibility and capacity.

Note also that not all the benchmarks that can be defined in this framework can be plausibly defended as fair. Some responsibility settings, some capability settings, some global mitigation pathways, and some estimates of adaptation need are in fact patently unfair. And yet, in the CERP framework, benchmarks can be defined in terms of such settings, and the results can be illuminating.

We’ll return to this critical point, but first let’s look at some indicative equity benchmarks. Here’s how the Calculator’s Equity Settings panel expresses the key choices that define them (and do note that if a Calculator user clicks past the above panel, they will get a richer set of controls reflecting other choices, allowing the user to define many more cases).


Note that while the equity benchmarks are defined in terms of a country’s responsibility and capability, the user has the flexibility to select the relative weighting of each. If one considers the two to be equally foundational principles, one can weight them equally (50% capability: 50% responsibility). If one considers capability to be of primary importance and responsibility to not require separate consideration, one can select a weighting of 100% capability : 0% responsibility (and vice versa). Or, one can choose anywhere in between. The indicative examples we show below include benchmarks that combine responsibility and capability on an equal basis, as well as examples that weight one or the other at 100%.

A bit more on progressivity

As is customary in discussions of fair effort-sharing, we define capability in terms of national income. Just as income is considered in a progressive manner in national tax policy; it can be considered in a progressive manner for the purposes of defining capability. And, as in tax policy, the key question is how progressively to account for income? Here are four indicative choices.

  • The “No Progressivity” setting in which there is no income threshold below which individual income is exempted from national capability, either on the basis of a poverty exclusion or a development exclusion. In such a case, when calculating capability, each dollar of income – even for the poorest of the world’s people – counts as much as each dollar of the world’s richest. This approach is inconsistent with the at least mildly progressive perspective that virtually all societies have adopted for the purpose of income taxation, and is impossible to justify in equity terms.
  • The “Low Progressivity” setting in which an income threshold is set, one that, while not high enough to be judged progressive in any meaningful sense, is significantly higher than 0. For example, $2,500 has been used to define a useful indicative “Low Progressivity” case.
  • The “Medium Progressivity” setting in which the income threshold is significantly higher than $2,500. Rather, in “Medium Progressivity” cases, the income threshold is set at $7,500 (approximately $20/day). This level is just a bit above a global poverty line that reflects empirical observations, so it should actually be taken as a low estimate of “medium” progressivity, and can reasonably be said to represent a “development threshold” below which income is legitimately prioritized for basic living requirements.
  • The “High Progressivity” setting in which the income threshold is set at the same “development threshold” level of $7,500 as in the “Medium Progressivity” case, with income above this threshold counting toward national capability at a steadily rising rate, until it reaches an luxury threshold (set for this analysis at $50,000), above which all income is counted towards national capability. These settings increase the overall progressivity of the income calculation just as a graduated tax schedule raises the progressivity of an income tax. Note that this is not an extravagantly progressive setting; the $50,000 figure falls below the income of the highest earning “one percent” of the global population.

A bit more on responsibility

As is customary in discussions of fair effort-sharing, we define responsibility in terms of a country’s cumulative emissions. The key setting here is the “responsibility start year” from which historic emissions are included in the reckoning of a country’s responsibility. Here are three indicative choices:

  • “Responsibility since 1990.” This corresponds roughly to the time when negotiations for an international legal agreement to limit GHGs began in earnest and the risks of rising GHGs were acknowledged by the IPCC. The 1990 date is difficult to defend, given that the UN Framework Convention was itself being negotiated at that time, and its authors cannot reasonably be said to have had 1990 in mind when they inscribed the term “historical” into the text. Still, the 1990 case is arguably fair, but only in cases where the benchmark includes capability weighting. This is because historical responsibility before 1990 is highly correlated with national capability.
  • “Responsibility since 1950.” This date marks a useful middle setting. It defines a period in which the climate threat was known, in which responsibility is comprehensible in terms of human lifetimes, reflects roughly the useful lifetimes of much infrastructure, and avoids some of the historical discontinuities that occur when, for example, wars remake national boundaries.
  • “Responsibility since 1850.” This date defines responsibility as cumulative emissions since a date that roughly corresponds to the time at which carbon dioxide emissions from fossil fuel combustion reached significant levels. This is also the earliest date for which plausible emissions data exist.

The user can make additional choices that influence the calculation of a country’s responsibility. One is which greenhouse gases to include when accounting of a country’s historical emissions. The indicative calculations shown below are based on emissions of fossil carbon dioxide and non-CO2 “Kyoto basket” GHGs, and exclude land-use emissions, though the Calculator gives the user the choice of including or excluding non-CO2 GHGs and land-use emissions.

Another important consideration is whether a country’s responsibility should be calculated on the basis of production-based or consumption-based accounting. Here we use production-based accounting, which reflects actual emissions within a country’s territory. The Calculator offers the option to account for emissions on a consumption basis (whereby emissions generated in the production of goods are attributed to the country that consumes those goods).

And finally, there is the choice to exclude emissions corresponding to consumption below a particular income threshold (say because they arise from the provision of basic needs). This is entirely analogous to the treatment of progressivity on the capability side.

Putting Responsibility and Capability together

These various choices are reflected on the Calculator’s introductory settings panel (shown above), and as follows:

  • The responsibility side of a benchmark (if there is one) can be set in terms of a 1850, 1950, or 1990 responsibility start date.
  • The capability side of a benchmark (if there is one) can be defined in terms of zero, medium, and high progressivity (as described above).

And, the user may set any possible weightings of the two principles, including:

  • Benchmarks that are defined by a combination (here 50/50) of responsibility and capability.
  • Capability-only benchmarks (in which the weighting of responsibility is dialed down to 0).
  • Responsibility-only benchmarks (in which the weighting of capability is dialed down to 0).

All of these benchmarks (and many more, if the user proceeds to the richer underlying set of controls) can be expressed within the CERP framework. This is true despite the fact that, normatively, the choices between them can be quite stark. A highly-progressive, capacity-only benchmark that is calculated in a manner that takes internal national income inequality into account reflects an entirely different ethical perspective than a responsibility-only benchmark that is indifferent to income inequality and calculated in terms of an 1850 responsibility start date. Yet both can be expressed in terms of dynamic responsibility and capability indicators.

Equity assessment: the CSO Equity Review coalition’s equity range

What do benchmarks like these mean in practice? How can they be used to inform the negotiations? To help “ratchet up” the overall level of ambition? These are big questions that involve both political and normative judgements. What we can say is that equity modeling can help make such judgements explicit and transparent, and by so doing can facilitate coherent engagement, reasoned negotiation and, we hope, convergence towards broadly shared understandings about the scale of the national actions that can plausibly be considered to be “fair.”

We show how this can work by recounting the process that led to the report Fair Shares: A Civil Society Equity Review of the INDCs[3] released in the run-up to Paris. As the CSO Equity Review coalition formed to undertake this initiative, it became quickly clear its constituent organizations held a broad range of views of equity, and could not expect to settle on one definitive equity benchmark. They were, however, committed to the dialogue, and as a matter of practicality, agreed to an “equity band” defined by high and low benchmarks that spanned their range of equity perspectives.

After considerable deliberation, the coalition agreed to define an equity band as follows:

  • It would reflect with balance the principle of common but differentiated responsibilities and respective capabilities. For this reason, it would be defined in terms of benchmarks that weighted responsibility and capacity equally.
  • The responsibility dimension of the equity band would be bracketed by the responsibility start dates 1850 and 1950.
  • The capability dimension of the equity band would be spanned by the “medium progressivity” and “high progressivity” choices as described above.

The coalition further agreed that a responsibility start date as recent as 1990, and definitions of capability that were “Low” progressivity, were ethically indefensible and unfair, and were to be excluded from the equity band. However, a 1990 / “Low progressivity” benchmark was still judged to be politically salient, so it would be informative and useful to include it in the analysis.


The result can be seen in Figure 5 of the pre-Paris report, above, where the national equity band is represented by the two green bars (shown here in per-capita terms) selected by the above decisions. This figure includes the 1990 / Low Progressivity benchmark, which is shown (in gray) for purposes of comparison.

The most valuable lesson of this exercise was that, despite the wide range of view represented by the equity band, and the inclusion of a benchmark well outside of the equity band, the results were still strikingly clear. Each country’s pledge could still be clearly assessed relative to the entire span of the benchmarks, and on that basis each country could be judged to be either a leader or a laggard.

The equity assessment debate is only beginning, and is not of course confined to this project. But this project does clearly demonstrate the potential for fruitful learning that is rooted in this kind of approach. For example the second CSO Equity Review coalition report, Setting the Path towards 1.5°C[4], includes two new benchmarks, designed explicitly to clarify the relative impact of capability and responsibility.

It does this by providing two additional benchmarks, one of which weights capability at 100% and responsibility at 0%, and one of which weights responsibility at 100% and capability at 0%. These benchmarks are illustrated in Figure 3 from Setting the Path:


The capability-only and responsibility-only benchmarks are, of course, the ones shown here in blue. Note that the example responsibility-only benchmark is calculated relative to 1850 and is thus a “deep history” benchmark, while the capability-only benchmark is calculated in “high progressivity” terms.

Note also how the dark green bar falls evenly between the two blue bars – a direct consequence of its 50/50 responsibility and capability weighting. If a 1990 responsibility-only benchmark and a Low progressivity capacity benchmark were added to the above chart, the grey bar would fall evenly between them.

Finally, note the key message from this exercise. Contrary to widespread belief, a central result of any equitable approach to global effort sharing – that the wealthy countries must provide significant levels of support to developing countries – is not a simple consequence of the historical responsibility approach. The capability-only benchmark just as strongly conveys this same result. (This is particularly true for wealthy countries with relatively low carbon intensities – think northern Europe). The point is that capacity-only and responsibility benchmarks can themselves be strong or weak, and that this matters.

The lesson

What’s the point? That the power of this approach comes from how it allows us to escape the pseudo-debate between, on the one hand, the claim that equity is an entirely subjective matter, a mere battle of opinions, and, on the other hand, the claim that one or another equity approach is the precisely “right one.” It does this by providing a quantitative framework within which explicit choices between well-specified approaches – e.g. more or less progressive responsibility and capability indexes – can be assessed and compared without being over-specified and reified. While this inevitably yields ranges instead of precise numbers, it also yields higher confidence, as a consequence of generating understandable results that transparently and traceably express explicit ethical-political choices.

To sum up: no particular equity benchmark is inherently part of the CERP framework proper. Rather this framework is intended help users articulate specific conceptions of equity, relate them to fundamental equity principles, and derive useful quantitative results from them, by for example using them to assess national pledges. In walking through these steps, users make very specific and transparent choices, which the CERP framework is set up to facilitate, codify, and illuminate.

The CSO Equity Review was, as far we know, the first attempt, by a fairly diverse group, to negotiate shared climate equity benchmarks. We consider it a success, and a useful validation of the claim that equity assessment can in fact be extremely helpful.


[1] This summary was done by the Equity / Effort-sharing Working Group of the Climate Action Network. See The Core Convention-based Equity Principles, a CAN position paper of September 2013. This discussion paper contains much more information of how the Working Group has defined the Convention’s core equity principles, and what kinds of indicators it sees as appropriate to their measurement.

[2]    This mitigation gap is defined relative to a global business-as-usual emissions path. Effort-sharing frameworks (unlike resource-sharing frameworks that divide up, say, a fixed emissions budget) require emissions baselines, because an “effort” must be measured against a business-as-usual pathway that reflects “no effort” or “no policies.” In the CERP framework, calculations are based on a set of national no-effort baselines that rely as heavily as possible on existing, widely-known and well-vetted national projections for all key indicators (i.e. population projections, GDP projections, carbon intensity projections) updated for recent history. For more on this, see Definition, sourcing, and updating of the emissions baselines. Also note that, as with global mitigation pathways, the Calculator can be adapted to support any well-define set of national business-as-usual pathways. Please contact us if you’re interested in exploring alternative mitigation pathways or business-as-usual pathways.