CLÁUSULAS ESPECIALES DE CONTRATACIÓN
CONTRATO DE TRABAJO SUJETO A MODALIDAD PARA SERVICIO ESPECÍFICO
Valuation of greenhouses gases is a very contentious issue because the assess- ment of the impacts is highly uncertain. Moreover, since the impacts are spread all over the whole world and into the future, the monetary evaluation is dependent on value choices, like discounting and equity weighting. Impacts due to climate change may be monetized by considering two different conceptual approaches. First, the costs of carbon might be based on abatement costs of reaching certain (arbitrary set) goal. This approach would be correct if one was sure the agreed policy target was also socially optimal. Estimate of abatement costs to reach Kyoto target by the EU15 countries were just used to value damage of carbon emissions last years in the ExternE project series. Methodologically more correct – at least following welfare economics ground – approach is, however, to estimate marginal damage costs of carbon, commonly referred to as the Social Costs of Carbon. Al- though, as noted by Anthoff (2007), the marginal damage figures are not the only measure used to quantify impacts from climate change28, their estimates have been
appearing more often in the literature.
Magnitude of social costs of carbon estimates do, however, significantly vary. Scope and structure of the assessment model present the first reason of variations; value of the estimate would then depend on number of impacts being covered, time horizon of impacts considered, or climate sensitivity assumed in given model (see Watkiss, 2007). Next, there are also two key parameters of modeling that certainly will influence magnitude of the estimates: it is discounting and equity weighting. As a meta-analysis of IAM studies by Richard Tol (2005) shows weighting impacts due to equity and giving higher weight to future outcomes, i.e. by applying lower discount rates might indeed result in more than one order larger value of the MSC.
To provide comprehensive picture on MSC, several runs by FUND model were performed within the NEEDS project. Anthoff (2007) reports a range of MSC estimated based on using several pure rates of time preference (such as 0%, 1%,
28 Some studies also presented total damage costs (e.g. Nordhaus and Boyer 2000; Tol
2002), or balanced growth equivalent (Stern 2006), or a Pareto optimal marginal damage costs, i.e. that are equal to marginal abatement costs (Nordhaus 2005).
and 3%) plus declining rates over time, without equity weighting (No_EqW)or equity weighted by world average (Aver_EqW) or EU income average (EU_EqW), including reporting a statistical inference for probabilistic MSC estimates. Values of MSC for given various assumptions of two key model parameters are displayed in Appendix 3Table 1 below (all in 2000 Euro prices).
Appendix 4.2. Table 1. MSC of CO2 estimates based on FUND model v. 3.0
'deterministic' 0% 1% 3% No_EqW 16.4 € 2.1 € ‐1.4 € Aver_EqW 41.4 € 7.7 € ‐1.4 € EU_EqW 197.3 € 36.7 € ‐6.8 € 1% trimmean 0% 1% 3% No_EqW 31.5 € 7.0 € ‐0.5 € Aver_EqW 75.8 € 20.3 € 1.7 € EU_EqW 360.9 € 96.8 € 8.1 € average 0% 1% 3% No_EqW 39.8 € 8.9 € ‐0.1 € Aver_EqW 91.5 € 24.3 € 2.4 € EU_EqW 435.6 € 115.9 € 11.6 € median 0% 1% 3% No_EqW 8.6 € 0.3 € ‐1.8 € Aver_EqW 27.2 € 5.4 € ‐1.5 € EU_EqW 129.5 € 25.9 € ‐6.9 €
Note. Based on NEEDS project cit. in Anthoff 2005; all values are in 2000 Euros.
MSC estimates if world-wide outcomes are weighted by the EU average are about one order higher than without weighting, for instance, almost 97 € for 1% PRTP and 1% trim mean. Median MSC values are smaller than 1%, 5% and 10% trimmed mean values, while mean values of MSC are the lowest ones. The highest discount rate, the smaller MSC of carbon is. Applying declining discount rate in deterministic model runs, MSC per ton of CO2 would be 3.8 €. Best guess MSC of
CO2 estimate based on deterministic runs, 1% PRTP and without equity weighting
yields a value of 2.1 € per ton CO2.
It is just a nature of damage estimation of climate change that the one (say true) value of MSC of carbon can’t exist. Any decision about the parameters will have to be just arbitrary based on normative notion followed by the decision maker. Due to the fact, modeling exercise requires having one unique number or distribu- tion of the variable, NEEDS coordination research team has widely discussed what a central value of parameters for discounting and weighting the MSC of carbon estimate shall be based on. As a result, a probabilistic estimate based on 1% PRTP, without equity weighting and taking 1% trimmed mean has been consid- ered as the central MSC of carbon value; this yields 6.96 € per ton of CO2 released
in decade 2000-2010. In our impact assessment we use 6 USD2000 as the lower
bound of damage due to climate change. Discussion in NEEDS led to suggestion that higher value of damage will better reflect actual policy targets as well as value of abatement costs estimates. Therefore, 21 € per ton of CO2 was suggested as the
central estimate of damage due to climate change; we use 20 USD2000 in our as-
due to climate change, we assume 40 USD2000 per ton of CO2 to be our upper
bound.
In total, five impact categories (health, loss of biodiversity, crops, building ma- terials, and climate change) involved by five classical pollutants (SO2, NOx, NH3,
NMVOC and two fractions of PM) plus impacts due to climate change caused by GHGs are considered in our impact assessment. Table 2 documents a relevance of each impact category for each pollutant. For instance, each of substance causes effect on human health (GHGs cause health effect indirectly), while the effects on materials might be incurred by emission of SO2 and NOx only.
Appendix4.2. Table 2. Impact categories relevant for each ExternE-relevant pollutant Human
health
Biodiver-
sity Crops Materials
Climate change Total SO2 € € €- € Σ € NOx € € € € Σ € PM2.5 € Σ € PMcoarse € Σ € NH3 € € €- Σ € NMVOC € €- € Σ € HMs, VOC € Σ € GHGs € Σ € Total Σ € Σ € Σ € Σ € Σ € Σ €