Valentina Bosetti

WITCH - A World Induced Technical Change Hybrid Model

The need for a better understanding of future energy scenarios, of their compatibility with the objective of stabilizing greenhouse gas concentrations, and of their links with climate policy, calls for the development of hybrid models. Hybrid because both the technological detail typical of Bottom Up (BU) models and the long run dynamics typical of Top Down (TD) models are crucially necessary. We present WITCH � World Induced Technical Change Hybrid model�� a neoclassical optimal growth model (TD) with energy input detail (BU). The model endogenously accounts for technological progress, both through learning curves affecting prices of new vintages of capital and through R&D investments. In addition, the model captures the main economic interrelationships between world regions and is designed to analyze the optimal economic and environment policies in each world region as the outcome of a dynamic game. This paper provides a detailed description of the WITCH model, of its baseline, and of the model calibration procedure.

The Role of R&D and Technology Diffusion in Climate Change Mitigation: New Perspectives Using the Witch Model

This paper uses the WITCH model, a computable general equilibrium model with endogenous technological change, to explore the impact of various climate policies on energy technology choices and the costs of stabilising greenhouse gas concentrations. Current and future expected carbon prices appear to have powerful effects on R&D spending and clean technology diffusion. Their impact on stabilisation costs depends on the nature of R&D: R&D targeted at incremental energy efficiency improvements has only limited effects, but R&D focused on the emergence of major new low-carbon technologies could lower costs drastically if successful – especially in the non-electricity sector, where such low-carbon options are scarce today. With emissions coming from multiple sources, keeping a wide range of options available matters for stabilisation costs more than improving specific technologies. Due to international knowledge spillovers, stabilisation costs could be further reduced through a complementary, global R&D policy. However, a strong price signal is always required.

Forestry and the Carbon Market Response to Stabilize Climate

This paper investigates the potential contribution of forestry management in meeting a CO2 stabilization policy of 550 ppmv by 2100. In order to assess the optimal response of the carbon market to forest sequestration we couple two global models. An energy-economy-climate model for the study of climate policies is linked with a detailed forestry model through an iterative procedure to provide the optimal abatement strategy. Results show that forestry is a determinant abatement option and could lead to significantly lower policy costs if included. Linking forestry management to the carbon market has the potential to delay the policy burden, and is expected to reduce the price of carbon of 40% by 2050. Biological sequestration will mostly come from avoided deforestation in tropical forests rich countries. The inclusion of this mitigation option is demonstrated to crowd out some of the traditional abatement in the energy sector and to lessen induced technological change in clean technologies.

The 2008 Witch Model: New Model Features and Baseline

WITCH is an energy-economy-climate model developed by the climate change group at FEEM. The model has been extensively used in the past 3 years for the economic analysis of climate change policies. WITCH is a hybrid top-down economic model with a representation of the energy sector of medium complexity. Two distinguishing features of the WITCH model are the representation of endogenous technological change and the game–theoretic set-up. Technological change is driven by innovation and diffusion processes, both of which feature international spillovers. World countries are grouped in 12 regions which interact with each other in a setting of strategic interdependence. This paper describes the updating of the base year data to 2005 and some new features: the inclusion of non-CO2 greenhouse gases and abatement options, the new specification of low carbon technologies and the inclusion of reducing emissions from deforestation and degradation.

The Future Prospect of PV and CSP Solar Technologies: An Expert Elicitation Survey

In this paper we present and discuss the results of an expert elicitation survey on solar technologies. Sixteen leading European experts from the academic world, the private sector and international institutions took part in this expert elicitation survey on Photovoltaic (PV) and Concentrated Solar Power (CSP) technologies. The survey collected probabilistic information on (1) how Research, Development and Demonstration (RD&D) investments will impact the future costs of solar technologies and (2) the potential for solar technology deployment both in OECD and non-OECD countries. Understanding the technological progress and the potential of solar PV and CPS technologies is crucial to draft appropriate energy policies. The results presented in this paper are thus relevant for the policy making process and can be used as better input data in integrated assessment and energy models.

The Dynamics of Carbon and Energy Intensity in a Model of Endogenous Technical Change

In recent years, a large number of papers have explored different attempts to endogenise technical change in climate models. This recent literature has emphasized that four factors Ð two inputs and two outputs Ð should play a major role when modeling technical change in climate models. The two inputs are R&D investments and Learning by Doing, the two outputs are energy-saving and fuel switching. Indeed, R&D investments and Learning by Doing are the main drivers of a climate-friendly technical change that eventually affect both energy intensity and fuel-mix. In this paper, we present and discuss an extension of the FEEM-RICE model in which these four factors are explicitly accounted for. In our new specification of endogenous technical change, an index of energy technical change depends on both Learning by Researching and Learning by Doing. This index enters the equations defining energy intensity (i.e. the amount of carbon energy required to produce one unit of output) and carbon intensity (i.e. the level of carbonization of primarily used fuels). This new specification is embodied in the RICE 99 integrated assessment climate model and then used to generate a baseline scenario and to analyze the relationship between climate policy and technical change. Sensitivity analysis is performed on different key parameters of the energy module in order to obtain crucial insights into the relative importance of the main channels through which technological changes affects the impact of human activities on climate.

Delayed Participation of Developing Countries to Climate Agreements: Should Action in the EU and US be Postponed?

This paper analyses the cost implications for climate policy in developed countries if developing countries are unwilling to adopt measures to reduce their own GHG emissions. First, we assume that a 450 CO2 (550 CO2e) ppmv stabilisation target is to be achieved and that Non Annex1 (NA1) countries decide to delay their GHG emission reductions by 30 years. What would be the cost difference between this scenario and a case in which both developed and developing countries start reducing their emissions at the same time? Then, we look at a scenario in which the timing of developing countries’ participation is uncertain and again we compute the costs of climate policy in developed and developing countries. We find that delayed participation of NA1 countries has a negative impact on climate policy costs. Economic inefficiencies can be as large as 10-25 TlnUSD. However, this additional cost wanes when developing countries are allowed to trade emission reductions from their baseline emission paths during the 30-year delay period. Thus, irrespective of whether NA1 countries are immediately assigned an emission reduction target or not, they should nonetheless be included in a global carbon market. Technology deployment is also affected by the timing of developing countries’ mitigation measures. Delayed NA1-country participation in a climate agreement would scale down the deployment of coal with CCS throughout the century. On the other hand, innovation in the form of energy R&D investments would be positively affected, since it would become crucial in developed countries. Finally, uncertainty about the timing of NA1-country participation does not modify the optimal abatement strategy for developed countries and does not alter policy costs as long as a global carbon market is in place.

The WITCH Model: Structure, Baseline, Solutions

WITCH – World Induced Technical Change Hybrid – is a regionally disaggregated hard-link hybrid global model with a neoclassical optimal growth structure (top-down) and a detailed energy input component (bottom-up). The model endogenously accounts for technological change, both through learning curves that affect the prices of new vintages of capital and through R&D investments. The model features the main economic and environmental policies in each world region as the outcome of a dynamic game. WITCH belongs to the class of Integrated Assessment Models as it possesses a climate module that feeds climate changes back into the economy. Although the model’s main features are discussed elsewhere (Bosetti et al., 2006), here we provide a more thorough discussion of the model’s structure and baseline projections, to describe the model in greater detail. We report detailed information on the evolution of energy demand, technology and CO2 emissions. We also explain the procedure used to calibrate the model parameters. This report is therefore meant to provide effective support to those who intending to use the WITCH model or interpret its results.

The Incentives to Participate in, and the Stability of, International Climate Coalitions: A Game-Theoretic Analysis Using the Witch Model

This paper uses WITCH, an integrated assessment model with a game-theoretic structure, to explore the prospects for, and the stability of broad coalitions to achieve ambitious climate change mitigation action. Only coalitions including all large emitting regions are found to be technically able to meet a concentration stabilisation target below 550 ppm CO2eq by 2100. Once the free-riding incentives of non-participants are taken into account, only a “grand coalition” including virtually all regions can be successful. This grand coalition is profitable as a whole, implying that all countries can gain from participation provided appropriate transfers are made across them. However, neither the grand coalition nor smaller but still environmentally significant coalitions appear to be stable. This is because the collective welfare surplus from cooperation is not found to be large enough for transfers to offset the free-riding incentives of all countries simultaneously. Some factors omitted from the analysis, which might improve coalition stability, include the co-benefits from mitigation action, the costless removal of fossil fuel subsidies, as well as alternative assumptions regarding countries’ bargaining behaviour.

Modelling Economic Impacts of Alternative International Climate Policy Architectures: A Quantitative and Comparative Assessment of Architectures for Agreement

This paper provides a quantitative comparison of the main architectures for an agreement on climate policy. Possible successors to the Kyoto protocol are assessed according to four criteria: economic efficiency; environmental effectiveness; distributional implications; and their political acceptability which is measured in terms of feasibility and enforceability. The ultimate aim is to derive useful information for designing a future agreement on climate change control.