Necessities and problems of coupling climate and socioeconomic models for integrated assessments studies from an economist's point of view

This presentation has two parts. The first part is more theoretical. We will examine the definition of Integrated Assessment Models of Climate Change and identify their main aims. We will also have look at the differences between climate and socioeconomic models. The second part will be applied. We present the Dynamics of Inertia and Adaptability Model (DIAM). That model will be used to study some of the fundamentals economic parameters of IAMs: the discount rate, the technical progress rate, the flexibility of energy systems, uncertainty and the final concentration target. We won\'t try to be exhaustive, see Weyant1 leading author of the corresponding IPCC chapter for that. Our goal is simply to convince the reader that these non realistic models can profitably be used to analyse real issues.climate change, integrated assessment

Scenarios, probability and possible futures

This paper provides an introduction to the mathematical theory of possibility, and examines how this tool can contribute to the analysis of far distant futures. The degree of mathematical possibility of a future is a number between O and 1. It quantifies the extend to which a future event is implausible or surprising, without implying that it has to happen somehow. Intuitively, a degree of possibility can be seen as the upper bound of a range of admissible probability levels which goes all the way down to zero. Thus, the proposition `The possibility of X is Pi(X) can be read as `The probability of X is not greater than Pi(X).Possibility levels offers a measure to quantify the degree of unlikelihood of far distant futures. It offers an alternative between forecasts and scenarios, which are both problematic. Long range planning using forecasts with precise probabilities is problematic because it tends to suggests a false degree of precision. Using scenarios without any quantified uncertainty levels is problematic because it may lead to unjustified attention to the extreme scenarios.This paper further deals with the question of extreme cases. It examines how experts should build a set of two to four well contrasted and precisely described futures that summarizes in a simple way their knowledge. Like scenario makers, these experts face multiple objectives: they have to anchor their analysis in credible expertise; depict though-provoking possible futures; but not so provocative as to be dismissed out-of-hand. The first objective can be achieved by describing a future of possibility level 1. The second and third objective, however, balance each other. We find that a satisfying balance can be achieved by selecting extreme cases that do not rule out equiprobability. For example, if there are three cases, the possibility level of extremes should be about 1/3.Futures, futurible, scenarios, possibility, imprecise probabilities, uncertainty, fuzzy logic

Transparency and control in engineering integrated assessment models.

Better software engineering such as archiving releases with version control, writing portable code, publishing documentation and results closely tied to the code improves integrated assessment models' transparency and control. A case study of four climate change policy analysis models found that source code and data was generally available, but for largermodels licenses were more restrictive with respect to modification and redistribution. It is suggested that Free software licenses such as the GNU GPL would improve transparency and control. Moreover, opening the source allows opening the development process, a potentially important tool to improve collaboration, data sharing and models integration.

Quasi-option value and climate policy choices

In the climate change issue, the environmental irreversibility (risk of an acceleration of mitigation policies if the worse happen) has to be balanced with the investment irreversibility (risk of over-cautious policies). To explore this balance, we define an option value for a precautionary climate policy. Using the simplest decision-making model, we expose how option value relates to the expected value of future information. Using quantitative data from an integrated as sessment model, we find that most of the times the environmental irreversibility dominates the investment irreversibility. For all cases explored here, the order of magnitude of the option value was significant, about 50% of the opportunity cost.Option value, Climate change, Irreversibility

ECONOMIC Potential of Renewable Energy in Vietnam's Power Sector

A bottom-up Integrated Resource Planning model is used to examine the economic potential of renewable energy in Vietnam’s power sector. In a baseline scenario without renewables, coal provides 44% of electricity generated from 2010 to 2030. The use of renewables could reduce that figure to 39%, as well as decrease the sector’s cumulative emission of CO2 by 8%, SO2 by 3%, and NOx by 4%. In addition,renewables could avoid installing 4.4GW in fossil fuel generating capacity, conserve domestic coal,decrease coal and gases imports, improving energy independence and security. Wind could become cost-competitive assuming high but plausible on fossil fuel prices, if the cost of the technology falls to 900 US$/kW

The real option with an absorbing barrier.

Ce papier analyse l'option réelle avec barrière inférieure. C'est le modèle d'un investissement irréversible soumis au risque de perdre l'option d'investir si on attend trop. La valeur critique pour investir décroit lorsque la barrière se rapproche, ou lorsque la volatilité augmente. L'incertitude a un effet ambigu sur le temps espéré de décision et sur la probabilité de résolution après N années. Les résultats numériques et analytiques s'appliquent aussi à une option financière aéricaine avec une "down-and-out barrier" sur un support payant des dividendes.option réelle, incertitude, irréversibilité

Risk aversion, intergenerational equity and climate change.

The paper investigates a climate-economy model with an iso-elastic welfare function in which one parameter gamma measures relative risk-aversion and a distinct parameter rho measures resistance to intertemporal substitution. We show both theoretically and numerically that climate policy responds differently to variations in the two parameters. In particular, we show that higher gamma but lower rho leads to increase emissions control. We also argue that climate-economy models based on intertemporal expected utility maximization, i.e. models where gamma = rho, may misinterpret the sensitivity of the climate policy to risk-aversion.risk aversion; equity; discounting; climate change

Recursive Intergenerational Utility in Global Climate Risk Modeling

This paper distinguishes relative risk aversion and resistance to intertemporal substitution in climate risk modeling. Stochastic recursive preferences are introduced in a stylized numeric climate-economy model using preliminary IPCC 1998 scenarios. It shows that higher risk aversion increases the optimal carbon tax. Higher resistance to intertemporal substitution alone has the same effect as increasing the discount rate, provided that the risk is not too large. We discuss implications of these findings for the debate upon discounting and sustainability under uncertainty. Ce texte étudie la différence entre l'aversion relative au risque et la résistance à la substitution intertemporelle dans la modélisation du risque climatique. Les préférences récursives stochastiques sont utilisées dans un modèle numérique stylisé utilisant les scénarios préliminaires GIEC 1998 sur l'économie et le climat. On montre qu'une aversion au risque plus forte conduit à augmenter le niveau optimal de taxation de l'énergie. Augmenter la résistance à la substitution intertemporelle a le même effet qu'augmenter le taux d'actualisation, tant que le risque n'est pas trop grand. Nous discutons les implications de ces résultats pour le débat sur l'actualisation et la durabilité sous incertitude.Recursive utility, risk, discounting, sustainability, climate, Utilité récursive, risque, actualisation, durabilité, climat