Ambiguity reduction by objective model selection, with an application to the costs of the EU 2030 climate targets

I estimate the cost of meeting the EU 2030 targets for greenhouse gas emission reduction, using statistical emulators of ten alternative models. Assuming a first-best policy implementation, I find that total and marginal costs are modest. The statistical emulators allow me to compute the risk premiums, which are small, because the EU is rich and the policy impact is small. The ensemble of ten models allows me to compute the ambiguity premium, which is small for the same reason. I construct a counterfactual estimate of recent emissions without the climate policy and use that to test the predictive skill of the ten models. The models that show the lowest cost of emission reduction also have the lowest skill for Europe in recent times

THE POLLUTER PAYS PRINCIPLE AND COST-BENEFIT ANALYSIS OF CLIMATE CHANGE: AN APPLICATION OF FUND

I compare and contrast five climate scenarios: (1) no climate policy; (2) non-cooperative cost-benefit analysis (NC CBA); (3) NC CBA with international permit trade; (4) NC CBA with joint and several liability for climate change damages; and (5) NC CBA with liability proportional to a country’s share in cumulative emissions. As estimates of the marginal damage costs are low, standard NC CBA implies only limited emission abatement. With international permit trade, emission abatement is even less, as the carbon tax is reduced in countries with fast-growing emissions, and because a permit market ignores the positive, dynamic externalities of abatement. Proportional liability shifts abatement effort towards the richer countries, but away from the fast-growing economies; again, long-term, global emission abatement is reduced. Joint and several liability would lead to more stringent climate policy. These findings are qualitatively robust to the size and accounting of climate change impacts, to the definition of liability, and to the baseline scenario.Climate change, cost-benefit analysis, liability, permit trade

Why Worry About Climate Change? A Research Agenda

Estimates of the marginal damage costs of carbon dioxide emissions suggest that, although climate change is a problem and some emission reduction is justified, very stringent abatement does not pass the cost-benefit test. However, current estimates of the economic impact of climate change are incomplete. Some of the missing impacts are likely to be positive and others negative, but overall the uncertainty seems to concentrate on the downside risks and current estimates of the damage costs may have a negative bias. The research effort on the economic impacts of climate change is minute, and should be strengthened, with a particular focus on the quantification of uncertainties; estimating missing impacts, interactions between impacts and higher-order effects; the valuation of biodiversity loss; the implications of extreme climate scenarios and violent conflict; and climate change in the very long term.Climate Change, Impacts, Valuation, Cost-benefit Analysis

A RATIONAL, SUCCESSIVE G-INDEX APPLIED TO ECONOMICS DEPARTMENTS IN IRELAND

A rational, successive g-index is proposed, and applied to economics departments in Ireland. The successive g-index has greater discriminatory power than the successive h-index, and the rational index performs better still. The rational, successive g-index is also more robust to difference in department size.rankings, individuals, departments

International inequity aversion and the social cost of carbon

I define the rate of inequity aversion, distinguishing between the pure rate and the consumption rate. I measure the rate of aversion to inequality in consumption as expressed in the development aid given by rich countries to poor ones between 1965 and 2005. There is an ambiguous relationship between the pure rate of inequity aversion and the consumption rate, driven by the rate of risk aversion. However, for a reasonable choice of the rate of risk aversion, rich countries are shown to be inequity averse, and increasingly so over time. The social cost of carbon is very sensitive to equity weighting and assumptions about the rate of risk and inequity aversion. Estimates for the consumption rate of inequity aversion for recent data suggest that the equity-weighted social cost of carbon is less than 50% larger than the unweighted estimate.Inequity aversion, risk aversion, income distribution, development aid, climate change, social cost of carbon

EMISSION ABATEMENT VERSUS DEVELOPMENT AS STRATEGIES TO REDUCE VULNERABILITY TO CLIMATE CHANGE: AN APPLICATION OF FUND

Poorer countries are generally believed to be more vulnerable to climate change than richer countries because poorer countries are more exposed and have less adaptive capacity. This suggests that, in principle, there are two ways of reducing vulnerability to climate change: economic growth and greenhouse gas emission reduction. Using a complex climate change impact model, in which development is an important determinant of vulnerability, the hypothesis is tested whether development aid is more effective in reducing impacts than is emission abatement. The hypothesis is barely rejected for Asia but strongly accepted for Latin America and, particularly, Africa. The explanation for the difference is that development (aid) reduces vulnerabilities in some sectors (infectious diseases, water resources, agriculture) but increases vulnerabilities in others (cardiovascular diseases, energy consumption). However, climate change impacts are much higher in Latin America and Africa than in Asia, so that money spent on emission reduction for the sake of avoiding impacts in developing countries is better spent on vulnerability reduction in those countries.climate change, climate change impacts, vulnerability, adaptive capacity, development

INTEGRATED ASSESSMENT MODELLING

integrated assessment

EXCHANGE RATES AND CLIMATE CHANGE: AN APPLICATION OF FUND

As economic and emissions scenarios assume convergence of per capita incomes, they are sensitivity to the exchange rate used for international comparison. Particularly, developing countries grow slower with a purchasing power exchange rate than with a market exchange rate. Different exchange rates may lead to scenarios with very different per capita income. However, these scenarios also assume convergence of energy intensities, which at least partly offsets the income effect, so that scenarios with different exchange rates would differ less in greenhouse gas emissions. Differences become smaller still if atmospheric concentrations and global warming is considered. However, differences become larger again if one considers the costs of meeting a certain stabilisation target, as the gap between baseline and target is more sensitive to the exchange rate used than the baseline itself. Differences also grow larger if one looks at climate change impacts, which are determined not just by climate change but also by development. The sensitivity to the exchange rate is purely due to imperfect data, imperfect statistical analysis of data, a crude spatial resolution, and imperfect models.Climate change, emissions scenarios, purchasing power parity, market exchange rate

ADAPTATION AND MITIGATION: TRADE-OFFS IN SUBSTANCE AND METHODS

climate change, adaptation, mitigation

Is the Uncertainty about Climate Change Too Large for Expected Cost-Benefit Analysis?

Cost-benefit analysis is only applicable if the variances of both costs and benefits are finite. In the case of climate change, the variances of the net present marginal costs and benefits of greenhouse gas emission reduction need to be finite. Finiteness is hard, if not impossible to prove. The opposite is easier to establish as one needs to shows that there is one, not impossible representation of the climate change with infinite variance. The paper shows that all relevant current variables of the FUND model have finite variances. However, there is a small chance that climate change reverses economic growth in some regions. In that case, the discount rate becomes negative and the net present marginal benefits of greenhouse gas emission reduction becomes very large. So large, that its variance is unbounded.Climate change, cost-benefit analysis, uncertainty