the impact of possible climate catastrophes on global warming policy abstract recent studies on global warming have introduced the inherent uncertainties associated with the costs and benefits of climate policies and have often shown that abatement policies are likely to be less aggressive or postponed in comparison to those resulting from traditional cost benefit analyses cba yet those studies have failed to include the possibility of sudden climate catastrophes the aim of this paper is to account simultaneously for possible continuous and discrete damages resulting from global warming and to analyse their implications on the optimal path of abatement policies our approach is related to the new literature on investment under uncertainty and relies on some recent developments of the real option in which we incorporated negative jumps climate catastrophes in the stochastic process corresponding to the net benefits associated with the abatement policies the impacts of continuous and discrete climatic risks can therefore be considered separately our numerical applications lead to two main conclusions i gradual continuous uncertainty in the global warming process is likely to delay the adoption of abatement policies as found in previous studies with respect to the standard cba however ii the possibility of climate catastrophes accelerates the implementation of these policies as their net discounted benefits increase significantly

the greenhouse effect damages costs and abatement the buildup of so called greenhouse gases in the atmosphere co2 in particular appears to be having an adverse impact on the global climate this paper briefly reviews current expectations with regard to physical and biological effects their potential costs to society and likely costs of abatement for a worst case scenario it is impossible to assess in economic terms the full range of possible non linear synergistic effects in the most favorable although not necessarily likely case of slow paced climate change however it seems likely that the impacts are within the affordable range at least in the industrialized countries of the world in the third world the notion of affordability is of doubtful relevance making the problem of quantitative evaluation almost impossible we tentatively assess the lower limit of quantifiable climate induced damages at 30 to 35 per ton of co2 equivalent worldwide with the major damages being concentrated in regions most adversely affected by sea level rise the non quantifiable environmental damages are also significant and should by no means be disregarded the costs and benefits of 1 reducing cfc use and 2 reducing fossil fuel consumption as a means of abatement are considered in some detail this strategy has remarkably high indirect benefits in terms of reduced air pollution damage and even direct cost savings to consumers the indirect benefits of reduced air pollution and its associated health and environmental effects from fossil fuel combustion in the industrialized countries range from 20 to 60 per ton of co2 eliminated in addition there is good evidence that modest e g 25 reductions in co2 emissions may be achievable by the u s and by implication for other countries by a combination of increased energy efficiency and restructuring that would permit simultaneous direct economic benefits savings to energy consumers of the order of 50 per ton of co2 saved a higher level of overall emissions reduction possibly approaching 50 could probably be achieved at little or not net cost by taking advantage of these savings we suggest the use of taxes on fossil fuel extraction or a carbon tax as a reasonable way of inducing the structural changes that would be required to achieve significant reduction in energy use and co2 emissions to minimize the economic burden and create a political constituency in support of the approach we suggest the substitution of resource based taxes in general for other types of taxes on labor income real estate or trade that are now the main sources of government revenue while it is conceded that it would be difficult to calculate the optimal tax on extractive resources we do not think this is a necessary prerequisite to policy making in fact we note that the existing tax system has never been optimized according to theoretical principles and is far from optimal by any reasonable criteria

discount rates equity weights and the social cost of carbon abstract equity weighting has been proposed as a way of allowing welfare equivalents to be included in the social cost of carbon since a dollar to a poor person is worth more than a dollar to a rich one here we use the page2002 integrated assessment model to show that the social cost of carbon is higher without equity weights an elasticity of marginal utility with respect to income of 0 than with them this might seem counter intuitive but it comes about because of the logical link between equity weights and discount rates as the elasticity goes from 0 to 0 5 to 1 0 the social rate of time preference rises and the drop in present values that results far outweighs the small increase in impacts that equity weights bring

reevaluation and renegotiation of climate change coalitions a sequential closed loop game approach abstract major international environmental problems can be characterized as stock externality phenomena long term international environmental coalitions are subject to unexpected shocks certain shocks might have strong impacts on regional environmental policies and their commitments to the coalition the open loop solutions in optimal control problems and differential games cannot capture regions reactions to those shocks in this paper we develop a feasible modeling approach that uses the closed loop strategies to study the issues of reevaluation and renegotiation of climate change coalitions for the purpose we design an algorithm that decomposes a closed loop strategy into a sequence of open loop equilibria and implement the algorithm in the rice model am econ rev 86 1996 741 an integrated assessment model of climate change and economies we analyze policy and methodological implications of the closed loop strategies through simulations of the rice model

the male marital earnings premium in the context of bride wealth payments evidence from south africa abstract this study explores the nature of the male marital earnings premium in the context of a developing country in which the payment of bride wealth is practiced we use data from the south african labor force survey of september 2004 and the labor force survey panel 2001 4 the first national panel available in south africa we show that a robust and positive premium to marriage in cross sectional estimations is substantially reduced after controlling for individual fixed effects furthermore we find evidence of an additional source of endogeneity created by the positive selection of men into marriage with faster earnings growth in the initial periods of the panel our results are to be expected if the payment of bride wealth or ilobolo by a prospective husband to the bride s family is a significant constraint to marriage among black men in south africa

tax distortions and global climate policy abstract we consider the efficiency implications of policies to reduce global carbon emissions in a world with pre existing tax distortions we first note that the weak double dividend the proposition that the welfare improvement from a tax reform where environmental taxes are used to lower distorting taxes must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion need not hold in a world with multiple distortions we then present a large scale computable general equilibrium model of the world economy with distortionary taxation we use this model to evaluate a number of policies to reduce carbon emissions we find that the weak double dividend is not obtained in a number of european countries results also demonstrate the point that the interplay between carbon policies and pre existing taxes can differ markedly across countries thus one must be cautious in extrapolating the results from a country specific analysis to other countries

valuing the impact of co2 emissions valuing the impacts of co2 emissions to the atmosphere has been widely debated with various studies suggesting very different costs when expressed in units of dollar per tonne of carbon emitted there are many complex issues involved and it is often difficult to determine the reasons for the wide range of costs proposed in this paper models based on two very different approaches the page and intera models are considered by applying these models to calculating the marginal impact of co2 emissions it is shown that what appear initially to be divergent estimates can be reconciled this process illustrates some of the key issues in this area and a perspective is provided on which marginal costs are appropriate for different policy decisions

how fast should we graze the global commons unlike the vast preponderance of planets earth has been bequeathed a hospitable environment in which to thrive up to now man s activities have affected this environment negligibly scientists are becoming convinced however that release of carbon dioxide co2 from combustion of fossil fuels will lead to a significant modification of the global climate see woodwell how should we think about such a destruction of our heritage should it be treated as anathema like bondage or should the pace and extent of use of our global commons be subject to the same reasoned balancing of costs and benefits as other economic activities the present paper takes the second approach asking how fast the global economy should allow a buildup of atmospheric co2 the first section reviews the current scientific knowledge on this subject while the second puts this into an optimal growth framework the third section then presents a numerical example while the last presents some realistic policy views on the subject this abstract was borrowed from another version of this item

a cost benefit analysis of slowing climate change there are many conflicting views regarding the true dimensions of the climate change problem often these viewpoints are based on different estimates of key parameters with little indication as to why parameter estimates vary so much and which ones might be the more reliable the prospects for a co ordinated strategy to tackle climate change appear dim little consensus has emerged for example regarding the costs of abating carbon emissions some take the view that considerable improvements in energy efficiency are available at negative cost by setting minimum efficiency standards for vehicles and domestic appliances e g mills et al 1991 others regard the macroeconomic costs of even small reductions in carbon emissions as substantial manne and richels 1993 in the judgement of other researchers a proportion of carbon emissions arise purely as a result of institutional failings either at a regional level in the subsidies paid to fossil fuel energy producers in the erroneous belief that this promotes economic growth shah and larsen 1994 in failure to deal with air pollution glomsrod et al 1992 and vehicle congestion in urban areas hughes 1994 or at a global level in failing to make appropriate transfers to those countries whose forests contain rich biodiversity which we would wish to preserve pearce 1991

rates of time preference for saving lives an important characteristic of many environmental programs is that their benefits extend far into the future the primary purpose of cleanups at hazardous waste disposal sites for example is often to prevent the contamination of groundwater that could pose risks to future residents at these sites such cleanups typically involve considerable capital and other costs which are incurred at the front end of the project and yield a stream of health benefits often in the form of cancer cases avoided that may not be recognized for many years this would not pose unusual problems for program evaluation if everyone were comfortable with the assignment of dollar values to these reductions in future risk see cropper and portney 1990 however regulatory agencies are sometimes reluctant to make such monetary valuations preferring instead to evaluate programs on a cost per life saved cpls basis office of management and budget 1991 this raises an interesting question should lives saved in the future be discounted for the purpose of calculating cpls or should they be counted the same as those saved tomorrow to shed light on this over the last year we have asked members of the public hypothetical questions that enable us to infer the rate at which they implicitly discount future lives saved john k horowitz and richard t carson 1990 asked similar questions of students in the remainder of this paper we summarize the results of this research details of which can be found elsewhere cropper et al 1991 1992

discounting and distributional considerations in the context of global warming the economics of global warming is reviewed with special emphasis on how the cost depends on the discount rate and on how costs in poor and rich regions are aggregated into a global cost estimate both of these factors depend on the assumptions made concerning the underlying utility and welfare functions it is common to aggregate welfare gains and losses across generations and countries as if the utility of money were constant but it is not if we assume that a e co2 equivalent dlubling implies costs equal to 1 5 of the income in both high and low income countries a pure rate of time preference equal to zero and a utility function which is logarithmic in income then the marginal cost of co2 emissions is estimated at 260 590 usd ton c for a time horizon in the range 300 1000 years an estimate which is large enough to justify significant reductions of co2 emissions on purely economic grounds the estimate is approximately 50 100 times larger than the estimate made by nordhaus in his dice model and the difference is almost completely due to the choice of discount rate and the weight given to the costs in the developing world as well as a more accurate model of the carbon cycle finally the sensitivity of the marginal cost estimate with respect to several parameters is analyzed

a mixed bentham rawls criterion for intergenerational equity theory and implications abstract this paper proposes a welfare criterion that balances the need for development and the concern for the least advantaged generations and explores its implications this criterion called the mixed bentham rawls criterion moderates the effect of discounting yet permits some degree of intertemporal trade off it is a weighted average of two terms a the sum of discounted utilities and b the utility level of the least advantaged generation we derive necessary conditions to characterize growth paths that satisfy our criterion and show that in some models with familiar dynamic specifications an optimal path exists and displays appealing characteristics

empirical and public choice evidence for hyperbolic social discount rates and the implications for intergenerational discounting the derivation of the correct discount rate for intergenerational projects in cost benefit analysis is particularly contentious public choice has resulted in lower discretionary exponential discount rates for many intergenerational projects in britain and the usa this is shown to be strong indirect evidence that the true social discount rate may be a hyperbolic rather than an exponential function there is also empirical evidence for this hypothesis the hyperbolic nature of discounting is also a standard finding in the behavioural sciences for intergenerational time frames hyperbolic discount rates should be employed together with exponential discount rates in cost benefit sensitivity analyses

learning and stock effects in environmental regulation the case of greenhouse gas emissions abstract this paper concerns the optimal regulation of greenhouse gases that lead to global climate change in particular we focus on uncertainty and learning which over time resolves uncertainty we present an empirical stochastic model of climate economy interactions and present results on the tension between postponing control until more is known vs acting now before irreversible climate change takes place uncertainty in our model is in the damage caused by global warming the results suggest that a temporary carbon tax may dominate a permanent one because a temporary tax may induce increased flexibility

emissions pricing spillovers and public investment in environmentally friendly technologies in a second best world of below optimal pollution pricing the public return to r d may be greater than under pigouvian pricing due to excess benefits of increasing abatement or it may be lower since private actors lack the incentives to take full advantage of the new cleaner technologies this paper uses a simple model to demonstrate the interaction between environmental policies r d externalities and the social return to innovation the results indicate that strong public support for innovation in abatement technologies is only justified if at least a moderate emissions policy is in place and spillover effects are significant if emissions policy can adjust to cost changes the public role may be enhanced since private actors will prefer to avoid ratcheting social gains from innovation increase only if innovation can allow emissions to be more fully priced technology policy is more effective with fuller emissions pricing and is better viewed as a complement to than a substitute for mitigation policy

estimation of the greenhouse gas externality with uncertainty the shadow price of carbon dioxide is the value of the external damage caused by an emission a shadow price model for calculating the present value of the external damage of a carbon dioxide emission is derived explicitly sixteen experts provided subjective high low and most likely parameter estimates because correct values for the eight model parameters are uncertain the estimation procedure retains parameter uncertainty while generating the main result which is a distribution of shadow price estimates major assumptions made in the estimation identify the basis for the results of the eight model parameters the discount rate dominates the determination of the shadow price for comparison expert estimates of the shadow price itself provide a second distribution of shadow price estimates

marginal abatement costs of greenhouse gas emissions a meta analysis in this paper we carry out a meta analysis of recent studies into the costs of greenhouse gas mitigation policies that aim at the long term stabilisation of these gases in the atmosphere we find the cost estimates of the studies to be sensitive to the stringency of the stabilisation target the assumed emissions baseline the way in which the time profile of emissions is determined in the model the choice of control variable co2 only versus multigas the number of regions and energy sources in the model and to a lesser degree the scientific forum in which the study was developed we find that marginal abatement costs of the stringent long term targets that are currently considered by the european commission are still very uncertain but might exceed the costs that have been suggested by recent policy assessments

accounting for global warming risks resource management under event uncertainty abstract optimal management of atmospheric pollution is discussed with a special emphasis on the uncertainty concerning the occurrence of undesirable events associated with the greenhouse effect the uncertainty considered here stems from our ignorance of the exact pollution level required to trigger the event rather than from the genuinely stochastic nature of the processes involved taking atmospheric pollution level as the state variable it is found that uncertainty implies the existence of an equilibrium interval within which the emission rate of the greenhouse gases should be kept equal to the natural removal rate of these gases processes initiated outside the equilibrium interval must converge monotonically to its nearest endpoint the determination of the interval requires no knowledge of the optimal policy in contrast ignoring event occurrence risk implies a single equilibrium level attracting the optimal process from any initial level

a review of the stern review on the economics of climate change the stern review calls for immediate decisive action to stabilize greenhouse gases because the benefits of strong early action on climate change outweighs the costs the economic analysis supporting this conclusion consists mostly of two basic strands the first strand is a formal aggregative model that relies for its conclusions primari ly upon imposing a very low discount rate concerning this discount rate aspect i am skeptical of the review s formal analysis but this essay points out that we are actual ly a lot less sure about what interest rate should be used for discounting climate change than is commonly acknowledged the review s second basic strand is a more intuitive argument that it might be very important to avoid possibly large uncertain ties that are difficult to quantify concerning this uncertainty aspect i argue that it might be recast into sound analytical reasoning that might justify some of the review s conclusions the basic issue here is that spending money to slow global warming should perhaps not be conceptualized primarily as being about consump tion smoothing as much as being about how much insurance to buy to offset the small change of a ruinous catastrophe that is difficult to compensate by ordinary savings

on international equity weights and national decision making on climate change abstract estimates of the marginal damage costs of carbon dioxide emissions require the aggregation of monetised impacts of climate change over people with different incomes and in different jurisdictions implicitly or explicitly such estimates assume a social welfare function and hence a particular attitude towards equity and justice we show that previous approaches to equity weighting are inappropriate from a national decision maker s point of view because domestic impacts are not valued at domestic values we propose four alternatives sovereignty altruism good neighbour and compensation with different views on concern for and liability towards foreigners the four alternatives imply radically different estimates of the social cost of carbon and hence the optimal intensity of climate policy

malthus and climate change betting on a stable population abstract a standard assumption in integrated assessment models of climate change is that population and productivity are growing but at a decreasing rate we explore the significance of the assumption of population and productivity growth for greenhouse gas abatement after all there has been no long run slowdown in the growth of productivity over the past few centuries and the rate of population growth has actually been increasing for the past 19 centuries even if either of these growth rates were expected to slow by how much is subject to great uncertainty we show computationally that such continued growth greatly increases the severity of climate change indeed we find that climate change is a problem in large part caused by exogenous population and productivity growth rapid reductions in growth make climate change a small problem smaller reductions in growth imply climate change is a very serious problem indeed analogously reductions in the growth rate of population can be effective in controlling climate change

targets for global climate policy an overview a survey of the economic impact of climate change and the marginal damage costs shows that carbon dioxide emissions are a negative externality the estimated pigou tax and its growth rate are too low to justify the climate policy targets set by political leaders a lower discount rate or greater concern for the global distribution of income would justify more stringent climate policy but would imply an overhaul of other public policies catastrophic risk justifies more stringent climate policy but only to a limited extent

costs of reducing global carbon emissions po rojecting the costs of reducing carbon emissions is extremely important and exceedingly difficult such projections are an integral component of cost benefit analyses of alternative policies for example for the global climate policy analysis described by william nordhaus in this symposium moreover the nature of the climate change problem dictates that costs be incurred long before benefits can be realized or accurately measured consequently the political spotlight predictably focuses on the cost estimates whenever specific policy options are contemplated projecting the costs of reducing carbon emissions is difficult because many assumptions must be made about how the world will evolve over a very long period of time with and without a control program typically some of these assumptions like population growth are taken from outside sources other factors like the response of energy demand to changes in economic output or energy prices are the result of modeling the behavior of economic actors in response to exogenous stimuli considerable uncertainty exists about both the exogenous factors and the best way to model the behavioral responses the global nature of the climate change problem adds yet another complication to the cost analysis scientists have concluded that it is the global concentration of carbon in the atmosphere that influences climate moreover since carbon in the atmosphere gets mixed more or less uniformly emissions anywhere change concentrations everywhere but with a long lead time current global carbon emissions are estimated to be only about 4 percent of the stock of co2 in the atmosphere attributable to human activity and about

the co2 abatement game costs incentives and the enforceability of a sub global coalition abstract this paper studies the economic incentives and the institutional issues governing the outcomes of a short term climate change policy package guided by the united nations framework convention on climate change and the berlin mandate initiatives game theoretic tools and the global trade environment interface are explored within a 26 region 13 commodity computable general equilibrium framework to characterize the incentives of oecd regions to comply with a non binding agreement in a carbon abatement coalition the results showed that in the absence of side payments the achievement of such a coalition might require the design of suitable trade instruments

bayesian learning growth and pollution abstract environmental problems such as climate change have great uncertainties current expectations are that uncertainties about climate change will be resolved quickly we examine this hypothesis theoretically and computationally we consider bayesian learning about the relationship between greenhouse gas levels and global mean temperature changes a key uncertainty learning is non trivial because of a stochastic shock to the realized temperature we find theoretically the expected learning time which is related to the variance of the shock and the emissions policy implying a tradeoff between the benefits of controlling emissions and information we imbed the learning model into an optimal growth model with a climate sector and solve the resulting dynamic program we find computationally that learning takes on average over 90 yr far longer than currently believed

politics and social costs estimating the impact of collective action on hazardous waste facilities firms that generate negative externalities may consider the effects of their location on the surrounding environment because of the right of their prospective neighbors to demand compensation for pollution and raise the transaction costs of location since communities vary both in the value individuals place on the environment and in the ability of residents to organize politically locations that generate the least political opposition may not be the locations that result in the lowest externalities this article tests whether the degree to which firms internalize their externalities depends on the ability of affected communities to engage in collective action the results indicate that firms processing hazardous waste when deciding where to expand capacity do take into account variations in the potential for collective action to raise their costs

a regional dynamic general equilibrium model of alternative climate change strategies outcomes and noncooperative equilibria this study finds that cooperative policies show much higher levels of emissions reductions than do noncooperative strategies that there are substantial differences in the levels of controls in both the cooperative and the noncooperative policies among different countries and that high income countries may be the major losers from cooperation jel h41 q4 q2 q20

the damage costs of climate change toward more comprehensive calculations it is argued that estimating the damage costs of a certain benchmark climate change is not sufficient what is needed are cost functions and confidence intervals although these are contained in the integrated models and their technical manuals this paper brings them into the open in order to stimulate discussion after briefly reviewing the benchmark climate change damage costs region specific cost functions are presented which distinguish tangible from intangible losses and the losses due to a changing climate from those due to a changed climate furthermore cost functions are assumed to be quadratic as an approximation of the unknown but presumably convex functions results from the damage module of the integrated climate economy model fund are presented next uncertainties are incorporated and expected damages are calculated it is shown that because of convex loss functions and right skewed uncertain ties the risk premium is substantial calling for more action than analysis based on best guess estimates the final section explores some needs for further scientific research

on modeling and interpreting the economics of catastrophic climate change with climate change as prototype example this paper analyzes the implications of structural uncertainty for the economics of low probability high impact catastrophes even when updated by bayesian learning uncertain structural parameters induce a critical tail fattening of posterior predictive distributions such fattened tails have strong im plications for situations like climate change where a catastrophe is theoretically possible because prior knowledge cannot place sufficiently narrow bounds on overall damages this paper shows that the economic consequences of fat tailed structural uncertainty along with unsureness about high temperature damages can readily outweigh the effects of discounting in climate change policy analysis