As a consequence of the flexibility mechanisms incorporated in the Kyoto Protocol, incentive-based policies such as emissions trading and the clean development mechanism are being widely discussed in the context of greenhouse gas (GHG) abatement. This paper examines various issues related to incentive-based approaches for India. Some of the specific questions it addresses are: does India stand to gain or lose if emissions trading is realized even if it remains outside such an arrangement? Are there any other incentive-based approaches, e.g., carbon taxes that India could adopt? In the ultimate analysis, however, market-based instruments (MBIs) for GHG abatement in India cannot be viewed in isolation from an overall incentive-based orientation towards environmental policy as well as broader economic and legal reform that creates a suitable milieu for MBIs. Therefore, the paper goes on to examine problems of implementing MBIs in general, particularly those related to monitoring of emissions and of enforcement. Several specific solutions are also proposed. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 24-26).

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first show that the weak double dividend, the proposition that the welfare improvement from a tax reform where environme ntal 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. A small analytic general equilib rium model is constructed to demonstrate this result. 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. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 17-18).

The role of black carbon (BC) aerosols in climate change is important because of its strong capability in causing extinction of solar radiation. A three-dimensional interactive aerosol-climate model has been used to study the climatic impact of BC. The interannual variations of BC solar forcing derived from 20-year transient integrations are up to 4 times as large as the means mainly related to changes in cloud cover, snow depth (about +/- 20% over many high- or even mid-latitude regions in Northern Hemisphere) and thus the surface albedo, all caused by BC solar forcing itself. With an absolute amount three times higher than that of the top of the atmosphere (TOA) forcing, the surface forcing of BC is an extremely important factor in analyzing the climate impact of BC. BC aerosols cause a “cloud burning” effect in several polluted regions and a “cloud enhancing” effect in some high-latitude sites. Combined with BC-caused changes in surface albedo, this is defined as a non-Twomey-Albrecht indirect forcing by BC, which alters the radiative budgets by changing cloud cover and some land-surface properties thermodynamically rather than microphysically. The result of this study does not indicate that BC aerosols contribute to a significant increase in land-surface temperature with annual emissions of 14 TgC. The calculated surface temperature change is determined by a subtle balance among changes in surface energy sources and sinks as well as changes in the hydrological cycle, all caused by BC radiative forcing. The result of this study shows that the influence of BC aerosols on climate and environment at the regional scale is more significant than at the global scale. Several important feedbacks between BC radiative effect and climate dynamics revealed in this study suggest the importance of using interactive aerosol-climate models to address the issues related to the climate impacts of aerosols. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 18-19). / Supported by the industrial consortium of the MIT Joint Program on the Science and Policy of Global Change and by the DOE DE-FG02-94ER61937 DE-FG02-93ER61713

In discussions of a cap-and-trade system for implementation of Kyoto Protocol-type quantity targets, a "safety valve" was proposed where, by government sales of emissions permits at a fixed price, the marginal cost of the effort could be limited to a predetermined level. The advantages seen for such a hybrid system included the shifting of the Kyoto architecture toward a price-based system, and the blunting of opposition to the Protocol on the basis of anticipated high cost. This paper reviews the theoretical underpinnings of the preference for a price instrument for controlling stock pollutants like greenhouse gases, and summarizes the arguments supporting and opposing the safety valve idea within the policy debate. If, in the face of uncertainty, emissions are to be limited to a fixed quantity target, then some means needs to be provided to avoid complete inflexibility. A safety valve can serve this function, although similar advantages can be achieved by the phasing in of quantity targets, coupled with provision for banking and borrowing. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 11).

At meetings in Bonn and Marrakech in 2001, the Conference of the Parties to the Framework Convention on Climate Change broke through an impasse on the detailed provisions needed to allow the Kyoto Protocol to enter into force. Key ingredients in the breakthrough included U.S. withdrawal from the process, an effective relaxation of emissions targets for Japan, Canada, and Russia, and provision of access to unrestricted emissions trading. We analyze the costs of implementation and the environmental effectiveness of the Bonn-Marrakech agreement, and its effect on the relative roles of CO₂ vs. non-CO₂ greenhouse gases. The ability of the major sellers of permits, notably Russia and Ukraine, to restrict access to permits, and the ability to trade across all greenhouse gases controlled under the Protocol, are both found to have a significant effect for both costs and effectiveness. Finally, the implications of the agreement for the future evolution of the climate regime are explored. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 16-17).

The transient response of both surface air temperature and deep ocean temperature to an increasing external forcing strongly depends on climate sensitivity and the rate of the heat mixing into the deep ocean, estimates for both of which have large uncertainty. In this paper we describe a method for estimating rates of oceanic heat uptake for coupled atmosphere/ocean general circulation models from results of transient climate change simulations. For models considered in this study, the estimates vary more than threefold. Nevertheless, values for all models fall in the 5-95% interval of the range implied by the climate record for the last century. The MIT 2D climate model, with an appropriate choice of parameters, matches changes in surface air temperature and sea level rise simulated by different models. It also reproduces the overall range of changes in precipitation. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change Website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 12-14).

Key uncertainties in the global carbon cycle are explored with a 2-D model for the oceanic carbon sink. By calibrating the key parameters of this ocean carbon sink model to widely referenced values, it produces an average oceanic carbon sink during the 1980s of 1.94 Pg/yr, consistent with the range estimated by the IPCC of 2.0 Pg/yr +/- 0.8 Pg/yr. A sensitivity analysis of the parameter values used as inputs to the 2-D ocean carbon sink model developed for this study suggests that the IPCC's range for the oceanic carbon sink of 1.2 to 2.8 Pg/yr during the 1980s may be too conservative. By applying the Probabilistic Collocation Method to this simple ocean carbon sink model, the uncertainty in the size of the oceanic sink for carbon and hence future atmospheric CO₂ concentrations is quantitatively examined. An average 1980s oceanic carbon sink of 2.06 ± 0.9 Pg/y (with 67% confidence) is estimated. This uncertainty is found to be dominated the uncertainty in by the rate of vertical mixing of dissolved carbon from the surface into the deep ocean which is parameterized in this study by vertical diffusion. It is observed that a wide range of parameter values can be used to balance the contemporary carbon cycle due to the large uncertainties in the total oceanic and terrestrial sinks. For a reference set of emissions similar to the IS92a scenario of the IPCC, the uncertainty in the atmospheric CO₂ concentration in 2100 is found to be 659 ppm +/- 35 ppm (with 67% confidence). This uncertainty is solely due to uncertainties identified in the "solubility pump" mechanism of the oceanic sink, which is only one of the many large uncertainties lacking a quantitative examination in the global carbon cycle. Such uncertainties have implications for the predictability of atmospheric CO₂ levels, a necessity for gauging the impact of different rates of anthropogenic CO₂ emissions on climate and for policy-making purposes. Because of the negative feedback between the natural carbon uptake by the terrestrial ecosystem and atmospheric CO₂ concentration, taking changes in the former into account leads to a smaller uncertainty in the latter compared to that in the case with the fixed terrestrial uptake. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website. (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 22-25).

Future global climate projections are subject to large uncertainties. Major sources of this uncertainty are projections of anthropogenic emissions. We evaluate the uncertainty in future anthropogenic emissions using a computable general equilibrium model of the world economy. Results are simulated through 2100 for carbon dioxide (CO₂), methane (CH4), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6), sulfur dioxide (SO₂), black carbon (BC) and organic carbon (OC), nitrogen oxides (NOx), carbon monoxide (CO), ammonia (NH3) and non-methane volatile organic compounds (NMVOCs). We construct mean and upper and lower 95% emissions scenarios (available from the authors at 1 degree by 1 degree latitude-longitude grid). Using the MIT Integrated Global System Model (IGSM), we find a temperature change range in 2100 of 0.9 to 4.0 degrees C, compared with the Intergovernmental Panel on Climate Change emissions scenarios that result in a range of 1.3 to 3.6 degrees C when simulated through MIT IGSM. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 23-25).

We apply the optimal fingerprint detection algorithm to three independent diagnostics of the recent climate record and derive joint probability density distributions for three uncertain properties of the climate system. The three properties are climate sensitivity, the rate of heat uptake by the deep ocean, and the strength of the net aerosol forcing. Knowing the probability distribution for these properties is essential for quantifying uncertainty in projections of climate change. We briefly describe each diagnostic and indicate its role in constraining these properties. Based on the marginal probability distributions, the 5 to 95% confidence intervals are 1.4 to 7.7K for climate sensitivity and 0.30 to 0.95 W/m^2 for the net aerosol forcing using uniform priors; and 1.3 to 4.2K and 0.26 to 0.88 W/m^2 using an expert prior for climate sensitivity. The oceanic heat uptake is not so well constrained. The uncertainty in the net aerosol forcing in either case is much less than the uncertainty range usually quoted for the indirect aerosol forcing alone. / Includes bibliographical references (p. 8-11). / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Supported in part by NOAA Office of Global Programs (NA06GP0061). Supported in part by the UK Natural Environment Research Council, and by UK DETR (PECD 7/12/37).

Controlling multiple substances that jointly contribute to climate warming requires some method to compare the effects of the different gases because the physical properties (radiative effects, and persistence in the atmosphere) of the greenhouse gases are very different. We cast such indices as the solution to a dynamic, general equilibrium cost-benefit problem where the correct indices are the relative shadow values of control on the various substances. We find that use of declining discount rate, as recommended by recent research, suggests that the current physical-based indices adopted in international negotiations overestimate the value of control of short-lived gases and underestimates the value of control of very long-lived species. Moreover, we show that such indices will likely need to be revised over time and this will require attention to the process by which decisions are made to revise them and how revisions are announced. / Includes bibliographical references (p. 18-19). / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)