Geoffrey J. Blanford

Managing the Transition to Climate Stabilization

It is becoming increasingly clear that economically efficient climate policies are unlikely to be implemented in the near term. Therefore an analysis is warranted that considers the implications of certain suboptimal transition policies. This analysis constructs a transition scenario based on realistic assumptions about the current trends in policy-making. The transition is examined in the context of varying assumptions about the stringency of the target and the availability of low- or no-carbon energy technologies in the future. In addition to evaluating the effects of suboptimal policies, the transitional analysis offers new insights about the intrinsic uncertainty regarding both the appropriate stabilization target and technology.

Trade-offs between mitigation costs and temperature change.

This paper uses the MERGE integrated assessment model to identify the least-cost mitigation strategy for achieving a range of climate policies. Mitigation is measured in terms of GDP foregone. This is not a benefit-cost analysis. No attempt is made to calculate the reduction in damages brought about by a particular policy. Assumptions are varied regarding the availability of energy-producing and energy-using technologies. We find pathways with substantial reductions in temperature change, with the cost of reductions varying significantly, depending on policy and technology assumptions. The set of scenarios elucidates the potential energy system transformation demands that could be placed on society. We find that policy that allows for “overshoot” of a radiative forcing target during the century results in lower costs, but also a higher temperature at the end of the century. We explore the implications of the costs and availability of key mitigation technologies, including carbon capture and storage (CCS), bioenergy, and their combination, known as BECS, as well as nuclear and energy efficiency. The role of “negative emissions” via BECS in particular is examined. Finally, we demonstrate the implications of nationally adopted emissions timetables based on articulated goals as a counterpoint to a global stabilization approach.

Modeling Uncertainty in Climate Change: A Multi-Model Comparison

The economics of climate change involves a vast array of uncertainties, complicating both the analysis and development of climate policy. This study presents the results of the first comprehensive study of uncertainty in climate change using multiple integrated assessment models. The study looks at model and parametric uncertainties for population, total factor productivity, and climate sensitivity. It estimates the pdfs of key output variables, including CO2 concentrations, temperature, damages, and the social cost of carbon (SCC). One key finding is that parametric uncertainty is more important than uncertainty in model structure. Our resulting pdfs also provide insights on tail events.

UNDERSTANDING THE SOCIAL COST OF CARBON: A MODEL DIAGNOSTIC AND INTER-COMPARISON STUDY

The social cost of carbon (SCC) is a monetary estimate of global climate change damages to society from an additional unit of carbon dioxide (CO2) emissions. SCCs are used to estimate the benefits of CO2 reductions from policies. However, little is known about the modeling underlying the values or the implied societal risks, making SCC estimates difficult to interpret and assess. This study performs the first in-depth examination of SCC modeling using controlled diagnostic experiments that yield detailed intermediate results, allow for direct comparison of individual components of the models, and facilitate evaluation of the individual model SCCs. Specifically, we analyze DICE, FUND, and PAGE and the multimodel approach used by the US Government. Through our component assessments, we trace SCC differences back to intermediate variables and specific features. We find significant variation in component-level behavior between models driven by model-specific structural and implementation elements, some resulting in artificial differences in results. These elements combine to produce model-specific tendencies in climate and damage responses that contribute to differences observed in SCC outcomes — producing PAGE SCC distributions with longer and fatter right tails and higher averages, followed by DICE with more compact distributions and lower averages, and FUND with distributions that include net benefits and the lowest averages. Overall, our analyses reveal fundamental model behavior relevant to many disciplines of climate research, and identify issues with the models, as well as the overall multimodel approach, that need further consideration. With the growing prominence of SCCs in decision-making, ranging from the local-level to international, improved transparency and technical understanding is essential for informed decisions.

More than one arrow in the quiver: Why “100% renewables” misses the mark

Jacobson et al. (1) aim to demonstrate that an all-renewable energy system is technically feasible. Not only are the study’s conclusions based on strong assumptions and key methodological oversights, but its framing also omits the essential notion of trade-offs. A far more relevant question is how renewable energy technologies relate to the broader set of options for meeting long-term societal goals like managing climate change. Even if the goal were to maximize the deployment of renewable energy (and not decarbonization more generally), Jacobson et al. still fail to provide a satisfactory analysis by glossing over fundamental implications of the technical and economic dimensions of intermittency. We briefly highlight two prominent examples, and then …

Impact of Revised CO2 Growth Projections for China on Global Stabilization Goals

Recent growth in carbon dioxide emissions from China’s energy sector has exceeded expectations. In a major US government study of future emissions released in 2007 (1), participating models appear to have substantially underestimated the near-term rate of increase in China’s emissions. We present a recalibration of one of those models to be consistent with both current observations and historical development patterns. The implications of the new specification for the feasibility of commonly discussed stabilization targets, particularly when considering incomplete global participation, are profound. Unless China’s emissions begin to depart soon from their (newly projected) business-as-usual path, stringent stabilization goals may be unattainable. The current round of global policy negotiations must engage China and other developing countries, not to the exclusion of emissions reductions in the developed world and possibly with the help of significant financial incentives, if such goals are to be achieved. It is in all nations’ interests to work cooperatively to limit our interference with the global climate.

Modeling Uncertainty in Integrated Assessment of Climate Change: A Multimodel Comparison

The economics of climate change involves a vast array of uncertainties, complicating our understanding of climate change. This study explores uncertainty in baseline trajectories using multiple integrated assessment models commonly used in climate policy development. The study examines model and parametric uncertainties for population, total factor productivity, and climate sensitivity. It estimates the probability distributions of key output variables, including CO2 concentrations, temperature, damages, and social cost of carbon (SCC). One key finding is that parametric uncertainty is more important than uncertainty in model structure. Our resulting distributions provide a useful input into climate policy discussions.

THE INAPPROPRIATE TREATMENT OF CLIMATE CHANGE IN COPENHAGEN CONSENSUS 2008

The Copenhagen Consensus, conducted at four-year intervals, is an explicit attempt to prioritise solutions to many of the world’s most pressing problems. In its 2008 exercise (CC08) (Lomborg, 2009), a panel of eminent scholars, on the basis of the input of a larger number of field experts, ranked proposed solutions to ten leading problems (see Table 1). Although we are pleased that one of the proposed solutions to climate change was raised from the bottom of the list in the 2004 exercise (Lomborg, 2004)) to the middle of the current list, we have several problems with the study design and the manner in which its results are being interpreted. As authors of the paper on climate change evaluated by the CC08 panel (Yohe et al., 2009), we are concerned that the