Steven K. Rose

The next generation of scenarios for climate change research and assessment

Advances in the science and observation of climate change are providing a clearer understanding of the inherent variability of Earth’s climate system and its likely response to human and natural influences. The implications of climate change for the environment and society will depend not only on the response of the Earth system to changes in radiative forcings, but also on how humankind responds through changes in technology, economies, lifestyle and policy. Extensive uncertainties exist in future forcings of and responses to climate change, necessitating the use of scenarios of the future to explore the potential consequences of different response options. To date, such scenarios have not adequately examined crucial possibilities, such as climate change mitigation and adaptation, and have relied on research processes that slowed the exchange of information among physical, biological and social scientists. Here we describe a new process for creating plausible scenarios to investigate some of the most challenging and important questions about climate change confronting the global community.

Bioenergy and climate change mitigation: an assessment

Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land‐use and energy experts, land‐use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life‐cycle assessment experts. We summarize technological options, outline the state‐of‐the‐art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end‐use efficiency, improved land carbon‐stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small‐scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ: high agreement; 100–300 EJ: medium agreement; above 300 EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr−1 to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large‐scale deployment (>200 EJ), together with BECCS, could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land‐intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.

Global climate policy impacts on livestock, land use, livelihoods, and food security.

Recent research has shed light on the cost-effective contribution that agriculture can make to global greenhouse gas abatement; however, the resulting impacts on agricultural production, producer livelihoods, and food security remain largely unexplored. This paper provides an integrated assessment of the linkages between land-based climate policies, development, and food security, with a particular emphasis on abatement opportunities and impacts in the livestock sector. Targeting Annex I countries and exempting non-Annex I countries from land-based carbon policies on equity or food security grounds may result in significant leakage rates for livestock production and agriculture as a whole. We find that such leakage can be eliminated by supplying forest carbon sequestration incentives to non-Annex I countries. Furthermore, substantial additional global agricultural abatement can be attained by extending a greenhouse gas emissions tax to non-Annex I agricultural producers, while compensating them for their additional tax expenses. Because of their relatively large emissions intensities and limited abatement possibilities, ruminant meat producers face the greatest market adjustments to land-based climate policies. We also evaluate the impacts of climate policies on livelihoods and food consumption in developing countries. In the absence of non-Annex I abatement policies, these impacts are modest. However, strong income and food consumption impacts surface because of higher food costs after forest carbon sequestration is promoted at a global scale. Food consumption among unskilled labor households falls but rises for the representative farm households, because global agricultural supplies are restricted and farm prices rise sharply in the face of inelastic food demands.

The Potential for REDD+: Key Economic Modeling Insights and Issues

This article takes stock of economic modeling tools and findings related to reducing greenhouse gas emissions from deforestation and forest degradation as well as other forestry activities in developing countries (REDD+), and discusses priorities for future research. The economics literature has identified opportunities for significant cost-effective climate change mitigation from both reducing deforestation and enhancing forest carbon stocks. Several studies estimate that including REDD+ could reduce the costs of achieving climate policy goals over both the near and longer terms. Studies also suggest that the near-term potential for REDD+, especially reduced deforestation, could be valuable in support of near-term emissions reduction strategies, hedging against uncertainties, and dampening future carbon market price volatility. However, the literature is evolving. Most early and many recent studies of REDD+ provide optimistic benchmark estimates, based on ideal, but unrealistic, assumptions about policies and institutions. The more recent literature, which analyzes dynamics; interactions among forestry activities, regions, and economic sectors; implementation requirements and costs; policy designs; and uncertainties suggests a more limited and nuanced mitigation role for REDD+, especially in the near future. There are also important modeling challenges. Together, these real-world complexities and modeling challenges indicate that the actual costs and net environmental benefits of potential REDD+ activities are uncertain and highly dependent on policy and implementation features.

Opportunities for advances in climate change economics

Target carbons costs, policy designs, and developing countries There have been dramatic advances in understanding the physical science of climate change, facilitated by substantial and reliable research support. The social value of these advances depends on understanding their implications for society, an arena where research support has been more modest and research progress slower. Some advances have been made in understanding and formalizing climate-economy linkages, but knowledge gaps remain [e.g., as discussed in (1, 2)]. We outline three areas where we believe research progress on climate economics is both sorely needed, in light of policy relevance, and possible within the next few years given appropriate funding: (i) refining the social cost of carbon (SCC), (ii) improving understanding of the consequences of particular policies, and (iii) better understanding of the economic impacts and policy choices in developing economies.

Model collaboration for the improved assessment of biomass supply, demand, and impacts

Existing assessments of biomass supply and demand and their impacts face various types of limitations and uncertainties, partly due to the type of tools and methods applied (e.g., partial representation of sectors, lack of geographical details, and aggregated representation of technologies involved). Improved collaboration between existing modeling approaches may provide new, more comprehensive insights, especially into issues that involve multiple economic sectors, different temporal and spatial scales, or various impact categories. Model collaboration consists of aligning and harmonizing input data and scenarios, model comparison and/or model linkage. Improved collaboration between existing modeling approaches can help assess (i) the causes of differences and similarities in model output, which is important for interpreting the results for policy‐making and (ii) the linkages, feedbacks, and trade‐offs between different systems and impacts (e.g., economic and natural), which is key to a more comprehensive understanding of the impacts of biomass supply and demand. But, full consistency or integration in assumptions, structure, solution algorithms, dynamics and feedbacks can be difficult to achieve. And, if it is done, it frequently implies a trade‐off in terms of resolution (spatial, temporal, and structural) and/or computation. Three key research areas are selected to illustrate how model collaboration can provide additional ways for tackling some of the shortcomings and uncertainties in the assessment of biomass supply and demand and their impacts. These research areas are livestock production, agricultural residues, and greenhouse gas emissions from land‐use change. Describing how model collaboration might look like in these examples, we show how improved model collaboration can strengthen our ability to project biomass supply, demand, and impacts. This in turn can aid in improving the information for policy‐makers and in taking better‐informed decisions.

Regional and sectoral estimates of the social cost of carbon: An application of FUND

The social cost of carbon is an estimate of the benefit of reducing CO2 emissions by one ton today. As such it is a key input into cost-benefit analysis of climate policy and regulation. We provide a set of new estimates of the social cost of carbon from the integrated assessment model FUND 3.5 and present a regional and sectoral decomposition of our new estimate. China, Western Europe and the United States have the highest share of harmful impacts, with the precise order depending on the discount rate. The most important sectors in terms of impacts are agriculture and increased energy use for cooling. We present an extensive sensitivity analysis with respect to the discount rate, equity weights, different socio economic scenarios and values for the climate sensitivity parameter.

Global forest carbon sequestration and climate policy design

Global forests could play an important role in mitigating climate change. However, there are significant implementation obstacles to accessing the worlds forest carbon sequestration potential. The timing of regional participation and eligibility of sequestration activities are issues. The existing forest carbon supply estimates have made optimistic assumptions about immediate, comprehensive, and global access. They have also assumed no interactions between activities and regions, and over time. We use a global forest and land use model to evaluate these assumptions with more realistic forest carbon policy pathways. We find that an afforestation only policy is fundamentally flawed, accelerated deforestation may be unavoidable, and a delayed comprehensive program could reduce, but not eliminate, near-term accelerated deforestation and eventually produce sequestration equivalent to idealized policies – but with a different sequestration mix than previously estimated by others and thereby different forests. We also find that afforestation and avoided deforestation increase the cost of one another.

The Time Evolution of the Social Cost of Carbon: An Application of Fund

The authors estimate the growth rate of the social cost of carbon. This is an indication of the optimal rate of acceleration of greenhouse gas emission reduction policy over time. The authors find that the social cost of carbon increases by 1.3% to 3.9% per year, with a central estimate of 2.2%. Previous studies found an average rate of 2.3% and a range of 0.9 to 4.1%. The rate of increase of the social carbon depends on a range of factors, including the pure rate of time preference, the rate of risk aversion, equity weighting, the socioeconomic and emission scenarios, the climate sensitivity, dynamic vulnerability, and the curvature of the impact functions.

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.