IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

18.8 Uncertainties, unknowns and priorities for research

Many of the inter-relationships between adaptation and mitigation have been described in previous assessments of climate policy, and the literature is rapidly expanding. Nevertheless, well-documented studies at the regional and sectoral level are lacking. Adaptation and mitigation studies tend to focus only on their primary domains, and few studies analyse the secondary consequences (e.g., of mitigation on impacts and adaptation options or of adaptation actions on greenhouse-gas emissions and mitigation options). Experiences with climate change adaptation are relatively recent and large-scale, and global actions, such as insurance, adaptation protocols or issues of liability and compensation, have not been tested.

Learning from the expanding case experience of inter-relationships is a priority. Reviews, syntheses and meta-analyses should become more common in the next few years. An analytical and institutional framework for monitoring the inter-relationships and organising periodic assessments needs to be developed. At present, no organisation appears to have a leading role in this area. The experiences of stakeholders in making decisions concerning both adaptation and mitigation should be compared. The experience of the research on land-use and land-cover change would be insightful (e.g., Geist and Lambin, 2002). Effective institutional development, use of financial instruments, participatory planning and risk-management strategies are areas for learning from the emerging experience (Klein et al., 2005).

A key research need is to document which stakeholders link adaptation and mitigation. Decisions oriented towards either adaptation or mitigation might be extended to evaluate unintended consequences, to take advantage of synergies or explicitly evaluate trade-offs. Yet, the constraints of organisational mandates and administrative capacity, finance and linking across scales and sectors (e.g., Cash and Moser, 2000) may outweigh the benefits of integrated decision-making. Formulation of policies that support renewable energy in developing countries is likely to meet fiscal, market, legal, knowledge and infrastructural barriers that may limit uptake.

The effects on specific social and economic groups need to be further documented. For example, development of hydroelectricity may reduce water availability for fish farming and irrigation of home gardens, potentially adversely affecting the food security of women and children (Andah et al., 2004; Hirsch and Wyatt, 2004). Linking carbon sequestration and community development could generate new opportunities for women and marginal socio-economic groups, but this will depend on many local factors and needs to be evaluated with empirical research.

The links between a broad climate-change response capacity, specific capacities to link adaptation and mitigation, and actual actions are poorly documented. Testing and quantification of the relationship between capacities to act and actual action is needed, taking into account sectoral planning and implementation, the degree of vulnerability, the range of technological options, policy instruments and information including experience of climate change.

Analytical frameworks for evaluating the links between adaptation and mitigation are inadequate, or in some cases competing. A suite of frameworks may be necessary for particular stakeholders and levels of decision-making. Decision frameworks relating adaptation and mitigation (separately or conjointly) need to be tested against the roles and responsibilities of stakeholders at all levels of action. Global optimising models may influence some decisions, while experience at the project level is important to others. The suitability of IAMs needs to be evaluated for exploring multiple metrics, discontinuities and probabilistic forecasts (Mastrandrea and Schneider, 2001, 2004; Schneider, 2003). Global cost-benefit models should include clear analyses of uncertainty in the use of valuation schemes and discounting as well as the assumptions inherent in climate impacts models (including the role of adaptation in reducing impacts). Hybrid approaches to integrated assessments across scales (top-down and bottom-up) should be further developed (Wilbanks and Kates, 2003). Representations of risks and uncertainties need to be related to decision frameworks and processes (Dessai et al., 2004; Kasperson and Kasperson, 2005; Lorenzoni et al., 2005). Climate risk, current and future, is only one aspect of adaptation-mitigation decision-making; the relative importance and effect of other drivers needs to be understood.

The magnitude of unintended consequences is uncertain. The few existing studies (e.g., Dang et al., 2003) indicate that the repercussions from mitigation for adaptation and vice versa are mostly marginal at the global level, although they may be significant at the regional scale. The effects on demand or total emissions are likely to be a small fraction of the global baseline. However, in some domains, such as water and land markets, and in some locales, the inter-relationships might affect local economies. Quantitative evaluation of direct trade-offs is missing: the metrics and methods for valuation, existence of thresholds in local feedbacks, behavioural responses to opportunities, risks and adverse impacts, documentation of the baseline and project scenarios, and scaling up from isolated, local examples to systemic changes are part of the required knowledge base.

At a global or international level, defining a socially, economically and environmentally justifiable mix of mitigation, adaptation and development remains difficult and a research need. While IAMs are relatively well developed, they can only provide approximate estimates of quantitative inter-relationships at a highly aggregated scale. Fourteen experts in estimating the social cost of carbon rated their estimates as low confidence, due to the many gaps in the coverage of impacts and valuation studies, uncertainties in projected climate change, choices in the decision framework and the applied discount rate (Downing et al., 2005). Estimates of the marginal abatement cost range from -2% to +8% of GDP, while estimates of the marginal damages avoided span three orders of magnitude (see Chapter 20). The marginal cost of adaptation has not been calculated, although some estimates assume a reduction in impacts due to adaptation (see Chapter 17). Combining the marginal abatement cost, marginal damages avoided and the marginal cost of adaptation into an optimal strategy for climate response is subject to considerable uncertainty that is unlikely to be effectively reduced in the near term (see Harvey, 2006).

A systematic assessment with a formal risk framework that guides expert judgement and grounded case studies, and interprets the sample of published estimates, is required if policy-makers wish to identify the benefits of climate policy (e.g., Downing et al., 2005). Existing estimates of damages avoided are based on a sample of sectors exposed to climate change and a small range of climate stresses. Better understanding across a matrix of climate change and exposure is required (Chapter 20; Fisher et al., 2007). Socio-economic conditions and locales that are likely to experience early and significant impacts (often called ‘hotspots’) should be a high priority for additional studies. The extent to which targets that are set globally are consistent with national or local mixes of strategies requires a concerted effort. The distributional effects would be an important factor in evaluating tolerable windows and trade-offs between adaptation and mitigation. The lack of high-quality studies of the benefits of mitigation, and the social cost of carbon, limits confidence in setting targets for stabilisation.

The relationship between development paths and adaptation-mitigation inter-relationships requires further research. Unintended consequences, synergies and trade-offs might be unique to some development paths; equally, they might be possible in many different paths. Existing scenarios of development paths are particularly inadequate in framing some of the major determinants of vulnerability and adaptation (Downing et al., 2003). Exogenous projections of GDP are a particular obstacle for modelling the inter-relationships between adaptation and mitigation. Few global scenarios address local food security in realistic ways (Downing and Ziervogel, 2005, but see related discussion of Millennium Development Goals in Chapters 9 and 20). Scenarios of abrupt climate change, streams of extreme events, and realistic social, economic and political responses would add insight into adaptive management (the ‘act, then learn, then act again’ approach). Few reference scenarios explicitly frame issues related to inter-relationships between adaptation and mitigation (e.g., from the extent to which a global decision-maker makes optimising judgements to the institutional setting for local projects to exploit synergies). While the direct energy input in large infrastructure projects may be small, including a shadow price for climate change externalities may shift adaptation portfolios. An assessment of actual shifts in energy demand and ways to reduce emissions is desirable. Most integrated assessments are at the large scale of regions to world views, although local dialogues are beginning to explore synergies (Munasinghe and Swart, 2005).

The feasibility and outcome of many of the inter-relationships depend on local conditions and management options. A systematic assessment and guidance for mitigating potentially adverse effects would be helpful. The nature of links between public policy and private action at different scales, and prospects for mainstreaming integrated policy, are worth evaluating. Many of the consequences depend on environmental processes that may not be well understood; for example, the resilience of systems to increased interannual climate variability and long-term carbon sequestration in agro-forestry systems.