In assessing impacts, vulnerability, and adaptation to climate change, a large
array of methods and tools pertain to specific sectors, scales of analysis,
and environmental and socioeconomic contexts. In this chapter, the term methods
refers to the overall process of assessment, including tool selection and application;
the term tools refers to the formulated means of assessment. It is not the intent
of this chapter to comprehensively canvas this full array of methods and tools;
clearly, such appraisal falls more properly within the purview of the individual
chapters in this volume. The purpose of this chapter is to address several overarching
methodological questions that transcend individual sectoral and regional concerns.
In so doing, this chapter focuses on five related questions:
- How can the current effects of climate change be detected? Is climate
change already having a discernible effect? One of the key methodological
problems is how to unequivocally identify a climate change signal in indicators
of change in biotic and abiotic systems. This problem is exemplified in Section
2.2 by focusing on biological indicators and methodological advances that
have been made since the Second Assessment Report (SAR).
- How can the future effects of climate change be anticipated, estimated,
and integrated? Since the SAR, an explosion of climate change vulnerability
and adaptation studies has occurred around the world, stimulated in large
part by the United Nations Framework Convention on Climate Change (UNFCCC)
and its national reporting requirements, as well as the availability of international
donor support to non-Annex I countries. Section 2.3
reflects on methodological developments and needs for such vulnerability and
adaptation studies, and Section 2.4 focuses on methods
for regional and cross-sectoral integration.
- How can impacts and adaptations be valued and costed? Ultimately,
decisions to avoid or reduce the adverse effects of climate change (or enhance
the benefits) require some means of appraisal (monetary or otherwise) of projected
impacts and alternative adaptation options. Section 2.5
reviews various methods for valuing and costing, including issues of nonmarket
effects, equity, integration, and uncertainty.
- How can uncertainties be expressed and characterized? From the science
of climate change to assessments of its impacts, uncertainties compound, resulting
in a "cascade of uncertainty" that perplexes decisionmaking. Section
2.6 canvasses the problems of, and methods for, incorporating uncertainty
into policy-relevant assessments.
- What frameworks are available for decisionmaking? Once adaptations
have been valued, the choice of adaptation requires methods of weighing and
balancing options. Section 2.7 summarizes the main decision
analytic frameworks (DAFs) that can be used in this context.
In addressing these questions, the following sections seek to furnish a brief
description of the state of methods at hand, methodological developments that
have occurred since the SAR, and needs and directions for applications and
methods development for the future. Section 2.8 contains