Socio-economic Scenario Development for Climate Change Analysis

Socio-economic scenarios constitute an important tool for exploring the long-term consequences of anthropogenic climate change and available response options. They have been applied for different purposes and to a different degree in various areas of climate change analysis, typically in combination with projections of future climate change. Integrated assessment modeling (IAM) has used them to develop greenhouse gas (GHG) emissions scenarios for the 21st century and to investigate strategies for mitigating GHG emissions on a global scale. Analyses of climate change impacts, adaptation and vulnerabilities (IAV) depend heavily on assumptions about underlying socio-economic developments, but have employed socio-economic scenarios to a lesser degree, due mainly to the multitude of contexts and scales of such analyses. A more consistent use of socio-economic scenarios that would allow an integrated perspective on mitigation, adaptation and residual climate impacts remains a major challenge. We assert that the identification of a set of global narratives and socio-economic pathways offering scalability to different regional contexts, a reasonable coverage of key socio-economic dimensions and relevant futures, and a sophisticated approach to separating climate policy from counter-factual "no policy" scenarios would be an important step towards meeting this challenge. Such "Shared Socio-economic Pathways" (SSPs) should be specified in an iterative manner and with close collaboration between IAM and IAV researchers to assure coverage of key dimensions, sufficient scalability and widespread adoption. They can be used not only as inputs to analyses, but also to collect the results of different climate change analyses in a matrix defined by two dimensions : climate exposure as characterized by a radiative forcing or temperature level and socio-economic development as classified by the SSPs. For some applications, SSPs may have to be augmented by "Shared Climate Policy Assumptions" (SPAs) capturing global components of climate policies that some studies may require as inputs. Finally, sufficient coverage of the relevant socio-economic dimensions for the analysis of mitigation, adaptation and residual climate impacts may be assessed by locating the SSPs along the dimensions of challenges to mitigation and to adaptation. We conclude that the development of SSPs, and integrated socio-economic scenarios more broadly, is a useful focal point for collaborative efforts between IAM and IAV researchers. This is likely to be a long-term and iterative enterprise comprising a collection of different activities : periodically taking stock of the evolving scenario work in both research communities, linking up individual efforts, and pursuing collaborative scenario work through appropriate platforms that still need to be established. In the short run, an important goal is to produce tangible outcomes that would allow the 5th Assessment Report of the IPCC to take a more integrated perspective on mitigation, adaptation and residual climate impacts.