The scientific community is developing new integrated global, regional, and sectoral scenarios to facilitate interdisciplinary research and assessment to explore the range of possible future climates and related physical changes could pose to human and natural systems; how these could interact with social, economic, and environmental development pathways; the degree to which mitigation and adaptation policies can avoid and reduce those risks; the costs and benefits of various policy mixes; residual impacts under alternative pathways; and the relationship with sustainable development. Working together, climate change researchers from a broad range of perspectives and disciplines are developing policy-relevant scenarios, exploring the implications of different possible futures for the challenges and opportunities human and natural systems could face with increasing climate change.
The new scenario process was initiated in a 2006 workshop (AGCI 2007) and developed further in many forms and places. Discourse at a number of subsequent workshops resulted in the preparation of a roadmap to develop new scenarios that was formalized at the Expert Meeting on Scenarios organized by the IPCC at Noordwijkerhout, Netherlands, in 2007. This roadmap details a process consisting of preparatory, parallel, and integration phases (Moss et al. 2008; Moss et al. 2010):
- In phase 1, the integrated assessment modeling community developed four emission pathways (Representative Concentration Pathways or RCPs) of how emissions could develop over the 21st century, taking into consideration the full basket of greenhouse gases, land use change, and other factors. The development of the four RCPs is documented in a special issue of Climatic Change (van Vuuren et al., 2011). These RCPs were used as a basis for simulations with earth system models as part of the Climate Model Intercomparison Project (CMIP-5), producing projections of the magnitude and extent of climate change over this century and, in some cases, to 2300 (Taylor et al., 2012).
- In phase 2, the integrated assessment modeling (IAM) and impacts, adaptation, and vulnerability (IAV) communities are developing new descriptions of future socioeconomic conditions (reported in an upcoming volume in the journal Climatic Change). In phase 3, scenarios for use by the climate change science community are being created, integrating the descriptions of socioeconomic development with the climate change projections and with assumptions about climate policies.
Over the past two years, researchers from the integrated assessment modeling (IAM) and impacts, adaptation and vulnerability (IAV) communities turned to the task of developing socioeconomic development pathways, with a series of meetings held to facilitate progress and synthesize approaches. A joint IPCC-NRC (U.S. National Research Council) workshop in Washington, DC, in February 2010 explored the needs for socioeconomic and environmental futures that could be used with climate scenarios (NRC, 2010) and served as a stimulus for a number of proposed frameworks within which such scenarios could be developed (van Vuuren et al., 2012; Kriegler et al., 2012). An IPCC Workshop on Socioeconomic Scenarios held in Berlin in November 2010 brought together researchers from the IAM, IAV, and climate modeling communities to consider the task and led to the adoption of a unified framework for the development of a small set of Shared Socioeconomic Pathways (SSPs) and their use in conjunction with the RCPs and associated climate model simulations to facilitate integrated research and assessment (IPCC, 2012).
Subsequent to the Berlin meeting, a team of authors produced a manuscript documenting an over-arching conceptual framework for the development and use of SSPs (Core Writing Team, 2011). In early November 2011, a meeting in Boulder, Colorado, was held to adopt a basic set of narratives for the SSPs and to lay out priorities for further activities (O’Neill et al., 2012). A workshop co-sponsored by the IPCC and the government of the Netherlands in the Hague in May 2012 afforded an opportunity to broaden the dialogue on the draft SSP narratives and to present initial quantifications of the SSPs. The meeting resulted in a draft plan of action for a range of joint IAV-IAM activities, to be pursued under the auspices of the ICONICS Committee.