Achievements and needs for the climate change scenario framework

Abstract

Long-term global scenarios have underpinned research and assessment of global environmental change for four decades. Over the past ten years, the climate change research community has developed a scenario framework combining alternative futures of climate and society to facilitate integrated research and consistent assessment to inform policy. Here we assess how well this framework is working and what challenges it faces. We synthesize insights from scenario-based literature, community discussions and recent experience in assessments, concluding that the framework has been widely adopted across research communities and is largely meeting immediate needs. However, some mixed successes and a changing policy and research landscape present key challenges, and we recommend several new directions for the development and use of this framework.

Keywords: Climate-change impacts; Climate-change mitigation; Projection and prediction; Socioeconomic scenarios; Sustainability.

The scenario framework and process for producing integrated studies combining future climate outcomes, societal conditions and policy assumptions. A more detailed version of this figure separating successive generations of concentration pathways, climate model simulations and integrated studies is available in the Supplementary Information.

Fig. 1. Application of SSPs by primary topic of analysis.

Areas of rectangles are proportional to the number of studies in each category. Colours represent applications of SSPs (blue shading), scenario methods (light grey) and extensions of SSP information (light brown). Applications include those primarily on climate impacts or adaptation (dark blue), drivers or mitigation (light blue), or address multiple topics equally (medium blue). Results based on 1,378 analyses published 2014–2019 that use or develop SSPs and, in many cases, apply RCPs as well. We exclude papers that use RCPs only. See Supplementary Information for methods and definitions and ref. for data.

Fig. 2. Numbers of applications of SSP–RCP combinations in 715 total studies applying integrated scenarios, published over the period 2014–2019.

Each cell represents an SSP–RCP combination, with colours indicating the number of applications. White cells indicate no applications. Green rectangles along the right side of the figure indicate totals for each RCP (rows); those along the bottom of the figure indicate totals for each SSP (columns). Unlikely SSP–RCP combinations indicate those in which integrated assessment models found the outcomes infeasible under the SSPs and SPAs assumed^,. Forcing levels labelled on the vertical axis are not spaced in exact correspondence to tick marks to improve clarity of the figure. RCP6.0 reaches approximately 5.5 W per m² forcing in 2100. See Supplementary Information for methods and ref. for data.