On Growth Projections in the Shared SocioeconomicPathways

The recently developed Shared Socioeconomic Pathways (SSPs) have enabledresearchers to explore coupled human–nature dynamics in new and morecomplex ways. Despite their wide applicability and unquestionable advantage overearlier scenarios, the utility of the SSPs for conducting societal impactassessments is impaired by shortcomings in the underlying economic growthprojections. In particular, the assumed economic convergence and absence ofmajor growth disruptions break with historical growth trajectories in thedeveloping world. The consequence is that the SSP portfolio becomes too narrow,with an overly optimistic lower band of growth projections. This is not atrivial concern, since resulting impact assessments are likely to underestimatethe full human and material costs of climate change, especially for the poorestand most vulnerable societies. In response, we propose that futurequantifications of the SSPs should incorporate the likelihood of growthdisruptions, informed by scenarios of the relevant political contexts thathistorically have been important in curbing growth.