Abstract
The recently developed Shared Socioeconomic Pathways (SSPs) have enabled researchers to explore coupled human–nature dynamics in new and more complex ways. Despite their wide applicability and unquestionable advantage over earlier scenarios, the utility of the SSPs for conducting societal impact assessments is impaired by shortcomings in the underlying economic growth projections. In particular, the assumed economic convergence and absence of major growth disruptions break with historical growth trajectories in the developing world. The consequence is that the SSP portfolio becomes too narrow, with an overly optimistic lower band of growth projections. This is not a trivial concern, since resulting impact assessments are likely to underestimate the full human and material costs of climate change, especially for the poorest and most vulnerable societies. In response, we propose that future quantifications of the SSPs should incorporate the likelihood of growth disruptions, informed by scenarios of the relevant political contexts that historically have been important in curbing growth.
Highlights
The recently developed Shared Socioeconomic Pathways (SSPs) have enabled researchers to explore coupled human–nature dynamics in new and more complex ways
How will climate change shape societies in coming decades, and what steps could be taken to avoid the gravest consequences? The recently developed Shared Socioeconomic Pathways (SSP) framework, which plays an integral role in the ongoing Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment cycle, constitutes the most comprehensive attempt to date to model societal development consistent with different climate change scenarios (O’Neill et al 2014; Riahi et al 2017)
We show that existing quantifications of the SSPs, despite their wide applicability and unquestionable advantage over earlier scenario exercises, have clear limitations for researchers seeking to conduct societal adaptation and impact assessments because of shortcomings in the economic growth models underlying the SSPs
Summary
The IPCC Fifth Assessment Report defines a scenario as a “plausible description of how the future may develop based on a coherent and internally consistent set of assumptions about key driving forces ... and relationships” (Field et al 2014, 1772). Economic convergence has been much less pronounced, despite significant educational improvements in poor countries (Acemoglu 2009; Rodrik 2014) This is visualized, which shows average economic growth since 1970 as a function of GDP per capita in 1970. SSP3 (along with SSP4) represents the most pessimistic scenario in the SSP framework, Figure 1B reveals that projected future growth rates for the least developed countries vastly exceed observed growth in the recent past. The only GDP growth projection in the SSP framework that departs from global economic convergence is the IIASA model’s quantification of SSP3 (Cuaresma 2017) This is the pathway that comes closest to historical trends and could as such better be considered “business as usual” than the most pessimistic scenario. We observe a powerful negative correlation between present development and future growth across all socioeconomic scenarios
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