Learn about the latest set of emissions scenarios, based on Shared Socio-economic Pathways (SSPs). Understand how SSPs differ from RCP scenarios and learn about key considerations when using SSPs in climate risk assessments.
Summary
Learn about the latest set of emissions scenarios, based on Shared Socio-economic Pathways (SSPs). Understand how SSPs differ from RCP scenarios and learn about key considerations when using SSPs in climate risk assessments.
Introduction
Engineers, planners, and decision-makers across the country are increasingly using climate model information to support the development of adaptation strategies to increase resilience to the heightened risks of climate change. Historical observations alone are not suitable to assess future climate-related risks. Practitioners using future climate data want to know how much the climate will change, and thus how much future climate risk they should expect to encounter in the coming decades or at the end of the century. However, how much the climate will change in the future will be determined by greenhouse gas emissions which, in turn, are strongly dependent on how society grows and develops. These growth patterns are influenced by a host of factors, including global cooperation on greenhouse gas reductions, political will, and technological advancements. Even seemingly small changes to any of these factors can result in very different outcomes. Therefore, rather than offer practitioners a single set of future climate data, it is best practice to provide a range of future climate scenarios that encompass various levels of greenhouse gas emissions. It is important to know about these scenarios – how they are defined and the key differences between them – prior to using future climate data.
Today, the scenarios used to characterize possible future development pathways for human societies are known as Shared Socioeconomic Pathways, or SSPs for short. The goal of this article is to introduce the SSPs, explain their similarities and differences compared to the previously used Representative Concentration Pathways (RCPs), and provide guidance to practitioners on considerations to keep in mind when selecting which scenarios to use.
What are Shared Socioeconomic Pathways (SSPs)?
Shared Socioeconomic Pathways are a set of narratives describing possible future development pathways for human society, particularly in relation to its use of fossil fuels and the social and economic factors which drive fossil fuel use. These pathways explore a range of technological, socioeconomic and policy futures as well as consider challenges to mitigation and adaptation.1 Five pathways have been developed by the international scientific community – sustainable development (SSP1), middle-of-the-road development (SSP2), regional rivalry (SSP3), inequality (SSP4) and fossil-fueled development (SSP5) – which allow practitioners to explore climate changes across a range of very different futures.
The five SSP pathways can be characterized in terms of the socioeconomic challenges they imply for mitigating and adapting to climate change (Figure 1). SSP1 (Sustainability) has few challenges to both mitigation and adaptation. In this pathway, policies focus on human well-being, clean energy technologies, and the preservation of the natural environment. In contrast, SSP3 (Regional Rivalry) is characterized by many challenges to both mitigation and adaptation. In this pathway, which relies heavily on fossil fuels and an increased use of coal, nationalism drives policy and focus is placed on regional and local issues rather than on global issues. The other SSPs “fill in the spectrum” of possible futures. SSP4 (Inequality), which follows a similar energy future to SSP1, is defined by many challenges to adaptation and few challenges to mitigation. SSP5 (Fossil-fueled Development), also heavily reliant on fossil fuels including coal, is characterized by many challenges to mitigation and few challenges to adaptation, while SSP2 (Middle of the Road) represents moderate challenges to both mitigation and adaptation and follows a pathway of balanced energy development…
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