In this section, the Shared Socio-Economic Pathway (SSP) scenarios are introduced and discussed. We use these scenarios extensively in the second chapter. A basic overview of them is provided in this section.
1.6.1
The IPCC and its assessment reports
TheIPCC (Intergovernmental Panel on Climate Change) is an intergovernmental body of the United Nations that releases reports that cover “scientific technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation”. This description of the IPCC is provided by the UN body itself in the document titled Principles Governing IPCC Work (approved at the 14th IPCC Session in Vienna).
Instead of conducting any independent or original research, the body compiles published peer (and non peer) reviewed sources to create its assessment reports that contain guidelines for nations in the form of a Summary for Policymakers document. In its latest assessment report (the Fifth Assessment in 2018), it released the Special Report on Global Warming of 1.5 ◦C
Figure 1.7: The SSP scenarios mapped into the challenges to mitigation-adaptation space. Image taken from the Wikipedia page to Shared Socioeconomic Pathways. By Sfdiversity - Own work, CC BY-SA 4.0, link
1.6.2
The Shared Socioeconomic Pathway (SSP) scenarios
The Shared Socio Economic Pathway scenarios (SSP scenarios) are a list of five storyline scenarios constructed formally for producing the Sixth IPCC Assessment Report. These storyline narratives are constructed to describe future socio-economic developments of the world. Each storyline is unique in its adaptation and mitigation challenges (towards cli- mate change). Every scenario has a unique country-level population and GDP projection till 2100. Figure 1.7 shows the map of these five scenarios in the adaptation-mitigation plane. Regional level population and income projections under five SSP scenarios till 2100 (starting from 2015) are shown in Appendix - Supplementary Figure B.11. The division methodology of regions are explained in Appendix Section A.5.2.
The SSP scenarios were first introduced in Riahi et al. [77]. Their storyline descriptions, presented below, are quoted directly from the original paper:
SSP1: Sustainability (Taking the Green Road)
“The world shifts gradually, but pervasively, toward a more sustainable path, emphasizing more inclusive development that respects perceived environmental boundaries. Manage-
ment of the global commons slowly improves, educational and health investments accelerate the demographic transition, and the emphasis on economic growth shifts toward a broader emphasis on human well-being. Driven by an increasing commitment to achieving devel- opment goals, inequality is reduced both across and within countries. Consumption is oriented toward low material growth and lower resource and energy intensity.” [77]
SSP2: Middle of the Road
“The world follows a path in which social, economic, and technological trends do not shift markedly from historical patterns. Development and income growth proceeds unevenly, with some countries making relatively good progress while others fall short of expecta- tions. Global and national institutions work toward but make slow progress in achieving sustainable development goals. Environmental systems experience degradation, although there are some improvements and overall the intensity of resource and energy use declines. Global population growth is moderate and levels off in the second half of the century. In- come inequality persists or improves only slowly and challenges to reducing vulnerability to societal and environmental changes remain.” [77]
SSP3: Regional rivalry (A Rocky Road)
“A resurgent nationalism, concerns about competitiveness and security, and regional con- flicts push countries to increasingly focus on domestic or, at most, regional issues. Policies shift over time to become increasingly oriented toward national and regional security is- sues. Countries focus on achieving energy and food security goals within their own regions at the expense of broader-based development. Investments in education and technological development decline. Economic development is slow, consumption is material-intensive, and inequalities persist or worsen over time. Population growth is low in industrialized and high in developing countries. A low international priority for addressing environmental concerns leads to strong environmental degradation in some regions.” [77]
SSP4: Inequality (A Road Divided)
“Highly unequal investments in human capital, combined with increasing disparities in economic opportunity and political power, lead to increasing inequalities and stratification both across and within countries. Over time, a gap widens between an internationally- connected society that contributes to knowledge- and capital-intensive sectors of the global
economy, and a fragmented collection of lower-income, poorly educated societies that work in a labor intensive, low-tech economy. Social cohesion degrades and conflict and unrest become increasingly common. Technology development is high in the high-tech economy and sectors. The globally connected energy sector diversifies, with investments in both carbon-intensive fuels like coal and unconventional oil, but also low-carbon energy sources. Environmental policies focus on local issues around middle and high income areas” [77]
SSP5: Fossil-Fueled Development (Taking the Highway)
“This world places increasing faith in competitive markets, innovation and participatory societies to produce rapid technological progress and development of human capital as the path to sustainable development. Global markets are increasingly integrated. There are also strong investments in health, education, and institutions to enhance human and social capital. At the same time, the push for economic and social development is coupled with the exploitation of abundant fossil fuel resources and the adoption of resource and energy intensive lifestyles around the world. All these factors lead to rapid growth of the global economy, while global population peaks and declines in the 21st century. Local environmental problems like air pollution are successfully managed. There is faith in the ability to effectively manage social and ecological systems, including by geo-engineering if necessary.” [77]
In the second chapter, I use the SSP scenarios primarily for the purpose of using their coun- try level population and income projections till 2100. Those act as inputs to the coupled human-land system model when I make projection for future land use. We also construct future yield scenarios (denoted by f scenarios) which are independent of the SSP scenar- ios. In an earlier paper [74], SSP storylines for future agricultural yield and consumption patterns were constructed. However, in my model I do not use these constructions. I show results for all possible yield scenarios under each SSP scenario.