The SSPs define the high-level evolution of human and natural societies over the 21st century through a narrative storyline and a set of quantified measures under the assumption of no significant climate feedback. In the absence of climate policies, the SSPs may lead to different climate forcing and to different changes in climate. The primary objective of the SSPs is to provide sufficient information and context for defining development pathways that can be used as a starting point for impacts, adaptation, and mitigation analyses.
Five SSPs have been designated to span a broad range of socioeconomic challenges to mitigation and challenges to adaptation. The SSPs are intended to be single pathways that are representative of the types of socioeconomic pathways that could occupy particular domains within the overall space. Each has implications for the health risks of climate change and the capacity of societies to adapt to and manage those risks.
SSP 1: Sustainability. This development pathway includes sustained efforts to achieve development goals, including rapid development of low-income countries, a reduction of inequality globally and nationally, high levels of education, governance and institutions facilitating development goals, and achievement of the Millennium Development Goals within the next decade or so. Reducing and managing the health risks of climate change makes significant progress as educated populations gain access to safe water, improved sanitation, medical care, and other factors that reduce vulnerability to climate change.
SSP2: Dynamics as Usual. This development pathway experiences trends typical of recent decades, with some progress towards achieving development goals, uneven progress in development of low-income countries, educational investments not high enough to rapidly slow population growth, delay in achievement of the Millennium Development Goals by several decades. Current health trends would continue, with advancements in access to safe water, improved sanitation, medical care, and other factors that reduce vulnerability to climate change in some countries, but with little progress in others. Without additional interventions, the health burdens of climate change increase in countries left behind in development, and are reduced in those making progress.
SSP3: Fragmentation. The world is separated into regions characterized by extreme poverty, pockets of moderate wealth, and many countries struggling to maintain living standards for strongly growing populations. Governance and institutions are relative weak, with poor cooperation. In this pathway, there is little progress in achieving the Millennium Development Goals, with growing numbers of people without access to safe water, improved sanitation, and medical care, and with increasing burdens of climate-sensitive health outcomes.
SSP4: Unequal World. In this pathway, there is a relatively small, rich global elite, with a large group of poor countries and populations. Governance and institutions are effective for and controlled by the elite, but are ineffective for most of the world population. Low educational levels, high burdens of climate-sensitive health outcomes, limited access to safe water, improved sanitation, and medical care, and other factors result in a world with high vulnerability to climate change.
SSP5: Conventional Development. This pathway stresses development oriented toward economic growth as the solution to social and economic problems. Challenges to adaptation are reduced through eradication of poverty and universal access to education, safe water, improved sanitation, and medical, resulting in attainment of the Millennium Development Goals by mid-century. The resulting increase in human and social capacity in low-income countries and parallel improvements in governance and institutions reduces many of the infectious disease risks of climate change.