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16 options + winter 2016/2017 www.iiasa.ac.at “There are actually an infinite number of pathways that the future could take,” explains IIASA Energy Program Director Keywan Riahi, one of the leaders of the SSP development, a multi‑year process that involved an interdisciplinary group of international researchers. “What the SSPs do is organize these into representative pathways, which researchers from many fields can draw upon in order to make consistent assumptions in their research.” The SSPs provide a common basis for climate modeling, impact, and policy response studies and allow researchers to incorporate variables related to the human factors in climate change. These factors could spell the difference between humanity’s ability to slow or stop the rise in greenhouse gases that is driving climate change, and play a major role in how well people will be able to adapt to the climate change that does occur. But in the past, climate research has had trouble accounting for these human factors, with many models relying on simple assumptions, which likely did not match those made in other studies. Brian O’Neill, a researcher at the National Center for Atmospheric Research, led the development of the SSP narratives. He  says, “The reason that we needed the SSPs is that for most questions about climate change, the answer is generally, ‘It depends.’ Usually  it depends on two things: how much the climate will change, and the societal conditions. So in order to do research on climate change futures we need to look at futures in which we get a lot of climate change or not as much, and also alternative futures for how society might turn out.” In the lead‑up to the latest report of the Intergovernmental Panel on Climate Change (IPCC), researchers had begun turning their focus from the physical science of climate change to how climate change will impact people, what makes people vulnerable to climate change, and how they can adapt to it. O’Neill says, “A world that has a lot of people in poverty, is not that well educated, has health systems that don’t work well, has poor governance, that’s a world where climate change impacts are going to be a lot more serious than one in which everyone is well‑educated, institutions function well, and health systems work.” How to make an SSP Researchers sometimes describe scenarios as “stories about the future.” But they are quick to point out that the SSPs are not fairy tales. O’Neill says, “The basic distinction is that these are stories that are grounded in scholarship on different aspects of society. They are based on our understanding of how elements of society work, and how they relate to each other— elements like economics, demography, urbanization, governance, and education. The goal here is to develop plausible alternative stories about future development pathways.” The process of SSP development involved researchers from around the world, in a series of meetings and interactions that spanned three years. They started with the narratives, a group of 60–70 researchers coming up with a set of realistic storylines that included insight from many different fields, from public health to education to economic development. “We wanted to both take advantage of as many different ideas from as many different perspectives as we could, and also to make sure that the narratives were as useful to as many different research communities as possible,” says O’Neill. After the narratives were defined, researchers turned to numbers. Through an iterative process, groups of researchers collaborated to produce quantitative projections for a number of variables that fit each of the five SSP narratives. The process started with population projections, which were led by IIASA researchers Samir KC and Wolfgang Lutz. “Population came first because it is needed as a multiplier to calculate demand in the future, for example to calculate how much energy will be required, how much water, and many other things,” says KC. “At  the same time when there are adverse effects of climate change, the population determines how many people are impacted as well as who and where. For example the air pollution group would need population to see how air pollution will affect the population.” 1960 1980 2000 2020 2040 2060 2080 2100 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 Population & Education 1960 1980 2000 2020 2040 2060 2080 2100 0 20 40 60 80 100 Urbanization 1960 1980 2000 0 200 400 600 800 1000 1200 Other Major Studies  IPCC SRES scenario range AR5 WGIII scenarios Interquartile range 100% (full) range  Grubler et al. range SSP Projections —SSP markers —SSP ranges (GDP) SSP5 SSP4 SSP3 SSP2 SSP1 2000 2020 2040 2060 2080 2100 0.00 0.05 0.10 0.15 0.20 Illiterate Share (SSP markers) DIGGING INTO THE DATA The SSPs each include projections for a variety of socioeconomic factors, such as population and education, urbanization, and economic development. These factors are vital for projections of greenhouse gas emissions—indeed, research shows that in some of the SSPs, the world would not be able to achieve climate  targets no matter how hard we try.