Tue / 11.02. @ 11:30
An overview of the main characteristics of five Shared Socioeconomic Pathways (SSPs) and related scenarios of Integrated Assessment Models (IAM scenarios) will be presented as one of the main building blocks of the “new scenario framework”.The process of developing the SSPs and IAM scenarios involved five key steps. First, the narratives were designed which provide the fundamental underlying logic for each SSP. Then, the narratives were translated into a common set of “input tables”, describing in qualitative terms the main SSP characteristics and scenario assumptions for, i.e., energy demand, fossil energy supply, energy conversion technologies and land-use change dynamics. In parallel, the narratives were translated into quantitative projections for main socioeconomic drivers, i.e., population, economic activity and urbanization. In the next step, six different IAMs are employed to translate the socioeconomic conditions of the SSPs into estimates of future energy use characteristics and greenhouse gas emissions. A total of 24 baseline scenarios were created by the different models simulating different SSPs and portraying a range of outcomes in the absence of additional climate policy (baseline SSP scenarios), though not all IAMs ran all SSPs. Finally, the six IAMs were employed to develop mitigation SSP scenarios examining how different levels of climate mitigation and adaptation would fit into the future described by each SSP. To model this, they used Shared Policy Assumptions (SPAs) around how quickly international collaboration on climate policy could occur and coverage of land use emissions within each SSP. Mitigation targets were defined by radiative forcing levels analogous to the previously developed Represented Contraction Pathways - RCPs (2.6, 4.5, 6.0 W/m2) + 1.9 W/m2 + 3.4 W/m2. Hence, a total of 81 mitigation scenarios were created, with RCP1.9 group representing different pathways by which global temperature rise could be limited to 1.5°C.All 1.5°C pathways share certain features – by mid-century, CO2 emissions falling to net-zero with renewables supplying 70 percent to 85 percent of electricity and unabated coal use being largely phased out. Also, all 1.5°C pathways with limited or no overshoot project the use of carbon dioxide removal (CDR) on the order of 100–1000 GtCO2 over the 21st century. CDR is necessary for both moving to net-zero emissions and for producing net-negative emissions to compensate for any overshoot of 1.5˚C. Still, it must be noted that CDR deployed at such a scale is unproven, and is a major risk to our ability to limit warming to 1.5˚C. The sector coupling and carbon-neutral energy storage technologies which are hot topics in the energy planning and modeling science could shed a different light on the need for CDR in 1.5°C pathways, couldn’t they?