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Since the early 1970s, scientists have used computer-basedquantitative scenario models of the world. For example, theWorld3 model (a systems dynamics model) was used tocreate the 12 scenarios of the “Limits to Growth” study in1972. 110 The model focused on capturing the inter-linkagesand feedbacks among key variables of interest: population,natural resources consumption, food availability,production and standard of living. The technologyoptimists’ response to this study was “Energy in a FiniteWorld” published in 1981 which provided a scientifictechnocraticpicture of how a sustainable world energysystem could be achieved from 1980 to 2030. 111 It wassupported by the MESSAGE model which focused on adetailed presentation of the technology system rather thanthe inter-linkages with other sectors, even though thestudy looked at a very wide range of sustainabledevelopment issues. The World3 and MESSAGE modelframeworks have greatly influenced global scenario modeldevelopment since. One group of models focuses oncapturing inter-linkages (e.g., energy – water) at theexpense of a detailed presentation of subsystems (e.g., theenergy technology system), whereas the other groupfocuses on a detailed modelling of the subsystemsthemselves which are only “soft-linked”. The twoapproaches highlight the two kinds of fundamental choicesthat scientists have in building global scenario models thatcan support the full range of SDGs - either soft-linkingexisting thematic models for the various SDGs, or buildingcomprehensive models with a focus on capturing allimportant inter-linkages and feedbacks but with lesssectoral/thematic detail. Pragmatically, this means that wewill always need various types of models to make sense ofour future policy choices to achieve the SDGs by 2030.Most likely there will not be one “best model” or modellingapproach.Generally speaking, global scenario models aim to providethe simplest representation of the highly complex SDGsystem that can replicate the essential dynamic elements ofthe system, in order to support decision-making for specificquestions. Different questions require different models.Many such models exist and aim to answer key questionsrelated to various parts of sustainable development. Areview of prominent sustainable development scenariosand the associated model frameworks was prepared inpreparation for the Rio+20 conference. 116 Lesson learntfrom these sustainable development scenarios were alsosummarized in the form of brief stories or narratives in thePrototype Global Sustainable Development Report 2014. 69One important finding was that the scenario modelcommunity remains fragmented into different schools ofthought and with little to no integration between efforts atthe national and global levels. Hence, the prototype report49proposed a UN SDG scenario modellers forum to bringthese communities together.2.3.1. Sustainable development scenarios for Rio+20 in2012Table 2-3 provides an overview of the SDG-related targetsconsidered in sustainable development scenarios forRio+20 in 2012. 69 The broad picture shows a selective, yetfairly good coverage of most of the SDGs. While none of thescenario models captures the full range of the SDGs, whenput together they provide a glimpse of SDG scenarios. Itshould also be noted that these global scenarios areoptimistic views that do not consider important constraintsat the local and national levels.According to Table 2-3, the coverage of SDG areas is neithercomplete nor uniform. Energy and water-related targetswere considered most often, highlighting the core areasaround which the models considered here tend to be built.Scenario targets related to energy are often expressed inabsolute value, which differs from those in the SDGs, whichare expressed as relative values or in reference to abaseline. Health is weakly covered. No scenarioincorporated explicit gender targets. No explicitindustrialization-related targets (or employment-relatedtargets) were considered. While two models consideredtargets related to inequality between countries, withincountryinequality does not appear in the targetsconsidered by any scenario. The urban dimension wasconsidered only in relation to air pollution. While some ofthe targets in Table 2-3 can be related to the area ofsustainable consumption and production, none refersexplicitly to it or to targets included under SDG12; this mayreflect the fact that SCP-related actions and targets areconsidered by modellers more as a means to achieve theother goals, than as a goal in themselves (industrializationperhaps falls in this category as well, as a strategy not anexplicit goal). There are no targets related to SDG16 onpeaceful and inclusive societies. Lastly, means ofimplementation, which are considered under SDG17 as wellas under other SDGs, do not figure as explicit targets inthese scenarios, as tends to be the practice.2.3.2. SDG coverage of the global scenario modelsRio+20 in 2012 and the adoption of the SDGs by theintergovernmental OWG in 2014 have spurred the interestin many new scenario and model developments, with theobjective to cover a significant portion of the SDGs andultimately even the whole range. This includes newpartnerships of established global change modellinggroups, such as the “The World in 2050 Project”, extensionsof macro-economic MDG models, plans by the BalatonGroup, plans for new broader scenarios for UNEP’s GEOreport and the International Resource Panel, as well as