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Scenarios are widely used for long-term climate and energy analysis. However, in the great majority of studies with a handful of scenarios or scenario categories, both scenario developers and users capture only a subset of future uncertainties. We propose three focal points for reinvigorating the scenario technique to expand uncertainty consideration: (1) to ensure that scenario developers embrace an increased space of multidimensional uncertainties, (2) to facilitate the process of scenario users capturing this space, and (3) to evaluate and iteratively revise the improvement progress. If these focal points are adopted, scenario studies in climate and energy analysis shall not simply stop after producing scenarios, but shall continue with techniques to facilitate elicitation of user-specific insights, as well as evaluation of both scenarios and scenario techniques. [ABSTRACT FROM AUTHOR]

Co-benefits of climate policies: a potential keystone of climate negotiations? This paper analyzes the challenges related to the assessment of co-benefits of climate policies underpinned by the implementation of multi-objective policies which seek synergies between climate policies and other development objectives (poverty alleviation, employment, health etc.). The analysis highlights the increasing interest in co-benefits in the latest 5th IPCC report, in particular by integrated models. Nevertheless, the quantified evaluation of co-benefits is still confronted to several methodological limitations which reduce the scope of co-benefits, particularly at the global level. In a growing context of climate-development approaches in climate negotiations, this article insists on the need to also assess cobenefits of other policies which induce a significant part of GHG emissions. Considering climate policies focused only on Greehouse Gases emissions reduction limits the range of policy instruments to carbon taxation, tradable carbon emissions permits or dedicated mitigation and adaptation funds. This also hinders the integration of climate objectives in non-climate policies. Analyzing impacts of development policies on Green Gases emissions in the form of co-benefits requires to broaden the range of policy instruments and to take into account other drivers of emissions such as land dynamics. Including these mechanisms in integrated models therefore represents new scientific frontiers for integrated models in the coming years. [ABSTRACT FROM AUTHOR]

The scientific community is now developing a new set of scenarios, referred to as Shared Socio-economic Pathways (SSPs) that will be contrasted along two axes: challenges to mitigation, and challenges to adaptation. This paper proposes a methodology to develop SSPs with a 'backwards' approach based on (i) an a priori identification of potential drivers of mitigation and adaptation challenges; (ii) a modelling exercise to transform these drivers into a large set of scenarios; (iii) an a posteriori selection of a few SSPs among these scenarios using statistical cluster-finding algorithms. This backwards approach could help inform the development of SSPs to ensure the storylines focus on the driving forces most relevant to distinguishing between the SSPs. In this illustrative analysis, we find that energy sobriety, equity and convergence prove most important towards explaining future difference in challenges to adaptation and mitigation. The results also demonstrate the difficulty in finding explanatory drivers for a middle scenario (SSP2). We argue that methodologies such as that used here are useful for broad questions such as the definition of SSPs, and could also be applied to any specific decisions faced by decision-makers in the field of climate change. [ABSTRACT FROM AUTHOR]

Abstract: Political attention has increasingly focused on limiting warming to 2°C. However, there is no consensus on both questions “Is the 2°C target achievable?” and “What should be done with this target that becomes increasingly difficult to achieve?”. This paper aims at disentangling the points of deep uncertainty underlying this absence on consensus. It first gives simple visualizations of the challenge posed by the 2°C target and shows how key assumptions (on the points of deep uncertainty) influence the answer to the target achievability question. It then proposes an “uncertainties and decisions tree”, linking different beliefs on climate change, the achievability of different policies, and current international policy dynamics to various options to move forward on climate change. [Copyright &y& Elsevier]