Downscaling long term socio-economic scenarios at city scale: A case study on Paris

International audienceThe NEDUM-2D model is used to downscale four global socioeconomic scenarios at city scale and simulate the evolution of the Paris urban area between 1900 and 2100. It is based on a dynamic extension of the classical urban economic theory, to explain the spatial distribution of land and real estate values, dwelling surfaces, population density and buildings heights and density. A validation over the 1900-2010 period shows that the model reproduces available data and captures the main determinants of city shape evolution. From four global scenarios and additional local inputs, 32 local scenarios are created and analyzed. Main drivers of urban sprawl and climate and flood vulnerability appear to be local demographic growth and local policies; global factors, such as energy and transport prices, even including possible peak-oil and carbon taxes, have only a limited influence on them. Conversely, transport-related greenhouse gases emissions are mainly driven by global factors, namely vehicle efficiency changes, not by land use. As a consequence, very strict urban policies — including reconstruction — would become necessary to control emissions from urban transportation if technologies reveal unable to do so. These scenarios are a useful input for the design and assessment of mitigation and adaptation policies at local scale

Modélisation de l’effet d’une taxe sur la construction : le Versement pour Sous-Densité

National audienceLe Versement pour Sous Densité est une mesure innovante qui a fait son entrée dans la loi française depuis mi-2012 et qui vise à limiter l’étalement urbain en taxant les nouvelles constructions qui n’atteignent pas un Seuil minimal de densité. Ce papier, à travers l’utilisation d’un modèle transportusage des sols (NEDUM 2D), quantifie les impacts potentiels de cette politique sur l’Ile-de-France et examine les conditions qui lui permettraient de gagner en efficacité tout en limitant les coûts sociaux de sa mise en œuvre. Les résultats de cette étude montrent que si cet outil est correctement utilisé, il peut contribuer à limiter l’étalement urbain tout en augmentant les surfaces construites et donc en diminuant le niveau des prix immobiliers et des loyers. De façon surprenante, il s’agit donc d’une taxe sur la construction qui a pour résultat un accroissement des surfaces des logements. Cependant la mise en œuvre de cette politique est compliquée puisque le choix du Seuil minimal de densité en conditionne largement l’efficacité. Si celui-ci est trop bas le versement peut avoir des impacts contre-productifs comme une accélération de l’étalement urbain. De plus, en fonction de l’objectif privilégié (limitation de l’étalement urbain, accès aux transports en commun, …), le choix du seuil optimal variera

Viticulture and Adaptation to Climate Change

International audienceThe aim of this article is to lay out a series of issues of current concern to researchers in the social sciences, regarding the impact of climate change on the vine and wine sector. The challenge lies in evaluating the cost of transition from one system to another through an integration of the direct and indirect effects of climate change. This adaptation, whether reactive or anticipatory, combines technical and organisational innovations with localisation strategies and institutional changes. Such actions could either try to maintain the existing situation as much as possible or could try to bifurcate towards deep changes, entailing very different costs. Given the multitude of uncertainties at play, not to mention the necessity for continuous adaptation to an ever-changing climate, these costs are hard to quantify. This article will illustrate two sets of measures for wine cultivation adaptation: 'no regrets' measures, which offer immediate benefits, and 'reversible and flexible' measures, which limit the inertia of wine-cultivating systems. In spite of the challenges, what stands out is the evident re-enforcement resulting from the collaboration between researchers and political and economic actors. In the field of wine cultivation, these collaborations can follow two paths: the study of the diversity of existing wine-growing systems and genetic resources or the possibility of more radical technological and social experimentation

Systematizing and upscaling urban climate change mitigation

The question of what cities can contribute to mitigation and adapting to climate change is gaining traction among researchers and policy makers alike. However, while the field is rich with case studies, methods that provide rich data across municipalities and potentially at global scale remain underdeveloped, and comparative insights remain scarce. Here we summarize contributions to the focus issue on 'Systematizing and Upscaling Urban Climate Solutions', also drawing from presentations given at an accompanying conference in 2018. We highlight four core areas for systematizing and upscaling urban climate mitigation solutions. First, with more and better (big) data and associated machine learning methods, there is increasing potential to compare types of cities and leverage collective understanding. Second, while urban climate assessments have mostly emphasized urban planning, demand-side action as related to both behavioral change and modified social practices relevant to urban space deserve more academic attention and integration across a diverse set of social sciences. Third, climate mitigation would be intangible as a single objective at the urban scale, and measures and solutions that coordinate mitigation coherently with adaptation and broader sustainable development goals require explicit conceptualization and systematization. Forth, all insights should come together to develop governance frameworks that translate scientific exercises into concrete, realistic and organized action plans on the ground, for all cities

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Risques face au changement climatique : inégalités d'exposition et adaptation en milieu urbain

International audienc

Table ronde "Adaptation au changement climatique"

National audienc

Urban Modeling to Inform Climate Policies: A Case-Study on Paris Urban Area

International audienceBecause they are home to more than half of the world population, and because most of the world economic activity takes place within them, cities are at the forefront of global environmental issues. Land use planning, urban transport and housing policies are now recognized as major tools for the reduction of both greenhouse gases emissions and vulnerability to climate change impacts. So far, however, how to use these tools efficiently remains unclear. At least three main difficulties explain this, and play a key role in urban climate policies analysis. First, urban climate policies are also not developed or implemented in a vacuum; they interact with other policy goals, such as economic competitiveness or social issues, giving rise to both synergies and conflicts. Second, inertia is a key factor when designing optimal climate policies: structural modifications in cities occur slowly over a long time horizon. Some immediate actions are required if cities are to be adapted to a different climate or to help reduce greenhouse gases emissions within a few decades. Third, the evolution of a city depends on several external factors, on which local policy-makers do not generally have much influence: demographic, socio-economic, cultural, political and technological changes will play a major role. Models to help policy makers to deal with the associated uncertainties have been developed at CIRED. Vincent Viguie will illustrate the benefits of such tools with the application to the Paris area

Colloque de restitution de la Convention Services Climatiques

International audienc

Multi-criteria decision making in urban adaptation policies

International audienc