The project aims, first, at evaluating the level of urban structure vulnerability (in terms of comfort losses ) and energy demand sensitivity (in terms of air cooling). due to heat waves

The second objective is the evaluation of potential adaptation strategies efficiency in response to these vulnerabilities.

For both issues, we will develop a systemic analysis based on strong interdisciplinary exchanges between climatologists, experts of the urban climate, building experts, urban planners and economists. In the conventional approach developed to study socio-economic impacts of global change, social sciences are often considered as “end-of-pipe” disciplines, only supposed to interpret results from natural sciences from a social-science standpoint-of-view. This project, on the opposite, aims at making natural and social scientists work together on a common issue. This is to be done through:

- project rationales and objectives that have been developed from the beginning by an interdisciplinary team;

- the use of modelling frameworks as a “tool” that supports the communication across different disciplines.

Since the systemic approach will be develop through a core of models, an important effort will concern the improvement of our models in order to make them match together. For example, new modules will be implemented in actual urban-weather model TEB in order to be able to assess indoor and outdoor thermal comfort or evaluate how adaptation strategies are efficient (air conditioning, greening of urban areas). Nevertheless, it is important to mention that the project does not aim at being as innovative in each discipline as a specific project could be in a single discipline, but rather at investigating a complex problem by coupling the tools (possibly in a simplified version) of each discipline within a systemic framework.

In the end, the project will integrate the results of a climate model, an urban-weather model, and a coupled housing-transportation model, into a unique investigation framework. The work program is built as a systematic sensitivity analysis, according to three main stages:

- First, we will carry out urban climate simulation for a given city – Paris – under meteorological conditions of large-scale heat waves. A large range of heat wave events, varying in intensity and duration, will be tested in order to develop a heat-wave seriousness indicator, that links large-scale climate information to local seriousness of the event (defined from comfort indicators and energy consumption at city- and neighbourhood-scale). The innovation is that this indicator will take into account the specifics of urban weather.

- Second, we will carry out urban climate simulations for a given heat wave – the 2003 event in Paris – and a large range of idealized stylized cities based on simple socio-economic scenarios taking into account population change, economic development, and various urban development strategies (including urban planning strategies to adapt to climate change and to mitigate future emissions, e.g., compact city, city with parks, etc.). Other scenarios such as the sprawling of the residential areas at the rim of the idealized stylized cities will also be considered so as to take into account the inertia of the decision mechanisms and their potential impact on the vulnerability of the built environment. Scenarios on the expected quality of buildings will be introduced. This sensitivity study will make possible to determine a heat-wave urban-vulnerability indicator, that links the characteristics of urban morphology to the vulnerability to a 2003-like event.

- Finally, we will compare the economic costs of several adaptation strategies (e.g. influence on housing prices (including quality index) or transportation demand) and the benefits (in terms of comfort and energy consumption), to assess the overall efficiency of these adaptation strategies.