Urban society is more and more complex: new sets of social relations, high degrees of connectivity and competitiveness objectives. If urbanity is made of resources accumulation, power concentration, territorial attractiveness and cultural life; it is also a new vector of risk, particularly due to concentration issue. External hazards, especially those due to climate change, become more significant when occurring in an urban environment: hazards are often magnified by urbanity. Meanwhile, risks and damages are less and less accepted by populations and economic activities. When cities are supposed to embody security and development, the latest events (heat waves, Xynthia) have highlighted their weaknesses and questioned the way risks are anticipated and managed.
These facts have led local authorities to the expression of new needs to improve city resilience. Defined as “the ability of a city to absorb disturbance and recover its functions after a disturbance” (Lhomme et al., 2010), urban resilience has become a new paradigm in risk management methods enabling to tackle the challenges identified above. Resilis project aims precisely at the development of those innovative solutions dedicated to improving urban resilience.
In this project, one of the main objectives is dedicated to the impacts of climate change on urban areas. Indeed, weather conditions are a stress factor for buildings and infrastructures. They are usually adapted to climate they are built in (e.g. traditional housing in warm countries), but modifications of climate standards can affect the comfort of both external and internal living places. The IPCC reported a global mean temperature increase about 1.1°C to 6.4 °C before the end of this centaury which could modify the global mean temperature balance on the Earth. More locally, this increase could be more important in dense cities in particular. So, an idea to control the radiative balance in cities would be to increase the albedo since it is an important component in the energy balance. The energy redistribution could be done via the use of reflected wall paintings or by changing the surface colorimetry. The consequences would be important to reduce the effects of urban heat island: consequences on comfort, sanitations risks, heat waves, cooling need reductions, etc….
The definition of resilience indicators needs to be done to characterise potential evolutions of climate in terms of air temperature (heating and cooling degree days), solar radiation and number of hours when the temperature is above 28°C. Therefore, structural trends to adopt in French cities facing global warming and its impacts in terms of drifts in energy consumptions in buildings and comfort in outside public spaces will be characterised for climate simulations (2050-2100) according to the scenarios B2 (moderate) and A2 (worse case) from the IPCC Special Report of Emissions Scenarios.
The main outcome will be the development of methods, tools or “guide of good practices” addressed to local authorities, networks operators, populations and all stakeholders. On the long term, the objective is to develop tools to prepare, adapt, and conceive technical and social systems so they are able to cope with, absorb and recover from climate change disturbances.