Evaluating the impacts of greening scenarios on thermal comfort and energy and water consumptions for adapting Paris city to climate change

Recent climate projections predict an amplification of global warming and more frequent extreme events such as heat waves. Therefore, the adaptation of cities to counterbalance these adverse changes is urgent. Among available adaptation strategies, urban greening is a measure that is frequently encouraged to improve thermal comfort or energy demand, but whose impacts are not well known at the scale of cities. In this study we evaluate the effects of various urban greening scenarios based on urban climate simulations across the Paris area. The modelling relies on the Town Energy Balance model. The scenarios tested consist of an increase in ground-based vegetation or an implementation of green roofs on compatible buildings, or the two combined. Results show that increasing the ground cover has a stronger cooling impact than implementing green roofs on street temperatures, and even more so when the greening rate and the proportion of trees are important. Green roofs are however the most effective way to reduce energy consumption, not only in summer but also on an annual basis. The effects the various greening measures may have over different seasons is finally addressed in order to draw up a comprehensive inventory of the climatic impacts of such strategies.