Regulating the damaged thermostat of the cities-Status, impacts and mitigation challenges

Increase of the urban ambient temperature caused by local and global phenomena is probably the more incontestable incident of climate change. Urban warming has a very significant impact on human life increasing the energy consumption, deteriorating the comfort levels, increasing the pollution concentration, threatening the human health and affecting the urban economy. Mitigation technologies aiming to countermeasure the impact of the phenomenon are rapidly developed and applied in real scale projects. The present paper aims to present in a critical and comprehensive way the recent scientific knowledge on the causes of urban warming and also stress the main problems and inconsistencies concerning the experimental and the theoretical findings and analysis. In parallel, it classifies and summarizes the main knowledge on the energy, environmental, health and economic impacts of urban warming. Quantitative information on the energy penalties, mortality rates and environmental degradation induced by urban warming is presented. Finally, it presents the main developments regarding urban mitigation techniques and technologies and in particular, urban greenery and planted roofs, cool pavements, cool roofs and increase of the urban albedo, decrease of the anthropogenic heat and use of the ground as a sink for heat dissipation.