Author | Esther FuldauerThis past month of June has seen a new episode of scorching heat, as a bubble of hot air was drawn northward by winds from North Africa. Cities across Europe saw how temperatures were driven up to 45ºC.These episodes of extreme weather are only going to become more frequent because of the effects of climate change. People in cities suffer the most, with pollution and heat produced by the concentration of human activities. Dark bare surfaces reflect the sun, and asphalt and dark roofs absorb heat and radiate it out again overnight. This phenomenon is called the Urban Heat Island Effect (UHIE), which can raise temperatures several degrees higher than in surrounding rural areas.
What are the strategies cities are taking to combat the urban heat island effect?With more people moving to cities and rapid urban development, heat islands can get even worse. Unfortunately, with rapid urbanization, green space is often an afterthought. Also, in old cities that built their infrastructure before anyone was aware of climate change, heatwaves are becoming even more dangerous. What can cities do to remedy this?
- 'Lightening' streets: Black asphalt streets, parking lots, and dark roofs can be covered with a more reflective gray coating. These changes drop urban air temperatures dramatically.
- Greening cities with gardens: Vegetation is a proven way to help lower temperatures, and cities in Europe have set targets to increase it. Paris has a target of 100,000ha, green roofs, and walls being part of the goal.
- Urban forest: Trees are high modifiers of urban microclimate cooling through shade and transpiration. Leaves reflect sunlight lowering the temperature in pedestrian areas protecting people from the sun with their shadow. They are also great at trapping humidity and rainwater.
- Green roofs: Plants and soils evaporate moisture cooling the air around a building and can reduce air conditioning use during periods of higher temperatures.
- Wind corridors: Air needs to flow between buildings so that pollution and heat don't concentrate in lower places. This is the case of the city of Stuttgart, which sits in a river basin, surrounded by steep hills that can trap both heat and polluted air over the region. They made their streets wider and lined them up with trees to direct the air currents.
- Water: Mist showers, fountains and reflective pools all bring the temperature down.