Cities are a crucial concern in dealing with climate change because an increasing proportion of the global population lives in urban areas. Meanwhile, because of human induced climate change, the frequency of extreme climate events is increasing worldwide. If we do nothing, current temperature extremes are projected to be exceeded across much of the Earth by 2100.
Anthropogenic emissions of greenhouse gases are altering our climate system, and more frequent and intense heat related disasters such as heatwaves, droughts, and wildfires have already led to increased mortality and morbidity.
Urban areas are generally warmer than adjacent rural and suburban areas. Urban heat islands are caused by use of materials such as metal, concrete, and brick that are highly efficient at absorbing and storing heat from the sun, a lack of vegetation limiting the cooling effect of evaporation from the soil and plant transpiration (evapotranspiration), and trapping of heat released by human activities (eg, transport, lighting, air conditioning) in “urban street canyons.”
The health risks of heat can be mitigated by reducing the accumulation of heat and applying cooling techniques. Possible strategies include altering individual behaviours, improving building design and city planning, and developing heat health warning systems.
Although cities have been centres of innovation and growth, and the engines of socioeconomic development, urban dwellers are vulnerable to the combined effects of urban heat islands and increasing heat from climate change. Research and policies need to focus on increasing climate ambition, curbing emissions, building resilience, and advancing science.