Future cities in a warming world

More than half the global population are already urban, and the UN and other organisations expect this share to rise in future. However, some researchers argue that the future of cities is far from assured. Cities are not only responsible for 70% or more of the world's CO2 emissions, but because of their dense concentration of physical assets and populations, are also more vulnerable than other areas to climate change. This paper attempts to resolve this controversy by first looking at how cities would fare in a world with average global surface temperatures 4 °C above pre-industrial levels. It then looks at possible responses, either by mitigation or adaptation, to the threat such increases would entail. Regardless of the mix of adaptation and mitigation cities adopt in response to climate change, the paper argues that peak urbanism will occur over the next few decades. This fall in the urban share of global population will be driven by the rise in biophysical hazards in cities if the response is mainly adaptation, and by the declining attraction of cities (and possibly the rising attraction of rural areas) if serious mitigation is implemented.