Editing IPCC:AR6/WGII/Chapter-6 (section)

=== FAQ 6.2 | What are the key climate risks faced by cities, settlements and vulnerable populations today, and how will these risks change in a mid-century (2050) 2°C warmer world? ===

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''Climate change will interact with the changing physical environment in cities and settlements to create or exacerbate a range of risks. Rising temperatures and heatwaves will cause human illness and morbidity, as well as infrastructure degradation and failures, while heavy rainfall and sea level rise will worsen flooding. Low-income groups and other vulnerable populations will be affected most severely because of where they live and their limited ability to cope with these stresses.''

Cities and settlements are constantly changing. Their populations grow and shrink, economic activities expand or decline, and political priorities shift. The risks that cities and their residents face are influenced by both urban change and climate change. The seriousness of these risks into the 21st Century will be shaped by the interactions between drivers of change including population growth, economic development and land use change.

In a warming world, increasing air temperature makes the urban heat island effect in cities worse. One key risk is heatwaves in cities that are ''likely'' to affect half of the future global urban population, with negative impacts on human health and economic productivity. Heat and built infrastructure such as streets and houses interact with each other and magnify risks in cities. For instance, higher urban temperatures can cause infrastructure to overheat and fail, as well as increase the concentration of harmful air pollutants such as ozone.

The density of roads and buildings in urban areas increases the area of impermeable surfaces, which interact with more frequent heavy precipitation events to increase the risk of urban flooding. This risk of flooding is greater for coastal settlements due to sea level rise and storm surges from tropical cyclones. Coastal inundation in the Miami-Dade region in Florida, USA, is estimated to have caused over USD 465 million in lost real estate value between 2005 and 2016, and it is ''likely'' that coastal flood risks in the region beyond 2050 will increase without adaptation to climate change.

Within cities, different groups of people can face different risks. Many low-income residents live in informal settlements alongside coasts or rivers, which greatly heightens exposure and vulnerability to climate-driven hazards. In urban areas in Ghana, for example, risks from urban flooding can compound health risks, and have resulted in outbreaks of malaria, typhoid and cholera. Those outbreaks have been shown to disproportionately affect poorer communities.

Severe risks in cities and settlements also arise from reduced water availability. As urban areas grow, the amount of water required to meet basic needs of people and industries increases. When increased demand is combined with water scarcity from lower rainfall due to climate change, water resource management becomes a critical issue. Low-income groups already face major challenges in accessing water, and the situation is ''likely'' to worsen due to growing conflicts over scarce resources, increasing water prices and diminishing infrastructure provisions in ever-expanding informal settlements.

These key risks already differ greatly between cities, and between different groups of people in the same city. By 2050, these discrepancies are likely to be even more apparent. Cities with limited financial resources, regulatory authority and technical capacities are less equipped to respond to climate change. People who already have fewer resources and constrained opportunities face higher levels of risk because of their vulnerability. As a result of this, key risks vary not only over time as climate change is felt more strongly, but also over space, between cities exposed to different hazards and with different abilities to adapt, and between social groups, meaning between people who are more or less affected and able to cope.

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