Adaptation, Climate Change

Key Concepts

Four key concepts are central to how the world's cities are adapting to climate change. Early climate change responses hinged on the not ion of reducing or offsetting human-caused greenhouse gases—an idea referred to as mitigation. However, some degree of climate change is now inevitable. The differential effect of climate change on natural and social systems is a function of three interrelated factors: sensitivity to biophysical change, the duration of their exposure to altered conditions (e.g., higher temperature, less rainfall), and the capacity to adapt to new conditions. Intense long-term exposure, extreme sensitivity, and low adaptive capacity will heighten vulnerability to harm, but some cities will be able to quickly “bounce back” from [Page 2]perturbations without suffering high death rates and/or long-term damage to infrastructure, life-sustaining systems, and social institutions. This capacity to withstand harm is termed resilience. Climate change adaptation seeks to forecast the likely impacts and then to figure out how best to modify cities to cope with these expected changes and their environmental, social, and financial consequences.

Likely Urban Effects of Climate Change

The Intergovernmental Panel on Climate Change has predicted that global warming will bring numerous biophysical changes to the world's cities, with knock-on environmental, social, political, and economic effects. For instance, with rising temperatures, heat waves in many places will become more frequent and severe, and urban “heat island” effects will kill many more people. Increased higher-intensity storm events and more rainfall will cause widespread flooding, with concomitant property and infrastructure damage. Frequent droughts will threaten food and water supplies. Increased insect-borne diseases will incapacitate many urban residents. Rising sea levels will devastate some low-lying coastal cities. Urban biodiversity will also likely decline markedly. However, these impacts will disproportionately affect cities in developing countries because of their predominantly warm climates, nature of existing built environments, scale and intensity of expected impacts, high costs of adaptation, and size of the affected populations. Large numbers of people will be displaced as climate refugees.

Numerous urban development practices will exacerbate these impacts, making adaptation more difficult. Unregulated clearing of vegetation increases stormwater run-off, worsening flooding and heightening landslide risk. Development on floodplains and coastlines increases vulnerability to flooding and coastal erosion, raising insurance premiums. Squatter settlements may be especially vulnerable because of unregulated construction methods, inadequate sanitation, their inappropriate location, and substandard infrastructure—flooding, landslides, fire, and epidemic disease will all take their toll. In addition, very high densities within many Asian, South American, and African megacities will expose more people to “heat island” effects. The challenge for urban professionals (e.g., planners, engineers, and healthcare practitioners, etc.) is how best to adapt cities to these and other expected changes.

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