The current urban population is approximately 4.4 billion people globally. About 3.4 billion people currently live in urban centers in what the United Nations (UN) terms ‘‘less developed regions.’’

Many informal settlements are ill prepared for climate change and face particularly high risks of floods and landslides as a result of poor-quality buildings and a lack of infrastructure to prevent flooding, withstand heavy storms, and cope with heat waves. In the absence of more effective policies, most of the world’s growth in urban population will be accommodated in informal settlements.

This paper considers how to build resilience to the impacts of climate change in informal settlements. It focuses on informal settlements in cities in low- and middle-income countries and how these concentrate at-risk populations. This paper also reviews what is being done to address climate resilience in informal settlements. In particular, community- and city-government-led measures to upgrade settlements can enhance resilience to climate-change risks and serve vulnerable groups. It also discusses how the barriers to greater scale and effectiveness can be overcome, including with synergies with the Sustainable Development Goals.