Cities, Settlements & Key Infrastructure - Frequently Asked Questions from Chapter 6 of the IPCC's 6th Assessment Report

Submitted by Geena Goodwin | published 23rd Jun 2022 | last updated 22nd Aug 2022
Photograph of busy street in the city of Kolkata, India.

Photograph of a busy street in the city of Kolkata, India. Image credit: Koushik Das on Unsplash


This material is an abridged version of the Frequently Asked Questions (FAQs) section of Chapter 6 of the 6th Assessment Report of the Intergovernmental Panel on Climate Change, Working Group 2: Impacts, Adaptation, and Vulnerability. The chapter considers the effect of climate change on cities, settlements, and key infrastructure.

Please access the original text (see 'Featured Download' in the right-hand column) for more detail, research purposes, full references, or to quote text.

Also see our related article on the full AR6 WGII report 'Summary for Policymakers'.


1. Why and how are cities, settlements, and different types of infrastructure especially vulnerable to the impacts of climate change?

Cities, settlements and infrastructure become vulnerable when investment decisions fail to take the risks of climate change fully into account. Such failures can result from a lack of understanding, competing priorities, a lack of finance or access to appropriate technology. Around the world, smaller cities and poorer populations are often most vulnerable and suffer the most over time, while large cities can register the greatest losses to individual events.

Billions of people live in towns and cities. Despite cities generating wealth, additional vulnerability to climate change is being created in urban areas every day. Demographic change, social and economic pressures and governance failures mean that increasing numbers of people who live in towns and cities are exposed to flooding, temperature extremes and water or food insecurity. This leads to an adaptation gap, where rich neighbourhoods can afford strategies to reduce vulnerability while poorer communities are unable to do the same. Climate change increases the variability and extremes of weather, exposing more people, businesses and buildings to floods and other events.

Settlements of up to 1 million people are the most rapidly expanding and also amongst the most vulnerable. These settlements often have limited community level organisation and might not have a dedicated local government. Coping with rapid population growth under conditions of climate change and constrained capacity is a major challenge.

For the poorest living in urban slums, informal settlements or renting across the city, lack of secure tenure and inadequate access to basic services compound vulnerability. But even the wealthy in large cities are not fully protected from climate change related shocks. Just like breaks in infrastructure between towns and rural settlements, big city infrastructure can be broken by even local landslides, floods or temperature events with consequences cascading across the city. Electricity blackouts are the most common and can affect water pumping, traffic regulation, streetlights as well as hospitals, schools and homes.

Focussing on vulnerability reduction is not easy. It requires joined up action across social and economic development sectors together with critical infrastructure planning. But there is considerable experience globally on what works and how to deliver reduced vulnerability for the urban poor and for cities as a whole. The challenge is to scale up this experience and accelerate its application to keep pace with climate change and address the adaptation gap.

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?

Climate change will interact with the changing physical environment in cities and settlements to create or exacerbate a range of risks. Rising temperatures and heat waves will cause human illness, 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.

The risks that cities and their residents face are influenced by both urban change and climate change. In a warming world, one key risk is heat waves in cities, that are likely to affect half of the future global urban population, and have 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 is greater for coastal settlements due to sea level rise and storm surges from tropical cyclones.

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.

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. They also vary 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.

3. What adaptation actions in human settlements can contribute to reducing climate risks and building resilience across building, neighbourhood, city, and global scales?

Settlements bring together many activities, so climate action will be most effective if it is integrated and collaborative. This requires (i) embedding information on climate change risks into decisions; (ii) building capacity of communities and institutions; (iii) using both nature-based and traditional engineering approaches; (iv) working in partnership with diverse local planning and community organisations; and, (v) sharing best practice with other settlements.

Settlements bring together people, buildings, economic activities and infrastructure services, and thus integrated, cross-sector, adaptation actions offer the best way to build resilience to climate change impacts.

Adaptation actions will be more effective if they are implemented in partnership with local communities, national governments, research institutions, and the private and third sector. Climate action should be mainstreamed into existing processes, including those that contribute to the UN Sustainable Development Goals (2015) and New Urban Agenda adopted at the UN Conference on Housing and Sustainable Urban Development (Habitat III) in 2016.

This integrated approach to adaptation in human settlements needs to be supported by various other actions, including potential co-benefits with carbon emissions reductions, public health, and ecosystem conservation goals.

  1. First, information on climate risks needs to be embedded into the architectural design, delivery and retrofitting of housing, transportation, spatial planning and infrastructure across neighbourhood and city scales.
    • E.g. making information on climate impacts widely available, updating design standards, and strengthening regulation to avoid development in high-risk locations.
  2. Second, the capacity of communities needs to be strengthened, especially amongst those in informal settlements, the poorest and other vulnerable groups including minorities, migrants, women, children, elderly, disabled, and people with  serious health conditions such as obesity.
    • E.g. raising awareness, incorporating communities into adaptation processes, and strengthening regulation, policies and provision of infrastructure services.
  3. Third, nature-based solutions should be integrated to work alongside traditional ‘grey’ or engineered infrastructure. Vegetation corridors, greenspace, wetlands and other green infrastructure can be woven into the built  environment to reduce heat and flood risks, whilst providing other benefits such as health and biodiversity.

Although even the largest city covers only a small area of the planet, all settlements are part of larger catchments from which people, water, food, energy, materials, and other resources support them. Actions within cities should be mindful of wider impacts and avoid displacing issues elsewhere.

4. How can actions that reduce climate risks in cities and settlements also help to reduce urban poverty, enhance economic performance, and contribute to climate mitigation?

If carefully planned, adaptation actions can reduce exposure to climate risk as well as reduce urban poverty, advance sustainable development and mitigate greenhouse gas emissions. When adaptation responses are equitable, and if a range of voices are heard in the planning process, the needs of the disadvantaged are more likely to be addressed and wider societal benefits can be maximized.

Urbanization is a global trend which is interacting with climate change to create complex risks in cities and settlements, especially for those that already have high levels of poverty, unemployment, housing informality, and backlogs of services. On top of reducing communities’ exposure to climate risk, adaptation actions can have benefits for reducing urban poverty and enhancing economic performance in ways that reduce inequality and advance sustainability goals. However, care needs to be taken to ensure climate adaptation planning and development of new infrastructure does not exacerbate inequality or negatively impact other sustainable development priorities.

In cities where growing numbers of people live in informal settlements, introducing risk-reducing physical infrastructure such as piped water, sanitation, drainage systems can enhance the quality of life of the community. At the same time, those measures can increase health outcomes and reduce urban inequalities by reducing exposure to flooding or heat impacts. For example, improvements to early warning systems can help people evacuate rapidly in case of storm surges or flooding.

Carefully planned nature-based solutions, such as public green space, improved urban drainage systems and storm water management, can deliver both health and development benefits. Many nature-based solutions entail bringing back plants and trees into cities which, as well as providing wellbeing benefits, also helps to reduce the concentration of heat-trapping greenhouse gases in the atmosphere.

When care is taken to ensure that adaptation responses are equitable, and that a range of voices are heard in planning, the needs of the disadvantaged are more likely to be addressed. In some cities, there is evidence of emerging trade-offs associated with climate adaptation actions where sea walls and temporary flood barriers were erected in economically valuable areas and not is less well-off areas. Going forward, it is important to ensure that vulnerable groups’ needs are carefully considered both in terms of climate and other risks as this has not been sufficiently done in the past.

5. What policy tools, governance strategies, and financing arrangements can enable more inclusive and effective climate adaptation in cities and settlements?

Inclusive and effective climate adaptation requires efforts are all levels of governance, including the public sector, the private sector, the third sector, communities and intermediaries such as universities or think tanks. It requires action fit for the diverse conditions in which it is needed. Collaborative dialogues can help to map both adaptation opportunities and potential negative impacts.

There is no one-size-fits-all approach to ensure that climate adaptation efforts have positive results and include the concerns of everyone affected. Cities and local communities are diverse, and thus they have diverse perspectives on what responses to prioritize. Moreover, adaptation efforts may impact people's lives in very different ways. Planning and decision-making must respond to marginalized voices and future generations (including children and youth).

Efforts to adapt to climate change can be incremental, reformist, or transformational, depending on the scale of the change required. Incremental action may address specific climate impacts in a given place, but do not challenge the social and political institutions that prevent people from bouncing back better. Reformist action may address some of the social and institutional drivers of exposure and vulnerability, but without addressing the underlying socio-economic structures that drive differential forms of exposure. Transformative action involves fundamental changes in political and socio-economic systems, oriented towards addressing vulnerability drivers (e.g., socio-economic inequalities, consumption cultures). All forms of adaptation are relevant to deliver resilient futures because of the variability of conditions in which adaptation action is needed.

Local and regional governments play an essential role in delivering action suited to local conditions in cities and settlements. Potential strategies range from land use management, building codes, critical infrastructure designs and community development actions, to different legal, financial, participatory decision-making and robust monitoring and evaluation arrangements. NGOs or third sector organisations can also play a coordinating role by building dialogues across governments, the private sectors, and communities. Local action tends to falter without the support of national governments as they are often facilitators of resources and finance.

Private actors can also drive adaptation action. However, private actors tend to join adaptation projects when there is an expectation of large profits, such as in interventions that increase real estate value. For instance, private-led adaptation can lead to ‘gentrification’ whereby low-income populations are relocated from urban centres and safer settlements. New institutional models such as public-private partnerships respond to the shortcomings of both the public and private sectors.

Adaptation action needs multiple approaches. For example, both actions that depend on dialogues between multiple actors (e.g., urban planning and zoning) and action that follows strong determination and leadership (e.g., declarations of emergency and target commitments). The growth of adaptation capacities, fostering dialogues, empowered communities, multi-scalar assessments, and foresight within current institutions can support effective and inclusive adaptation action that is also sustained in the long term.

Further resources