Climate change adaptation is the process of adjusting to the effects of climate change. These can be both current or expected impacts. Adaptation aims to moderate or avoid harm for people. It also aims to exploit opportunities. Humans may also intervene to help adjustment for natural systems. There are many adaptation strategies or options. They can help manage impacts and risks to people and nature. We can classify adaptation actions in four ways. These are infrastructural and technological; institutional; behavioural and cultural; and nature-based options.: fig. 16.5 The need for adaptation varies from place to place. It depends on the risk to human or ecological systems. Adaptation is particularly important in developing countries. This is because developing countries are most vulnerable to climate change. So they bear the brunt of the effects of climate change. Adaptation needs are high for food and water. They are high for other sectors that are important for economic output, jobs and incomes.
Adaptation planning is important to help countries manage climate risks. Plans, policies or strategies are in place in more than 70% of countries. Other levels of government like cities and provinces also use adaptation planning. So do economic sectors. Developing countries can receive international funding to help develop national adaptation plans. This is important to help them implement more adaptation. The adaptation carried out so far is not enough to manage risks at current levels of climate change.: 20  : 130  And adaptation must also anticipate future risks of climate change. The costs of climate change adaptation are likely to cost billions of dollars a year for the coming decades. In many cases the cost will be less than the damage that it avoids.

Definition
The IPCC defines climate change adaptation in this way:

"In human systems, as the process of adjustment to actual or expected climate and its effects in order to moderate harm or take advantage of beneficial opportunities.": 5 
"In natural systems, adaptation is the process of adjustment to actual climate and its effects; human intervention may facilitate this.": 5 Adaptation actions can be incremental  or transformative. Incremental actions  are actions that aim to maintain the essence and integrity of a system. Transformative actions are actions that change the fundamental attributes of a system in response to climate change and its impacts.

Understanding the need
Research on climate change adaptation has been ongoing since the 1990s. The number and variety of subtopics has greatly increased since then. Adaptation has become an established policy area in the 2010s and since the Paris agreement, and an important topic for policy research.: 167

Climate change impacts research
Scientific research into climate change adaptation generally starts with analyses of the likely effects of climate change on people, ecosystems and the environment. These impacts cover its effects on lives, livelihoods, health and well-being, ecosystems and species, economic, social and cultural assets, and infrastructure. : 2235  Impacts may include changed agricultural yields, increased floods, and droughts or coral reef bleaching. Analysis of such impacts is an important step in understanding current and future adaptation needs and options.As of 2022, the level of warming is 1.2°C (2.2°F) above levels before the industrial revolution. It is on track to increase to 2.5 to 2.9°C (4.5 to 5.2°F) by the end of the century. This is causing a variety of secondary effects.
Many negative effects of climate change involve changes in extremes or the way conditions vary rather than changes in average conditions. For example, the average sea level in a port might not be as important as the height of water during a storm surge. That is because a storm surge can cause flooding. The average rainfall in an area might not be as important as how frequent and severe droughts and extreme precipitation events become.

Disaster risks, response and preparedness
Climate change contributes to disaster risk. So experts sometimes see climate change adaptation as one of many processes within disaster risk reduction. In turn, disaster risk reduction is part of the broader consideration of sustainable development. Climate change adaptation and disaster risk reduction have similar goals (to reduce potential impacts of hazards and increase the resilience of people at risk). They use similar concepts and are informed by similar sources and studies.Disasters are often triggered by natural hazards. A natural event such as a fire or flood is not of itself a disaster: it's only when it affects people or is caused by them that is counts as a disaster. It is argued that natural disasters are always linked to human action or inaction or rooted in anthropogenic processes. Disasters, economic loss and the underlying vulnerabilities that drive risk are increasing. Global risks like climate change are having major impacts everywhere.  Scientists forecast climate change will increase the frequency and severity of extreme weather events and disasters. So adaptation may include measures to increase preparedness and relevant disaster response capacities.

Aims
For humans, adaptation aims to moderate or avoid harm, and to exploit opportunities. For natural systems, humans may intervene to help adjustment.

Policy aims
The Paris Agreement of 2015 requires countries to keep global temperature rise this century to less than 2°C above pre-industrial levels, and to pursue efforts to limit the temperature increase to 1.5°C. Even if greenhouse gas emissions are stopped relatively soon, global warming and its effects will last many years. This is due to the inertia of the climate system. So both carbon neutrality ("net zero") and adaptation are necessary.The Global Goal on Adaptation was also established under the Paris Agreement. The specific targets and indicators for the Global Goal are in development as of 2023. It will support the long-term adaptation goals of the governments that are parties to the agreement. It also aims to fund support for the most vulnerable countries’ adaptation needs in the context of the 1.5/2°C goal. It has three core components. These are reducing vulnerability to climate change, enhancing adaptive capacity, and strengthening resilience.

Reduce risk factors: vulnerability and exposure
Adaptation can help decrease climate risk by addressing three interacting risk factors. These are hazards, vulnerability and exposure. It is not possible to directly reduce hazards. This is because hazards are affected by current and future changes in climate. Instead, adaptation addresses the risks of climate impacts that arise from the way climate-related hazards interact with the exposure and vulnerability of  human and ecological systems.: 145–146  Exposure refers to the presence of people, livelihoods, ecosystems and other assets in places that could suffer negative effects. It is possible to reduce exposure by retreating from areas with high climate risks, such as floodplains. Improving systems for early warnings and evacuations are other ways to reduce exposure.: 88  The IPCC defines climate change vulnerability as "the propensity or predisposition to be adversely affected" by climate change. It can apply to humans but also to natural systems. Human and ecosystem vulnerability are interdependent.: 12  According to the IPCC, climate change vulnerability encompasses a variety of concepts and elements, including sensitivity or susceptibility to harm and lack of capacity to cope and adapt.: 5  Sensitivity to climate change could be reduced by for example increasing the storage capacity of a reservoir, or planting crops that are more resistant to climate variability. It is also possible to reduce vulnerability in towns and cities with green garden spaces. These can reduce heat stress and food insecurity for low-income neighbourhoods.: 800 Ecosystem-based adaptation is one way to reduce vulnerability to climate hazards. For instance, mangroves have the ability to dampen storm energy. So they can help prevent flooding. In this way, protection of the mangrove ecosystem can be a form of adaptation. Insurance and livelihood diversification increase resilience and decrease vulnerability. Other ways to decrease vulnerability include strengthening social protection and building infrastructure more resistant to hazards.

Increase adaptive capacity
Adaptive capacity in the context of climate change covers human, natural or managed systems. It looks at how they respond to both  climate variability and extremes. It covers the ability of a system  to adjust to climate change to moderate potential damages, to take advantage of opportunities, or to cope with consequences. Adaptive capacity is not the same as adaptation itself. Adaptive capacity is the ability to reduce the likelihood of negative impacts of climate-related hazards. It does this through the ability to design and implement effective adaptation strategies, or to react to evolving hazards and stresses. Societies that can respond to change quickly and successfully have a high adaptive capacity. Conversely, high adaptive capacity does not necessarily lead to successful adaptation action. It does not necessarily succeed in goals of equity and enhancing well-being.: 164  For example, adaptive capacity in Western Europe is generally considered to be high. Experts  have documented the risks of warmer winters increasing the range of livestock diseases. But many parts of Europe were still badly affected by outbreaks of bluetongue virus in livestock in 2007.In general, adaptation capacity differs between high and low-income countries.  By some indices such as ND-GAIN, high-income countries tend to have higher adaptive capacity. However, there is strong variation within countries.: 164 The determinants of adaptive capacity include:: 895–897 
Economic resources: Wealthier nations are better able to bear the costs of adaptation to climate change than poorer ones.
Technology: Lack of technology can impede adaptation.
Information and skills: Information and trained personnel are necessary to assess and implement successful adaptation options.
Social infrastructure
Institutions: Nations with well-developed social institutions are likely to have greater adaptive capacity than those with less effective institutions. These are typically developing nations and economies in transition.
Equity: Some believe that adaptive capacity is greater where there are government institutions and arrangements in place that allow equitable access to resources.Adaptive capacity is closely linked to social and economic development. In general higher levels of development mean higher adaptive capacity. However, some development locks people into certain patterns or behaviours. And the most developed areas may have low adaptation capacity to new types of natural hazards that they have not previously experienced.Measures to promote sustainable development often overlap with those for adaptive capacity. Both types of activity can reduce climate risk while also yielding development benefits.  These activities can include: Improving access to resources, reducing poverty, lowering inequities of resources and wealth among groups, improving education and information, improving infrastructure, improving institutional capacity and efficiency, and promoting local indigenous practices, knowledge, and experiences.: 899

Strengthening resilience
The IPCC considers climate resilience to be “the capacity of social, economic and ecosystems to cope with a hazardous event or trend or disturbance”. It includes the abilities to reorganise and learn.: 7  This definition is similar to that of climate change adaptation. However resilience involves a more systematic approach to absorbing change. It involves using those changes to become more efficient. The idea is that people can intervene to reorganise the system when disturbance creates an opportunity to do so.: 174  They could guide the reorganisation in more desirable directions such as social or development goals.Implemented adaptation most often builds upon resilience as a way of bouncing back to recover after a disturbance. Experts consider it to be incremental rather than transformational.: 130, 134  On the other hand, climate resilience-focused projects can be activities to promote and support transformational adaptation. This is because transformational adaptation is connected with implementation at scale and ideally at the system-level.: 72 : 26 Strengthening resilience is therefore important for maintaining a capacity for transformation. Transformations, and the processes of transition, cover the major systems and sectors at scale. These are energy, land and ecosystems, urban and infrastructure, and industrial and societal.: 125  Transformations may fail if they do not integrate social justice, consider power differences and political inclusion, and if they do not deliver improvements in incomes and wellbeing for everyone.: 171 Climate resilient development is a closely related area of work and research topic that has recently emerged. It describes situations in which adaptation, mitigation and development solutions are pursued together. It is able to benefit from synergies from among the actions and reduce trade-offs.: 172

Co-benefits with mitigation
Strategies to limit climate change are complementary to efforts to adapt to it.: 128  Limiting warming, by reducing greenhouse gas emissions and removing them from the atmosphere, is also known as climate change mitigation.There are some synergies or co-benefits between adaptation and mitigation. Synergies include the benefits of public transport for both mitigation and adaptation. Public transport has lower greenhouse gas emissions per kilometer travelled than cars. A good public transport network also increases resilience in case of disasters. This is because evacuation and emergency access becomes easier. Reduced air pollution from public transport improves health. This in turn may lead to improved economic resilience, as healthy workers perform better.

Options by type of action
There are many adaptation responses. We sometimes call them adaptation measures, strategies or solutions. They help manage impacts and risks to people and nature.
Current adaptation focuses on near-term climate risks. It also focuses on particular sectors, such as water and agriculture, and on regions, such as Africa and Asia. It is important to close gaps between adaptation that is carried out and the needs relative to today's climate in order to reduce risks to a tolerable level. However, future adaptation must also anticipate future climate change risks. Some options may become less effective or entirely unfeasible as global warming increases.
Adaptation responses fall into four categories that all directly aim to reduce risks and exploit opportunities:: 2428 
Infrastructural and technological adaptation (including engineering, built environment, and high-tech solutions);
Institutional adaptation (economic organizations, laws and regulation, government policies and programmes);
Behavioural and cultural (individual and household strategies as well as social and community approaches);
Nature-based solutions (including ecosystem-based adaptation options).We can also group options is in three categories:
1. Structural and physical adaptation (including engineering and built environment, technological, ecosystem-based, services);
2. Social adaptation (educational, informational, behavioural);
3. Institutional adaptation (economic organizations, laws and regulation, government policies and programmes).: 845 Other ways to distinguish types of adaptation are anticipatory versus reactive, autonomous versus planned and incremental versus transformational.: 134 
Incremental adaptation actions aim to maintain the essence and integrity of a system. Transformative actions change the fundamental attributes of a system in response to climate change and its impacts.
Autonomous adaptation is adaptation responds to experienced climate and its effects. It does not involve explicit planning and does not specifically focus on addressing climate change. Planned adaptation can be reactive or anticipatory. Anticipatory adaptation is undertaken before impacts are apparent. Relying on autonomous adaptation to climate change can result in substantial costs. It is possible to avoid many of these costs with planned adaptation.: 904

Infrastructural and technological options
Built environment
Built environment options include installing or upgrading infrastructure to protect against flooding, sea level rise, heatwaves and extreme heat. They also include infrastructure to respond to changed rainfall patterns in agriculture. This could be infrastructure for irrigation. These are explained further in the section below "by type of climate change impact".

Early warning systems
Climate services
Institutional options
Institutional responses include zoning regulations, new building codes, new insurance schemes, and coordination mechanisms.Policies are important tools to integrate issues of climate change adaptation. At the national level, adaptation strategies appear in National Adaptation Plans (NAPS) and National Adaptation Programmes of Action (NAPA). They also occur in national climate change policies and strategies. These are at different levels of development in different countries and in cities. This is discussed further in the section below on "implementation".
Cities, states, and provinces often have considerable responsibility in land use planning, public health, and disaster management. Institutional adaptation actions occur more frequently in cities than in other sectors.: 2434  Some have begun to adapt to threats intensified by climate change, such as flooding, bushfires, heatwaves, and rising sea levels.

Building codes
Managing the codes or regulations that buildings must conform to is important for keeping people healthy and comfortable during extremes of hot and cold and protecting them from floods.: 953–954  There are many ways to do this. They include increasing the insulation values, adding solar shading, increasing natural ventilation or passive cooling, codes for green roofs to reduce urban heat island effects or requiring waterfront properties to have higher foundations.: 953–954  Land use zoning controls are central to investment in urban development. They can reduce risks to areas threatened by floods and landslides.: 942–943

Insurance
Insurance spreads the financial impact of flooding and other extreme weather events. There is an increasing availability of such options.: 814  For example, index-based insurance is a new product which triggers payment when weather indices such as precipitation or temperature cross a threshold. It aims to help customers such as farmers deal with production risks. Access to reinsurance may make cities more resilient.  Where there are failures in the private insurance market, the public sector can subsidize premiums. One study identified key equity issues for policy considerations:
Transferring risk to the public purse does not reduce overall risk;
Governments can spread the cost of losses across time rather than space;
Governments can force home-owners in low-risk areas to cross-subsidize the insurance premiums of those in high-risk areas;
Cross-subsidization is increasingly difficult for private sector insurers operating in a competitive market;
Governments can tax people to pay for tomorrow's disaster.Government-subsidized insurance, such as the U.S. National Flood Insurance Program, comes under criticism for providing a perverse incentive to develop properties in hazardous areas. This increases overall risk.  Insurance can also undermine other efforts such as property level protection and resilience to increase adaptation. Appropriate land-use policies can counter this behavioural effect. These policies limit new construction where there are current or future climate risks. They also encourage the adoption of resilient building codes to mitigate potential damages.

Coordination mechanisms
Coordination helps achieve goals shared by a range of people or organizations.  Examples are information-sharing or joint implementation of adaptation options.  Coordination helps use resources effectively. It avoids duplication, promotes consistency across government, and makes it easier for all people and organizations involved to understand the work.: 5  In the food production sector, adaptation projects financed through the UNFCCC often include coordination between national governments and administrations at the state, provincial or city level. There are fewer examples of coordination between community-level and national government.

Behavioural and cultural options
Individuals and households play a central role in adaptation. There are many examples particularly in the global south. Behavioural adaptation is a change in the strategies, practices and actions that help to reduce risk. These can include protecting homes from flooding, protecting crops from drought, and adopting different income-earning activities. Behavioural change is the most common form of adaptation.: 2433

Change in diets and food waste
Food waste spoilage increases with exposure to higher temperatures and humidity. It also increases with extreme events such as flooding and contamination.: 787  This can happen at different points in the food supply chain. Thus it can be a risk to food security and nutrition. Adaptation measures can review the production, processing and other handling practices of suppliers. Examples include further sorting to separate damaged products, drying the product for better storage or improved packaging.: 787  Other behaviour change options for retailers and consumers include accepting  fruit and vegetables that appear less than perfect, redistributing food surpluses, and lowering prices on nearly expired food.Dietary change options in regions with excess consumption of calories include replacing meat and dairy foods with a higher share of plant-based foods. This has both mitigation and adaptation benefits. Plant-based options have much lower energy and water requirements. Adaptation options can investigate the dietary patterns that are better suited to the regional, socioeconomic and cultural context. Social-cultural norms strongly affect preferences for foods. Policies such as subsidies, taxes, and marketing can also support dietary choices that help adaptation.: 799

Change in livelihood strategies
Agriculture offers many opportunities for adaptation. These include changing planting times, or changing to crops and livestock that are better adapted to climate conditions and presence of pests. Other examples are breeding more resilient crops and selecting genetically modified crops.: 787  All these aim to improve food security and nutrition.

Seasonal migration
Seasonal migration or mobility includes traditional strategies such as pastoralism or seeking seasonal employment in urban centres. and is They are normally voluntary and economically motivated. Weather fluctuations and extremes can influence migration.: 2428  Weather variability is an important contributor to declines in agricultural incomes and employment. Climate change has made these impacts more likely. As a result migration has increased, particularly rural to urban movement. Migration, including seasonal migration, counts as behavioural climate adaptation. But many other factors influence migration decisions. It is difficult to say how much climate change influences migration.: 2428

Nature-based options
Nature-based solutions (NBS) work with nature and ecosystems to provide benefits to both societies and overall biodiversity. In the context of climate change, they provide adaptation and mitigation options that benefit and support wild species and habitats. In doing this they often contribute to other sustainable development goals.: 303 
Nature-based solutions is an overarching term that includes actions known as ecosystem-based adaptation. However NBS is not restricted to climate change, and often also refers to climate change mitigation. So it is a less specific term.: 284  Both approaches require benefits to people and nature to be delivered simultaneously.

Supporting ecosystems and biodiversity
Ecosystems adapt to global warming depending on their resilience to climate change. Humans can help adaptation in ecosystems in order to strengthen biodiversity. One example is to increase links between ecosystems so that species can migrate on their own to more favourable climate conditions. Another is to assist this migration through human transport of plants or animals. Another example is to use scientific research and development to help coral reefs survive climate change. Protection and restoration of natural and semi-natural areas also helps build resilience, making it easier for ecosystems to adapt.

Supporting people and societies
Many actions that promote adaptation in ecosystems also help humans adapt via ecosystem-based adaptation and nature-based solutions. For instance, restoration of natural fire regimes makes catastrophic fires less likely and reduces the human exposure to this hazard. Giving rivers more space allows natural systems to store more water. This makes floods in inhabited areas less likely. The provision of green spaces and tree planting creates shade for livestock. There is a trade-off between agricultural production and the restoration of ecosystems in some areas.

Options by type of impact
Some adaptation options tackle specific climate hazards like floods or drought. Other options emerge when there are risks from different hazards as well as other factors that contribute to them such as with migration.

Flooding
Flooding can occur in cities or towns as urban flooding. It can also take place by the sea as coastal flooding. Sea level rise can make coastal flooding worse. In some areas there are also risks of glacial lake outburst floods.
There are many adaptation options for flooding:
Installing better flood defences such as flood barriers, sea walls and increased pumping capacity
Installing devices to prevent seawater from backflowing into storm drains
Rainwater storage to deal with increased run-off from rainfall. This includes reducing paved areas or changing to water-permeable pavements, adding water-buffering vegetation, adding underground storage tanks, and subsidizing household rain barrels
Raising pumps at wastewater treatment plants
Buying out homeowners in flood-prone areas
Raising street level to prevent flooding
Using and protecting mangroves
Glacial lakes in danger of outburst flooding can have their moraines replaced with concrete dams to provide protection. This may also provide hydroelectric powerMore frequent drenching rains may make it necessary to increase the capacity of stormwater systems. This separates stormwater from blackwater, so that overflows in peak periods do not contaminate rivers. One example is the SMART Tunnel in Kuala Lumpur.
New York City produced a comprehensive report for its Rebuilding and Resiliency initiative after Hurricane Sandy. It includes making buildings less prone to flooding. It also aims to make specific problems encountered during and after the storm less likely to recur. These include weeks-long fuel shortages even in unaffected areas due to legal and transportation problems, flooded health care facilities, insurance premium increases, damage to electricity and steam generation and distribution networks, and flooding of subway and roadway tunnels.

Sea level rise
Heat waves
A 2020 study projects that regions inhabited by one third of the human population could become as hot as the hottest parts of the Sahara within 50 years. This will happen without a change in patterns of population growth and without migration, unless there is a sharp reduction in greenhouse gas emissions to limit warming to 1.5 °C. The most affected regions have little adaptive capacity as of 2020.Cities are particularly affected by heat waves due to the urban heat island effect. Climate change does not cause urban heat islands. But it leads to more frequent and more intense heat waves which in turn amplify the urban heat island effect in cities.: 993  Compact, dense urban development may increase the urban heat island effect. This results in higher temperatures and increased exposure.Tree cover and green space can reduce heat in cities. They act as sources of shade and promote evaporative cooling. Other options include green roofs, passive daytime radiative cooling applications, and the use of lighter-coloured surfaces and less absorptive building materials in urban areas. These reflect more sunlight and absorb less heat. It may be necessary to change city trees to more heat-tolerant varieties.Methods for adapting to increased heat include:

The use and development of air conditioning and cooling systems. Adding air conditioning can make schools and workplaces cooler. But it results in additional greenhouse gas emissions unless it uses renewable energy.
Solar-energy passive cooling systems for houses and/or refrigeration.

Changed rainfall patterns in agriculture
Cclimate change is altering global rainfall patterns. This affects agriculture. Rainfed agriculture accounts for 80% of global agriculture. Many of the 852 million poor people in the world live in parts of Asia and Africa that depend on rainfall to cultivate food crops. Climate change will modify rainfall, evaporation, runoff, and soil moisture storage. Extended drought can cause the failure of small and marginal farms. This results in increased economic, political and social disruption.
Water availability strongly influences all kinds of agriculture. Changes in total seasonal precipitation or its pattern of variability are both important. Moisture stress during flowering, pollination, and grain-filling harms most crops. It is particularly harmful to corn, soybeans, and wheat. Increased evaporation from the soil and accelerated transpiration in the plants themselves will cause moisture stress.
There are many adaptation options. One is to develop crop varieties with greater drought tolerance and another is to build local rainwater storage. Using small planting basins to harvest water in Zimbabwe has boosted maize yields. This happens whether rainfall is abundant or scarce. And in Niger they have led to three or fourfold increases in millet yields.Climate change can threaten food security and water security. It is possible to adapt food systems to improve food security and prevent  negative impacts from climate change in the future.

More spending on irrigation
Demand for water for irrigation is likely to rise in a warmer climate. This will increase competition between agriculture and urban and industrial users. Agriculture is already the largest consumer of water in semi-arid regions. Falling water tables and the resulting increase in  energy to pump water will make irrigation more expensive. This is particularly the case when drier conditions will require more water per acre. Other strategies can make the most efficient use of water resources. The International Water Management Institute has suggested five strategies that could help Asia feed its growing population in light of climate change. These are modernizing existing irrigation schemes to suit modern methods of farming; supporting farmers' efforts to find their own water supplies by tapping into groundwater in a sustainable way; looking beyond conventional Participatory Irrigation Management schemes by working with the private sector; expanding capacity and knowledge; and investing outside the irrigation sector.

Drought and desertification
Reforestation is one way to stop desertification fueled by climate change and non-sustainable land use. One of the most important projects is the Great Green Wall that aims to stop the southward expansion of the Sahara desert. By 2018 only 15% of it had been carried out. But there are already many positive effects. These include the restoration of over 12 million acres (5 million hectares) of degraded land in Nigeria; the planting of roughly 30 million acres of drought-resistant trees across Senegal; and the restoration of 37 million acres of land in Ethiopia. Tree maintenance led to the refilling of groundwater wells with drinking water, additional food supplies for rural towns, and new sources of work and income for villagers.

Added migration pressures
Migration events have many causes. The environment is one of many factors. Economic, demographic or political factors are often important in migration decisions. Climate change is an indirect or less important cause.: 1079–1080 Migration is a form of adaptation. People may be able to generate more income, diversify livelihoods, and spread climate risk. But there are other ways of looking at migration and environmental change. Migration can be a human rights issue or a security issue. The human rights framing suggests developing protection frameworks for migrants.  Increased border security may be an implication of treating migration as a national security issue. It is possible to combine both approaches, taking national concerns into account in accordance with human rights.Would-be migrants often need access to social and financial capital. These include support networks in the chosen destination and funds or physical resources to move. Migration is often the last adaptive response households will take when they face environmental factors that threaten their livelihoods and other strategies would not work. Measures to increase adaptive capacity, such as social protection and promoting women's empowerment, can help people with little power  in migration decisions.: 25  Sometimes people are unwilling or unable to migrate. In such cases it may be necessary for the government to intervene to keep people safe.: 1079–1081 Many discussions around migration are based on projections. Relatively few use current migration data. Migration related to sudden events like hurricanes, wildfires, heavy rains, floods, and landslides is often short-distance, involuntary, and temporary. Slow-impact events such as droughts and slowly rising temperatures have more mixed effects. But they are more likely to lead to longer-term changes.: 1079

International impacts and cascading risk
International climate risks are climate risks that cross national borders. Sometimes the impacts of climate change in one country or region can have further consequences for people in other countries. Risks can spread from one country to a neighbouring country, or from one country to distant regions. Risks can also cascade and have knock-on effects elsewhere, across multiple borders and sectors. For example, an impact of the floods in Thailand in 2011 was disruption to manufacturing supply chains affecting the automotive sector and electronics industry in Japan, Europe and the USA.: 2441–2444 Options for adapting are less developed. They include developing resilient infrastructure in the originating country, increasing storage facilities to allow more buffer in the recipient country, or diversifying and re-routing trade.: 2441–2444

Options by sector
This section looks at the main sectors and systems affected by climate change. Experts have assessed the risks and adaptation options for them.: ix

Ecosystems and their services
The main risks to ecosystems from climate change are biodiversity loss, ecosystem structure change, increased tree mortality, increased wildfire, and ecosystem carbon losses. These risks are linked. Loss of species can increase the risks to ecosystem health.: 279  Wildfire is an increasing risk for people as well as to ecosystems in many parts of the world.: 290  Wildfires and increased pest infestations due to climate change caused much of the recent tree mortality in North America. : 280 Risks to seas and coastal areas include coral bleaching linked with ocean warming. This can change the composition of ecosystems. Coral bleaching and mortality also increase the risks of flooding on nearby shorelines and islands. Ocean acidification attributed to climate change drives change in coral reefs and other ecosystems such as rocky shores and kelp forests.: 142 Ecosystems can respond to climatic and other environmental pressures in different ways. Individual organisms can respond through growth, movement and other developmental processes. Species and populations can relocate or genetically adapt. Human interventions can make ecosystems more resilient and help species adapt. Examples are protecting larger areas of semi-natural habitat and creating links between parts of the landscape to help species move.: 283 Ecosystem-based adaptation actions provide benefits for both ecosystems and humans. They include restoring coastal and river systems to reduce flood risk and improve water quality, creating more green areas in cities to reduce temperatures, and reinstating natural fire regimes to reduce risk of severe wildfires. There are many ways to reduce the risk of disease outbreaks. They include building surveillance systems of pathogens affecting humans, wildlife and farm animals.: 288, 295

Assisted migration
Assisted migration is the act of moving plants or animals to a different habitat. The destination habitat may or may not have once previously held the species. The only requirement is the destination habitat must provide the bioclimatic requirements to support the species. Assisted migration aims to remove the species from a threatening environment. It aims to give them a chance to survive and reproduce in an environment that does not pose an existential threat to the species.Assisted migration is a potential solution to changes in environments due to climate change that are faster than natural selection can adapt to. It has the potential to allow species that have poor natural dispersal abilities to avoid extinction. However it has also sparked debate over the possibility of the introduction of invasive species and diseases into previously healthy ecosystems. Despite these debates, scientists and land managers have already begun the process of assisted migration for certain species. There have been several studies of the climate adaptive potential of butterflies.

Health
Climate change-related risks to health include direct risks from extreme weather such as cold waves, storms, or prolonged high temperatures. There are also indirect risks such as mental health impacts of undernutrition or displacement caused by extreme weather.: 1076  Similarly there are mental health risks from loss of access to green spaces, reduced air quality, or from anxiety about climate change.: 1076, 1078  There are further risks from changes in conditions for transmission of infectious diseases. Malaria and dengue are particularly climate-sensitive.: 1062 There are several approaches to adapt to new or increased infectious disease risks. These include vector control through  improved housing and better sanitation conditions through WASH services. It could also include insecticide-treated bed nets and indoor spraying. For food-borne diseases it includes food processing and storage.: 1107 Adaptation options for heat include expanding access to air conditioning and establishing heat action plans that include early warning systems for heatwaves. Other options are passive cooling systems to include shading and ventilation. These could be part of improved building and urban design and planning, green infrastructure or public cooling centres.: 1108–1109 Adaptation options to respond to mental health impacts include increasing funding and access to mental healthcare, incorporating mental health into climate resilience and disaster risk planning, and improving post-disaster support.: 1112  Mental health also benefits from broader activities such as design of healthy natural spaces, education and cultural activities. It is also closely related to food security and nutrition.

Cities
Rising temperatures and heatwaves are key risks for cities. With warmer temperatures the urban heat island effect is likely to get worse. Population growth and land use change will influence human health and productivity risks in cities.: 993  Urban flooding is another key risk. This is especially the case in coastal settlements where flood risks are exacerbated by sea-level rise and storm surges. A further set of risks arises from reduced water availability. When supply cannot meet demand from expanding settlements, urban residents become exposed to water insecurity and climate impacts. This is especially so during periods of lower rainfall. These key risks differ greatly between cities, and between different groups of people in the same city.: 993 Adaptation options for cities include flood control measures within and outside properties and urban drainage projects. Other examples are  nature-based solutions such as bioswales or other vegetated infrastructure and restoration and/or protection of mangroves along coastlines. Vegetation corridors, greenspace, wetlands and other green infrastructure can also reduce heat risks. Building designs such as installing air conditioning, ‘cool roofs’  with high-reflectance materials or solar chimneys can also help. Several institutional adaptations are particularly important for cities, for example legislation of building codes, zoning and land use measures.: 952 Many cities have integrated city-wide adaptation strategies or plans that bring together social and economic activities, civil authorities and infrastructure services. Such actions are more effective if they are implemented in partnership with local communities, national governments, research institutions, and the private and third sector.: 994

Water
Climate change is affecting the overall and seasonal availability of water across regions. Climate change is projected to increase the variability of rain.  There will be impacts on water quality as well as quantity. Floods can wash pollutants into water bodies and damage water infrastructure. In many places, particularly in the tropics and sub-tropics, there are longer dry spells and droughts, sometimes over consecutive years. These have contributed to drier soil conditions, lower groundwater tables and reduced or changed flows of rivers. There are risks to ecosystems, and across many water-using sectors of the economy.: 660  Agriculture is likely to be affected by changes in water availability, putting food security at risk. Irrigation has often contributed to groundwater depletion and changes in the water cycle. It can sometimes make a drought worse.: 1157 Some of the most popular adaptations in agriculture include choosing less water-intensive crops or drought and flood-resistant varieties. They include shifting the timing of sowing and harvesting according to the start of the rainy season. There are other technological options available for saving water.: 584  Water is used for hydroelectric generation, for cooling of power plants, and in other industries such as mining. Adapting hydroelectric plant designs and control systems to operate with less water or diversifying in energy generation with other renewables are effective options.: 626

Livelihoods and communities
Climate change affects livelihoods and living conditions in significant ways. These include access to natural resources and ecosystems, land and other assets.  Access to basic infrastructure services such as water and sanitation, electricity, roads, telecommunications is another aspect of vulnerability of communities and livelihoods to climate change.: 1119 The biggest livelihood-related risks stem from losses of agricultural yields, impacts on human health and food security, destruction of homes, and loss of income. There are also risks to fish and livestock that livelihoods depend on. : 1178  Some communities and livelihoods also face risks of irreversible losses and challenges to development, as well as more complex disaster risks.: 1214 The consequences of climate change are the most severe for the poorest populations. These are disproportionately more exposed to hazards such as temperature extremes and droughts. They usually have fewer resources and assets and less access to funding, support and political influence. There are other forms of disadvantage due to discrimination, gender inequalities and through lack of access to resources This includes people with disabilities or minority groups.: 1251 Across livelihoods sectors for households and communities the most common adaptation responses are engineered and technological options. These include traditional infrastructure to protect a specific land use, ecosystem approaches such as watershed restoration or climate-smart agriculture technologies. Adaptation requires public and private investment in various natural assets. It also requires  institutions that prioritize the needs of communities, including the poorest.: 1253

Options by region
Developing countries tend to be more vulnerable to climate change than developed countries.: 957  Based on development trends in 2001, scientists have found that few developing countries would have the capacity to efficiently adapt to climate change.: 957  This was partly due to their low adaptive capacity and the high costs of adaptation in proportion to their GDP.
Examples:

Africa: Africa's major economic sectors are vulnerable to observed climate variability.: 435  This vulnerability contributed to Africa's weak adaptive capacity. As a result Africa is highly vulnerable to future climate change. Projected sea-level rise is likely to increase the socio-economic vulnerability of African coastal cities.
Asia: Climate change can result in the degradation of permafrost in boreal Asia. This will make climate-dependent sectors more vulnerable and affect the region's economy.: 536 
Australia and New Zealand: In Australia and New Zealand, most human systems have considerable adaptive capacity. Some Indigenous communities have low adaptive capacity.: 509 
Europe: Scientists judge the adaptation potential of socioeconomic systems in Europe as relatively high in 2001.: 643  This is due to Europe's high GNP, stable growth, stable population, and well-developed political, institutional, and technological support systems.
Latin America: The adaptive capacity of socioeconomic systems in Latin America is very low, particularly with regard to extreme weather events. As a result the region is highly vulnerability.: 697 
Polar regions: The Arctic is extremely vulnerable to climate change. It was predicted in 2007 that there would be major ecological, sociological, and economic impacts in the region.: 804–805 
Small islands: Scientists found in 2007 that small islands were particularly vulnerable to climate change.: 689

Costs
Economic costs
The economic costs of adaptation to climate change will depend on how much the climate changes. Higher levels of warming lead to considerably higher costs. Globally, adaptation is likely to cost tens or hundreds of billions of dollars annually for the next several decades. The IPCC's most recent summary states that adaptation will cost $15 to 411 billion per year for climate change impacts to 2030. Most estimates are well above $100 billion.": Cross-Chapter Box FINANCE  Because these costs are much higher than the finance available, there is an adaptation gap. This is especially pressing in developing countries.: SPM C1.2  This gap is widening: ch 17 and forms a major barrier to adaptation. This widening has become apparent because the overwhelming majority of global tracked climate finance goes to  mitigation. Only a small proportion goes on adaptation.More regional estimates are also available. For example, the Asian Development Bank has a series of studies on the Economics of Climate Change in the Asia-Pacific region. These studies provide cost analysis of both adaptation and mitigation measures. The WEAP (Water Evaluation And Planning system) assists water resources researchers and planners in assessing impacts of and adaptations to climate change. The United Nations Development Programme's Climate Change Adaptation Portal includes studies on climate change adaptation in Africa, Europe and Central Asia, and Asia and the Pacific.

Cost benefit analysis
As of 2007 there was still a lack of comprehensive, global cost and benefit estimates for adaptation.: 719  Since then, an extensive research literature has emerged. Studies generally focus on adaptation in developing countries or within a sector. For many adaptation options in specific contexts, the investment will be lower than the avoided damages. But global estimates have considerable uncertainty.: ch 15 : Cross-Chapter Box FINANCE

International finance
The United Nations Framework Convention on Climate Change incorporates a financial mechanism to developing country parties to support them with adaptation. This is in Article 11 of the convention. Until 2009, three funds existed under the UNFCCC financial mechanism. The Global Environmental Facility administers the Special Climate Change Fund (SCCF) and the Least Developed Countries Fund (LDCF). The Adaptation Fund resulted from negotiations during COP15 and COP16 in 2009 and 2010. It has its own Secretariat. Initially, when the Kyoto Protocol was in operation, the Adaptation Fund was financed by a 2% levy on the Clean Development Mechanism (CDM).
At the 2009 Copenhagen Summit, nations committed to the goal of sending $100 billion per year to developing countries for climate change mitigation and adaptation by 2020. The Green Climate Fund was created in 2010 as one of the channels for mobilizing this climate finance. The 2015 Paris conference, COP21, clarified that the $100 billion per year should involve a balanced split between mitigation and adaptation. As of December 2020, the promised $100 billion per year had not been fully delivered. Most developing country finance was still targeted towards mitigation. Adaptation received only 21% of the public finance provided in 2020.Global adaptation financing from multilateral development banks exceeded €19 billion in 2021. This implies a rising trend in the financing of adaptation. Multilateral banks made a commitment to increase adaptation financing in a joint declaration on climate change at COP27. This particularly targets low-income nations, small island developing states, and underprivileged people.  The European Investment Bank has said that it will raise the share it contributes to 75% for projects focusing on climate adaptation. The bank  usually contributes up to 50% to a project it participates in.
Also in 2022, nations agreed on a proposal to establish a loss and damage fund to support communities in averting, minimizing, and addressing damages and risks where adaptation is not enough or comes too late.

Additionality
A key feature of international adaptation finance is the concept of additionality. This reflects the linkages between adaptation finance and other levels of development aid. Many developed countries already provide international aid assistance to developing countries. This   addresses challenges such as  poverty, malnutrition, food insecurity, availability of drinking water, indebtedness, illiteracy, unemployment, local resource conflicts, and lower technological development. Climate change threatens to exacerbate or stall progress on fixing some of these problems, and creates new ones. Additionality refers to the extra costs of adaptation to avoid existing aid being redirected.
The four main definitions of additionality are:
Climate finance classified as aid, but additional to the Millennium Development Goals;
Increase on previous year's Official Development Assistance (ODA) spent on climate change mitigation;
Rising ODA levels that include climate change finance but where it is limited to a specified percentage; and
Increase in climate finance not connected to ODA.A criticism of additionality is that it encourages business as usual. This is because it does not account for the future risks of climate change. Some advocates have proposed integrating climate change adaptation into poverty reduction programs.From 2010 to 2020, Denmark increased its global warming adaptation aid by one third, from 0.09% of GDP to 0.12% of GDP. But this did not involve additional funds. Instead, the aid was taken from other foreign assistance funds. Politiken wrote: "Climate assistance is taken from the poorest."

Challenges
Differing time scales
Adaptation can occur in anticipation of change or be a response to those changes. For example, artificial snow-making in the European Alps responds to current climate trends. The construction of the Confederation Bridge in Canada at a higher elevation takes into account the effect of future sea-level rise on ship clearance under the bridge.Effective adaptive policy can be difficult to implement because policymakers are rewarded more for enacting short-term change, rather than long-term planning. Since the impacts of climate change are generally not seen in the short term, policymakers have less incentive to act. Furthermore, climate change is occurring on a global scale. This requires a global framework for adapting to and combating climate change. The vast majority of climate change adaptation and mitigation policies are being implemented on a more local scale. This is because different regions must adapt differently. National and global policies are often more challenging to enact.

Maladaptation
Much adaptation takes place in relation to short-term climate variability. But this may cause maladaptation to longer-term climate trends. The expansion of irrigation in Egypt into the Western Sinai desert after a period of higher river flows is maladaptation given the longer-term projections of drying in the region. Adaptations at one scale can have impacts at another by reducing the adaptive capacity of other people or organizations. This is often the case when broad assessments of the costs and benefits of adaptation are examined at smaller scales. An adaptation may benefit some people, but have a negative effect on others. Development interventions to increase adaptive capacity have tended not to result in increased power or agency for local people. Agency is a central factor in all other aspects of adaptive capacity and so planners need to pay more attention to this factor.

Limits to adaptation
People have always adapted to climate change. Some community coping strategies already exist. Examples include changing sowing times or adopting new water-saving techniques. Traditional knowledge and coping strategies must be maintained and strengthened. If not there is a risk of weakening adaptive capacity as local knowledge of the environment is lost. Strengthening these local techniques and building upon them also makes the adoption of adaptation strategies more likely. This is because it creates more community ownership and involvement in the process.  In many cases this will not be enough to adapt to new conditions. These may be outside the range of those previously experienced, and new techniques will be necessary. The incremental adaptations become insufficient as the vulnerabilities and risks of climate change increase. This creates a need for transformational adaptations which are much larger and costlier. Current development efforts increasingly focus on community-based climate change adaptation. They seek to enhance local knowledge, participation and ownership of adaptation strategies.

Incentivizing private investment in adaptation
Climate change adaptation is a much more complex investment area than mitigation. This is mainly because of the lack of a well-defined income stream or business case with an attractive return on investment on projects. There are several specific challenges for private investment:
Adaptation is often needed in non-market sectors or is focused on public goods that benefit many. So there is a shortage of projects that are attractive to the private sector;
There is a mismatch between the timing of investments needed in the short term and the benefits that may occur in the medium or long term. Future returns are less attractive to investors than short-term returns;
There is a lack of information about investment opportunities. This especially concerns uncertainties associated with future impacts and benefits. These are key considerations when returns may accrue over longer timeframes;
There are gaps in human resources and capacities to design adaptation projects and understand financial implications of legal, economic and regulatory frameworks.However, there is considerable innovation in this area. This is increasing the potential for private sector finance to play a larger role in closing the adaptation finance gap. Economists state that climate adaptation initiatives should be an urgent priority for business investment.

Trade-offs with mitigation
Trade-offs between adaptation and mitigation may occur when climate-relevant actions point in different directions. For instance, compact urban development may lead to reduced greenhouse gas emissions from transport and building. On the other hand, it may increase the urban heat island effect, leading to higher temperatures and increasing exposure, making adaptation more challenging.

Planning and implementation
Climate adaptation planning aims to manage the level of risks of negative impacts. Adaptation planning is similar to risk management. It is a continuing process of assessment, action, learning and adjustment, rather than a single set of decisions. In this way planning and implementing adaptation are both closely connected.: 133 Adaptation planning is an activity. But it is also associated with a type of adaptation. Planned adaptation is sometimes distinguished from autonomous adaptation.Another important concept in adaptation planning is mainstreaming. Mainstreaming means integrating climate change into established strategies, policies or plans. This can be more efficient than developing separate climate adaptation activities and is more likely to succeed.: 28 : 15  It can also be more sustainable. It involves changing the mindsets and practices of policymakers to bring in new issues and have them widely accepted.: 968 A key entry point for this type of integration is national development planning. It needs to take into account new and existing national policies, sectoral policies and budgets. Similarly, mainstreaming adaptation in cities should consider existing city plans, such as land use planning.: 166  There approach also has shortcomings. One criticism is that it has reduced the visibility of stand-alone adaptation programmes.: 166 Adaptation planning usually draws on assessments of risks and vulnerability to climate change. It evaluates the relative benefits and costs of different measures to reduce these risks. Following planning, the next stage is implementation. Guidance has been developed that outline these general stages of an adaptation process, such as the EU Adaptation Support Tool.
Preparing the ground for adaptation
Assessing climate change risks and vulnerabilities
Identifying adaptation options
Assessing adaptation options
Implementing adaptation
Monitoring and evaluating adaptationAs of 2022, adaptation efforts have focused more on adaptation planning than on implementation. All regions and sectors have made progress. However the gaps between current needs and current implementation continues to grow.: 20  : 130 Monitoring and evaluation of adaptation is crucial to ensure that adaptation action is proceeding as planned. It also provide lessons  to improve them and understand which additional actions are necessary. Development and use of monitoring and evaluation systems is increasing at national and local levels. As of 2020, around a quarter of countries had a monitoring and evaluation framework in place.: 28  : 20

By country and city
National governments typically have the key role in setting policies, planning, coordinating and distributing finance for climate adaptation. They are  also accountable to the international community through international agreements. Many countries document their adaptation plans in their NDCs submitted under the Paris Agreement and/or national adaptation plans. Developing countries can receive support with international funding to help them develop their national adaptation plans.As of 2020, 72% of countries had a high level adaptation instrument – such as a plan, policy or strategy. Relatively few had progressed to the tangible implementation of projects: at least not to significantly reduce the climate risk their populations are exposed to.Countries have also made progress in developing plans for subnational government authorities. These include county/provincial level, sectors and city plans. In 2020, around 21% of countries had sub-national plans and 58% had sectoral plans.As of 2022, there is better integration of adaptation priorities into other national plans and planning systems. Planning is also more inclusive. This means that climate laws and policies increasingly reference different groups such as persons with disabilities, children, young people and future generations.Many cities have integrated city-wide adaptation strategies or plans that bring together their social and economic activities, civil authorities and infrastructure services.: 994    A survey of 812 global cities found that 93% reported they are at risk from climate change, 43% did not have an adaptation plan in 2021, and 41% of cities had not carried out a climate risk and vulnerability assessment.

Global goals
Sustainable Development Goal 13 aims to strengthen countries' resilience and adaptive capacities to climate-related issues. This adjustment includes many areas such as infrastructure, agriculture and education. The Paris Agreement includes several provisions for adaptation. It seeks to promote the idea of global responsibility, improve communication via the adaptation component of the Nationally Determined Contributions, and includes an agreement that developed countries should provide some financial support and technology transfer to promote adaptation in more vulnerable countries.The United Nations estimates Africa would need yearly funding of $1.3 trillion to achieve the Sustainable Development Goals in the region, considering population growth. The International Monetary Fund also estimates that $50 billion may be needed only to cover the expenses of climate adaptation.

History
When climate change first became prominent on the international political agenda in the early 1990s, talk of  adaptation was considered an unwelcome distraction from the need to reach agreement on effective measures for mitigation - which has mainly meant reducing the emissions of greenhouse gases. A few voices had spoken out in favour of adaptation even in the late 20th and early 21st century. In 2009 and 2010, adaptation began to receive more attention during international climate negotiations. This was after limited progress at the Copenhagen Summit had made it clear that achieving international consensus for emission reductions would be more challenging than had been hoped. In 2009, the rich nations of the world committed to providing a total of $100 billion per year to help developing nations fund their climate adaptation projects. This commitment was underscored at the 2010 Cancún Summit , and again at the 2015 Paris Conference. The promise was not fulfilled, but the amount of funding provided by the rich nations for adaptations did increase over the 2010 - 2020 period.Climate change adaptation has tended to be more of a focus for local authorities, while national and international politics has tended to focus on mitigation. There have been exceptions - in countries that feel especially exposed to the effects of climate change, sometimes the focus has been more on adaptation even at national level.

See also
Adaptation in Africa
Green bond
Climate change adaptation strategies on the German coast
Climate finance
Climate justice
Climate Vulnerability Monitor

References
External links
The Intergovernmental Panel on Climate Change (IPCC) Working Group II assesses the scientific literature on adaptation: Working Group II — IPCC
The weADAPT platform encourages the sharing of experiences from adaptation projects to accelerate learning and climate action.