Cities are home to half of the world's population, consume two-thirds of energy and 70% of natural resources, and contribute more than 70% of global CO emissions. Cities and regions are also especially vulnerable to climate-related hazards and pollution. Climate hazard and pollution also disproportionately affect the poor, increasing inequality. With half of the world's population residing in urban areas, there will be an increase in energy use that comes with climate change. One of them will be air conditioning, since as climate change is accompanied by higher temperatures, many people will begin to need more cooling systems, so this translates into more air conditioning and newer models of cooling systems. Although more people live in cities, which can lead to shortages, cities emit less carbon than rural areas because house sizes are smaller, gas heating is used more instead of propane, carbon-fueled transportation is less used, and more people share common spaces such as laundry rooms and kitchens. Although cities create some problems, it is important to realize that higher population density generates less carbon emissions, which benefits climate change.[16]​[17]​.

Contenido

La perspectiva de la investigación sobre las ciudades y el cambio climático se inició en la década de 1990, cuando la comunidad internacional empezó a ser cada vez más consciente de las posibles repercusiones del cambio climático.[18]​ Los especialistas en estudios urbanos Michael Hebbert y Vladmir Jankovic sostienen que este campo de investigación surgió de un conjunto más amplio de investigaciones sobre los efectos del desarrollo urbano y la vida en el medio ambiente que comenzó ya en la década de 1950.[18]​ Desde entonces, la investigación ha indicado las relaciones entre el cambio climático y la urbanización sostenible: el aumento del empleo en las ciudades reduce la pobreza y aumenta la eficiencia.[19]​.

La Red de Investigación del Cambio Climático Urbano del Instituto de la Tierra de la Universidad de Columbia ha publicado dos evaluaciones internacionales.[20]​ La primera de ellas (ARC3.1) se publicó en 2011,[21]​ y la segunda de ellas (ARC3.2) se publicó en 2018.[20]​ Estos documentos actúan como resúmenes académicos sobre esta materia de forma similar a los informes del Grupo Intergubernamental de Expertos sobre el Cambio Climático. Se está elaborando un tercer informe desde 2020.[22]​.

Cities as laboratories

Cities are a good object of study because they can invest heavily in large-scale experimental policies that could be applied elsewhere (such as San Diego's advanced urban planning practices, which could be applied elsewhere in the United States).[23][24] Various scholars approach this question in different ways, but describe this "urban laboratory" environment for testing a wide variety of practices.[25][24] For example, the book Life After Carbon documents a number of cities that act as "urban climate innovation laboratories".[26]​ These cities as laboratories offer an effective way to detect climate change by observing the effects of the greenhouse effect on rooftops, street trees and other environmental variables within an urban environment.[27]​ This method of observing the effects of heat waves in cities will offer a way to confront the problem of the heat effect, which will be solved by cities in the future.[27]​.

Impact on health

It has been observed that climate change has caused an impact on human health and livelihoods in urban environments. In these, cities are affected by multiple climatic and non-climatic risks that magnify the damage caused to human health. For example, heat waves have intensified in cities due to the combination of multiple factors that add to climate change. The impact on human health in urban environments is most profound in economically and socially marginalized urban residents.[28]​.

The Intergovernmental Panel on Climate Change (IPCC) defines resilience as "the capacity of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity for self-organization and the capacity to adapt to stress and change."[29] One of the most important notions emphasized by the theory of urban resilience is the need for urban systems to increase their capacity to absorb environmental disturbances. By focusing on three generalizable elements of the resilience movement, Tyler and Moench's urban resilience framework serves as a model that can be applied for local planning on an international scale.

The first element of urban climate resilience focuses on “systems” or the physical infrastructure embedded in urban systems. A fundamental concern of urban resilience is linked to the idea of maintaining support systems that, in turn, enable supply and exchange networks for populations in urban areas.[29]​ These systems refer to both the physical infrastructure of the city and the ecosystems found within or around the urban center, while working to provide essential services such as food production, flood control or runoff management.[29]​ For example, electricity from The city, a necessity of urban life, depends on the operation of distant generators, networks and reservoirs. The failure of these basic systems endangers human well-being in these urban areas, making it crucial to maintain them in the face of imminent environmental disruptions. Societies need to build resilience into these systems to achieve such a feat. Resilient systems work to "ensure that functionality is maintained and can be restored across system links"[29]​ despite some failures or operational disturbances. Ensuring the functionality of these important systems is achieved by instilling and maintaining flexibility in the presence of "safe failure".[29]​ Resilient systems achieve flexibility by ensuring that key functions are distributed so that they are not all affected by a given event at once, often called spatial diversity, and that they have multiple methods to satisfy a given need, often called functional diversity.[29]​ The presence of safe failures also plays a critical role in maintaining these systems, which work by absorbing sudden shocks that can even exceed design thresholds. There is no doubt that environmental disturbances will test the dexterity of these systems, so the presence of safe failures seems to be a necessity.[29]​.

Additionally, another important component of these systems is resilience. In the event that dangerous weather events affect these urban centers, recovery or "rebound" is of great importance. In fact, in most disaster studies, urban resilience is often defined as “the ability of a city to recover from destruction.” This idea of ​​rebound of urban systems is also rooted in government literature on the same topic. For example, the U.S. government's first Intelligence and Security Coordinator described urban resilience as “the ability to absorb shocks and rebound back into operation, or at least enough resilience to avoid… system collapse.” Given these quotes, the rebound discourse has been and should continue to be an important part of the urban climate resilience framework.[30] Other theorists have criticized this idea of ​​rebound, citing that it privileges the status quo, rather than advocating for the notion of "rebound forward", allowing for the evolution and improvement of the system.[31]​.

The next element of urban climate resilience focuses on the social agents (also described as social actors) present in urban centers. Many of these agents depend on urban centers for their own existence, so they share a common interest in working to protect and maintain their urban environment.[29] Agents in urban centers have the ability to deliberate and make decisions rationally, which plays an important role in the theory of climate resilience. The role of local governments and community organizations cannot be overlooked, as they will be forced to make key decisions regarding the organization and delivery of key services and plans to combat the imminent effects of climate change.[29]​ Perhaps most importantly, these social agents must increase their capacities in terms of the notions of "ingenuity and responsiveness."[29]​ Responsiveness refers to the ability of social agents and groups to organize and reorganize, as well as the ability to anticipate and plan for disruptive events. Resourcefulness refers to the ability of social actors in urban centers to mobilize various assets and resources in order to act.[29] Urban centers will be better able to defend themselves in the heat of climate disruptions when responsiveness and ingenuity are effectively achieved collectively.

Las ciudades de distintas partes del mundo se enfrentan a retos y oportunidades diferentes y únicos ante el cambio climático. Sin embargo, un factor que las vincula es su inevitable adhesión a los "patrones globales dominantes de urbanización e industrialización", que a menudo catalizan "la modificación a gran escala de los impulsores de los procesos hidrológicos y biogeoquímicos".[32]​ Los patrones de urbanización e industrialización son especialmente evidentes en regiones como Asia, África y América del Sur, regiones que actualmente se entiende que experimentan rápidos cambios relacionados con la población y el poder económico.[32]​.

Africa

Africa is urbanizing faster than any other continent[33]​ and it is estimated that by 2030 more than one billion Africans will live in cities.[34]​ This rapid urbanization, coupled with the many complex interrelated challenges of climate change, pose a major obstacle to Africa's sustainable development.[35]​ Much of this urban development is informal, with urban residents settling in informal settlements and slums often on the outskirts of Africa. cities.[36]​ This phenomenon suggests that lower-income countries should be the target of initiatives to increase the sustainability of infrastructure. A recent study has concluded that in "countries with a per capita income of less than $15,000 per year (in 2011 PPP dollars) carbon pricing has, on average, progressive distributional effects" and that "carbon pricing tends to be regressive in countries with relatively higher income," indicating that imposing and changing carbon prices could incentivize governments to shift to green energy as a means of reference energy consumption for developing peri-urban areas.[37]​ Although urbanization is seen positively, its effects can be negative for urbanized people. African cities are exposed to multiple climate threats, such as floods, drought, water stress, sea level rise, heat waves, storms and cyclones, as well as the effects related to food insecurity and disease outbreaks such as cholera and malaria caused by floods and droughts.[38]​.

Climate impacts in rural areas, such as desertification, biodiversity loss, soil erosion and declining agricultural productivity, are also driving the migration of poor rural communities to cities.[39]​ To achieve sustainable development and climate resilience in cities in Africa, and elsewhere, it is important to take into account these urban-rural interrelationships.[33]​ There is increasing attention to the important role that peri-urban areas play in the climate resilience of cities, especially with regard to the ecosystem services provided by these areas, which are rapidly deteriorating in sub-Saharan Africa.[40]​ Peri-urban ecosystems can perform functions such as flood control, reducing the urban heat island effect, air and water purification, supporting food and water security, and waste management.[41]​.

Asia

China currently has one of the fastest growing industrial economies in the world, and the effects of this rapid urbanization have not been without consequences for climate change. The country is one of the largest by area, and therefore the most prominent region in terms of urbanization is the Yangtze River Delta, or YRD, since it is considered "the most developed, dynamic, densely populated and concentrated industrial area in China" and supposedly "is becoming an influential world-class metropolitan area and plays an important role in the economic and social development of China."[42]​ In this way, urbanization in China could be understood as closely related not only to the functionality of its economic system, but with the society that integrates it; something that turns climate change mitigation into an intersectional issue that affects more than just infrastructure.[43]​.

Historically, data have shown that "climate change has been shaping the Delta and its socioeconomic development" and that such socioeconomic development in the region "has shaped its geography and built environment, which, however, are not adaptable to future climate change."[42] Thus, it has been stated that "it is imperative to adopt policies and programs to mitigate and adapt to climate change" in the DRY, specifically, policies aimed at reducing the impact of certain climate threats based on the geography of the DRY. This includes the region's current infrastructure in mitigating flood disasters and promoting efficient energy use at the local level.[42]​.

A nationwide policy analysis conducted in the arid lands of northern China presents the notion of "sustainable urban landscape planning (SULP)" which specifically aims to "prevent the occupation of important habitats and natural corridors, prime cropland and floodplains".[44]​ The research indicates that the adoption of SULP in the future can "effectively manage the impacts of climate change on water resource capacity and reduce water stress" not only within of the experimental model of northern China, but for "dry lands around the world".[44]

South Asia's urban population grew by 130 million people between 2001 and 2011 - more than the entire population of Japan - and is projected to increase by almost 250 million by 2030.[45] However, urbanization in South Asia is characterized by increased poverty, slums, pollution, crowding and congestion.[46] At least 130 million South Asians - more than the entire population of Japan. population of Mexico - live in informal urban settlements characterized by poor construction, insecurity of tenure and unserviced plots.[45]​ Despite being a water-rich area, climate projection models suggest that, by 2050, between 52 and 146 million people living in South Asia could face increased water scarcity due to climate change, representing 18% of the world's population exposed to water scarcity.[47]​ Access to water in cities is especially critical in South Asia, where more than 40% of the world's poor (living on less than $1.25 a day) and 35% of the world's undernourished live there.[47]​ A study conducted in some Himalayan cities in India and Nepal found that none of them have a robust water planning and governance system to address the challenges posed by rapid urbanization and change. climate.[48]​ Khulna, Bangladesh, also faces many problems related to water insecurity. When sea levels begin to rise, due to climate change, salinity will shift inland, reducing the amount of drinking water available to the residents of Khulna. Plans have been put in place to improve water quality in cities, but this decreases availability for inhabitants of informal urban areas. For now, they depend on using as little water as possible, specifically for their crops.[49]​.

North and South America

Areas of South America have also been cited in recent studies that highlight the dangers of urbanization on local and transnational climates and for a country like Brazil, one of the most populated nations in the world, as well as the majority owner of the Amazon rainforest. The United Nations Development Program highlights that the Amazon rainforest plays a "key role in global climate systems", due to its great usefulness in capturing CO2 emissions.[50] UN research has indicated that, because Brazil's climate depends so closely on the health of the rainforest, deforestation measures are currently considered to have adverse effects on the "natural adaptive capacities" of the rainforest to extreme climate changes, thus predisposing Brazil to what is expected to be greater volatility in temperature and precipitation patterns.[50] More specifically, it is expected that if global warming continues on its current course without extensive mitigation strategies being put in place, what is currently projected to be a 2 °C average increase in global temperature could lead to a 4 °C increase both in the interior of the country and in the surrounding Amazon region.[50] Rapid urbanization in other countries will also lead to greater resource needs. This includes raw materials that will cause further deforestation of the Amazon rainforest to obtain them. This will inevitably create many more climate problems as we continue to lose more trees in the Amazon rainforest.[51]​.

The issue of climate change in Brazil does not begin and end with what has already been done with respect to urbanization; It is an issue deeply rooted in socioeconomic contexts. Factor analysis and multilevel regression models sponsored by the US Forest Service revealed that, for all of Brazil, "income inequality significantly predicts higher levels of a key component of vulnerability in Brazilian urban municipalities to flood risks."[52]​.

The future of Brazil's climate effect is likely to change, as through its NDC Brazil has committed to reduce its greenhouse gas emissions by 37% below 2005 levels by 2025.[53]​ This will be a challenge for Brazilian cities, as 86% of the country's population lives in urban areas, and this is likely to increase to 92% by 2050.[53]​ As for to deforestation, since Brazil is home to the Amazon rainforest, it has always had a high rate of deforestation.[54]​ Brazilian deforestation reached its highest point in 2004, with 27.77 thousand kilometers of forest destroyed, had its lowest point in 2012, with only 4.57 thousand kilometers of forest destroyed, and has since risen again, with 10.85 thousand kilometers of forest destroyed.[55]​.

The United States, as one of the largest industrialized nations in the world, also has problems of infrastructural insufficiency related to climate change. Take as an indicator a study on the topology of Las Vegas. Research that created three land use and land cover maps, or LULC maps, of Las Vegas in 1900 (although hypothetical), 1992, and 2006 found that "urbanization in Las Vegas produces a classic urban heat island (UHI) at night, but a minor cooling trend during the day."[56] In addition to temperature changes in the city, "increased surface roughness," caused by the addition of skyscrapers/narrow buildings, "has a mechanical effect of slowing down the climatological wind field over the urban area."[56] These non-natural environmental phenomena reinforce the idea that urbanization plays a role in determining the local climate, although researchers acknowledge that more on-the-ground studies are needed.

Se han formado varias comunidades internacionales de ciudades y políticas importantes para incluir más ciudades en la acción climática.

Global Compact of Mayors for Climate and Energy

• - UN course on cities and climate change.

Cities are home to half of the world's population, consume two-thirds of energy and 70% of natural resources, and contribute more than 70% of global CO emissions. Cities and regions are also especially vulnerable to climate-related hazards and pollution. Climate hazard and pollution also disproportionately affect the poor, increasing inequality. With half of the world's population residing in urban areas, there will be an increase in energy use that comes with climate change. One of them will be air conditioning, since as climate change is accompanied by higher temperatures, many people will begin to need more cooling systems, so this translates into more air conditioning and newer models of cooling systems. Although more people live in cities, which can lead to shortages, cities emit less carbon than rural areas because house sizes are smaller, gas heating is used more instead of propane, carbon-fueled transportation is less used, and more people share common spaces such as laundry rooms and kitchens. Although cities create some problems, it is important to realize that higher population density generates less carbon emissions, which benefits climate change.[16]​[17]​.

Contenido

La perspectiva de la investigación sobre las ciudades y el cambio climático se inició en la década de 1990, cuando la comunidad internacional empezó a ser cada vez más consciente de las posibles repercusiones del cambio climático.[18]​ Los especialistas en estudios urbanos Michael Hebbert y Vladmir Jankovic sostienen que este campo de investigación surgió de un conjunto más amplio de investigaciones sobre los efectos del desarrollo urbano y la vida en el medio ambiente que comenzó ya en la década de 1950.[18]​ Desde entonces, la investigación ha indicado las relaciones entre el cambio climático y la urbanización sostenible: el aumento del empleo en las ciudades reduce la pobreza y aumenta la eficiencia.[19]​.

La Red de Investigación del Cambio Climático Urbano del Instituto de la Tierra de la Universidad de Columbia ha publicado dos evaluaciones internacionales.[20]​ La primera de ellas (ARC3.1) se publicó en 2011,[21]​ y la segunda de ellas (ARC3.2) se publicó en 2018.[20]​ Estos documentos actúan como resúmenes académicos sobre esta materia de forma similar a los informes del Grupo Intergubernamental de Expertos sobre el Cambio Climático. Se está elaborando un tercer informe desde 2020.[22]​.

Cities as laboratories

Cities are a good object of study because they can invest heavily in large-scale experimental policies that could be applied elsewhere (such as San Diego's advanced urban planning practices, which could be applied elsewhere in the United States).[23][24] Various scholars approach this question in different ways, but describe this "urban laboratory" environment for testing a wide variety of practices.[25][24] For example, the book Life After Carbon documents a number of cities that act as "urban climate innovation laboratories".[26]​ These cities as laboratories offer an effective way to detect climate change by observing the effects of the greenhouse effect on rooftops, street trees and other environmental variables within an urban environment.[27]​ This method of observing the effects of heat waves in cities will offer a way to confront the problem of the heat effect, which will be solved by cities in the future.[27]​.

Impact on health

It has been observed that climate change has caused an impact on human health and livelihoods in urban environments. In these, cities are affected by multiple climatic and non-climatic risks that magnify the damage caused to human health. For example, heat waves have intensified in cities due to the combination of multiple factors that add to climate change. The impact on human health in urban environments is most profound in economically and socially marginalized urban residents.[28]​.

The Intergovernmental Panel on Climate Change (IPCC) defines resilience as "the capacity of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity for self-organization and the capacity to adapt to stress and change."[29] One of the most important notions emphasized by the theory of urban resilience is the need for urban systems to increase their capacity to absorb environmental disturbances. By focusing on three generalizable elements of the resilience movement, Tyler and Moench's urban resilience framework serves as a model that can be applied for local planning on an international scale.

The first element of urban climate resilience focuses on “systems” or the physical infrastructure embedded in urban systems. A fundamental concern of urban resilience is linked to the idea of maintaining support systems that, in turn, enable supply and exchange networks for populations in urban areas.[29]​ These systems refer to both the physical infrastructure of the city and the ecosystems found within or around the urban center, while working to provide essential services such as food production, flood control or runoff management.[29]​ For example, electricity from The city, a necessity of urban life, depends on the operation of distant generators, networks and reservoirs. The failure of these basic systems endangers human well-being in these urban areas, making it crucial to maintain them in the face of imminent environmental disruptions. Societies need to build resilience into these systems to achieve such a feat. Resilient systems work to "ensure that functionality is maintained and can be restored across system links"[29]​ despite some failures or operational disturbances. Ensuring the functionality of these important systems is achieved by instilling and maintaining flexibility in the presence of "safe failure".[29]​ Resilient systems achieve flexibility by ensuring that key functions are distributed so that they are not all affected by a given event at once, often called spatial diversity, and that they have multiple methods to satisfy a given need, often called functional diversity.[29]​ The presence of safe failures also plays a critical role in maintaining these systems, which work by absorbing sudden shocks that can even exceed design thresholds. There is no doubt that environmental disturbances will test the dexterity of these systems, so the presence of safe failures seems to be a necessity.[29]​.

Additionally, another important component of these systems is resilience. In the event that dangerous weather events affect these urban centers, recovery or "rebound" is of great importance. In fact, in most disaster studies, urban resilience is often defined as “the ability of a city to recover from destruction.” This idea of ​​rebound of urban systems is also rooted in government literature on the same topic. For example, the U.S. government's first Intelligence and Security Coordinator described urban resilience as “the ability to absorb shocks and rebound back into operation, or at least enough resilience to avoid… system collapse.” Given these quotes, the rebound discourse has been and should continue to be an important part of the urban climate resilience framework.[30] Other theorists have criticized this idea of ​​rebound, citing that it privileges the status quo, rather than advocating for the notion of "rebound forward", allowing for the evolution and improvement of the system.[31]​.

The next element of urban climate resilience focuses on the social agents (also described as social actors) present in urban centers. Many of these agents depend on urban centers for their own existence, so they share a common interest in working to protect and maintain their urban environment.[29] Agents in urban centers have the ability to deliberate and make decisions rationally, which plays an important role in the theory of climate resilience. The role of local governments and community organizations cannot be overlooked, as they will be forced to make key decisions regarding the organization and delivery of key services and plans to combat the imminent effects of climate change.[29]​ Perhaps most importantly, these social agents must increase their capacities in terms of the notions of "ingenuity and responsiveness."[29]​ Responsiveness refers to the ability of social agents and groups to organize and reorganize, as well as the ability to anticipate and plan for disruptive events. Resourcefulness refers to the ability of social actors in urban centers to mobilize various assets and resources in order to act.[29] Urban centers will be better able to defend themselves in the heat of climate disruptions when responsiveness and ingenuity are effectively achieved collectively.

Las ciudades de distintas partes del mundo se enfrentan a retos y oportunidades diferentes y únicos ante el cambio climático. Sin embargo, un factor que las vincula es su inevitable adhesión a los "patrones globales dominantes de urbanización e industrialización", que a menudo catalizan "la modificación a gran escala de los impulsores de los procesos hidrológicos y biogeoquímicos".[32]​ Los patrones de urbanización e industrialización son especialmente evidentes en regiones como Asia, África y América del Sur, regiones que actualmente se entiende que experimentan rápidos cambios relacionados con la población y el poder económico.[32]​.

Africa

Africa is urbanizing faster than any other continent[33]​ and it is estimated that by 2030 more than one billion Africans will live in cities.[34]​ This rapid urbanization, coupled with the many complex interrelated challenges of climate change, pose a major obstacle to Africa's sustainable development.[35]​ Much of this urban development is informal, with urban residents settling in informal settlements and slums often on the outskirts of Africa. cities.[36]​ This phenomenon suggests that lower-income countries should be the target of initiatives to increase the sustainability of infrastructure. A recent study has concluded that in "countries with a per capita income of less than $15,000 per year (in 2011 PPP dollars) carbon pricing has, on average, progressive distributional effects" and that "carbon pricing tends to be regressive in countries with relatively higher income," indicating that imposing and changing carbon prices could incentivize governments to shift to green energy as a means of reference energy consumption for developing peri-urban areas.[37]​ Although urbanization is seen positively, its effects can be negative for urbanized people. African cities are exposed to multiple climate threats, such as floods, drought, water stress, sea level rise, heat waves, storms and cyclones, as well as the effects related to food insecurity and disease outbreaks such as cholera and malaria caused by floods and droughts.[38]​.

Climate impacts in rural areas, such as desertification, biodiversity loss, soil erosion and declining agricultural productivity, are also driving the migration of poor rural communities to cities.[39]​ To achieve sustainable development and climate resilience in cities in Africa, and elsewhere, it is important to take into account these urban-rural interrelationships.[33]​ There is increasing attention to the important role that peri-urban areas play in the climate resilience of cities, especially with regard to the ecosystem services provided by these areas, which are rapidly deteriorating in sub-Saharan Africa.[40]​ Peri-urban ecosystems can perform functions such as flood control, reducing the urban heat island effect, air and water purification, supporting food and water security, and waste management.[41]​.

Asia

China currently has one of the fastest growing industrial economies in the world, and the effects of this rapid urbanization have not been without consequences for climate change. The country is one of the largest by area, and therefore the most prominent region in terms of urbanization is the Yangtze River Delta, or YRD, since it is considered "the most developed, dynamic, densely populated and concentrated industrial area in China" and supposedly "is becoming an influential world-class metropolitan area and plays an important role in the economic and social development of China."[42]​ In this way, urbanization in China could be understood as closely related not only to the functionality of its economic system, but with the society that integrates it; something that turns climate change mitigation into an intersectional issue that affects more than just infrastructure.[43]​.

Historically, data have shown that "climate change has been shaping the Delta and its socioeconomic development" and that such socioeconomic development in the region "has shaped its geography and built environment, which, however, are not adaptable to future climate change."[42] Thus, it has been stated that "it is imperative to adopt policies and programs to mitigate and adapt to climate change" in the DRY, specifically, policies aimed at reducing the impact of certain climate threats based on the geography of the DRY. This includes the region's current infrastructure in mitigating flood disasters and promoting efficient energy use at the local level.[42]​.

A nationwide policy analysis conducted in the arid lands of northern China presents the notion of "sustainable urban landscape planning (SULP)" which specifically aims to "prevent the occupation of important habitats and natural corridors, prime cropland and floodplains".[44]​ The research indicates that the adoption of SULP in the future can "effectively manage the impacts of climate change on water resource capacity and reduce water stress" not only within of the experimental model of northern China, but for "dry lands around the world".[44]

South Asia's urban population grew by 130 million people between 2001 and 2011 - more than the entire population of Japan - and is projected to increase by almost 250 million by 2030.[45] However, urbanization in South Asia is characterized by increased poverty, slums, pollution, crowding and congestion.[46] At least 130 million South Asians - more than the entire population of Japan. population of Mexico - live in informal urban settlements characterized by poor construction, insecurity of tenure and unserviced plots.[45]​ Despite being a water-rich area, climate projection models suggest that, by 2050, between 52 and 146 million people living in South Asia could face increased water scarcity due to climate change, representing 18% of the world's population exposed to water scarcity.[47]​ Access to water in cities is especially critical in South Asia, where more than 40% of the world's poor (living on less than $1.25 a day) and 35% of the world's undernourished live there.[47]​ A study conducted in some Himalayan cities in India and Nepal found that none of them have a robust water planning and governance system to address the challenges posed by rapid urbanization and change. climate.[48]​ Khulna, Bangladesh, also faces many problems related to water insecurity. When sea levels begin to rise, due to climate change, salinity will shift inland, reducing the amount of drinking water available to the residents of Khulna. Plans have been put in place to improve water quality in cities, but this decreases availability for inhabitants of informal urban areas. For now, they depend on using as little water as possible, specifically for their crops.[49]​.

North and South America

Areas of South America have also been cited in recent studies that highlight the dangers of urbanization on local and transnational climates and for a country like Brazil, one of the most populated nations in the world, as well as the majority owner of the Amazon rainforest. The United Nations Development Program highlights that the Amazon rainforest plays a "key role in global climate systems", due to its great usefulness in capturing CO2 emissions.[50] UN research has indicated that, because Brazil's climate depends so closely on the health of the rainforest, deforestation measures are currently considered to have adverse effects on the "natural adaptive capacities" of the rainforest to extreme climate changes, thus predisposing Brazil to what is expected to be greater volatility in temperature and precipitation patterns.[50] More specifically, it is expected that if global warming continues on its current course without extensive mitigation strategies being put in place, what is currently projected to be a 2 °C average increase in global temperature could lead to a 4 °C increase both in the interior of the country and in the surrounding Amazon region.[50] Rapid urbanization in other countries will also lead to greater resource needs. This includes raw materials that will cause further deforestation of the Amazon rainforest to obtain them. This will inevitably create many more climate problems as we continue to lose more trees in the Amazon rainforest.[51]​.

The issue of climate change in Brazil does not begin and end with what has already been done with respect to urbanization; It is an issue deeply rooted in socioeconomic contexts. Factor analysis and multilevel regression models sponsored by the US Forest Service revealed that, for all of Brazil, "income inequality significantly predicts higher levels of a key component of vulnerability in Brazilian urban municipalities to flood risks."[52]​.

The future of Brazil's climate effect is likely to change, as through its NDC Brazil has committed to reduce its greenhouse gas emissions by 37% below 2005 levels by 2025.[53]​ This will be a challenge for Brazilian cities, as 86% of the country's population lives in urban areas, and this is likely to increase to 92% by 2050.[53]​ As for to deforestation, since Brazil is home to the Amazon rainforest, it has always had a high rate of deforestation.[54]​ Brazilian deforestation reached its highest point in 2004, with 27.77 thousand kilometers of forest destroyed, had its lowest point in 2012, with only 4.57 thousand kilometers of forest destroyed, and has since risen again, with 10.85 thousand kilometers of forest destroyed.[55]​.

The United States, as one of the largest industrialized nations in the world, also has problems of infrastructural insufficiency related to climate change. Take as an indicator a study on the topology of Las Vegas. Research that created three land use and land cover maps, or LULC maps, of Las Vegas in 1900 (although hypothetical), 1992, and 2006 found that "urbanization in Las Vegas produces a classic urban heat island (UHI) at night, but a minor cooling trend during the day."[56] In addition to temperature changes in the city, "increased surface roughness," caused by the addition of skyscrapers/narrow buildings, "has a mechanical effect of slowing down the climatological wind field over the urban area."[56] These non-natural environmental phenomena reinforce the idea that urbanization plays a role in determining the local climate, although researchers acknowledge that more on-the-ground studies are needed.

Se han formado varias comunidades internacionales de ciudades y políticas importantes para incluir más ciudades en la acción climática.

Global Compact of Mayors for Climate and Energy

• - UN course on cities and climate change.