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107-605: Ambos Nogales (Spanish for "both Nogales") refers to the two cities of Nogales, Arizona , United States , and Nogales, Sonora , Mexico . They lie 60 miles directly south of Tucson, Arizona , divided by the Mexico–United States barrier . Though divided by the border between their respective nation states , the two municipalities have historically shared a sense of community alluded to in their description as "Ambos Nogales," as well as other sayings and phrases alluding to this camaraderie. The motto of Nogales, Sonora,

214-577: A central area containing buildings with special economic, political, and religious significance. Archaeologists refer to this area by the Greek term temenos or if fortified as a citadel . These spaces historically reflect and amplify the city's centrality and importance to its wider sphere of influence . Today cities have a city center or downtown , sometimes coincident with a central business district . Cities typically have public spaces where anyone can go. These include privately owned spaces open to

321-665: A central authority. The term can also refer either to the physical streets and buildings of the city or to the collection of people who dwell there and can be used in a general sense to mean urban rather than rural territory . National censuses use a variety of definitions – invoking factors such as population , population density , number of dwellings , economic function, and infrastructure – to classify populations as urban. Typical working definitions for small-city populations start at around 100,000 people. Common population definitions for an urban area (city or town) range between 1,500 and 50,000 people, with most U.S. states using

428-461: A central point. This form could evolve from successive growth over a long time, with concentric traces of town walls and citadels marking older city boundaries. In more recent history, such forms were supplemented by ring roads moving traffic around the outskirts of a town. Dutch cities such as Amsterdam and Haarlem are structured as a central square surrounded by concentric canals marking every expansion. In cities such as Moscow , this pattern

535-432: A city compared with surrounding rural areas." This relative warmth is caused by "heat trapping due to land use, the configuration and design of the built environment , including street layout and building size, the heat-absorbing properties of urban building materials, reduced ventilation, reduced greenery and water features, and domestic and industrial heat emissions generated directly from human activities". Throughout

642-401: A city is that trees also help fight global warming by absorbing CO 2 from the atmosphere. Painting rooftops white has become a common strategy to reduce the heat island effect. In cities, there are many dark coloured surfaces that absorb the heat of the sun in turn lowering the albedo of the city. White rooftops allow high solar reflectance and high solar emittance, increasing the albedo of

749-552: A combination of these. Societies that live in cities are often called civilizations . The degree of urbanization is a modern metric to help define what comprises a city: "a population of at least 50,000 inhabitants in contiguous dense grid cells (>1,500 inhabitants per square kilometer)". This metric was "devised over years by the European Commission , OECD , World Bank and others, and endorsed in March [2021] by

856-620: A continuous urban landscape called urban agglomeration , conurbation , or megalopolis (exemplified by the BosWash corridor of the Northeastern United States .) The emergence of cities from proto-urban settlements , such as Çatalhöyük , is a non-linear development that demonstrates the varied experiences of early urbanization . The cities of Jericho , Aleppo , Byblos , Faiyum , Yerevan , Athens , Matera , Damascus , and Argos are among those laying claim to

963-430: A distinctive elite social class, but it should indeed be considered a city based on a functional redefinition of urban development. In particular, Jenné-Jeno featured settlement mounds arranged according to a horizontal, rather than vertical, power hierarchy, and served as a center of specialized production and exhibited functional interdependence with the surrounding hinterland. More recently, scholars have concluded that

1070-477: A grid plan with specialized districts used across the Hellenistic Mediterranean . The urban-type settlement extends far beyond the traditional boundaries of the city proper in a form of development sometimes described critically as urban sprawl . Decentralization and dispersal of city functions (commercial, industrial, residential, cultural, political) has transformed the very meaning of

1177-524: A heat wave, as it deprives urban residents of the cool relief found in rural areas during the night. Increased temperatures have been reported to cause heat illnesses , such as heat stroke , heat exhaustion , heat syncope , and heat cramps . Extreme heat is the deadliest form of weather in the U.S. Per a study by Professor Terri Adams-Fuller, heat waves kill more people in the U.S. than hurricanes, floods, and tornadoes combined. These heat illnesses are more common within medium-to-large metro areas than

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1284-511: A key role in both the economy and government. Late antique cities in the East were also undergoing intense transformations, with increased political participation of the crowds and demographical fluctuations. Christian communities and their doctrinal differences increasingly shaped the urban fabric. The locus of power shifted to Constantinople and to the ascendant Islamic civilization with its major cities Baghdad , Cairo , and Córdoba . From

1391-679: A large percentage of solar heat creating warmer near-surface temperatures. Paving with light-coloured concrete, in addition to replacing asphalt with light-coloured concrete, communities may be able to lower average temperatures. However, research into the interaction between reflective pavements and buildings has found that, unless the nearby buildings are fitted with reflective glass, solar radiation reflected off light-coloured pavements can increase building temperatures, increasing air conditioning demands. There are specific paint formulations for daytime radiative cooling that reflect up to 98.1% of sunlight. Green roofs are excellent insulators during

1498-601: A line of telephone poles were installed along the border cut through Ambos Nogales and guard posts were implemented at the crossing gates between the two settlements. Additional material was added to the border by the United States in response to the Mexican Revolution (1911–1918) with the addition of a barbed wire fence. The next addition, also by the United States, was a six-foot-high chain link fence including electric lights and new gatehouses on both

1605-531: A minimum between 1,500 and 5,000 inhabitants. Some jurisdictions set no such minima. In the United Kingdom , city status is awarded by the Crown and then remains permanent. (Historically, the qualifying factor was the presence of a cathedral , resulting in some very small cities such as Wells , with a population of 12,000 as of 2018 , and St Davids , with a population of 1,841 as of 2011 .) According to

1712-703: A privileged elite among towns having won self-governance from their local lord or having been granted self-governance by the emperor and being placed under his immediate protection. By 1480, these cities, as far as still part of the empire, became part of the Imperial Estates governing the empire with the emperor through the Imperial Diet . By the 13th and 14th centuries, some cities become powerful states, taking surrounding areas under their control or establishing extensive maritime empires. In Italy, medieval communes developed into city-states including

1819-539: A result of this warming, monthly rainfall is about 28% greater between 20 and 40 miles (32 and 64 km) downwind of cities, compared with upwind. Some cities show a total precipitation increase of 51%. One study concluded that cities change the climate in area two–four times larger than their own area. One 1999 comparison between urban and rural areas proposed that urban heat island effects have little influence on global mean temperature trends . Others suggested that urban heat islands affect global climate by impacting

1926-510: A result, high daytime surface temperatures within the UHI can be easily seen via thermal remote sensing . As is often the case with daytime heating, this warming also has the effect of generating convective winds within the urban boundary layer . At night, the situation reverses. The absence of solar heating leads to the decrease of atmospheric convection and the stabilization of urban boundary layer. If enough stabilization occurs, an inversion layer

2033-495: A rule cannot produce their own food and therefore must develop some relationship with a hinterland that sustains them. Only in special cases such as mining towns which play a vital role in long-distance trade, are cities disconnected from the countryside which feeds them. Thus, centrality within a productive region influences siting, as economic forces would, in theory, favor the creation of marketplaces in optimal mutually reachable locations. The vast majority of cities have

2140-724: A significant increase in Surface Urban Heat Island Intensity (SUHII) from 1985 to 2017, influenced by both geographic direction and time. This research, enhancing the understanding of SUHII's spatial and temporal variations, emphasizes the need for precise urban planning to mitigate the health impacts of urban heat islands. Surface UHI's are more prominent during the day and are measured using the land surface temperature and remote sensing. UHIs also impair water quality . Hot pavement and rooftop surfaces transfer their excess heat to stormwater, which then drains into storm sewers and raises water temperatures as it

2247-474: A study by Hyunkuk Cho of Yeungnam University, an increased number of days with extreme heat each year correlates to a decrease in student test scores. High UHI intensity correlates with increased concentrations of air pollutants that gathered at night, which can affect the next day's air quality . These pollutants include volatile organic compounds , carbon monoxide , nitrogen oxides , and particulate matter . The production of these pollutants combined with

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2354-616: A study by Professor Francisco Salamanca Palou and colleagues, this residual heat can cause nighttime increases of up to 1 °C in urban areas. Increased energy use from air conditioners also contributes to carbon emissions, which doubly exacerbates the effects of UHIs. Strategies to improve urban resilience by reducing excessive heat in cities include: Planting trees in cities, cool roofs (painted white or with reflective coating) and light-coloured concrete, green infrastructure (including green roofs ), passive daytime radiative cooling . The temperature difference between urban areas and

2461-549: A super-wealthy elite living in gated communities and large masses of people living in substandard housing with inadequate infrastructure and otherwise poor conditions. Cities around the world have expanded physically as they grow in population, with increases in their surface extent, with the creation of high-rise buildings for residential and commercial use, and with development underground. Urbanization can create rapid demand for water resources management , as formerly good sources of freshwater become overused and polluted, and

2568-423: A temple. A minority viewpoint considers that cities may have arisen without agriculture, due to alternative means of subsistence (fishing), to use as communal seasonal shelters, to their value as bases for defensive and offensive military organization, or to their inherent economic function. Cities played a crucial role in the establishment of political power over an area, and ancient leaders such as Alexander

2675-441: A warming world, increasing air temperature makes the urban heat island effect in cities worse. One key risk is heatwaves in cities that are likely to affect half of the future global urban population, with negative impacts on human health and economic productivity." There are unhelpful interactions between heat and built infrastructure: These interactions increase the risk of heat stress for people living in cities. Aside from

2782-567: A workers' town associated with the pyramid of Senusret II , and the religious city Amarna built by Akhenaten and abandoned. These sites appear planned in a highly regimented and stratified fashion, with a minimalistic grid of rooms for the workers and increasingly more elaborate housing available for higher classes. In Mesopotamia, the civilization of Sumer , followed by Assyria and Babylon , gave rise to numerous cities, governed by kings and fostered multiple languages written in cuneiform . The Phoenician trading empire, flourishing around

2889-409: Is Juntos por amor a Nogales , meaning "United by the love of Nogales". Ambos Nogales has become a subject of anthropological and archaeological research due to the ways in which the material presence of the border wall has impacted the lives of those living in these cities. Investigation of community, migration , immigration (both legal and illegal), drug trafficking , gang violence , and all of

2996-522: Is a greenhouse gas whose formation will accelerate with the increase of temperature. Climate change is not a cause but an amplifier of the urban heat island effect. The IPCC Sixth Assessment Report from 2022 summarized the available research accordingly: "Climate change increases heat stress risks in cities [...] and amplifies the urban heat island across Asian cities at 1.5 °C and 2 °C warming levels, both substantially larger than under present climates [...]." The report goes on to say: "In

3103-407: Is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas. Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons and decreases the occurrence of weak tornadoes . The UHI decreases air quality by increasing

3210-406: Is formed. This traps urban air near the surface, keeping surface air warm from the still-warm urban surfaces, resulting in warmer nighttime air temperatures within the UHI. Generally speaking, the difference in temperature between the urban and surrounding rural area is more pronounced at night than in daytime. For example, in the United States, the temperature in urban areas tends to be warmer than

3317-475: Is released into streams, rivers, ponds, and lakes. Additionally, increased urban water body temperatures lead to a decrease in biodiversity in the water. For example, in August 2001, rains over Cedar Rapids, Iowa led to a 10.5 °C (18.9 °F) rise in the nearby stream within one hour, resulting in a fish kill which affected an estimated 188 fish. Since the temperature of the rain was comparatively cool,

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3424-517: Is still clearly visible. A system of rectilinear city streets and land plots, known as the grid plan , has been used for millennia in Asia, Europe, and the Americas. The Indus Valley Civilization built Mohenjo-Daro , Harappa , and other cities on a grid pattern, using ancient principles described by Kautilya , and aligned with the compass points . The ancient Greek city of Priene exemplifies

3531-548: Is the UHI Index of the surveyed area. The measure of Celsius-hours might be averaged over many days, but is specified as Celsius-hours per averaged day. The index was created to estimate the expected use of air conditioning and resulting greenhouse gas emissions in California. The index does not consider values of or differences in wind-speed, humidity, or solar influx , which might influence perceived temperature or

3638-441: Is the increased energy required for air conditioning and refrigeration in cities that are in comparatively hot climates. The heat island effect costs Los Angeles about US$ 100 million per year in energy (in the year 2000). Through the implementation of heat island reduction strategies, significant annual net energy savings have been calculated for northern locations such as Chicago, Salt Lake City, and Toronto. Every year in

3745-420: Is the most urban continent, with four-fifths of its population living in cities, including one-fifth of the population said to live in shantytowns ( favelas , poblaciones callampas , etc.). Batam , Indonesia , Mogadishu , Somalia , Xiamen , China , and Niamey , Niger , are considered among the world's fastest-growing cities, with annual growth rates of 5–8%. In general, the more developed countries of

3852-603: The Republic of Venice and the Republic of Genoa . In Northern Europe, cities including Lübeck and Bruges formed the Hanseatic League for collective defense and commerce. Their power was later challenged and eclipsed by the Dutch commercial cities of Ghent , Ypres , and Amsterdam . Similar phenomena existed elsewhere, as in the case of Sakai , which enjoyed considerable autonomy in late medieval Japan. In

3959-947: The United Nations ... largely for the purpose of international statistical comparison". The word city and the related civilization come from the Latin root civitas , originally meaning 'citizenship' or 'community member' and eventually coming to correspond with urbs , meaning 'city' in a more physical sense. The Roman civitas was closely linked with the Greek polis —another common root appearing in English words such as metropolis . In toponymic terminology, names of individual cities and towns are called astionyms (from Ancient Greek ἄστυ 'city or town' and ὄνομα 'name'). Urban geography deals both with cities in their larger context and with their internal structure. Cities are estimated to cover about 3% of

4066-505: The Uruk period . In the fourth and third millennium BC , complex civilizations flourished in the river valleys of Mesopotamia , India , China , and Egypt . Excavations in these areas have found the ruins of cities geared variously towards trade, politics, or religion. Some had large, dense populations , but others carried out urban activities in the realms of politics or religion without having large associated populations. Among

4173-730: The civilization of Djenne-Djenno was likely established by the Mande progenitors of the Bozo people . Their habitation of the site spanned the period from 3rd century BCE to 13th century CE. Archaeological evidence from Jenné-Jeno, specifically the presence of non-West African glass beads dated from the third century BCE to the fourth century CE, indicates that pre-Arabic trade contacts probably existed between Jenné-Jeno and North Africa. Additionally, other early urban centers in West Africa, dated to around 500 CE, include Awdaghust , Kumbi Saleh ,

4280-508: The commune ( in France and Chile ; or comune in Italy). Urban heat island Urban areas usually experience the urban heat island ( UHI ) effect, that is, they are significantly warmer than surrounding rural areas . The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak, under block conditions, noticeably during

4387-427: The government workers . (This arrangement contrasts with the more typically horizontal relationships in a tribe or village accomplishing common goals through informal agreements between neighbors, or the leadership of a chief.) The governments may be based on heredity, religion, military power, work systems such as canal-building, food distribution, land-ownership, agriculture, commerce, manufacturing, finance, or

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4494-507: The grey-headed flying fox ( Pteropus poliocephalus ) and the common house gecko ( Hemidactylus frenatus ). Grey-headed flying foxes, found in Melbourne, Australia , colonized urban habitats following the increase in temperatures there. Increased temperatures, causing warmer winter conditions, made the city more similar in climate to the more northerly wildland habitat of the species. With temperate climates, urban heat islands will extend

4601-538: The knowledge economy . A new smart city paradigm, supported by institutions such as the RAND Corporation and IBM , is bringing computerized surveillance , data analysis, and governance to bear on cities and city dwellers. Some companies are building brand-new master-planned cities from scratch on greenfield sites. Urbanization is the process of migration from rural to urban areas, driven by various political, economic, and cultural factors. Until

4708-564: The service economy and public-private partnerships , with concomitant gentrification , uneven revitalization efforts , and selective cultural development. Under the Great Leap Forward and subsequent five-year plans continuing today, China has undergone concomitant urbanization and industrialization and become the world's leading manufacturer . Amidst these economic changes, high technology and instantaneous telecommunication enable select cities to become centers of

4815-457: The summer and winter . The main cause of the UHI effect is from the modification of land surfaces while waste heat generated by energy usage is a secondary contributor. Urban areas occupy about 0.5% of the Earth's land surface but host more than half of the world's population. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island

4922-514: The use of lighter-colored surfaces and less absorptive building materials. These reflect more sunlight and absorb less heat. Climate change is not the cause of urban heat islands but it is causing more frequent and more intense heat waves which in turn amplify the urban heat island effect in cities. Compact, dense urban development may increase the urban heat island effect, leading to higher temperatures and increased exposure. A definition of urban heat island is: "The relative warmth of

5029-666: The world population now lives in cities, which has had profound consequences for global sustainability . Present-day cities usually form the core of larger metropolitan areas and urban areas —creating numerous commuters traveling toward city centres for employment, entertainment, and education. However, in a world of intensifying globalization , all cities are to varying degrees also connected globally beyond these regions. This increased influence means that cities also have significant influences on global issues , such as sustainable development , climate change , and global health . Because of these major influences on global issues,

5136-535: The " Global North " remain more urbanized than the less developed countries of the " Global South "—but the difference continues to shrink because urbanization is happening faster in the latter group. Asia is home to by far the greatest absolute number of city-dwellers: over two billion and counting. The UN predicts an additional 2.5 billion city dwellers (and 300 million fewer country dwellers) worldwide by 2050, with 90% of urban population expansion occurring in Asia and Africa. Megacities , cities with populations in

5243-539: The "functional definition", a city is not distinguished by size alone, but also by the role it plays within a larger political context. Cities serve as administrative, commercial, religious, and cultural hubs for their larger surrounding areas. The presence of a literate elite is often associated with cities because of the cultural diversities present in a city. A typical city has professional administrators , regulations, and some form of taxation (food and other necessities or means to trade for them) to support

5350-532: The 18th century), Ile-Ifẹ̀ (70,000 to 105,000 inhabitants in the 14th and 15th centuries), Niani (50,000 inhabitants in 1400 AD) and Timbuktu (100,000 inhabitants in 1450 AD). In the West, nation-states became the dominant unit of political organization following the Peace of Westphalia in the seventeenth century. Western Europe's larger capitals (London and Paris) benefited from the growth of commerce following

5457-420: The 18th century, an equilibrium existed between the rural agricultural population and towns featuring markets and small-scale manufacturing. With the agricultural and industrial revolutions urban population began its unprecedented growth, both through migration and demographic expansion . In England , the proportion of the population living in cities jumped from 17% in 1801 to 72% in 1891. In 1900, 15% of

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5564-718: The 30th and 18th centuries BC. Mesoamerica saw the rise of early urbanism in several cultural regions, beginning with the Olmec and spreading to the Preclassic Maya , the Zapotec of Oaxaca, and Teotihuacan in central Mexico. Later cultures such as the Aztec , Andean civilizations , Mayan , Mississippians , and Pueblo peoples drew on these earlier urban traditions. Many of their ancient cities continue to be inhabited, including major metropolitan cities such as Mexico City , in

5671-750: The 9th through the end of the 12th century, Constantinople , the capital of the Eastern Roman Empire , was the largest and wealthiest city in Europe, with a population approaching 1 million. The Ottoman Empire gradually gained control over many cities in the Mediterranean area, including Constantinople in 1453 . In the Holy Roman Empire , beginning in the 12th century, free imperial cities such as Nuremberg , Strasbourg , Frankfurt , Basel , Zürich , and Nijmegen became

5778-566: The Andes, the first urban centers developed in the Norte Chico civilization , Chavin and Moche cultures, followed by major cities in the Huari , Chimu , and Inca cultures. The Norte Chico civilization included as many as 30 major population centers in what is now the Norte Chico region of north-central coastal Peru . It is the oldest known civilization in the Americas, flourishing between

5885-529: The Great founded and created them with zeal. Jericho and Çatalhöyük , dated to the eighth millennium BC , are among the earliest proto-cities known to archaeologists. However, the Mesopotamian city of Uruk from the mid-fourth millennium BC (ancient Iraq) is considered by most archaeologists to be the first true city, innovating many characteristics for cities to follow, with its name attributed to

5992-481: The U.S. 15% of energy goes towards the air conditioning of buildings in these urban heat islands. It was reported in 1998 that "the air conditioning demand has risen 10% within the last 40 years." Increases in air conditioning use also serve to worsen the effects of UHIs at night. While cooler nights are often a reprieve from heat waves during the day, the residual heat created by the use of air conditioning systems can lead to higher nighttime temperatures. According to

6099-524: The UHI effect within urban areas is the UHI Index created by the Californian EPA in 2015. It compares the temperature of a surveyed area and rural reference points upwind from the surveyed area, at a height of two meters above ground level. The difference in temperature in degrees Celsius is taken hourly and differences with an increased urban temperature compared to the reference points are summed up, creating an amount of degree-Celsius-hours, which

6206-451: The UHI. Heat islands can be affected by proximity to different types of land cover, so that proximity to barren land causes urban land to become hotter and proximity to vegetation makes it cooler. High levels of air pollution in urban areas can also increase the UHI, as many forms of pollution change the radiative properties of the atmosphere. UHI not only raises urban temperatures but also increases ozone concentrations because ozone

6313-578: The United States and Mexican sides of the border. This chain-link fence constituted the barrier separating Ambos Nogales for the next 65 years and became a symbol of the relationship established between the two cities (see "Changes in Public Perception of the Border"). City Historically, city dwellers have been a small proportion of humanity overall, but following two centuries of unprecedented and rapid urbanization , more than half of

6420-409: The activities associated with these has occurred at Ambos Nogales due to its unique identity and geographic position. The barrier dividing Nogales, Arizona and Nogales, Sonora has undergone a handful of material changes from the 19th century up to the present. It was not until 1898 that a material division other than stone cairns and obelisks marked the division between the United States and Mexico,

6527-536: The ancient capital of Ghana, and Maranda , a center located on a trade route between Egypt and Gao. The dissolution of the Roman Empire in the West was connected with profound changes in urban fabric of western Europe. In places where Roman administration quickly weakened urbanism went through a profound crisis, even if it continued to remain an important symbolic factor. In regions like Italy or Spain cities diminished in size but nevertheless continued to play

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6634-464: The athletic, artistic, spiritual, and political life of the polis. Rome was the first city that surpassed one million inhabitants. Under the authority of its empire , Rome transformed and founded many cities ( Colonia ), and with them brought its principles of urban architecture, design, and society. In the ancient Americas , early urban traditions developed in the Andes and Mesoamerica . In

6741-407: The benefit of mitigating the urban heat island effect, especially in cities that are in warmer climates. These spaces prevent carbon imbalances, extreme habitat losses, electricity and water consumption, and human health risks. The urban structure generally follows one or more basic patterns: geomorphic, radial, concentric, rectilinear, and curvilinear. The physical environment generally constrains

6848-421: The built environment. Seasonal variability is less well understood than diurnal variability of the urban heat island temperature difference. Complex relationships between precipitation, vegetation, solar radiation, and surface materials in various local climate zones play interlocking roles that influence seasonal patterns of temperature variation in a particular urban heat island. One method to quantify

6955-497: The city can be another way of increasing albedo and decreasing the urban heat island effect. It is recommended to plant deciduous trees because they can provide many benefits such as more shade in the summer and not blocking warmth in winter. Trees are a necessary feature in combating most of the urban heat island effect because they reduce air temperatures by 10 °F (5.6 °C), and surface temperatures by up to 20–45 °F (11–25 °C). Another benefit of having trees in

7062-504: The city or area the effect is occurring. Additionally, covering rooftops with a reflective coating, has shown to be an effective measure to reduce solar heat gain. A study led by Oscar Brousse from University College London, which simulated the impact of various cooling measures in London found that rooftops, which were either painted white or had reflective coating, proved to be the most effective solution for reducing outdoor temperatures at

7169-561: The day; materials commonly used in urban areas for pavement and roofs, such as concrete and asphalt , have significantly different thermal bulk properties (including heat capacity and thermal conductivity ) and surface radiative properties ( albedo and emissivity ) than the surrounding rural areas. This causes a change in the energy budget of the urban area, often leading to higher temperatures than surrounding rural areas. Pavements , parking lots , roads or, more generally speaking transport infrastructure , contribute significantly to

7276-405: The daytime, particularly when the skies are cloudless, urban surfaces are warmed by the absorption of solar radiation . Surfaces in the urban areas tend to warm faster than those of the surrounding rural areas. By virtue of their high heat capacities , urban surfaces act as a reservoir of heat energy. For example, concrete can hold roughly 2,000 times as much heat as an equivalent volume of air. As

7383-633: The deaths could be attributed to the hot pavement of the city. Similar events have been documented across the American Midwest, as well as Oregon and California. Rapid temperature changes can be stressful to aquatic ecosystems. With the temperature of the nearby buildings sometimes reaching a difference of over 50 °F (28 °C) from the near-surface air temperature, precipitation warms rapidly, and run-off into nearby streams, lakes and rivers (or other bodies of water) to provide excessive thermal pollution . The increase in thermal pollution has

7490-542: The early Old World cities, Mohenjo-daro of the Indus Valley civilization in present-day Pakistan , existing from about 2600 BC, was one of the largest, with a population of 50,000 or more and a sophisticated sanitation system . China's planned cities were constructed according to sacred principles to act as celestial microcosms . The Ancient Egyptian cities known physically by archaeologists are not extensive. They include (known by their Arab names) El Lahun ,

7597-632: The effect on temperature, UHIs can produce secondary effects on local meteorology, including the altering of local wind patterns, the development of clouds and fog , the humidity , and the rates of precipitation. The extra heat provided by the UHI leads to greater upward motion, which can induce additional shower and thunderstorm activity. In addition, the UHI creates during the day a local low pressure area where relatively moist air from its rural surroundings converges, possibly leading to more favorable conditions for cloud formation. Rainfall rates downwind of cities are increased between 48% and 116%. Partly as

7704-484: The emergence of an Atlantic trade. However, most towns remained small. During the Spanish colonization of the Americas, the old Roman city concept was extensively used. Cities were founded in the middle of the newly conquered territories and were bound to several laws regarding administration, finances, and urbanism. The growth of the modern industry from the late 18th century onward led to massive urbanization and

7811-777: The first comprehensive numerical treatment to predict the effects of the urban heat island (UHI) in 1969. The heat island effect was found to be the net result of several competing physical processes. In general, reduced evaporation in the city center and the thermal properties of the city building and paving materials are the dominant parameters. Modern simulation environments include ENVI-met , which simulates all interactions between building and ground surfaces, plants and ambient air. There are several causes of an urban heat island (UHI) related to common urban design aspects. For example, dark surfaces absorb significantly more solar radiation , which causes urban concentrations of roads and buildings to heat more than suburban and rural areas during

7918-812: The first millennium AD, the Khmer capital of Angkor in Cambodia grew into the most extensive preindustrial settlement in the world by area, covering over 1,000 km and possibly supporting up to one million people. West Africa already had cities before the Common Era , but the consolidation of Trans-Saharan trade in the Middle Ages multiplied the number of cities in the region, as well as making some of them very populous, notably Gao (72,000 inhabitants in 800 AD), Oyo-Ile (50,000 inhabitants in 1400 AD, and may have reached up to 140,000 inhabitants in

8025-485: The flow of the water in ways that can mitigate UHI effect. One way is using a stormwater management technique called pervious pavement system (PPS). This technique has been used in over 30 countries and found to be successful in stormwater management and UHI mitigation. The PPS allows water to flow through the pavement allowing for the water to be absorbed causing the area to be cooled by evaporation. Green parking lots use vegetation and surfaces other than asphalt to limit

8132-440: The form in which a city is built. If located on a mountainside, urban structures may rely on terraces and winding roads. It may be adapted to its means of subsistence (e.g. agriculture or fishing). And it may be set up for optimal defense given the surrounding landscape. Beyond these "geomorphic" features, cities can develop internal patterns, due to natural growth or to city planning . In a radial structure, main roads converge on

8239-567: The growing season, therefore altering breeding strategies of inhabiting species. This can be best observed in the effects that urban heat islands have on water temperature (see effects on water bodies ). Urban heat islands caused by cities have altered the natural selection process. Selective pressures like temporal variation in food, predation and water are relaxed causing a new set of selective forces to roll out. For example, within urban habitats, insects are more abundant than in rural areas. Insects are ectotherms . This means that they depend on

8346-771: The higher temperatures in UHIs can quicken the production of ozone . Ozone at surface level is considered to be a harmful pollutant. Studies suggest that increased temperatures in UHIs can increase polluted days but also note that other factors (e.g. air pressure , cloud cover , wind speed ) can also have an effect on pollution. Studies from Hong Kong have found that areas of the city with poorer outdoor urban air ventilation tended to have stronger urban heat island effects and had significantly higher all-cause mortality compared to areas with better ventilation. Another study employing advanced statistical methods in Babol city, Iran, revealed

8453-800: The international community has prioritized investment in sustainable cities through Sustainable Development Goal 11 . Due to the efficiency of transportation and the smaller land consumption , dense cities hold the potential to have a smaller ecological footprint per inhabitant than more sparsely populated areas. Therefore, compact cities are often referred to as a crucial element in fighting climate change. However, this concentration can also have some significant negative consequences, such as forming urban heat islands , concentrating pollution , and stressing water supplies and other resources. A city can be distinguished from other human settlements by its relatively great size, but also by its functions and its special symbolic status , which may be conferred by

8560-469: The jet stream. UHIs have the potential to directly influence the health and welfare of urban residents. As UHIs are characterized by increased temperature, they can potentially increase the magnitude and duration of heat waves within cities. The number of individuals exposed to extreme temperatures is increased by the UHI-induced warming. The nighttime effect of UHIs can be particularly harmful during

8667-478: The lack of a shared framework for making such comparisons. Stormwater management is another option to help mitigate the effect of the urban heat island. Stormwater management is the controlling the water produced by the storm in a way that protects property and infrastructure. Urban infrastructure like streets, sidewalks, and parking lots do not allow for water to penetrate into the earth's surface causing water to flood. By using stormwater management, you can control

8774-420: The land surface of the Earth. Town siting has varied through history according to natural, technological, economic, and military contexts. Access to water has long been a major factor in city placement and growth, and despite exceptions enabled by the advent of rail transport in the nineteenth century, through the present most of the world's urban population lives near the coast or on a river. Urban areas as

8881-475: The longest continual inhabitation . Cities, characterized by population density , symbolic function, and urban planning , have existed for thousands of years. In the conventional view, civilization and the city were both followed by the development of agriculture , which enabled the production of surplus food and thus a social division of labor (with concomitant social stratification ) and trade . Early cities often featured granaries , sometimes within

8988-497: The multi-millions, have proliferated into the dozens, arising especially in Asia, Africa, and Latin America. Economic globalization fuels the growth of these cities, as new torrents of foreign capital arrange for rapid industrialization, as well as the relocation of major businesses from Europe and North America, attracting immigrants from near and far. A deep gulf divides the rich and poor in these cities, which usually contain

9095-417: The operation of air conditioners. If a city or town has a good system of taking weather observations the UHI can be measured directly. An alternative is to use a complex simulation of the location to calculate the UHI, or to use an approximate empirical method. Such models allow the UHI to be included in estimates of future temperatures rises within cities due to climate change. Leonard O. Myrup published

9202-617: The other sources of the problem, replacing dark roofing requires the least amount of investment for the most immediate return. A cool roof made from a reflective material such as vinyl reflects at least 75 percent of the sun's rays, and emit at least 70 percent of the solar radiation absorbed by the building envelope. Asphalt built-up roofs (BUR), by comparison, reflect 6 percent to 26 percent of solar radiation. Using light-coloured concrete has proven effective in reflecting up to 50% more light than asphalt and reducing ambient temperature. A low albedo value, characteristic of black asphalt, absorbs

9309-685: The overall albedo of the city. Concentric expansion of cities is unfavourable in terms of the urban heat island phenomenon. It is recommended to plan the development of cities in strips, consistent with the hydrographic network, taking into account green areas with various plant species. In this way, it was planned to build urban settlements stretching over large areas, e.g. Kielce , Szczecin and Gdynia in Poland, Copenhagen in Denmark and Hamburg , Berlin and Kiel in Germany. Planting trees around

9416-436: The pedestrian level, outperforming solar panels, green roofs, and tree cover. The study simulated the impact of various cooling measures in London during a 2018 heatwave, finding that the so-called cool roofs could reduce average outdoor temperatures by 1.2 °C, and up to 2 °C in certain areas. In comparison, additional tree cover reduced temperatures by 0.3 °C and solar panels by 0.5° C. Relative to remedying

9523-596: The potential to increase water temperature by 20 to 30 °F (11 to 17 °C). This increase causes the fish species inhabiting the body of water to undergo thermal stress and shock due to the rapid change in temperature of their habitat. Permeable pavements may reduce these effects by percolating water through the pavement into subsurface storage areas where it can be dissipated through absorption and evaporation. Species that are good at colonizing can use conditions provided by urban heat islands to thrive in regions outside of their normal range. Examples of this include

9630-480: The price of labor and equipment in that market, which is typically lower in more developed markets where there is more experience designing and installing green roofs. The individualized context of each green roof presents a challenge for making broad comparisons and assessments, and focusing only on monetary costs may leave out the social, environmental, and public health benefits green roofs provide. Global comparisons of green roof performance are further challenged by

9737-601: The production of pollutants such as ozone , and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems . Not all cities have a distinct urban heat island, and the heat island characteristics depend strongly on the background climate of the area in which the city is located. The impact in a city can change a lot based on its local environment. Heat can be reduced by tree cover and green space which act as sources of shade and promote evaporative cooling. Other options include green roofs , passive daytime radiative cooling applications, and

9844-500: The public as well as forms of public land such as public domain and the commons . Western philosophy since the time of the Greek agora has considered physical public space as the substrate of the symbolic public sphere . Public art adorns (or disfigures) public spaces. Parks and other natural sites within cities provide residents with relief from the hardness and regularity of typical built environments . Urban green spaces are another component of public space that provides

9951-435: The rest of the U.S., largely in part due to UHIs. Heat illnesses can also be compounded when combined with air pollution which is common in many urban areas. Heat exposure can have adverse effects on mental health. Increases in temperature can contribute to increased aggression, as well as more cases of domestic violence and substance abuse. Greater heat can also negatively impact school performance and education. According to

10058-810: The rise of new great cities, first in Europe and then in other regions, as new opportunities brought huge numbers of migrants from rural communities into urban areas. England led the way as London became the capital of a world empire and cities across the country grew in locations strategic for manufacturing . In the United States from 1860 to 1910, the introduction of railroads reduced transportation costs, and large manufacturing centers began to emerge, fueling migration from rural to city areas. Some industrialized cities were confronted with health challenges associated with overcrowding , occupational hazards of industry, contaminated water and air, poor sanitation , and communicable diseases such as typhoid and cholera . Factories and slums emerged as regular features of

10165-698: The same location as Tenochtitlan ; while ancient continuously inhabited Pueblos are near modern urban areas in New Mexico , such as Acoma Pueblo near the Albuquerque metropolitan area and Taos Pueblo near Taos ; while others like Lima are located nearby ancient Peruvian sites such as Pachacamac . From 1600 BC, Dhar Tichitt , in the south of present-day Mauritania , presented characteristics suggestive of an incipient form of urbanism. The second place to show urban characteristics in West Africa

10272-561: The shade and evaporative cooling effect of trees. Other causes of a UHI are due to geometric effects. The tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated. This is called the " urban canyon effect ". Another effect of buildings is the blocking of wind, which also inhibits cooling by convection and prevents pollutants from dissipating. Waste heat from automobiles, air conditioning, industry, and other sources also contributes to

10379-430: The surrounding area by about 1-7 °F (0.6-4 °C) during the daytime, and about 2-5 °F (1-3 °C) warmer at night. However, the difference is more pronounced during the day in arid climates such as those in southeastern China and Taiwan. Studies have shown that diurnal variability is impacted by several factors including local climate and weather, seasonality, humidity, vegetation, surfaces, and materials in

10486-406: The surrounding suburban or rural areas can be as much as 5 °C (9.0 °F). Nearly 40 percent of that increase is due to the prevalence of dark roofs, with the remainder coming from dark-coloured pavement and the declining presence of vegetation. The heat island effect can be counteracted slightly by using white or reflective materials to build houses, roofs, pavements, and roads, thus increasing

10593-618: The temperature of the environment to control their body temperature, making the warmer climates of the city perfect for their ability to thrive. A study done in Raleigh, North Carolina conducted on Parthenolecanium quercifex (oak scales), showed that this particular species preferred warmer climates and were therefore found in higher abundance in urban habitats than on oak trees in rural habitats. Over time spent living in urban habitats, they have adapted to thrive in warmer climates than in cooler ones. Another consequence of urban heat islands

10700-489: The term and has challenged geographers seeking to classify territories according to an urban-rural binary. Metropolitan areas include suburbs and exurbs organized around the needs of commuters , and sometimes edge cities characterized by a degree of economic and political independence. (In the US these are grouped into metropolitan statistical areas for purposes of demography and marketing .) Some cities are now part of

10807-412: The turn of the first millennium BC , encompassed numerous cities extending from Tyre , Cydon , and Byblos to Carthage and Cádiz . In the following centuries, independent city-states of Greece , especially Athens , developed the polis , an association of male landowning citizens who collectively constituted the city. The agora , meaning "gathering place" or "assembly", was the center of

10914-497: The urban heat island effect. For example, pavement infrastructure is a main contributor to urban heat during summer afternoons in Phoenix , United States. Another major reason is the lack of evapotranspiration (for example, through lack of vegetation) in urban areas. The U.S. Forest Service found in 2018 that cities in the United States are losing 36 million trees each year. With a decreased amount of vegetation, cities also lose

11021-446: The urban landscape. In the second half of the 20th century, deindustrialization (or " economic restructuring ") in the West led to poverty , homelessness , and urban decay in formerly prosperous cities. America's "Steel Belt" became a " Rust Belt " and cities such as Detroit , Michigan, and Gary, Indiana began to shrink , contrary to the global trend of massive urban expansion. Such cities have shifted with varying success into

11128-589: The volume of sewage begins to exceed manageable levels. The local government of cities takes different forms including prominently the municipality (especially in England , in the United States , India , and other British colonies ; legally, the municipal corporation ; municipio in Spain and Portugal , and, along with municipalidad , in most former parts of the Spanish and Portuguese empires) and

11235-414: The warm weather months and the plants cool the surrounding environment. Plants can improve air quality as they absorb carbon dioxide and concomitantly produce oxygen. Green roofs can also have positive impacts on stormwater management and energy consumption. Cost can be a barrier to implementing a green roof. Several factors influence the cost of a green roof, including design and soil depth, location, and

11342-523: The world's population lived in cities. The cultural appeal of cities also plays a role in attracting residents. Urbanization rapidly spread across Europe and the Americas and since the 1950s has taken hold in Asia and Africa as well. The Population Division of the United Nations Department of Economic and Social Affairs reported in 2014 that for the first time, more than half of the world population lives in cities. Latin America

11449-543: Was Dia , in present-day Mali , from 800 BC. Both Dhar Tichitt and Dia were founded by the same people: the Soninke , who would later also found the Ghana Empire . Another ancient site, Jenné-Jeno , in what is today Mali , has been dated to the third century BCE. According to Roderick and Susan McIntosh, Jenné-Jeno did not fit into traditional Western conceptions of urbanity as it lacked monumental architecture and

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