DBJ Research Center on Global Warming
Discussion Paper Series No. 43 (7/2011)

Cities and Heat-island

Katsuhisa Uchiyama

This paper is a preliminary material in the draft form to stimulate discussion
and comments from academics and policy makers. Views expressed in thispaper are those of the author(s) and do not necessarily reflect the official
views of the Development Bank of Japan.

1

Cities and Heat-island
Katsuhisa Uchiyama

1. Introduction
While global warming problem is widely recognized as an important subject to be solved, it
is also noticeable that the temperature of urban area rises in recent years. It was cool in themorning and evening even in summer in the metropolises such as Tokyo. However, people
are hit by the record heat wave every year, and the temperature stops falling down even ifnight comes. Walking in the town of tall buildings in the daytime of summer, most people
will feel that the aggravation of urban environment proceeds, because the narrow street
space is polluted by heat emissions from buildings and automobiles, by the concentrationof them, and by the multiplex reflection of heat from roads and buildings. The reports
about the number of victims of heat stroke are seen frequently these days. Air conditioners
are always indispensable in such cities to get along comfortably. People continue to use air
conditioners even though they notice that the waste heat from air conditioners is one of
the factors of the temperature rise, and then they are falling into a vicious circle. In addition
to summer, the number of the days whose daily lowest temperature is below 0 ºC decreases
in winter.
The temperature of the center of Tokyo rose at about 3 ºC in the past 100 years,
as we see it in detail in the next section. Various influences such as health damage and the
localized torrential downpour in summer arise to our life from this phenomenon. As for
global warming problem, according to the IPCC (Intergovernmental Panel on Climate
Change) 3rd report, the average earth's surface temperature will rise to 1.4-5.8 ºC from1990 through 2100. The unstabilization of climate condition and the bad influences tomankind associated with it are being expected. The temperature change of Tokyo in thepast 100 years might as well be expressing and anticipating exactly the average temperaturechange of the whole earth in the 21st century. Therefore, it can be said that even thevarious influences that have occurred in urban regions at present are the precious datasuggesting the figure of the future earth. If no countermeasure is touched from now on, it
seems that urban environment becomes worse all the more with the influences of global
warming.
The various phenomena associated with the rise of urban temperature are known

2
as "heat-island phenomenon" these days. This phenomenon is also observed in many citiesof the world, and thought to originate in the advancement of urbanization and in waste
heat associated with the intensive energy consumption in cities.
The quantity of energy which mankind uses is said about 0.01% of the energy
which the ground surface receives from solar radiation, and therefore the direct influenceof the waste heat from energy consumption is not so much if we see it with the scale of thewhole earth. As it is well known, it is not heat emissions from cities but greenhouse gasses
by fossil fuel combustion and so on that influence on global warming. The influences ofartificial exhaust heat, however, cannot be disregarded when discussing urban regions
limitedly, because energy consumption is carried out in local places such as cites. Thinking
of a unit area, the central districts of Tokyo and New York are said to radiate the energy
which is close to the quantity they receive from the sun. Therefore the situation will be not
too much to say with "the heat contamination of city." However, it has not beenrecognized as an important problem very much, partly because there were little concrete
damage and influence so far.
The purpose of this paper is to consider the problem of urban warming, focusing
on the heat antipollution measures for the solution of the urban problem rather than theprevention measure of greenhouse gases. We will recognize the heat contamination of
cities called heat-island phenomenon as an important problem that equals to urban
pollution problems, and then we will examine it comprehensively.

2. Heat-island Phenomenon
As for the scientific aspects of heat-island phenomenon, many researchers are proceedingwith the clarification vigorously. In this section, we will survey the characteristic points ofheat-island phenomenon such as the situations, causes and influences, based on the existing
research results.

2.1 What is Heat-island Phenomenon?
"Urban climate" is a climate as a conclusion of the climate change caused by theadvancement of urbanization. Heat-island phenomenon is one of the characteristics of theurban climate. Heat-island phenomenon is a phenomenon that the temperature of an urban
region becomes higher in comparison with the suburban area. When we draw the3isotherms of temperature about the area where an urban region and a suburban area are
combined, the form of the distribution becomes the state of closed-shaped curve aroundthe center of the city. It looks like the contour lines seen in the map of an island on theocean, and then has come to be called heat-island by the analogy.
It has known that the temperature of urban region becomes higher in comparison
with suburbs since the old days. Howard (1833) was the first research which showed thefact using the observation of the climate data during 1807-1816 in London. In London at
the beginning of the 19th century, the progress of urbanization was remarkable with thedevelopment of industries and the concentration of population by the Industrial
Revolution. Therefore, it is inferred that not only the natural environment and ecosystembut also the climate of the urban region was changing very much. After that thetemperature rise in urban region seems to be observed even in the big cities in Europe suchas Berlin, Vienna, and Paris at the beginning of the 20th century. It is said that Duckworth
and Sandberg (1954), the meteorologists of the United States, were the first paper which
named this phenomenon "heat-island" and have come to collect the concerns. Heat-island
phenomenon is being observed in many cities in the world these days, and making the life
in urban region uncomfortable. Because of this, the accumulation of observations andresearches is carried out as one of the fields of urban environmental problems in Europe
and America. In Japan the occurrences of it are confirmed in not only big cities but also
small and medium sized cities. The researches are advanced vigorously among
meteorologists, geographers, urban engineering scholars and architecture scholars.

2.2 Characteristics of Heat-island Phenomenon
Heat-island phenomenon is thought generally to distinguish from global warming since thecauses are different each other. However, both of them have many common points at thesame time. The remarkable feature of heat-island phenomenon is that it combines thenature of global warming problem and the nature of air pollution problem. The similarities
with global warming are, firstly, that the pollutants themselves are not harmful. Most ofgreenhouse gases such as carbon dioxide do not bring harm to mankind, animals andplants as chemical substances. As well as greenhouse gases, "heat," which is the pollutant
bringing heat-island phenomenon, does not cause fatal damage to the life and living of
citizens to the amount of some extent.
Secondly, both of them are the problem of climate change caused by economic
activities of human, and also the problem that the polluters are the victims at the same time.

4
The victims by global warming are mankind, and the emissions of greenhouse gases which
are the cause of it are also associated with human activities. As seen in the following
subsection, the cause of heat-island phenomenon is the waste heat discharged byanonymous people in cities, and the sufferers from unpleasantness are also the urban
residents. That is, both of them are caused by the increase of energy consumption
associated with economic activities.
On the other hand, the first point in common between heat-island phenomenon
and air pollution problem is that the damage from a unit of contamination differs by timeand space. Nitrogen oxides and sulfur oxides are the flow pollutants from the viewpoint oftime, because they are purified in several hours or several days after they are discharged
into the atmosphere. Heat also has the similar pattern to them. In addition, the extent ofdamage differs at daytime and night, and depends on the season. It is contrastive with thedamage by greenhouse gases which are the stock pollutants and remain in the atmosphere
for a very long period to keep the bad influences going on.
From the viewpoint of space, heat-island phenomenon becomes a serious
problem just in an urban region, in other words, the polluted range is limited in a particulararea. This point is similar to the air pollution caused by nitrogen oxides and sulfur oxides.
Heat-island phenomenon is a problem in a domestic, moreover, a limited urban region, andits causes are clear to some extent. Consequently, if we see it from a different angle, thissuggests there are comparatively few obstacles to promote measures.
In contrast, the mechanism of global warming is very complex and there are manyto elucidate, although the primary cause of it is thought to be the accumulation ofgreenhouse gasses into the atmosphere. As for global warming, the estimated rise of
temperature and the influences on mankind are uncertain. Therefore, it is the subject tothink for a very long period of a few hundred years, and it is necessary to tackle themeasure with international cooperation. But it is not necessarily easy to promote effective
measures because of the political, economical and social differences among nations.
The second point in common is that the damage increases sharply when the levelof pollution exceeds a critical value. The appropriate environmental standards are set up
and the discharge regulation is carried out so as not to exceed it, because nitrogen oxides
and sulfur oxides do harm to human health directly through air pollution. Heat-island
phenomenon causes the increase of health damage such as heat stroke when thetemperature exceeds a critical point.

2.3 Situation of Temperature

5

We start to see the transition of the temperature of cities in order to confirm the actual
condition of heat-island phenomenon. According to the Meteorological Agency (1999), theannual average temperature rise of the Japanese metropolises for the past 100 years is 2.9ºC in Tokyo at the maximum, 2.1 ºC in Sendai at the minimum, and 2-3 ºC in general. Also
as for the big cities, the rise of temperature is higher in winter than in summer, and the riseof the lowest temperature at night is higher than that of the highest in daytime on average(Table 1). On the other hand, the rises of the annual average temperature, the averagetemperatures in January and August in small and medium sized cities where the effect ofurbanization is relatively not so much are lower than those in big cities. They are about
0.9-1.0 ºC, and there is little difference among seasons. The rise of the daily lowest
temperature is 1.4 ºC, which is low in comparison with 3.6 ºC of the average of big cities.
As seen from the above observations, the characteristics of heat-island phenomenon arethat it is more obvious in winter than in summer, more distinct at the lowest temperature atnight than at the highest temperature in the daytime, and more notable in big cities. Thisphenomenon is seen not only in Japan but also in the cities of the world in common.
<Table 1 is around here.>
Table 2 shows the annual change of the number of "tropical days" on which thetemperature rises above 30 ºC, "ice days" on which the temperature stays below 0 ºC, and"sweltering nights" on which the temperature does not fall below 25 ºC, from 1951 to 2000.
The number of ice days shows a tendency to decrease in Sapporo and Sendai. Especially in
Sapporo, it decreases greatly from 1991 through 2000 compared with the former years, andwe are able to infer the temperature rises in winter. There is a tendency to increase in thenumber of tropical days in the big cities such as Tokyo, Nagoya and Osaka, and more than
50-70 tropical days are observed every year from 1991 through 2000. The number ofsweltering nights is also in an increasing trend, and the pace to increase is faster than thatof tropical days. This shows that temperature at night is hard to fall down.
<Table 2 is around here.>
The point we must pay attention on evaluating the change of urban temperature isthat it is necessary to distinguish the influence caused by urbanization from the influencecaused by global warming. However, it is very hard in general to calculate the influence6caused by urbanization strictly, because urbanization has progressed to a greater or lessextent in the long run in cities of any kinds of scale.
The Meteorological Agency carried out a minute analysis for the temperature risein Japan excluding the elements of urbanization (Meteorological Agency, 1999). The
estimated rise of average temperature for the past 100 years in Japan was approximately 0.7ºC.
The Ministry of the Environment (2001) introduced some temperature
distribution maps on the typical summer days (fair and weak wind days covered with a
Pacific high pressure, from June to September in 1997-1999). According to the maps of the
Kanto region, a high temperature area of above 30 ºC appears from Nerima-ward over thesoutheast part of Saitama Prefecture around 10 a.m. This area expands all over the Kanto
plains around 2 p.m., and still remains from the northern part of Saitama Prefecture to thesouthern part of Gunma Prefecture even in the evening at 6 p.m. The temperature does
not fall down very much even at night in the center of Tokyo compared with the suburbs,
and the condition of high temperature continues until dawn. We can see easily that
heat-island phenomenon is formed (Figure 1).
<Figure 1 is around here.>
Another characteristic point reported on it is that the total number of hours
exposed to the high temperature of above 30 ºC from July to September is increasing
sharply. Based on the analysis, it increases three times in Sendai, twice in Tokyo andNagoya when comparing 1980 and 2000. In addition, more serious matter as a condition ofheat contamination is the expansion of the areas where the total number of hours of above
30 ºC increases. The reasons such a high temperature continues for a long time are inferred
as follows. First, the air warmed in the center of Tokyo is carried to the inland by the sea
wind from Tokyo Bay or Sagami Bay in the Kanto region. Second, the cool wind from the
Echigo region flows into the Kanto region during the middle of the night but does notreach the southeast part of Saitama Prefecture.

2.4 Influence
The influences associated with heat-island phenomenon are, firstly, the effects caused byclimate change on our daily life. It is temperature to be obvious. The high temperature of
the daytime in summer, especially the one above 35 ºC, gives people unpleasantness.

7
Heat-island phenomenon brings a sleeping difficulty, because it appears at night remarkably
and especially increases the number of sweltering nights in summer.
It is pointed out that there may be the relevance between the short time torrential
downpour in summer observed recently and heat-island phenomenon. Some people died
due to the house inundation and so on by a local downpour. The frequency of heavy rainof 10 mm and more per hour has a tendency to increase. Especially the number of theheavy downpour of over 100 mm per hour was ten times in 1999, six times in 2000,
whereas it was zero-twice in the first half of the 1990s in Japan. According to someresearches, it is thought that cumulonimbi grow easily in urban areas. The mechanism isthat urban atmospheric convection meets the wet air current from the ocean and becomesan active updraft due to the urban high temperature. As for the time zone when heavy rain
falls, the share of the evening (5 p.m.-8 p.m.) decreases to about 40%, and instead of thisthe share of the middle of the night (9 p.m.-12 a.m.) and early afternoon (1 p.m.-3 p.m.)increases to about 20% each by the observation at Otemachi in Tokyo. These observed
facts meet with the characteristics of heat-island phenomenon which temperature in cities
rises to high even in the morning and does not fall down easily even at night.
The second influence is much increase of energy demand. Cities are huge energy
consumption places, and radiate enormous waste heat at the same time. Heat-island
phenomenon has a close relation with the energy consumption in cities. The more rise ofurban temperature by artificial exhausted heat brings the excessive energy consumption
especially for air conditioning. This forms a vicious circle. The increasing number of severe
heat days and sweltering nights in midsummer pushes up the demand of electric power for
air conditioning. It is easy for us to imagine that the increase of energy consumption
becomes enormous quantity as a city total even if it is very little for each office andresidence.
The third influence, which is the most anxious about, is the damage to humanhealth. Human health condition is fragile against an extreme climate change rather than astable climate. The severe heat in midsummer is considered as a typical case of the extreme
climate change. More serious damage to human body we should be anxious about is theincrease of heat stroke though unpleasantness and sleeping difficulty at a sweltering night.
The number of persons carried by ambulances with the symptom of heat stroke has atendency to increase year by year (Figure 2). The relation with the rise of temperature byheat-island phenomenon is suspected. According to the research by Ando with thecooperation of the Tokyo Fire Defense Agency (Ando, 1998), it is reported that there is an
obvious positive correlation among the daily average temperature, the daily highest

8temperature and the number of sufferers of heat stroke when the temperature exceeds acertain level. Sufferers begin to appear with the highest temperature of around 29 ºC, andhave a tendency to increase sharply with that of around 31 ºC in Tokyo (Figure 3).
Considering the number of sufferers of heat stroke per 1 million of population, it is one
person at around 33 ºC, and two persons and more when the temperature reaches 34 ºC.
The very characteristic point is that the speed of the increase is like an exponential function.
It is forecasted that the temperature rise of only 1 ºC brings too many sufferers after it
exceeds 34 ºC. Seeing the sufferers by age, they are distributed to all the age classes of over
15 years. But it is known that the occurrence rate is extremely high for elder people of over
80 years.
<Figure 2 is around here.><Figure 3 is around here.>

3. Causes, Measures and Problems
3.1 Causes
It is artificial exhaust heat and the change of city form that generally pointed out as main
factors which influence the formation of heat-island. In fact, it seems that these factors are
acting compositely. We examine them in the following.
It is needless to say that the artificial exhaust heat is the result of energy
consumption such as petroleum, gas and electricity. The input energy is distributed andconsumed for the use of industries, transportations and other private sectors with the formof electricity and so on. However, the energy used effectively is only 30-40% of all the
input energy, and the rest is discharged into the atmosphere as waste heat in Japan.
Moreover, the energy used effectively is 37.5% of all the input energy in 1975, and it
became worse to 33% in 1994.
The energy such as petroleum, gas and electricity is finally radiated in the form of
thermal energy into the atmosphere. The sources of waste heat are buildings (residences
and offices), business activities such as factories, automobiles and so on. By investigating
the change of the energy consumption in Tokyo Metropolitan area, we are able tounderstand that the transportation sector and the business sector are contributing to theincrease of the energy consumption very much. The reasons in the transportation sector

9
are the increasing number of automobiles and the deterioration of fuel efficiency by theenlargement of automobile size. In the business sector, the reasons are the increase of floor
space by the occurrence of higher office buildings with wide basement space, the increaseof energy consumption per unit floor area by air conditioning and electronic equipment forbusiness, the diffusion of vending machines, and the extension of business hour of service
industries such as convenience stores and food restaurants. In the household sector, thereasons are the increase of the number of household itself, and the increase of energy
consumption per household by the widespread of electronic goods.
One more important factor giving the influence to urban temperature is thechange of ground surface. The decrease of water and green areas due to urbanization
causes the loss of the mechanism that latent heat of evaporation drops the urban
temperature. Most of green areas in Tokyo are small while the supply of parks is inprogress. Many small rivers disappeared along with the urbanization, and the rest of therivers are hardened with concrete walls or became culverts. The characteristic point inurban area is that most part of ground surface is covered with such materials as concrete
constructions or asphaltic paving, whereas the surface in suburban area is covered with soil.
Even if it rains on such a concrete surface, it returns to dry with little ground permeation,and then the amount of water evaporation from the surface decreases. As a result, most ofenergy from solar radiation and artificial exhaust heat becomes sensible heat, and raises
urban temperature directly.
Moreover, concrete and asphalt have big heat capacity in comparison with soil,
and have the nature that they are hard to get cold easily once they warm up. By this natureof heat storage, buildings and asphaltic roads radiate the heat saved in daytime slowly
during night, and then raise urban temperature at night.
Building high constructions expands the surface area of city, therefore it affects
negative on the thermal environment of the city. In addition, it is known that heat is easy to
be concentrated near the ground surface in the urban region where constructions ofvarious heights line up.
As mentioned above, the waste heat associated with economic activities and thechange of ground surfaces (the decrease of green spaces and the increase of artificial
surfaces) are conceivable as main factors of the rise of urban temperature. These factors are
acting compositely. It is difficult to evaluate them indiscriminately because their importancevaries in city scale, the structure of blocks and geographical features. The observations byremote sensing method and simulations by models are advanced in order to solve these
problems.

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3.2 Measures and Problems
Heat-island phenomenon has come to attract attention recently as an urban environmental
problem, and has more opportunities to be reported on the media. The Ministry of theEnvironment and some local governments including Tokyo have started the consideration
for the measures. Many scholars and researchers are tackling scientific studies toward theelucidation of the phenomenon and promoting more detailed studies using remote sensing
and model simulation methods as well as climate observations. These research results,
however, are on the way of accumulation at present.
It is hard to say that heat-island phenomenon is heading for the improvement
because administrative agencies have just begun the measures. We are able to imagine easily
that the influences and the damages by heat-island phenomenon are getting more serious
for the near term. We hope that some measures are taken promptly before the present
situation is gets worse. It is because there is a fear that heat-island phenomenon brings
health damage to the city inhabitants when the temperature exceeds a certain critical leveland because causes are comparatively definite. As for several measures, the efficacy is
confirmed to a certain extent by the simulations.
One of the problems is, however, these measures are whether or notcost-effective. The cost of them is not necessarily definite. Especially, the confirmation of
the cost and benefit is indispensable as for measures the public sector manages.
Furthermore, it is necessary to give priority which measure should be taken based on theevaluation of these measures, but such a work is delayed at present. The accumulation
regarding the cost and benefit evaluation is hastened because there is a possibility that highcost measures are implemented without these evaluation and examination.

4. Urban Atmosphere and Social Common Capital
4.1 Urban Atmosphere as Social Common CapitalSocial common capital presented by Uzawa (1994, 2000, 2005) provides members of asociety with those services and institutional arrangements that are crucial in maintaining
human and cultural life. Social common capital in principle is not appropriated toindividual members of the society but rather is held as common property resources to be11
managed by the commons in question, without, however, precluding private ownershiparrangements. Nor is it to be controlled bureaucratically by the state (Uzawa 2005). It is
generally classified into three categories: natural capital, social infrastructure, andinstitutional capital.
Natural capital consists of the natural environment and natural resources such as
forests, rivers, lakes, wetlands, oceans, water, soil, and the earth's atmosphere. Social
infrastructure is consists of roads, bridges, public mass transportation systems,
communication and postal services, and public utilities. They are the facilities forming a city.
Therefore a city is considered as the accumulation of social common capital which
provides urban inhabitants with services.
Urban atmosphere can be placed on one of the components of social common
capital when we think of it as a part of natural environment in a city.

4.2 Improvement of Artificial Ground Surface: Recovery of Water andSoil
The measures for heat-island have a role to restore urban atmosphere. The main policy to
do them is considered to revive the "water" which increases latent heat, and the "soil"
which includes green spaces. This is nothing else but the improvement of artificial groundsurface in urban region. It is considered as a trial to recover the natural state.
The restoration of water is to improve the water circulation of cities. One of thecauses of heat-island phenomenon is the expansion of the impermeable ground surface
such as concrete and asphaltic surface. This has led to the collapse of natural water
circulation systems in cities. There are two types of water circulation in cities, one is natural
circulation and another is artificial circulation of waterworks and sewer. The water
environment in cities is consists of both of them with the mutual relevance. Under thenatural circulation, rainfall infiltrates into underground and is reserved. The part of it
evaporates from ground surface and the rest forms water veins. The part which does not
infiltrate completely streams on ground surface and then flows into rivers. The evaporationfrom ground surface drops the temperature near there. The expansion of impermeablesurface associated with urbanization, however, reduces the water around the groundsurface and underground water, and increases the flow to rivers. Thus, it became difficult
to keep the natural water circulation.
Rivers have come to play the big role of drainage path together with the
expansion of impermeable ground surface; that is, it became general that river walls turned

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to concrete and that waterways were repaired to straight lines. Rainfall in a city flows out
from the city in a short time in such a way. The quantity of the flow is increasing year by
year. It often excesses the capacity of rivers and causes floods inside the city because there
is no process of water reservation on the way. The flood damage after the torrential
downpour in summer is considered to be a phenomenon related to urbanization andheat-island.
In addition to the usual water resource policies such as flood control andwaterworks, the importance of the recovery and preservation of the environment is risingin recent years. Especially the preservation and improvement of natural water circulation
attract people's attention. This is the conversion from the former idea of the speedy
exclusion of rainfall outside of city to the new idea of the enlargement of the quantity of
infiltration and reservation inside city. In order to make use of the water retention
capability of ground, it is considered to use rainfall permeation facilities as the technology
of improvement in water circulation, to recover river walls, and to improve the water
environment in parks. Rainfall permeation facility is the one to restore water to ground as
before urbanization. Water permeable paving is a type of it, for example. It is expected thatthe stock water in city leads to mitigate the heat-island phenomenon by making use of it as
measures of latent heat supply.
The recovery of ground surface plays an important role as well as natural water
circulation. Heat-island phenomenon is a problem arising from the change of land use incity, that is, the change from soil to artificial surface. Therefore, an effective measure is therevival of the former land use from the artificial surface in the city as much as possible.
Practically speaking, it is almost impossible to restore to the original land condition in thecity. Adopting water permeable paving or other water retention materials as measures is,however, a trial to recover the ground surface with the water retention capability. This is,
so to speak, to try to replace natural capital with artificial capital similar to it. Rooftop
gardening and wall surface greening as well as the improvements of green spaces are
considered to be the restoration of ground surface or soil inside city.
Green space has a close connection to both of water and soil. It is needless to saythat the capability of green space is effective for the mitigation of heat-island phenomenon.
Although rooftop gardening is promoted as one of the measures for urban tree-planting, itis necessary to secure the sufficient water supply as a precondition to it. As for roadsidetrees and greenbelts, it is difficult to take full advantage of their capability without thesufficient water supply when there is much impermeable ground surface around them.

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4.3 The Improvement of City Form
As city has an irreversible nature, it is difficult to change the form. The restoration of waterand soil is a trial to improve the form, and the efforts such as water permeable paving androoftop gardening are being carried out. But they have only limited effects in the whole
improvement of the city.
The point that an examination is needed on the relations between heat-island
phenomenon and city form is the handling of automobiles in city. The exhaust heat fromcars is considered to be controllable by raising the cost of using cars through theenvironmental tax, and moreover, by introducing fuel cell cars in the future. But it isexpected to take much time for the diffusion.
Cities depending on automobiles are not necessarily desirable from the viewpointof not only heat-island phenomenon but also global warming. Public transportation
systems are appropriate rather than automobiles in the center of a city with the high density.
On the other hand, automobiles are still effective traffic means in the suburbs and low
density areas. The role of automobiles inside city is different from outside, and therefore, it
is desirable to use them with the understanding of the effectiveness. In this sense, there
seems to be a point to be improved in the present form of the city where automobiletransportation systems are highly developed.
The conventional urban planning including zoning or floor-area ratio restrictions
has a lot of limits when we try to improve the city form in our country by the restoration ofwater and soil, and by the control of automobiles. Making synthetic policies is general in
Europe on the occasion of the urban planning instead of such a conventional one. The
policies such as a strategic vision of city, a fund-raising means, a tax system, a standard forenvironmental protection, employment, an income distribution, and so on are treated
together in it. In other words, the point of view that city is an object of the managementwith the various measures is dominant. The density in the central part of a city is high inmany European cities. Therefore, they think automobile traffic is not suitable. They
implement the exclusion of the through traffic, the yield of the right-of-way to pedestrians,
and the control of the parking area in the center of the city, by using the combination ofvarious measures. They also practice urban tree-planting and create open spaces. These
efforts are based on the idea of "sustainable city." There are some cases that good urban
environment increases the asset value of the land and buildings. In this way, the goodurban environment yields a good circulation with the improvement of the city form.

14

References
Ando, M. (1998), "The Effects of Global Warming on Human Health: Heat Stress andHeat Stroke," Global Environment, Vol. 2, No. 2, pp. 119-126. (in Japanese)
Duckworth, F. S. and J. S. Sandberg (1954), "The Effect of Cities upon Horizontal andVertical Temperature Gradients," Bulletin of American Meteorological Society, Vol. 35,
pp. 198-207.
Howard, L. (1833), Climate of London deduced from Meteorological Observations, 3rd edition, in 3
volumes, Harvey & Darton.
Meteorological Agency (1999), Abnormal Weather Report '99. (in Japanese)
Ministry of the Environment (2001), A report on the Analysis of Current Status and the Measuresfor Heat-Island Phenomenon. (in Japanese)
Uchiyama, K. (2003), "Heat-island Effects in City," in Uzawa, H., Kuninori, M. and K.
Uchiyama (eds.) Reflections on the City in the 21st Century: City as Social Overhead Capital2, pp. 249-284, Tokyo: University of Tokyo Press. (in Japanese)
Uzawa, H. (1994), "The Concept of Social Overhead Capital," in Uzawa, H. and A. Mogi
(eds.) Social Overhead Capital: Cities and the Commons, pp. 15-45, Tokyo:
University of Tokyo Press. (in Japanese)
Uzawa, H. (2000), Social Common Capital, Tokyo: Iwanami Shoten. (in Japanese)
Uzawa, H. (2005), Economic Analysis of Social Common Capital, New York: Cambridge
University Press.

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Table 1: Trends of Average Temperature (Annual, January, August), Daily Highest
Temperature (Annual Average), and Daily Lowest Temperature (Annual Average) of
Big Cities in Japan.
Changes during 100Years (ºC/100 Years)
City

Average Temperature

Daily Highest

Daily Lowest

AnnualJan.

Aug.

(Annual Average)(Annual Average)

Sapporo

+2.3

+3.1

+1.3

+0.9

+4.1

Sendai

+2.1

+3.4

+0.5

+0.4

+3.0

Tokyo

+2.9

+3.8

+2.4

+1.6

+3.7

Nagoya

+2.4

+3.5

+1.6

+0.6

+3.6

Kyoto

+2.3

+3.1

+2.2

+0.4

+3.6

Fukuoka

+2.3

+1.8

+1.9

+0.9

+3.8

Average of Big Cities

+2.4

+3.1

+1.7

+0.8

+3.6

+1.0

+0.9

+0.9

+0.6

+1.4

Average of Small andMedium-sized Cities(Note) 1. The trend is calculated by regression analysis and converted to the changes of 100 years.
2. The sample period is 1900-97 for Sapporo, Tokyo and Fukuoka, 1927-97 for Sendai, 1923-97 for
Nagoya, 1914-97 for Kyoto, and 1990-97 for small and medium-sized cities.
3. Big cities: Cities with the population of more than 900 thousand, and with continuous andappropriate observations since at least 1931.
4. Small and medium-sized cities: Following 15 cities with the little influence of urbanization.
Abashiri, Nemuro, Ishinomaki, Yamagata, Mito, Iida, Fushiki, Hamamatsu, Hikone,
Sakaiminato, Hamada, Tadotsu, Miyazaki, Naze, Ishigaki.

(Source) Meteorological Agency (1999).

16
Table 2: Ice Days, Tropical Days, and Sweltering Nights(Days/Year)
Ice Days

Average 1951-80

Average 1961-90

Average 1971-00(Average 1991-00)

Sapporo

51

51

48

35

Sendai

2

3

2

1

Tokyo

0

0

-

-

Nagoya

0

0

-

-

Osaka

-

-

-

-

Fukuoka

0

0

-

-

Average 1951-80

Average 1961-90

Average 1971-00(Average 1991-00)

Sapporo

7

7

8

7

Sendai

17

17

17

19

Tokyo

45

45

46

51

Nagoya

57

57

58

63

Osaka

63

66

68

72

Fukuoka

53

54

53

54

Average 1951-80

Average 1961-90

Average 1971-00(Average 1991-00)

Sapporo

-

0

0

-

Sendai

0

0

1

1

Tokyo

14

18

23

30

Nagoya

5

8

13

20

Osaka

26

28

32

38

Fukuoka

19

23

27

34

Tropical Days

Sweltering Nights(Note)

1. Ice Day: Day on which the maximum temperature drops below 0 degrees.
Toropical Day: Day with temperatures exceeding 30 degrees.
Sweltering Night: Day with the minimum temperature exceeding 25 degrees.
2. As for Osaka, the figures are average from 1969 (average 1969-80 and 1969-90), because of
the moving of observation point.
3. "0" shows there is at least one observation during the period. "-" shows there is noobservation during the period.

(Source) Japan Weather Association, Weather Almanac.

17
Figure 1: Air Temperature Distribution(Source) Ministry of Environment (2001).

18
Figure 2: The Number of People Taken to Hospital by Ambulance for Heat Stroke:
1985-1999 (3-Year Moving Average)(Persons)(Year)(Note) The original data is from Tokyo Fire Department.
(Source) Ministry of Environment (2001).

Figure 3: Relation between Daily Maximum Temperature and Ratio of Sufferers of Heat
Stroke (per 1Milion People)
Number of Sufferers (per 1M People)

Japan
China

Maximum Temperature of the Day (degree C)(Source) Ando (1998).