NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Manifestation ofManifestation of climatic climatic changechange from long term from long term observations inobservations in Eastern Eastern
MediterraneanMediterranean – –
The role ofThe role of urban effecturban effect
D. Founda, M. Petrakis, C. Giannakopoulos
National Observatory of Athens, Institute for Environmental Research and Sustainable Development
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
“Look into the past to see the future”
Climatic research worldwide is based on historical records and long term observational data
Climatic change: the result of natural climate variability + variations due to anthropogenic driving forcing
Natural climate variability: solar radiation, volcanic activity, aerosols concentration, ocean circulation etc..
Anthropogenic: GHG concentrations, Land use/Land cover changes
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Global warming
The ‘average’ surface air temperature of the Earth (land + oceans) rose by approximately 0.740 C over the last 100 years
The warming rate is higher in the second half of the century
Warming rate in the Northern Hemisphere is higher than in Southern Hemisphere
Large spatial variability in climate change
It is quite important to study climate changes on regional or local scales
Seasonal variability
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Air temperature trends in E. Mediterranean- Seasonal differentiations
E. Mediterranean (June-August)
E. Mediterranean (Dec-Feb)
From NCEP/NCAR database
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Seasonal differentiations
Long term variation of air temperature in three cities of E. Mediterranean in winter
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Seasonal differentiations
Long term variation of air temperature in three cities of E. Mediterranean in summer
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Climatic research in Greece and Eastern Mediterranean is inevitably connected with the historical records of National Observatory of Athens (NOA)
The oldest Research Institute of the country and one of the oldest ones in Eastern Mediterranean and Southeastern Europe, founded in 1842
The historical record of NOAThe historical record of NOA
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
• First meteorological observations in Athens in 1833 – not complete record until 1858
•Since 1858 uninterrupted measurements in Athens – relocation of the station within the centre of the city
•Since 1890, a complete, continuous and reliable climatic record at the same location in Athens (Thission - near Acropolis)
•Perhaps the most important contribution of NOA in the study of climate in Greece
The historical record of NOAThe historical record of NOA
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Also,
In 1894 NOA installed a national network of more than 30 meteorological stations at several places of the country
Measured meteorological parameters: air temperature, atmospheric pressure, humidity, wind speed-direction, precipitation, cloudiness (3 observations/day)
In 1932, the network was undertaken by the newly established HNMS.
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Today,
Two A' class meteorological stations at Thission (historical) and Penteli (since 1998)
•Air temperature- soil temperature at several depths
•Humidity of the air -Atmospheric pressure
•Wind speed-direction
•Precipitation, cloudiness
•Sunshine duration
•Solar radiation (since 1954)
•Sunshine duration
•Illuminance (since 1992)
•Visibility
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Variety of local climates in Greece
Need for a dense network of stations
161 automatic met stations (Davis) installed by NOA
Data available to the public online
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Past Climate in Greece-Air temperature Past Climate in Greece-Air temperature trendstrends
According to the results from several studies (e.g Feidas et al., 2004, Philandras et al., 2010):
• A cooling in the annual temperature in Greece from 1951-1976 (statistically significant) is observed
• More pronounced in continental areas of Northern Greece (e.g 0.60C/decade at Trikala)
• The decade of 1970, the coldest one over Hellenic region.
• Seasonal analysis indicated cooling trends in both winter and summer seasons from 1951-1976 (statistically significant and more pronounced in summer)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Past Climate in Greece-Air Past Climate in Greece-Air temperature trendstemperature trends
A warming in the annual temperature in Greece from 1976 and onwards is observed
This is mainly due to positive trends in summer temperature (Athens and continental areas of Northern Greece experience the most pronounced warming in summer 10 C/decade)
In winter, most parts of Greece reveal no significant negative trends
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
20
21
22
23
24
25
1860 1880 1900 1920 1940 1960 1980 2000
Year
Air
tem
pera
ture
(ο
C)
NOANOA follows the large scale air temperature follows the large scale air temperature variations of the variations of the Northern HemisphereNorthern Hemisphere
Annual air temperature at NOA for the last 150 years
mean annual temp. at NOA
16
17
18
19
20
1895 1915 1935 1955 1975 1995 2015
Air
te
mp
era
ture
(C
)
annual mean maximum temp at NOA
202122232425
1895 1915 1935 1955 1975 1995 2015Air
tem
per
atu
re (
C)
annual mean minimum temp. at NOA
12.5
13.5
14.5
15.5
16.5
1895 1915 1935 1955 1975 1995 2015
Year
Air
te
mp
era
ture
(C
)
Variation of annual mean, maximum and minimum temperature at NOA
(1897-2010)2010
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Mean summer temperature at NOA (1897-2010)
Trends 1897-2010: + 0.160 C/decade, or ~ 1.80 C
Trends 1976-2010: +0.9 0 C/decade, or ~ 30 C
Mean summer temperature at NOA
24
25
26
27
28
29
30
1880 1900 1920 1940 1960 1980 2000 2020
year
Air
tem
per
atu
re (
C)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Mean winter temperature at NOA (1897-2010)
Trends 1897-2010: +0.020 C/decade, or ~ 0.220 C
Trends 1976-2010: +0.15 0 C/decade, or ~ 0.50 C
Mean winter temperature at NOA
6
7
8
9
10
11
12
13
1880 1900 1920 1940 1960 1980 2000 2020
year
Air
tem
per
atu
re
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Temperature extremes
What is extremeWhat is extreme??
Use of threshold values
Link with catastrophic events
Use of percentiles
• The value of 323200CC is not extreme in Athens but is not extreme in Athens but it is extreme in Moscowit is extreme in Moscow. .
• The value of 101000C is not extreme in March in C is not extreme in March in Athens but it is extreme in June.Athens but it is extreme in June.
•An increase in the mean maximum temperature from 353500CC to 373700CC can increase mortality
•An increase in the mean maximum temperature from 225500CC to 227700CC will have an impact on ecosystem
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
1970 1975 1980 1985 1990 1995 2000 2005
YEAR
3 5
3 6
3 7
3 8
3 9
4 0
4 1
4 2
4 3
4 4
Tem
pera
ture
thre
shol
d
1
11
21
31
41
The value of The value of 335500CC corresponds to the corresponds to the 9090thth percentile in summer in Athens (for the percentile in summer in Athens (for the period 1961-1990)period 1961-1990)..
Temperature extremes
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Use of thresholds
Daily Tmax> 37 0 C (close to human body temperature, roughly 95th percentile)
Daily Tmax > 40 0 C (psychological threshold value for Athenians – several activities paralyze)
131 out of the 381 hot days (150 year period) occurred during 2001-2010.
0
5
10
15
20
25
30
Year
Num
ber
of d
ays/
year >37deg >40deg
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
A sequence of at least 3 consequtive days with Tmax above a threshold value. Changes in:
Frequency of occurrence
Duration
Heat wavesHeat waves
Number of heat waves >37 deg
0
1
2
3
4
5
1864 1874 1884 1904 1914 1924 1934 1944 1954 1964 1974 1984 1994 2004 2014
Year
Nu
mb
er o
f h
eat
wav
es
Number of heat waves/year in Athens for the last 150 years
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
YEAR
35.0
35.5
36.0
36.5
37.0
37.5
38.0
38.5
39.0
39.5
40.0
40.5
41.0
Tem
per
atu
re t
hre
sho
ld
3
4
5
6
7
8
9
Mean duration (days) of warm episodes in Athens during the last
century
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
YEAR
5
10
15
20
25
30
DA
TE
OF
MA
Y
1 8
1 9
2 0
2 1
2 2
2 3
2 4
2 5
2 6
2 7
2 8
2 9
A shift of the occurrence of hot days earlier in May
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
A case study: Summer 2007Summer 2007 in Greece. How extreme was itHow extreme was it?
All time record summerAll time record summer with respect to
Highest temperature ever recorded at NOA (44.8(44.8)) (previous record 4343 00CC in June 1916)
Mean summer Tmax (34.9 (34.9 00CC)) ( climatic value 31.631.6 0C)
Mean summer Tmin (24.4 (24.4 00CC)) (climatic value 21.6 21.6 00CC)
Number of days > 373700CC (2626 totally)
Number of days >404000CC (88 totally)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
The most important impact of the extremely hot and dry conditions in Greece during summer 2007 was the ignition of the most destructive forest fires of the country.
Soil dehydration, following the prolonged dry period in combination with hot temperatures and strong winds in summer 2007, yielded favorable conditions for the ignition and spread of forest fires.These fires were responsible for the destruction of 2% of the Greek land surface and the death of 64 humans.
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
28
29
30
31
32
33
34
35
36
1890 1905 1920 1935 1950 1965 1980 1995 2010
year
Mea
n s
um
mer
tem
per
atu
re
(o C
)
0.00E+00
5.00E+05
1.00E+06
1.50E+06
2.00E+06
2.50E+06
3.00E+06
3.50E+06
Bu
rned
surface (acres)
2007
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
More RecordsMore Records
20102010: the warmest year ever (: the warmest year ever (19.619.600 C C- - 17.7 17.7 climatic valueclimatic value) after 2007 (19.1)) after 2007 (19.1)
All months of 2010 were much warmer than All months of 2010 were much warmer than their climatic values, but their climatic values, but
AugustAugust was the warmest August ever was the warmest August ever ((36.136.100 C C, mean maximum temp-, mean maximum temp-32.3 climatic 32.3 climatic valuevalue ) )
NovemberNovember was the warmest November ever was the warmest November ever ((3.53.500 warmer from its normal value warmer from its normal value))
Decade 2001-2010Decade 2001-2010 the warmest decade the warmest decade ever.ever.
(six out of the warmest years occurred (six out of the warmest years occurred during the decade 2001-2010)during the decade 2001-2010)
June 2010June 2010: the : the earliest heat waveearliest heat wave ever ever
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Global warming or urbanization?Global warming or urbanization?
Urban Heat Island (UHI)Urban Heat Island (UHI) – a well documented – a well documented phenomenon in cities expressed as the phenomenon in cities expressed as the temperature difference between urban and temperature difference between urban and surrounding rural areassurrounding rural areas
Urban heat islands should be considered on three different scales
First, there is the mesoscale of the whole city.
Second is the local scale on the order of the size of a park.
Third scale is the microscale of the garden and buildings near the meteorological observing site.
Of the three scales the microscale and local-scale effects generally are larger than mesoscale effects.
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Removal of urban influenceRemoval of urban influence for the estimationfor the estimation
ofof global warmingglobal warming
‘‘Urbanization adjustments’Urbanization adjustments’ (statistical adjustments)(statistical adjustments)
Removal of urban stations from networkRemoval of urban stations from network
However, However,
In large cities : In large cities :
Additive effect of Additive effect of global warming + urbanizationglobal warming + urbanization
Greatest Greatest impacts in all sectorsimpacts in all sectors health, energy, health, energy, economyeconomy
(etc), due to (etc), due to higher population densityhigher population density
Global warming or urbanization?Global warming or urbanization?In their effort to estimate global warming scientist In their effort to estimate global warming scientist usuallyusually decide….decide….
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Significant research on UHI in Athens Significant research on UHI in Athens
(e.g Katsoulis and Theoharatos 1985; Philandras et al., 1999; Santamouris et al., 2001, 2007; Livada et al., 2005 etc).
UHI in AthensUHI in Athens, of the order of , of the order of 4-54-500 C C between between urban urban and and suburbansuburban stations (Livada et al, 2005) stations (Livada et al, 2005)
ButBut
UHIUHI can be of the order of can be of the order of 101000 C C between between rural stationsrural stations and the and the central zonecentral zone
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Significant research on Significant research on spatial variabilityspatial variability of UHI in Athensof UHI in Athens
Studies concerning the Studies concerning the rates of changes rates of changes ofof UHI over UHI over time time are missing are missing
It is important to know whether the It is important to know whether the intensity of the urban heat islandintensity of the urban heat island in a in a city continues to city continues to amplifyamplify, if it , if it hashas moderatedmoderated or or has has stabilizedstabilized
Trends of UHITrends of UHI
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
NOA urban in a park (unchanged
surrounding on local/micro scale)
Helliniko(HEL) urban coastal
Tatoi(TAT) rural / suburban
Tanagra (TAN) rural (military airport)
Aliartos (ALI) rural
Comparison of air temperature trends between..
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
y = 0,0918x - 150,12
y = 0,1003x - 168,62
28293031323334353637
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
Year
Sum
mer
max
tem
pera
ture
HEL max NOA maxLinear (NOA max) Linear (HEL max)
Summer maximumSummer maximum temperature at temperature at NOA (urban)NOA (urban) and and HEL (coastal urban)HEL (coastal urban) stations stations
Similar trendsSimilar trends
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Summer average temperature
22
23
24
25
26
27
28
29
30
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
Year
Air
tem
per
atu
re rural1
rural2
urban1
urban2
Summer maximum and minimum tempearure
0
5
10
15
20
25
30
35
40
1970 1980 1990 2000 2010 2020
Year
Air
tem
per
atu
re
rural1(max)
rural1(min)
rural2(max)
rural2(min)
urban1(max)
urban1(min)
urban2(max)
urban2(min)
Changes in average, maximum and minimum temperature
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Temporal variation of UHI
y = 0,0403x - 79,433
y = 0,0403x - 79,989
-0,8
-0,4
0
0,4
0,8
1,2
1,6
1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
Su
mm
er U
HI
(C)
NOA-TAN (avg) HEL-TAN(avg)Linear (HEL-TAN(avg)) Linear (NOA-TAN (avg))
Temporal variation of UHI
y = 0,0214x - 41,927
y = 0,0214x - 41,385
-0,5
0
0,5
1
1,5
2
2,5
1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
UH
I (C
)
HEL-TAT(avg) NOA-TAT(avg)Linear (NOA-TAT(avg)) Linear (HEL-TAT(avg))
Summer UHI trendsSummer UHI trends
UHI (Turban –Trural)
UHI (Turban – Tsuburban)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
y = -0,0008x + 11,586
y = -0,0005x + 11,589
6
7
8
9
10
11
12
13
1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
Air
tem
pera
ture
(C)
HEL avg NOA avg
Linear (NOA avg) Linear (HEL avg)
WinterWinter temperature at temperature at NOA (urban)NOA (urban) and and HEL (coastal urban)HEL (coastal urban) stations stations
Similar trends (no significant trend)Similar trends (no significant trend)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Winter UHI trendsWinter UHI trends
UHI (Turban –Trural)
UHI (Turban – Tsuburban)
y = 0,02x - 37,871
y = 0,0203x - 37,867
0
0,51
1,52
2,53
3,5
1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
UH
I (C
)
NOA-TAN avg HEL-TAN avgLinear (NOA-TAN avg) Linear (HEL-TAN avg)
y = 0,0105x - 17,945
y = 0,0101x - 17,949
0
1
2
3
4
1970 1975 1980 1985 1990 1995 2000 2005 2010
year
UH
I (C
)
HEL-TAT avg NOA-TAT avgLinear (HEL-TAT avg) Linear (NOA-TAT avg)
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Cases of Cases of heat wavesheat waves in a in a citycity
MaximumMaximum (Day) temperature (Day) temperature
Maximum temperature-Summer 2007
20
25
30
35
40
45
50
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89
Summer day
Air
tem
pera
ture
Athens Elefsis
During heat waves, maximum (day) temp. in the city (Athens) is lower to the one at the rural /Industrial area of Elefsis
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Cases of Cases of heat wavesheat waves in a city in a city
MinimumMinimum (Night)(Night) temperature temperature
Mininum temperature -Summer 2007
15171921232527293133
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89
Summer day
Air t
empe
ratu
re
Athens Elefsis
HeatWave1
During heat waves, minimum (night) temp. in the city (Athens) is much higher than at the rural /Industrial area of Elefsis
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Some conclusionsSome conclusions
SummerSummer air temperature trends after 1976 at air temperature trends after 1976 at two two urban urban stations in Athens are of the order of stations in Athens are of the order of 1100 C/decade C/decade
UHIUHI in in summersummer increases at a rate of the order of increases at a rate of the order of 0.40.400C /decadeC /decade (rural-urban) or (rural-urban) or 0.2 0.2 00/decade/decade (urban –suburban)(urban –suburban)
RoughlyRoughly
““60%60% of warming is due to of warming is due to global warmingglobal warming and and the rest the rest 40%40% is due to is due to urban effect’urban effect’
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Some conclusionsSome conclusions
WinterWinter air temperature air temperature after 1976after 1976 at two at two urbanurban stations in Athens reveal stations in Athens reveal no no significant trendsignificant trend
UHI in winter,UHI in winter, increases at a rate of the increases at a rate of the order of order of 0.2 0.2 00/decade/decade
UHI compensates the possible decrease of UHI compensates the possible decrease of air temperature in winterair temperature in winter
NATIONAL OBSERVATORY OF ATHENS
INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT
Significant increase of summer air temperature in Greece and especially in Athens, after the mid 70’s
Decade 2001-2010: the warmest ever in Athens
Pronounced increase in the frequency of hot days, heat waves
Summer 2007: the most extreme summer in Athens according to NOA’s temperaure record.
YEAR 2010: the warmest year ever in Athens
Less important variations during the cold period of the year
UHI accounts partly for the significant increase of the mean temperature in Athens
Night temperatures at urban areas much higher, especially during severe heat waves- threat for human health and mortality
General Conclusions