NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Manifestation of climatic change from long term observations in Eastern Mediterranean – The role of urban 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” ØClimatic research worldwide is based on historical records and long term observational data ØClimatic change: the result of natural climate variability + variations due to anthropogenic driving forcing ØNatural climate variability: solar radiation, volcanic activity, aerosols concentration, ocean circulation etc. . ØAnthropogenic: GHG concentrations, Land use/Land cover changes

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Global warming ØThe ‘average’ surface air temperature of the Earth (land + oceans) rose by approximately 0. 740 C over the last 100 years ØThe warming rate is higher in the second half of the century ØWarming rate in the Northern Hemisphere is higher than in Southern Hemisphere ØLarge spatial variability in climate change ØIt is quite important to study climate changes on regional or local scales ØSeasonal 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 The historical record of NOA 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

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT The historical record of NOA • 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

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 Today, INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT 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 trends 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. 60 C/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 temperature trends A warming in the annual temperature in Greece from 1976 and onwards is observed ØThis 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) ØIn winter, most parts of Greece reveal no significant negative trends

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Annual air temperature at NOA for the last 150 years NOA follows the large scale air temperature variations of the Northern Hemisphere

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

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

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Temperature extremes What is extreme? ØUse of threshold values ØLink with catastrophic events ØUse of percentiles The value of 320 C is not extreme in Athens but it is extreme in Moscow. • The value of 100 C is not extreme in March in Athens but it is extreme in June. • • An increase in the mean maximum temperature from 350 C to 370 C can increase mortality • An increase in the mean maximum temperature from 250 C to 270 C will have an impact on ecosystem

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Temperature extremes The value of 350 C corresponds to the 90 th percentile in summer in Athens (for the period 1961 -1990).

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 95 th 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.

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Heat waves ØA sequence of at least 3 consequtive days with Tmax above a threshold value. Changes in: ØFrequency of occurrence ØDuration Number of heat waves/year in Athens for the last 150 years

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Mean duration (days) of warm episodes in Athens during the last century

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT A shift of the occurrence of hot days earlier in May

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT A case study: Summer 2007 in Greece. How extreme was it? it All time record summer with respect to ØHighest temperature ever recorded at NOA (44. 8) (previous record 43 0 C in June 1916) ØMean summer Tmax (34. 9 0 C) ( climatic value 31. 6 0 C) ØMean summer Tmin (24. 4 0 C) (climatic value 21. 6 0 C) ØNumber of days > 370 C (26 totally) ØNumber of days >400 C (8 totally)

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT ØThe 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. ØSoil 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

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT More Records 2010: the warmest year ever (19. 60 C- 17. 7 climatic value) after 2007 (19. 1) ØAll months of 2010 were much warmer than their climatic values, but ØAugust was the warmest August ever (36. 10 C, mean maximum temp-32. 3 climatic value ) ØNovember was the warmest November (3. 50 warmer from its normal value) ØDecade ever 2001 -2010 the warmest decade ever. Ø(six out of the warmest years occurred during the decade 2001 -2010) ØJune 2010: the earliest heat wave ever

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Global warming or urbanization? Urban Heat Island phenomenon in cities difference between areas (UHI) – a well documented expressed as the temperature urban and surrounding rural Urban heat islands should be considered on three different scales First, there is the mesoscale of the whole city. ØSecond is the local scale on the order of the size of a park. ØThird scale is the microscale of the garden and buildings near the meteorological observing site. ØOf 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 Global warming or urbanization? In their effort to estimate global warming scientist usually decide…. ØRemoval of urban influence for the estimation of global warming Ø‘Urbanization adjustments’ (statistical adjustments) ØRemoval of urban stations from network However, In large cities : ØAdditive effect of global warming + urbanization ØGreatest impacts in all sectors health, energy, economy (etc), due to higher population density

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT 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 Athens, of the order of 4 -50 C between urban and suburban stations (Livada et al, 2005) But UHI can be of the order of 100 C between rural stations and the central zone

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Significant research on spatial variability of UHI in Athens Studies concerning the rates of changes of UHI over time are missing It is important to know whether the intensity of the urban heat island in a city continues to amplify, if it has moderated or has stabilized Trends of UHI

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Comparison of air temperature trends between. . 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

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Summer maximum temperature at NOA (urban) and HEL (coastal urban) stations Similar trends

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Changes in average, maximum and minimum temperature

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Summer UHI trends UHI (Turban –Trural) UHI (Turban – Tsuburban)

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Winter temperature at NOA (urban) and HEL (coastal urban) stations Similar trends (no significant trend)

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Winter UHI trends UHI (Turban –Trural) UHI (Turban – Tsuburban)

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Cases of heat waves in a city Maximum (Day) temperature 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 heat waves in a city Minimum (Night) temperature 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 conclusions Summer air temperature trends after 1976 at two urban stations in Athens are of the order of 10 C/decade UHI in summer increases at a rate of the order of 0. 40 C /decade (rural-urban) or 0. 2 0/decade (urban – suburban) Roughly “ 60% of warming is due to global warming and the rest 40% is due to urban effect’

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Some conclusions Winter air temperature after 1976 at two urban stations in Athens reveal no significant trend UHI in winter, increases at a rate of the order of 0. 2 0/decade UHI compensates the possible decrease of air temperature in winter

NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT General Conclusions üSignificant increase of summer air temperature in Greece and especially in Athens, after the mid 70’s üDecade 2001 -2010: the warmest ever in Athens üPronounced increase in the frequency of hot days, heat waves üSummer 2007: the most extreme summer in Athens according to NOA’s temperaure record. üYEAR 2010: the warmest year ever in Athens üLess important variations during the cold period of the year üUHI accounts partly for the significant increase of the mean temperature in Athens üNight temperatures at urban areas much higher, especially during severe heat waves- threat for human health and mortality