1. 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

2. 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

3. 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 0.74 0 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

4. 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

5. 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

6. 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

7. 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 NOA

8. 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 NOA

9. 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.

10. 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

11. 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

12. 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 0.6 0 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)

13. 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  This is mainly due to positive trends in summer temperature (Athens and continental areas of Northern Greece experience the most pronounced warming in summer  1 0 C/decade)  In winter, most parts of Greece reveal no significant negative trends

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

15. Variation of annual mean, maximum and minimum temperature at NOA (1897-2010) 2010

16. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Mean summer temperature at NOA (1897-2010) Trends 1897-2010: + 0.16 0 C/decade, or ~ 1.8 0 C Trends 1976-2010: +0.9 0 C/decade, or ~ 3 0 C

17. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Mean winter temperature at NOA (1897-2010) Trends 1897-2010: +0.02 0 C/decade, or ~ 0.22 0 C Trends 1976-2010: +0.15 0 C/decade, or ~ 0.5 0 C

18. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Temperature extremes What is extreme?  Use of threshold values  Link with catastrophic events  Use of percentiles 32 0 C is not extreme in Athens but it is extreme in Moscow. The value of 32 0 C is not extreme in Athens but it is extreme in Moscow. 10 0 C is not extreme in March in Athens but it is extreme in June. The value of 10 0 C is not extreme in March in Athens but it is extreme in June. 35 0 C37 0 CAn increase in the mean maximum temperature from 35 0 C to 37 0 C can increase mortality 25 0 C27 0 CAn increase in the mean maximum temperature from 25 0 C to 27 0 C will have an impact on ecosystem

19. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT The value of 35 0 C corresponds to the 90 th percentile in summer in Athens (for the period 1961-1990). Temperature extremes

20. 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.

21. 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 waves Number of heat waves/year in Athens for the last 150 years

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

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

24. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Summer 2007 How extreme was it A case study: Summer 2007 in Greece. How extreme was it? All time record summer All time record summer with respect to (44.8)43 0 C  Highest temperature ever recorded at NOA (44.8) (previous record 43 0 C in June 1916) (34.9 0 C) 31.6  Mean summer Tmax (34.9 0 C) ( climatic value 31.6 0 C) (24.4 0 C) 21.6 0 C  Mean summer Tmin (24.4 0 C) (climatic value 21.6 0 C) 37 0 C26  Number of days > 37 0 C (26 totally) 40 0 C8  Number of days >40 0 C (8 totally)

25. 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.

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

27. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT More Records 2010: the warmest year ever (19.6 0 C- 17.7 climatic value) after 2007 (19.1)  All months of 2010 were much warmer than their climatic values, but  August was the warmest August ever (36.1 0 C, mean maximum temp-32.3 climatic value )  November was the warmest November ever (3.5 0 warmer from its normal value)  Decade 2001-2010 the warmest decade ever.  (six out of the warmest years occurred during the decade 2001-2010)  June 2010: the earliest heat wave ever

28. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT Global warming or urbanization? Urban Heat Island (UHI) – a well documented phenomenon in cities expressed as the temperature difference between urban and surrounding 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.

29. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT  Removal of urban influence for the estimation of global warming of global warming  ‘Urbanization adjustments’ (statistical adjustments)  Removal of urban stations from network However, In large cities :  Additive effect of global warming + urbanization  Greatest impacts in all sectors health, energy, economy (etc), due to higher population density Global warming or urbanization? In their effort to estimate global warming scientist usually decide….

30. 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 4-5 0 C between urban and suburban stations (Livada et al, 2005) But UHI can be of the order of 10 0 C between rural stations and the central zone

31. 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 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

32. NATIONAL OBSERVATORY OF ATHENS INSITUTE FOR ENVIRONMENTAL RESEARCH AND SUSTAINABLE DEVELOPMENT NOAurban 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..

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

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

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

36. 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)

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

38. 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

39. 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

40. 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 1 0 C/decade UHI in summer increases at a rate of the order of 0.4 0 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’

41. 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

42. 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