1. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Water cycle and climate change Professor Lennart Bengtsson Max-Planck – Institute for Meteorology, Hamburg, Germany Environmental System Science Centre, Reading University, UK

2. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences How is the water distributed on the Earth?

3. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

4. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The Heat Balance of the Atmosphere Incoming energy from the Sun balances the outgoing energy from the Earth

5. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

6. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The Global Water Cycle Solar forcing and atmospheric circulation are the drivers of the water cycle

7. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Annual precipitation

8. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Precipitation in January

9. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Precipitation in July

10. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The role of the water cycle in the climate system Precipitation is crucial for life on the planet The largest warming factor of the atmosphere is through the relaease of latent heat amounting to 80-90 WM -2 The net transport of water from ocean to the land surfaces amounts to some 40000 km 3 /year Precipitation over land is about 3 times as high Water vapour is the dominating greenhouse gas. Removing the effect of water vapour in long wave radiation reduces climate warming at 2 x CO 2 by a factor of more than 3. (For the GFDL model from 3.38 K to 1.05 K).

11. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

12. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

13. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

14. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Interannual variability in precipitation El Nino and Southern Oscillation

15. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

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17. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

18. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences El Nino changes precipitation patterns

19. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

20. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Forest fires in Indonesia

21. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Natural variability in precipitation patterns The North Atlantic Oscillation NAO

22. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The North Atlantic Oscillation Negative phase

23. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The North Atlantic Oscillation Positive phase

24. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

25. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

26. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The water cycle in a warmer climate How will it change?

27. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Integrated Water vapour 1978- 1999 ECHAM5: T106/L31 using AMIP2 boundary conditions Preliminary results: Globally averaged results vary between 25.10 mm (1985) and 26.42 mm (1998) Mean value for the 1990s is 1% higher than in the 1980s Interannual variations are similar as in ERA-40 Variations follow broadly temperature observations from MSU (tropospheric channel) under unchanged relative humidity (1°C is equivalent to some 6%).

28. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

29. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

30. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences How does the greenhouse warming work? Greenhouse gas warming (early ideas) Joseph Fourier (1827) „The atmosphere is relatively transparent to solar radiation, but highly absorbent to thermal radiation“ John Tyndall (1861) Water vapour and CO 2 are dominant absorbers Water vapour feedback and climate sensitivity Svante Arrhenius (1896) „On the influence of carbonic acid in the air upon the temperature of the ground“ Thomas C. Chamberlin (1899) „An attempt to frame a working hypothesis of the cause of glacial periods on an atmospheric basis“ „Water vapor confessedly the greatest thermal absorbent in the atmosphere is dependent on temperature for its amount and if another agent, as CO2, not so dependent, raises the temperature of the surface, it calls into function a certain amount of water vapor which further absorbs heat, raises the temperature and calls forth more vapor....“ (in a letter to C. G. Abbott, 1905).

31. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

32. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

33. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences How does the greenhouse warming work? Clausius-Clapeyron relation (1832) The fractional change in e s (de/e) resulting from a small change in temperature is proportionell to T -2 A 200K, a 1K increase results in a 15 % increase in water vapour; at 300Kt it causes a 6% increase

34. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

35. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences The feedback problem

36. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Annual mean global values of relative humidity f (in %) vertically averaged for 850-300 hPa and vertically integrated absolute humidity q (in kg/m 2 ).

37. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Feedback results from different models

38. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences IPCC on water vapour feedback 1990: The best understood feedback mechanism is water vapor feedback, and this is intuitively easy to understand. 1992: There is no compelling evidence that water vapor feedback is anything other than positive - although there may be difficulties with upper tropospheric water vapor. 1995: Feedback from the redistribution of water vapor remains a substantial source of uncertainty in climate models - Much of the current debate has been addressing feedback from the tropical upper troposphere

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41. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Long Term Variations in the Water Cycle Is the Weather more extreme Today than earlier?

42. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Precipitation intensity Observations and Model Results

43. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Railway Station in Dresden 17 August 2002

44. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences 17. August20029397000? 31. März18458775700 3. Februar18628244490 6. September18908274460 12. April18657483480 17. März19407783360 20. Februar18767763290 17. Januar19207723190 11. April19007733100 7. Mai18967323070 10. März18817263090 ELBE IN DRESDEN cmm 3 /s Quelle: Deutsches Hydrologisches Jahrbuch Extreme flooding in Elbe

45. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences No upward trends in the occurence of extreme floods in central Europe Letter to Nature, 11 September 2003 Mudelsee, Börngen, Tetzlaff and Grünewald ( Uni. Leipzig, Techn Uni Cottbus)

46. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

47. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences No long term Trend in Extra- tropical Storms WASA, 1998: Changing Waves and Storms in the North Atlantic. Bull. Amer. Met. Soc. Weisse, von Storch und Feser, 2004 Alexandersson, 2004

48. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

49. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Transient eddies in ECHAM Hamburg latest GCM Roeckner et al., (2003), MPI-Report 349 Resolution used T63L31 (top at 10hPa) Water vapour, cloud liquid water and cloud ice in semi-Lagrangian flux form- scheme

50. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences How are transient eddies identified? Date sets are needed at least every 6 hour We use a method proposed by Hodges (Hodges, 1999, MWR) We use the vorticity at 850hPa A transient eddy must exist for >48hours and be extended over at least1000km

51. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Storm tracks DJF 2002/03 at 850 hPa ERA 40

52. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Validation using ERA40 present climate 3 AMIP-type experiments 1979-1999 using observed SST and sea-ice ( with AMIP-2 protocol ( WGNE,1996) ERA40 1979-2002

53. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences ERA 40 storm track density and intensity DJF

54. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Storm tracks ERA40 (left) ECHAM5 ( right) NH(DJF)

55. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Extra-Tropical and Tropical Storms in a warmer climate Changes in 2070-2100 (21C) compared to 1970-2000 (20C) Scenario A1B

56. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Change in storm track density

57. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Change in storm track intensity

58. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Changes in storm tracks (21C-20C) north British isles (left), Mediterranean area (right)

59. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Tropical Storms Hurricanes and Typhoons

60. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Ranked by the number of lives throughout the world from 1947 to 1980, the 10 major types of disaster (not including droughts and other disasters affecting agriculture) were: 1.Tropical cyclones, hurricanes, typhoons499,000 2.Earthquakes450,000 3.Floods (other than associated with 1. above)194,000 4.Thunderstorms and tornadoes29,000 5.Snowstorms10,000 6.Volcanoes9,000 7.Heatwaves7,000 8.Avalanches5,000 9.Landslides5,000 10.Tidal waves (tsunamis)5,000 Type of disasterDeaths (nearest thousand)

61. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Hurricane Floyd approaching Florida

62. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

63. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

64. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

65. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences But now Hurricane Katrina Exp cost: 200G$

66. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Changes in storm track density (21C-20C) MJJASO

67. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Change in storm tracks (21C- 20C) number( max intensity) Tropics

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70. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Extreme weather conditions (What could we expect?)

71. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Climate change experiment at MPI for Met, Hamburg Increase in intense precipitation

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73. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences

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75. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Summary Climate observations so far There are no clear indication of an intensification of the global water cycle, but precipitation has increased over many parts of high and middle latitudes of the Northern Hemisphere. Water vapour has increased in the atmosphere which has enhanced the greenhouse effect. The severe floooding incidents in recent years are in all likelyhood due to natural processes and enhanced by increasing human exposure to events caused by severe weather.

76. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Summary What may happen? Extra-tropical storms have not intensified and are not expected to intensify in a warmer climate. In western Europe the storms at the end of the 19th century were as intense as those of the last decades. Intense winter storms depend on the temperatur difference between Arctic and middle latitudes. An increase warming in the Arctic (melting of sea-ice) will reduce the temperature gradient. Convective weather systems ( mainly in Summer) are expected to intensify as the higher concentration of water vapour will be able to release more latent heat, lead to more intense precipitaion and increase risk of flooding

77. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Summary Changes in the water cycle It is expected that the overall global precipitation will increase and be more dominated by intense precipitation. Modell experiments indicate changes in storm tracks and weather patterns also leading to reduced precipitation in many areas. The largest stress on Society is likely to occur in regions with systematic reduction in precipitation. Particularly exposed regions could be the Mediterranian and Middle East, Southern Australia and South Africa

78. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Summary What may happen in the tropics? Higher sea surface temperatures will enhance the tropical storms (hurricanes). At the same time expected increasing vertical wind shear will reduce the positive feedback between the convective elements of the storm and the main hurricane vortex and result in a weakening of the storm. Model calculations show that this feedback is very important and generally leads to a reduction in the number of hurricanes. However, when and where ideal conditions exist more intense hurricanes are likely to develop. It is expected that the overall global precipitation will increase and be more dominated by intense precipitation. Modell experiments indicate changes in storm tracks and weather patterns also leading to reduced precipitation in many areas.

79. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences END

80. 12-14 November 2005 Vatican Water and the Environment The Pontificial Academy of Sciences Content of lecture The Global Water Cycle Variations in the Water Cycle on different time scales (Is the weather now more extreme than earlier?) Anthropogenic Climate change and expected Consequences for the Water Cycle Extra-tropial and tropical Storms Extreme Weather conditions (What could be expected?) Summary and concluding Remarkes