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Water cycle and climate change Professor Lennart Bengtsson

Water cycle and climate change Professor Lennart Bengtsson

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Water cycle and climate change Professor Lennart Bengtsson

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  1. Water cycle and climate changeProfessor Lennart Bengtsson Max-Planck –Institute for Meteorology, Hamburg, GermanyEnvironmental System Science Centre, Reading University, UK Water and the Environment The Pontificial Academy of Sciences

  2. How is the water distributed on the Earth? Water and the Environment The Pontificial Academy of Sciences

  3. Water and the Environment The Pontificial Academy of Sciences

  4. The Heat Balance of the Atmosphere Incoming energy from the Sun balances the outgoing energy from the Earth Water and the Environment The Pontificial Academy of Sciences

  5. Water and the Environment The Pontificial Academy of Sciences

  6. The Global Water Cycle Solar forcing and atmospheric circulation are the drivers of the water cycle Water and the Environment The Pontificial Academy of Sciences

  7. Annual precipitation Water and the Environment The Pontificial Academy of Sciences

  8. Precipitation in January Water and the Environment The Pontificial Academy of Sciences

  9. Precipitation in July Water and the Environment The Pontificial Academy of Sciences

  10. 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 km3/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 CO2 by a factor of more than 3. (For the GFDL model from 3.38 K to 1.05 K). Water and the Environment The Pontificial Academy of Sciences

  11. Water and the Environment The Pontificial Academy of Sciences

  12. Water and the Environment The Pontificial Academy of Sciences

  13. Water and the Environment The Pontificial Academy of Sciences

  14. Interannual variability in precipitation El Nino and Southern Oscillation Water and the Environment The Pontificial Academy of Sciences

  15. Water and the Environment The Pontificial Academy of Sciences

  16. Water and the Environment The Pontificial Academy of Sciences

  17. Water and the Environment The Pontificial Academy of Sciences

  18. El Nino changes precipitation patterns Water and the Environment The Pontificial Academy of Sciences

  19. Water and the Environment The Pontificial Academy of Sciences

  20. Forest fires in Indonesia Water and the Environment The Pontificial Academy of Sciences

  21. Natural variability in precipitation patterns The North Atlantic Oscillation NAO Water and the Environment The Pontificial Academy of Sciences

  22. The North Atlantic Oscillation Negative phase Water and the Environment The Pontificial Academy of Sciences

  23. The North Atlantic OscillationPositive phase Water and the Environment The Pontificial Academy of Sciences

  24. Water and the Environment The Pontificial Academy of Sciences

  25. Water and the Environment The Pontificial Academy of Sciences

  26. The water cycle in a warmer climate How will it change? Water and the Environment The Pontificial Academy of Sciences

  27. 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%). Water and the Environment The Pontificial Academy of Sciences

  28. Water and the Environment The Pontificial Academy of Sciences

  29. Water and the Environment The Pontificial Academy of Sciences

  30. 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 CO2 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). Water and the Environment The Pontificial Academy of Sciences

  31. Water and the Environment The Pontificial Academy of Sciences

  32. Water and the Environment The Pontificial Academy of Sciences

  33. How does the greenhouse warming work? Clausius-Clapeyron relation (1832) The fractional change in es (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 Water and the Environment The Pontificial Academy of Sciences

  34. Water and the Environment The Pontificial Academy of Sciences

  35. The feedback problem Water and the Environment The Pontificial Academy of Sciences

  36. Annual mean global values of relative humidity f (in %) vertically averaged for 850-300 hPa and vertically integrated absolute humidity q (in kg/m2). Water and the Environment The Pontificial Academy of Sciences

  37. Feedback results from different models Water and the Environment The Pontificial Academy of Sciences

  38. 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 Water and the Environment The Pontificial Academy of Sciences

  39. Water and the Environment The Pontificial Academy of Sciences

  40. Water and the Environment The Pontificial Academy of Sciences

  41. Long Term Variations in the Water CycleIs the Weather more extreme Today than earlier? Water and the Environment The Pontificial Academy of Sciences

  42. Precipitation intensity Observations and Model Results Water and the Environment The Pontificial Academy of Sciences

  43. Railway Station in Dresden 17 August 2002 Water and the Environment The Pontificial Academy of Sciences

  44. cm m3/s 17. August 2002 939 7000? 31. März 1845 877 5700 3. Februar 1862 824 4490 6. September 1890 827 4460 12. April 1865 748 3480 17. März 1940 778 3360 20. Februar 1876 776 3290 17. Januar 1920 772 3190 11. April 1900 773 3100 7. Mai 1896 732 3070 10. März 1881 726 3090 ELBE IN DRESDEN Extreme flooding in Elbe Water and the Environment The Pontificial Academy of Sciences Quelle: Deutsches Hydrologisches Jahrbuch

  45. 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) Water and the Environment The Pontificial Academy of Sciences

  46. Water and the Environment The Pontificial Academy of Sciences

  47. 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 Water and the Environment The Pontificial Academy of Sciences

  48. Water and the Environment The Pontificial Academy of Sciences

  49. Transient eddies in ECHAMHamburg 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 Water and the Environment The Pontificial Academy of Sciences

  50. 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 Water and the Environment The Pontificial Academy of Sciences