Modelling the response to solar forcing in the troposphere and in the ocean

1. Modelling the response to solar forcingin the troposphere and in the ocean Ulrich Cubasch Freie Universität Berlin

2. Outline • Motivation and background • Description of the model • The experiments and results • the last 1000 years • the last 150 years, and detection and attribution • idealized experiments • Summary

3. Motivation and Background

4. External Forcing Anthropogenic forcing The climate system

5. solar variability • 11-year cycle (Schwalbe-cycle): ca. 0.1 % ~ 0.24 W/m2 at the surface • 80-year cycle (Gleissberg-cycle): ca. 0.24 - 0.3 % 0.5-0.75 W/m2 at the surface • many more.....

6. Description of a model

7. The ECHO-G Model atmosphere:ECHAM 4: • vertical resolution: 19 levels • horizontal resolution: T30 (approx. 3,75°) ocean:HOPE-G • T42 Arakawa E-Grid (approx. 2,8°), equator refinement • vertical resolution: 20 levels

8. The climate during the last 1000 years

9. The „Mann et al“- curve (Hockey-stick)

10. Experiments • Erik starting at the year 1000 • Columbus starting at the year 1500 remark: there are nowadays a lot more 3-d experiments around by NCAR, the Hadley Centre, DMI,….

11. Zorita et al, 2004 The solar and volcanic forcing and the model response

12. EBM multi-proxy Mann et al treerings (Jones et al) treerings (Esper et al) 3d-model bore hole

13. Jansen et al, 2007 The forcing and the temperature response by various models

14. reconstructed modelled The winter temperature anomaly during the late Maunder Minimum (1675-1715) reconstructed modelled

15. high index The two states of the North Atlantic oscillation (NAO) low index

16. NAO phases and European temperatures during the LMM  ~ first half of the LMM Low Index phase  Cooling ~ second half of the LMM High Index phase Warming Fischer-Bruns

17. stormtrackdifference relative to reference LMM11671-1684 NAO- and Cooling [gpm] LMM2 1685-1708 NAO+ andWarming [gpm] Fischer-Bruns

18. The climate during the last 150 years - and the detection and attribution of climate change Note: this period has been simulated by many models

19. Response to the individual factors

20. The observed near surface temperature for the northern hemisphere

21. The observed near surface temperature for the northern hemisphere and simulated with solar forcing only

22. The observed near surface temperature for the northern hemisphere and simulated with solar forcing, volcanic forcing and both together

23. observation The observed near surface temperature for the northern hemisphere and simulated with all combinations of forcing

24. all forcings natural forcings only observed The observed near surface temperature for the northern hemisphere and simulated with all combinations of forcing for various models (Hegerl et al, 2007)

25. The guess-pattern for the GHG, for a solar experiment (S76), and the observed trend for 1971 to 2000 (30 year trends)

26. 2004 The observations (HadCRUT2v) in the phase space of solar and GHG pattern (30 year trends)

27. Idealized experiments S76: Sinusoidal forcing with a period of 76 years and an amplitude of the net radiative forcing 2.5 W/m2 S11:Sinusoidal forcing with a period of 11 years and an amplitude net radiative forcing of 1.25 W/m2

28. S76 S11 The idealized forcing in comparison to the solar forcings derived by various groups

29. The forcing and the evolution of the global mean temperature for the S11 and S76 experiment

30. The temperature response pattern to solar forcing

31. modelled S11 NCEP-reanalysis GPRC Xie & Arkin The precipitation anomaly in the tropical Pacific during solar maximum van Loon and Meehl 2006

32. modelled (S11) observed (van Loon) The precipitation anomaly during solar maximum van Loon and Meehl 2006

33. suggested mechanism • more insolation • stronger trade winds • more equatorial upwelling • La Nina like response with rain over Indonesia/Australia • remote response to the US west coast

34. Oceanic response

35. White et al, 1997 – The response of global upper ocean temperature to changing solar irradiance GISST (1901-1990)

36. S11 S76 The solar induced temperature change in the Atlantic ocean (GEOSEC)

37. theoretical lag: p/4 = 1/8 cycle theoretical lag theoretical lag www.physics.buffalo.edu/SPS/main.html The penetration of the solar signal into the ocean diff. coeff. 10-4 m2/s

38. 100 50 20 10 The spectrum of the meridional overturning for different experiments

39. Summary • The troposphere and the ocean show a distinct response to variations in the solar forcing. • This particular visible in extreme situations like the late Maunder and the Dalton Minimum. However, the models show a larger response than the reconstruction from proxy records. • The observations of the recent years agree better with the temperature response pattern for the greenhouse gases than with the solar response pattern. • The observed and the modelled responses for the precipitation in the tropical pacific agree quite well. • The solar warming signal penetrates into the ocean. For the 11 year cycle the ocean behaves to a first approximation like a diffusive medium.

40. Outlook • more simulations, also with higher resolution, for the last 1000 years • simulations for the Holocene • analysis of weather-sun relationships