1. Introduction to coupled climate modelling Andy Pitman

2. Outline What is it What can you do What can’t you do What opportunities exist with Mk3L ? Assuming you want papers in top journals like Climate Dynamics and J. Climate.

3. background: Climate models are how we project the future of the Earth’s climate They are different from Earth System models – Mk3 is a climate system model, not an Earth System Model It is absolutely not an EMIC

4. Climate models work …

5. Most of the time. All models are not equally good, and no one model is best. No single measure of model performance presently exists [though we are working on it]

6. Climate models work stunningly well at large spatial scales [continental to global] Superbly on long time scales [seasonal to multi-annual averages] [they do not all capture all modes of variability equally well] For prognostic and diagnostic quantities

7. Climate models work Isotherms show temperature, colours show error

8. Climate models work Rainfall [annual] Which is observed and which is modelled ?

9. Climate models work Adequately at regional scales [say averages over >9 grid squares] For prognostic and diagnostic quantities but be very very careful:

10. Most climate models work Or at least, some models work 40% error 30-50% error

11. Most climate models work Or at least, some models work 25% error 40% error 30-50% error

12. Climate models work Climate models are not equal … observed

13. Climate models work Though perhaps don’t look too close MAM precip over eastern Pacific obs

14. Bad, does not matter Bad & matters Good and matters

15. Climate models work Unreliably at local scales Increasingly unreliably at monthly – daily scales Combining these to look at fine resolution and short time scales requires –(a) great care; –(b) close contact with model developers

16. Don’t use the models blindly – work with a “real” climate modeller ! Evaluate for your specific purpose climate modellers do not assert that the models are reliable below continental scales [IPCC, 2001, Chapter 8] they remain are our best tool … Climate models work

17. CSIRO Mk3L Personal view – do not use this model for this:

18. Personal view – don’t use it for this

19. What should we use it for? LatLonlevelsTotal 4 x 7404859600 3.3 x 5.65464103584 2.8 x 2.86412815122880 1.25 x 1.25 144288301244160 You can run 35 of the 3.3 x 5.6 model for one run of the 2.8 x 2.8

20. What should we use it for? For multi-realization experiments

21. What should we use it for? For multi-realization experiments – why ?

22. What should we use it for Models do not agree … but physics or chaos ?

23. … sensitivity of adding new processes [nitrogen]

24. What should we use it for? Understanding abrupt change

26. Summary In my view, if you want to explore regionally-specific issues, with a state of the art climate model, build links to groups that run such a model [CSIRO Mk3, CCAM or wait for ACCESS] This is not what the CSIRO-Mk3L is for

27. Summary A cheap coupled climate model is not to be used as if it were an expensive high resolution model You must design experiments in full understanding of the strengths and weaknesses of the “L” in CSIRO Mk3L

28. Summary Weaknesses: –Poorer regional skill –Poorer signal-noise ratio from local perturbations Strengths –Capacity to run “n” realizations where “n” might be 10, 20, 50 … –Use it for uncerainty analysis, estimation of probability –Use it to build and test parameterization

29. Summary CSIRO Mk3L is a low resolution coupled climate model Its weaknesses can be overcome by careful experimental design If you are not a climate modeller seek advice on design - from a “real” climate modeller – someone who builds rather than uses them Then do innovative science like Manabe, Staniforth, Murphy etc and bask in the glory of Nature and Science papers