1. COSTOC-2006-32 Olivier MestreMétéo-FranceFrance Ingebor AuerZAMGAustria Enric AguilarU. Rovirat i VirgiliSpain Paul Della-MartaMeteoSwissSwitzerland Vesselin AlexandrovNIMHBulgaria Sylvie JourdainMétéo-FranceFrance ADVANCES IN HOMOGENISATION METHODS OF CLIMATE SERIES: AN INTEGRATED APPROACH

3. COSTOC-2006-32 Homogenisation : WHY? Exemple of PAU-UZEIN temperatures Juin 1912 PAU-LESCAR (EN)2005 PAU-UZEIN (AERO)

4. COSTOC-2006-32 Station Silistra

5. COSTOC-2006-32 Station Dobrich

6. COSTOC-2006-32 Anomalies of annual minimum temperature in Kjustendil (raw data)

7. COSTOC-2006-32 Raw series of annual Maximum Temperatures (TX) PAU-UZEIN

8. COSTOC-2006-32 Homogenisation of Pau Maximum Temperatures « before »« after »

9. COSTOC-2006-32 Decomposition of climatological series

10. COSTOC-2006-32 Usual method: relative homogeneity PRINCIPLE : removing the climatic signal to put into evidence artificial shifts in the series minus Tested series Reference series COMPARISON series

11. COSTOC-2006-32 Two problems DETECTION OF SHIFTS CORRECTION OF SHIFTS

12. COSTOC-2006-32 Many solutions ! DETECTION Visual, Craddock test, Student t-test, Likelihood ratio test (SNHT), Potter test, Bayesian procedures, Local contrast test, Pettitt test, penalized likelihood, MASH… CORRECTION Composite reference series, interpolated reference series, multiple non-homogeneous series (MASH), ANOVA (Mestre)…

13. COSTOC-2006-32 Statistical problems Related to detection power and level of the procedures, which are the best ones? Related to correction how to ensure unbiased corrections?

14. COSTOC-2006-32 Practical problems Data requirements, depending on parameters: spatial correlation Nature of correction: raw monthly estimated coefficients, annual coefficients? What about close shifts? What about gaps? Trust metadata or statistics? Trust relative homogenisation or parallel measurements?

15. COSTOC-2006-32 Why COST? Many procedures, many authors, that might lead to different results Few intercomparisons COST is an ideal platform for the exchange of experiences, harmonisation of approaches and the development of joint methods

16. COSTOC-2006-32 Objectives To achieve a general method for homogenising climate and environmental datasets Provide practical rules for the implementation of homogenisation. Provide tools for comparison and evaluation of different methods. Analyse the strengths and weaknesses of the methods for different applications. Provide methods for evaluating uncertainties resulting from homogenisation.

17. COSTOC-2006-32 Scientific Program Inventory of existing detection and correction methods Compilation of a benchmark dataset to be used across the Action Selection, comparison and evaluation of existing detection methods Selection, comparison and evaluation of existing correction methods Documentation of practical recommendations Selection, comparison and evaluation of existing correction methods for daily data Presentation and release of the new common method

18. COSTOC-2006-32 Is this ambitious? YES

19. COSTOC-2006-32 Why ? Because we want to make a synthesis of the most appropriate methods, based on objective comparisons and sharing of practical experiences Because we feel that the corresponding software has to be released – just editing recommandations would be useless

20. COSTOC-2006-32 Is this TOO Ambitious? NO

21. COSTOC-2006-32 Why ? We have a clear view of what has to be done Benchmark dataset conception (simulated and real cases) Coding and testing the procedures is rather easy, and may be done by students To test real cases and edit practical recommandations, we get together highly trained climatologists

22. COSTOC-2006-32 Structure of the proposal Working groups WG1 inventory WG3 Correction WG2 Detection WG4 Daily values WG5 Implement Benchmark Report Method Final report Software

23. COSTOC-2006-32 Dissemination plan Mailing list: costh@meteo.frcosth@meteo.fr Web site: domain name « homogenisation.org » is available, with free software and documentation Publications Workshops Training sessions (ENM)

24. COSTOC-2006-32 Benefits Standardisation of homogenisation procedures in Europe Results of climate studies based on homogenised series could be easily compared Provide a benchmark dataset that can be used to test future methods Significant advances in daily data homogenisation All this will result in an increased confidence in European (and global) assessments of mean and extreme Climate Change

25. COSTOC-2006-32 Benefits Links to European projects : CIRCE, MACE, ECA&D… Economical impacts: risk assessment (extremes: insurance companies) Calibration of weather derivatives

26. COSTOC-2006-32 Participants From 17 countries Around 60 participants –60% plan to participate actively to the Action –40% are mainly interested by the results –45% may have students working on the Action

27. COSTOC-2006-32 Conclusion Many procedures Few intercomparisons Daily data correction has to be developed  Need of a COST concerted Action