1. Jim Hurrell OceanObs09 21-25 September 2009 OceanObs09: Ocean Information for Society Day III: Delivering Services to Society Session B: Forecasting Decadal-to-Centennial Prediction: Opportunities and Challenges Jim Hurrell Climate and Global Dynamics Division, NCAR jhurrell@ucar.edu

2. Jim Hurrell OceanObs09 21-25 September 2009 Seasonal to Interannual Prediction Decadal prediction Centennial prediction Initial value problem Boundary value problem Boundary value Climate Prediction + Initial value

3. Jim Hurrell OceanObs09 21-25 September 2009 OceanObs09: Ocean Information for Society Day III: Delivering Services to Society Session B: Forecasting CWP on Decadal Climate Variability, Predictability and Prediction Contributing Authors G. Danabasoglu T. Delworth D. Dommenget H. Drange K. Drinkwater S. Griffies W. Hazeleger N. Holbrook B. Kirtman N. Keenlyside M. Latif J. Marotzke J. Murphy G. Meehl T. Palmer H. Pohlman T. Rosati R. Seager D. Smith R. Sutton A. Timmerman K. Trenberth J. Tribbia M. Visbeck

4. Jim Hurrell OceanObs09 21-25 September 2009 OceanObs09: Ocean Information for Society Day III: Delivering Services to Society Session B: Forecasting CWP on Decadal Climate Variability, Predictability and Prediction Contributing Authors G. Danabasoglu T. Delworth D. Dommenget H. Drange K. Drinkwater S. Griffies W. Hazeleger N. Holbrook B. Kirtman N. Keenlyside M. Latif J. Marotzke J. Murphy G. Meehl T. Palmer H. Pohlman T. Rosati R. Seager D. Smith R. Sutton A. Timmerman K. Trenberth J. Tribbia M. Visbeck

5. Jim Hurrell OceanObs09 21-25 September 2009 Linear trend of surface temperatures 1901 – 2005 ( C Century -1 ) Mixture of internal variability and forced climate change IPCC (2007) °

6. Jim Hurrell OceanObs09 21-25 September 2009 Change in Winter Sea Level Pressure (1980-2008) (hPa)Dec-Mar Pressure Falls Pressure Rises Decadal Climate Variability 1900-2009

7. Jim Hurrell OceanObs09 21-25 September 2009 Sahel Rainfall Decadal Climate Variability Interhemispheric SST Contrast NH Cold NH Warm Strong relationship to SST changes

8. Jim Hurrell OceanObs09 21-25 September 2009 Warm North Atlantic linked to … More rain Less rain North Atlantic SST Ting et al. (2008) Forced component Internal variability Courtesy T. Delworth Drought Hurricanes

9. Jim Hurrell OceanObs09 21-25 September 2009 Open Questions and Challenges To what extent is decadal variability predictable? Higher Extratropical SST Predictability IPCC AR4 Models (8900 yrs Control) 10 yr means Potential Predictability in Surface Temperature Boer and Lambert (2008) potential predictability variance fraction (σ v 2 /σ 2 )

10. Jim Hurrell OceanObs09 21-25 September 2009 Open Questions and Challenges To what extent is decadal variability predictable? Courtesy Tom Delworth in Hurrell et al. (2009) Phenomena: Idealized Predictability Experiments Perturbed ensemble members evolve coherently for two decades

11. Jim Hurrell OceanObs09 21-25 September 2009 Projected Atlantic SST Change Forced by External Processes o “Committed” o Future Δradiative forcing External Forcing Open Questions and Challenges To what extent is decadal variability predictable? What are the mechanisms for decadal variability? Interactions of Forced and Natural Variability Latif et al. (2009) Internal Processes o Low-pass filtering of noise o Slow internal variations o Coupled Internal Processes

12. Jim Hurrell OceanObs09 21-25 September 2009 Does oceanic variability have atmospheric relevance? Open Questions and Challenges Pohlmann et al. 2006 + AMOC - AMOC

13. Jim Hurrell OceanObs09 21-25 September 2009 Global Number of Temperature Observations (1980-2006) Courtesy Tony Rosati in Hurrell et al. (2009) Do we have the proper tools to realize the predictability? Open Questions and Challenges  Adequate climate observing system? Argo A major challenge for climate analysis and prediction: uneven observational coverage in both space and time; deep ocean and ice covered regions are poorly observed.

14. Jim Hurrell OceanObs09 21-25 September 2009 Temperature North Atlantic Anomalies (Upper 300 m) Salinity Best method of initialization? Need for coupled data assimilation  Reliable assimilation systems to initialize models? Proper tools to realize the predictability? Issues: Changing and incomplete observing system Corrections to data bases (e.g., XBT, Argo) – needed for continual updates to re-analyses Require reliable estimates of uncertainty in analyses Treatment of salinity in the pre-Argo era Understanding the differences in the analyses requires controlled experimentation – same data, QC, forcing, …. See Rienecker et al. and Balmaseda et al.

15. Jim Hurrell OceanObs09 21-25 September 2009 Do we have the proper tools to realize the predictability?  Adequate climate observing system?  Reliable assimilation systems to initialize models? Open Questions and Challenges Internal Variability Scenario Model Internal Scenario Model Decadal Mean Surface TGlobal Regional Sources of uncertainty Hawkins and Sutton 2009  Are models “good enough” to make skillful predictions? Rienecker et al. Balmaseda et al.

16. Jim Hurrell OceanObs09 21-25 September 2009 Model Fidelity Improving Ocean Models − A key for improved ocean synthesis and prediction Atlantic MOC index from a suite of coupled climate models different ocean models different atm resolution Hurrell et al. (2009)

17. Jim Hurrell OceanObs09 21-25 September 2009 First Attempts at Decadal Prediction Correlation skill in predicting 10-yr mean SAT anomalies (Hashing indicates skill over radiative forcing only) Keenlyside et al. 2008 10-yr, 3-member hindcasts Every 5 years from 1955-2005 ECHAM5/MPI-OM Initial Conditions: coupled model SSTs restored to observed anomalies

18. Jim Hurrell OceanObs09 21-25 September 2009 First Attempts at Decadal Prediction Observations Global Surface Temperature Initialization strategies and other aspects differ considerably All include estimates of changes in external forcing Large differences in future predictions

19. Jim Hurrell OceanObs09 21-25 September 2009 Decadal Prediction Protocol (CMIP5) 10 year integrations with initial dates from 1960-2005 Ensemble predictions (minimum 3 members) Ocean initial conditions should be in some way representative of the observed anomalies or full fields for the start date Land, sea-ice and atmosphere initial conditions left to the discretion of individual modeling groups 1960, 1980, and 2005 integrations extended 30 years WCRP/IGBP Aspen Workshop (July 2006)

20. Jim Hurrell OceanObs09 21-25 September 2009 Concluding Thoughts Decadal prediction will require: –Better characterization and mechanistic understanding (determines level of predictability) –Advanced assimilation and initialization systems –Advanced models (resolution, physics) –Estimates of future changes in radiative forcing –Sustained global observations Decadal climate variability: –Mixture of internal variability and forced climate change –Significant societal relevance: will be part of IPCC AR5 –Time to explore is now, but: Increased dialog with sector communities to –make best use of predictions, better define requirements and drive improvement in predictive systems

21. Jim Hurrell OceanObs09 21-25 September 2009 Ocean observations are critical for decadal prediction: For model improvement and verification For initialization and characterization of decadal variability Ocean Observations Must continually assess utility of existing and planned ocean observations for decadal prediction systems Sustain existing observing system components: e.g., Argo, altimetry, SST, sea ice Moorings (tropical, boundary current, OceanSITES) Address under-sampling Full water column observations (initialize MOC) Utility of Argo-type measurements below 2000 m Need for denser observing system in “critical regions” to assess observational requirements for decadal information

22. Jim Hurrell OceanObs09 21-25 September 2009 Thank You Happy Birthday Lisa!