Jim Hurrell OceanObs09 21-25 September 2009
OceanObs09: Ocean Information for SocietyDay III: Delivering Services to Society
Session B: Forecasting
Decadal-to-Centennial Prediction:Opportunities and Challenges
Jim Hurrell
Climate and Global Dynamics Division, NCAR
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
Jim Hurrell OceanObs09 21-25 September 2009
OceanObs09: Ocean Information for SocietyDay III: Delivering Services to Society
Session B: Forecasting
CWP on Decadal Climate Variability, Predictability and Prediction
Contributing Authors
G. DanabasogluT. DelworthD. DommengetH. DrangeK. DrinkwaterS. GriffiesW. HazelegerN. Holbrook
B. KirtmanN. KeenlysideM. LatifJ. MarotzkeJ. MurphyG. MeehlT. PalmerH. Pohlman
T. RosatiR. SeagerD. SmithR. SuttonA. TimmermanK. TrenberthJ. TribbiaM. Visbeck
Jim Hurrell OceanObs09 21-25 September 2009
OceanObs09: Ocean Information for SocietyDay III: Delivering Services to Society
Session B: Forecasting
CWP on Decadal Climate Variability, Predictability and Prediction
Contributing Authors
G. DanabasogluT. DelworthD. DommengetH. DrangeK. DrinkwaterS. GriffiesW. HazelegerN. Holbrook
B. KirtmanN. KeenlysideM. LatifJ. MarotzkeJ. MurphyG. MeehlT. PalmerH. Pohlman
T. RosatiR. SeagerD. SmithR. SuttonA. TimmermanK. TrenberthJ. TribbiaM. Visbeck
Jim Hurrell OceanObs09 21-25 September 2009
Linear trend of surface temperatures1901 – 2005 ( C Century-1)
Mixture of internal variability and forced climate change
IPCC (2007)
°
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
1900-2009
Jim Hurrell OceanObs09 21-25 September 2009
Sahel Rainfall
Decadal Climate Variability
Interhemispheric SST Contrast
NH Cold
NH Warm
Strong relationship to SST changes
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 variabilityCourtesy T. Delworth
DroughtDrought
Hurricanes
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 (σv2/σ2)
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
Perturbedensemble membersevolvecoherentlyfor twodecades
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 noiseo Slow internal variationso Coupled
Internal Processes
Jim Hurrell OceanObs09 21-25 September 2009
• Does oceanic variability have atmospheric relevance?
Open Questions and Challenges
Pohlmann et al. 2006
+ AMOC- AMOC
Jim Hurrell OceanObs09 21-25 September 2009
Global Number of Temperature Observations (1980-2006)
Courtesy Tony Rosatiin 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.
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 ofuncertainty
Hawkins and Sutton 2009
Are models “good enough” to make skillful predictions?
Rienecker et al.Balmaseda et al.
Jim Hurrell OceanObs09 21-25 September 2009
First Attempts at Decadal PredictionCorrelation skill in predicting 10-yr mean SAT anomalies
(Hashing indicates skill over radiative forcing only)
Keenlyside et al. 2008Keenlyside 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
Jim Hurrell OceanObs09 21-25 September 2009
First Attempts at Decadal Prediction
Observations
Observations
Global Surface Temperature
• Initialization strategies and other aspects differ considerably
• All include estimates of changes in external forcing
• Large differences in future predictions
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)
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
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
Jim Hurrell OceanObs09 21-25 September 2009
Thank You
Happy Birthday Lisa!