2. Climate change, extreme sea levels & hydrodynamical models

3. Introduction
Quantifying the impacts of climate change upon extreme sea levels.
Spatial variation in impacts.
Scientific tools -
Observational data,
Process knowledge,
Numerical models
Statistical tools
Extreme value theory,
Spatial statistics,
Nonparametric regression
Multivariate analysis

4. Hydrodynamical models

5. North Sea models
< 35km NEAC grid <
12km NISE grid
V V

6. Scientific problems Observational climate data
Observational climate data for
Model output verified against observational sea level data.
Test for evidence for temporal change in extreme values.
Numerical climate model
Generate 30-year long stationary sequences of sea level data.
Climate input data generated using ECHAM-4 climate model under two scenarios: current CO2, double current CO2.
Interest is in comparing extremal characteristics of the spatio-temporal fields generated under the two scenarios.

7. Previous findings Surge residuals Annual maxima
Univariate extreme value modelling for each site
Use the GEV (Generalized Extreme Value) distribution
Changes in 50 year surge residuals (in cm) as a result of a doubling of CO2 levels

8. Statistical methods for spatial extremes

9. An example Insert a map here: simulated parameter surface
Spatial variability
Spatial coherence
Residual spatial dependence
Initial location = 0,
Scale = 1,
Shape = -0.35,
Dependence = 0.7
Insert a
map here:
simulated
parameter
surface

10. Methods
Insert a
diagram here

11. Multivariate extremes
General theory
Componentwise maxima
Multivariate extreme value distribution
Modelling of marginal and dependence characteristics
Parameter linking
Inference
2-step likelihood estimation
Independence working assumption
Sandwich variance estimator
Fix margins, transform and estimate 
1-step likelihood estimation.
BEVL (Bivariate Extreme
Value Logistic) distribution

12. A local grid-based method
Evaluation
points
Kernels

13. Acknowledgements Supervisors Janet Heffernan Jonathan Tawn
Assistance and advice
Johan Segers, Vadim Kuzmin, Alexandra Ramos,
Christopher Ferro, Alec Stephenson, Matthew Killeya
Images
Web sources (list available on request)
Lamb, H. (1991) Historic storms of the North Sea, British Isles and Northwest Europe, CUP, Cambridge.

14. Apparent independence