Some Global Impacts of Sea-Level Rise: A Case Study of Flooding Robert J. Nicholls 1

1. Some Global Impacts of Sea-Level Rise: A Case Study of Flooding Robert J. Nicholls1 Plan • Sea Level and the Coast • Global Assessment • Methods • IS92a Results -- across the range of climate sensitivity • SRES Results -- across different socio-economic futures • Concluding Remarks 1. Presently Middlesex University, UK (r.nicholls@mdx.ac.uk) From 1 January 2004, University of Southampton, UK

2. Processes controlling sea-levelchange Relative sea-level changes

3. Sea-Level Rise at New York City1850 to 2100 IPCC TAR range due to SRES emission scenarios

4. S750 S550 IS92a ‘unmitigated’ Sea Level Under StabilisationIllustrating the large ‘commitment’ HadCM2 Model Results

5. Coastal Population Distribution Population and Population Density vs. Distance and Elevationin 1990

6. Coastal Megacities (>8 million people)UN Forecast for 2010 Tianjin Dhaka Seoul Osaka Istanbul Tokyo New York Shanghai Los Angeles Manila Bangkok Lagos Bombay Lima Karachi Madras Jakarta Rio de Janeiro Buenos Aires Calcutta

7. UNFCCC (mitigation & adaptation(?)) Regional Co-operation Coastal Management (Adaptation) Linking Climate Change to Policy Scale Assessments Relevant Policies Top/Down Bottom/Up Integrated Models GLOBAL Synthesis/ Upscaling REGIONAL Impact/ NATIONAL Adaptation /LOCAL Assessments

8. Coastal Flood Plain

9. Sea-level rise and flood return period

10. Research Questions With consistent ‘climate and socio-economic scenarios’ (e.g., IS92a): 1. Is global-mean sea-level rise a problem, if ignored? 2. What are the benefits of stabilising greenhouse forcing (mitigation policy)?

11. Background • Developed from the original Global Vulnerability Analysis (Hoozemans et al., 1993); • Based on a database of 192 polygons (roughly speaking the coastal countries); • Storm characteristics are assumed constant; • Assumes a constant slope across the flood plain; • Defence standards derived from GDP/capita; • Failure compromises entire flood plain; • Results are only meaningful at the regional and global scale.

12. Improvements • Dynamic sea level, coastal population and standard of protection scenarios; • But standard of protection only evolves in response to the 1990 climate (i.e. sea-level rise is ignored); • Higher costs of protecting deltaic areas are considered; • Increased flood risk within the coastal flood plain is evaluated; • Minimum 1990 defence standards are assumed as 1 in 10 year.

13. Methodology Global Sea-level Rise Scenarios Subsidence Storm Surge Relative Sea-Level Flood Curves Rise Scenarios Coastal Raised Flood Levels Topography Size of Flood Hazard Zones Population Density Protection Status (1in 10, 1 in 100, etc.) People in the Hazard Zone (“EXPOSURE”) Average Annual People Flooded, etc. (“RISK”)

14. OUTPUT People in the hazard zone (PHZ): number of people exposed to flooding by storm surge; Average annual people flooded (AAPF): the average annual number of people who experience flooding by storm surge (also described as people at risk (PAR)); People to respond (PTR): the average annual number of people who experience flooding by storm surge more than once per year. PAR PHZ PTR

15. Population Scenario • population growth in the coastal flood plain is double national trends. Protection Scenario • in phase evolving protection with increasing GDP/capita (and ignoring sea-level rise)

16. ValidationModel vs. National estimates

17. ResultsIS92a World

18. Global Incidence of Flooding Evolving Protection and No Sea-Level Rise 30 20 People Flooded (Millions/yr) 10 0 1990 2020s 2050s 2080s Time (years)

19. Scenario Valuesfor an IS92a World Year Global sea- Subsidence Global Global GDP 12 level rise (cm) (cm) (10 Population (billions) 1990 US$) Low Mid High 1990 0 0 0 0 5.3 20 2020s 4 11 22 0 or 5 8.1 65 2050s 10 27 49 0 or 10 9.8 113 2080s 19 45 80 0 or 14 10.7 164 2100 23 55 96 0 or 17 11.0 189

20. People Flooded -- relative to an evolving non-climate baseline 3000 Low Scenario Mid Scenario High Scenario 2000 % Increase 1000 0 2020s 2050s 2080s

21. People Flooded -- relative to an evolving non-climate baseline 10000 Low Scenario Mid Scenario High Scenario 1000 %Increase 100 10 1 2020s 2050s 2080s

22. Vulnerable RegionsMid estimate in the 2080s

23. StabilisationIS92a World

24. S750 S550 IS92a ‘unmitigated’ Sea-Level Scenariosfor one climate sensitivity HadCM2 Model Results

25. 100 Unmitigated S750 People Flooded (millions/year) 50 S550 No Climate Change 0 2020s 2050s 2080s Flood Impacts Under Stabilisation

26. Stabilisation and Climate SensitivityUnmitigated (IS92a) and Stabilisation Scenarios (S750 and S550) Calculations by Jason Lowe, Hadley Centre

27. Stabilisation in an ‘IS92a World’ Additional People Flooded (millions/year)

28. ResultsSRES Scenarios

29. SRES: Sea-Level Rise ScenariosHadCM3 Model -- Climate Sensitivity Constant

30. Global Incidence of Flooding Evolving Protection and No Sea-Level Rise

31. Additional People Floodedwith global sea-level rise

32. Stabilisation under SRESfollowing Swart et al (2002)

33. Concluding Remarks • Sea-level rise could be a serious problem for coastal flooding, but the uncertainties are large; • Mitigation reduces but does not avoid flood impacts, and some impacts are only delayed; • A combined strategy of mitigation and adaptation would seem prudent -- but what mixture? • Next steps: the DINAS-COAST Project

34. RELEVANT PUBLICATIONS • HOOZEMANS, F.M.J., MARCHAND, M., PENNEKAMP, H.A., STIVE, M., MISDORP, R. & BIJLSMA, L., 1992. The impacts of sea-level rise on coastal areas: Some global results. In:Proceedings ‘The Rising Challenge of the Sea’, Margarita Island, Venezuela, March 9-13 1992. NOAA, Silver Spring, Md. pp. 275-292. • HOOZEMANS, F.M.J., MARCHAND, M. & PENNEKAMP, H.A., 1993. A Global Vulnerability Analysis: Vulnerability Assessment for Population, Coastal Wetlands and Rice Production on a Global Scale. 2nd edition. Delft Hydraulics, the Netherlands. • PARRY, M., ARNELL, N., HULME, M., NICHOLLS, R. & LIVERMORE, M. 1998. Adapting to the inevitable. Nature, 395, 741. • NICHOLLS, R.J., HOOZEMANS, F.M.J., & MARCHAND, M. 1999. Increasing flood risk and wetland losses due to global sea-level rise: Regional and global analyses. Global Environmental Change, 9, S69-S87. • PARRY, M., ARNELL, N., McMICHAEL, T., NICHOLLS, R., MARTENS, P., KOVATS, S., LIVERMORE, M., ROSENZWEIG, C., IGLESIAS, A. & FISCHER, G., 2001. Millions at risk: defining critical climate threats and targets. Global Environmental Change, 11(3), 1-3. • ARNELL, N.W., CANNELL, M.G.R., HULME, M., KOVATS, R.S., MITCHELL, J.F.B., NICHOLLS, R.J. PARRY, M.L., LIVERMORE,, M.T.J. & WHITE, A. 2002. The consequences of CO2 stabilisation for the impacts of climate change Climatic Change, 53, 413-446. • NICHOLLS, R.J. and SMALL, C., 2002. Improved Estimates of Coastal Population and Exposure to Hazards Released. EOS Transactions, 83(2), 301 and 305. (downloadable at www.survas.mdx.ac.uk) • NICHOLLS, R.J. 2002. Analysis of global impacts of sea-level rise: A case study of flooding. Physics and Chemistry of the Earth, 27, 1455-1466. • SMALL, C. & NICHOLLS, R.J. 2003, A Global Analysis of Human Settlement in Coastal Zones, Journal of Coastal Research, 19(3), 584-589. • NICHOLLS, R.J., 2003. Coastal Flooding and Wetland Loss in the 21st Century: Changes Under The SRES Climate And Socio-Economic Scenarios. Global Environmental Change, accepted. • NICHOLLS, R.J. & LOWE, J.A., in review. Benefits of Climate Mitigation for Coastal Areas. Submitted to Global Environmental Change.

35. Web Sites • SURVAS • http://www.survas.mdx.ac.uk/ • DINAS-COAST • http://www.pik-potsdam.de/dinas-coast/