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

Processes controlling sea-level change Relative sea-level changes

Sea-Level Rise at New York City 1850 to 2100 IPCC TAR range due to SRES emission scenarios

Sea Level Under Stabilisation Illustrating the large ‘commitment’ IS92a ‘unmitigated’ S550 S750 HadCM2 Model Results

Population and Population Density vs. Distance and Elevation in 1990 Coastal Population Distribution Population and Population Density vs. Distance and Elevation in 1990

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

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

Coastal Flood Plain

Sea-level rise and flood return period

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)?

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.

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.

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

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

Population Scenario Protection 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)

Validation Model vs. National estimates

Results IS92a World

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

Scenario Values for an IS92a World Year Global sea- Subsidence Global Global GDP level rise (cm) (cm) Population (billions) (10 12 1990 US$) Low Mid High 1990 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

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

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

Vulnerable Regions Mid estimate in the 2080s

Stabilisation IS92a World

Sea-Level Scenarios for one climate sensitivity IS92a ‘unmitigated’ S550 S750 HadCM2 Model Results

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

Stabilisation and Climate Sensitivity Unmitigated (IS92a) and Stabilisation Scenarios (S750 and S550) Calculations by Jason Lowe, Hadley Centre

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

Results SRES Scenarios

SRES: Sea-Level Rise Scenarios HadCM3 Model -- Climate Sensitivity Constant

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

Additional People Flooded with global sea-level rise

Stabilisation under SRES following Swart et al (2002)

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

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.

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