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 Remarks1. 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

6

8 S

ea L

evel (m

)

1850 1900 1950 2000 2050 2100 Time (yrs)

Observations Scenarios

IPCC TAR range due to SRES emission scenarios

4

Sea Level Under StabilisationIllustrating the large ‘commitment’

IS92a ‘unmitigated’S550

S750HadCM2 Model Results

5

Population and Population Density vs. Distance and Elevation

in 1990

Coastal Population Distribution

6

Coastal Megacities (>8 million people)

UN Forecast for 2010

Istanbul

LagosLima

Buenos Aires Rio de JaneiroMadras

KarachiJakarta

Calcutta

Bombay

Bangkok

Manila

Shanghai

Osaka

Tokyo

Seoul

Tianjin

Dhaka

New York

Los Angeles

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GLOBAL

REGIONAL

NATIONAL/LOCAL

Scale

UNFCCC(mitigation &

adaptation(?))

Regional Co-operation

Relevant Policies

CoastalManagement(Adaptation)

Bottom/UpTop/Down

Synthesis/

Upscaling

Impact/Adaptation

Assessments

Assessments

Integrated Models

Linking Climate Change to Policy

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.

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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

Relative Sea-LevelRise Scenarios

Raised Flood Levels

Global Sea-levelRise Scenarios

Size of Flood Hazard Zones

People in theHazard Zone

Subsidence

Storm SurgeFlood Curves

Coastal Topography

PopulationDensity

Protection Status(1in 10, 1 in 100, etc.) (“EXPOSURE”)

(“RISK”)Average AnnualPeople Flooded, etc.

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OUTPUTPeople 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.

PHZPAR

PTR

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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)

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ValidationModel vs. National estimates

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08

National Assessments

Glo

bal

Mo

del

No SLR SLR = 1 m

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ResultsIS92a World

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

0

10

20

30 P

eop

le F

lood

ed (

Mill

ion

s/yr

)

1990 2020s 2050s 2080sTime (years)

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Scenario Valuesfor an IS92a World

Global sea-level rise (cm)

Year

Low Mid High

Subsidence(cm)

GlobalPopulation(billions)

Global GDP(10 12

1990 US$)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 1642100 23 55 96 0 or 17 11.0 189

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People Flooded -- relative to an evolving non-climate baseline

0

1000

2000

3000

2020s 2050s 2080s

% In

cre

as

e

Low Scenario Mid Scenario

High Scenario

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People Flooded -- relative to an evolving non-climate baseline

1

10

100

1000

10000

2020s 2050s 2080s

%In

crea

se

Low Scenario

Mid Scenario

High Scenario

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Vulnerable RegionsMid estimate in the 2080s

C

A

C

B

PEO PLE AT RISK(m illio ns p e r re g io n)

> 50 m illio n

10 - 50 m illio n

< 10 m illio n

re g io n b o und a ry

vulne ra b le isla nd re g io n

Pa c ificO c e a nSM ALLISLAN D S

C a rib b e a n

Ind ia nO c e a nSM ALL ISLAN D S

C

B

A

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StabilisationIS92a World

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Sea-Level Scenariosfor one climate sensitivity

IS92a ‘unmitigated’S550

S750HadCM2 Model Results

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Flood Impacts Under Stabilisation

0

50

100

2020s 2050s 2080s

Pe

op

le F

loo

de

d (

mill

ion

s/y

ear

)

UnmitigatedS750S550

No Climate Change

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Stabilisation and Climate Sensitivity Unmitigated (IS92a) and Stabilisation Scenarios (S750 and S550)

Calculations by Jason Lowe, Hadley Centre

0

50

100

150

1950 2000 2050 2100 2150 2200

Time

Sea

lev

el

(cm

)

High ClimateSensitivity

Mid ClimateSensitivity

Low ClimateSensitivity

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

0

20

40

2020s 2050s 2080s 2110s 2140s

Ad

dit

ion

al P

eop

le F

loo

ded

S550 S750 IS92a

(b) Low climate sensitivity

0

100

200

2020s 2050s 2080s 2110s 2140s

Ad

dit

ion

al P

eop

le F

loo

ded

S550 S750 IS92a

(c) Mid climate sensitivity (HadCM2)

0

200

400

600

2020s 2050s 2080s 2110s 2140s

Ad

dit

ion

al P

eop

le F

loo

ded

S550 S750 IS92a

(d) High climate sensitivity

0

20

40

1990 2020s 2050s 2080s 2110s 2140s

Peo

ple

Flo

od

ed

(a) Baseline: No global sea-level rise

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ResultsSRES Scenarios

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

0.0

0.1

0.2

0.3

0.4

1990 2010 2030 2050 2070 2090

Time (yrs.)

Glo

ba

l-M

ea

n R

ise

(m

)

A1FIB1

A2B2

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

0

10

20

30

1990 2020s 2050s 2080s

AA

PF

(m

illi

on

s/ye

ar)

A1FI

A2

B1

B2

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Additional People Floodedwith global sea-level rise

0

10

20

2020s 2050s 2080s

AA

PF

(m

illi

on

s/y

ear)

A1FI

A2

B1

B2

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Stabilisation under SRESfollowing Swart et al (2002)

0

10

20

30

40

A1FI A2 B1 B2

Peo

ple

Flo

od

ed (

mil

lio

ns/

yr.)

No SLR Unmitigated

"S650" "S550"

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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

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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 21 st 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.

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Web Sites

• SURVAS– http://www.survas.mdx.ac.uk/

• DINAS-COAST– http://www.pik-potsdam.de/dinas-coast/