1

Case Study on Sea-LevelRise Impacts

Robert NichollsFlood Hazard Research Centre

Middlesex University, London, UKr.nicholls@mdx.ac.uk

OECD Workshop on the Benefits of Climate PolicyImproving Information for Policy Makers

12-13 December 2002

PLAN

• Sea-Level Rise Scenarios

• Why care?

• Impacts

• Concluding Remarks

2

Processescontrolling

sea-levelchange

Relative sea-level changes

Global Component ofSea-Level Rise

Ocean Volume controlled by:• Ocean temperature -- thermal expansion;

• Melting/collapse of land-based ice:– small glaciers;

– Greenland;

– Antarctica (West Antarctic Ice Shelf collapse);

• The hydrological cycle.

3

Regional/Local Components ofSea-Level Change

• Regional meteo-oceanographic factors– pattern of thermal expansion

– wind and pressure effects

• Vertical land movement– glacial-isostatic adjustment (GIA)

– tectonics

– neotectonics

– human-induced subsidence

Sea-Level Rise at New York City1850 to 2100

6

8

Sea

Lev

el (

m)

1850 1900 1950 2000 2050 2100 Time (yrs)

Observations Scenarios

4

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

bal

-Mea

n R

ise

(m)

A1FIB1A2B2

Sea-Level Rise ScenariosStabilisation with HadCM2 Model

0

0.5

1

1950 2000 2050 2100 2150 2200 2250 2300

Time (years)

Hei

gh

t (m

)

GGa1S750S550

5

Population (bars) andPopulation Density(lines) vs. Distance

and Elevationin 1990

Coastal Megacities (>8 million people)

Forecast for 2010

Is tanbul

LagosLima

Buenos Aires R io de JaneiroMadras

KarachiJakarta

Calcutta

Bombay

Bangkok

Manila

S hanghai

Osaka

T okyo

S eoul

T ianjin

Dhaka

New York

Los Angeles

6

Coastal Ecosystems

KEY:• mangroves, o saltmarsh, x coral reefs

National Vulnerability Profiles

ANTIGUA

WITH MEASURES

WITH MEASURES

NO MEASURES

NO MEASURES

peopleaffected

peoplea ffected

protectioncosts

protectioncosts

peoplea t risk

peopleat risk

wetlandat loss

wetlandat loss

landat loss

landa t losscapital

valueat loss

capita lva lueat loss

peopleat risk

peoplea t risk

ARGENTINA

NIGERIA

VENEZUELA

based on expert judgement

based on analyses

LOW

Vulnerability profile classes

MEDIUMHIGHCRITICAL

URUGUAY

TONGA

SEYCHELLES

SENEGAL

POLAND

NEVIS

NETHERLANDS

MAURITIUS

MARSHALLS

KIRIBATI

JAPAN

GUYANA

EGYPT

BENIN

BANGLADESH

7

SENSITIVE SYSTEMS

• Populated deltas;

• Small islands, especially atolls;

• Coastal ecosystems.

Definition of Impacts

POTENTIAL IMPACTS

SEA-LEVEL RISE

INITIAL IMPACTS

RESIDUAL IMPACTS

REACTIVE ADAPTATION

ANTICIPATORY ADAPTATION

8

The Co-Evolving Coastal System

OTHER STRESSES

CLIMATE CHANGE/

SEA-LEVELRISE

NATURAL SYSTEM

SENSITIVITY ADAPTIVE CAPACITY

SOCIO-ECONOMIC SYSTEM

SENSITIVITY ADAPTIVE CAPACITY

Coastal Flood Methodology

Relative Sea-LevelRise Scenarios

Raised Flood Levels

Global Sea-levelRise Scenarios

Size of FloodHazard 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.

9

Global Incidence of FloodingNo Sea-Level Rise

0

10

20

30 P

eopl

e F

lood

ed (

Mill

ions

/yr)

1990 2020s 2050s 2080sTime (years)

GLOBAL FLOODINGResponse Surfaces for 1990 and 2100

0

200

400

600

800

0 0.25 0.5 0.75 1

Global-Mean Sea-Level Rise (m)

Peo

ple

(m

illio

ns)

AAPFPHZPTR

0

200

400

600

800

0 0.25 0.5 0.75 1

Global-Mean Sea-Level Rise (m)

In 1990 In 2100

Constant Protection

Evolving Protection

10

People Flooded Under Evolving Protection -- relative to an evolving non-climate baseline

0

1000

2000

3000

2020s 2050s 2080s

% In

crea

se

Low Scenario Mid Scenario High Scenario

Vulnerable RegionsMid estimate in the 2080s

C

A

C

B

PEOPLE AT RISK(millions per region)

> 50 million

10 - 50 million

< 10 million

region boundary

vulnerable island region

Pa c ificOcea nSMALLISLANDS

Ca ribbea n

India nOcea nSMALL ISLANDS

C

B

A

11

Additional People FloodedUnmitigated (IS92a) vs. Mitigated Emissions

0

25

50

75

100

2020s 2050s 2080s

Peo

ple

Flo

od

ed (m

illio

ns/

year

)UnmitigatedS750S550

Sea-Level Rise ScenariosStabilisation with HadCM2 Model

0

0.5

1

1950 2000 2050 2100 2150 2200 2250 2300

Time (years)

Hei

gh

t (m

)

GGa1S750S550

12

Coastal Wetland LossesOnly considers sea-level rise

0

10

20

2020s 2050s 2080s 2110s 2140s 2170s 2200s 2230s

Net

Lo

sses

(%

)

Unmitigated S750 S550

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

bal

-Mea

n R

ise

(m)

A1FIB1A2B2

13

Concluding Remarks 1• Sea-level rise could be a serious problem in

coastal zones, but the uncertainties are large;

• Impacts are strongly influenced by humanactivities and choices;

• Reducing greenhouse gas emissions could avoidsome sea-level rise impacts, but only delay others;

• An unquantified benefit of mitigation is to reducethe risk of large/abrupt sea-level rises;

• Much of the benefits of mitigation for coastalzones lie in the 22nd Century and beyond -- buthow to evaluate and communicate?

Concluding Remarks 2• Coastal zones need adaptation, within the context

of wider coastal management;

• Small islands have special adaptation needs;

• Some useful further research:– Full assessment of the range of possible impacts, including low

probability/high impact events;

– Improved top-down tools to quantify and explore and mapvulnerable ‘hotspots’;

– The adaptation process in coastal zones as this remains a majorgap in our understanding;

– other climate change, particularly changing storm conditions.

14

Case Study on Sea-LevelRise Impacts

Robert NichollsFlood Hazard Research Centre

Middlesex University, London, UKr.nicholls@mdx.ac.uk

OECD Workshop on the Benefits of Climate PolicyImproving Information for Policy Makers

12-13 December 2002