climate change, sea-level rise, and coastal …...source: nicholls (2010) book on “understanding...

Climate Change, Sea-Level Rise, and Coastal Migration

Prof. Robert J. Nicholls

School of Civil Engineering and the Environment and the Tyndall Centre for Climate Change Research

University of Southampton

Southampton SO17 1BJ

United KingdomEmail: [email protected]

Climate Change and Security

Trondheim 21-24 June 2010

Plan

• Introduction

• People and coasts

• Magnitude of sea-level rise

• Impacts of sea-level rise

• Responses to sea-level rise

• Concluding thoughts

Coastal Migration and Sea-Level Rise

• Widely assumed to be a major 21st Century process with >100 million environmental refugees “expected” (mainly from small islands and deltas).

• “Observations” reported in Wikipedia– “In 1995, half of Bhola Island in Bangladesh became

permanently flooded, leaving 500,000 people homeless”

– The inhabitants of the Carteret Islands in Papua New Guinea are also among the first climate refugees due to sea level rise attributed to global warming and climate change

– In Alaska, the village of Shishmaret, located on the 100 km long barrier island of Sarichef, also faces evacuation as rising temperatures cause the melting of sea ice and the thawing of the permafrost.

Coasts and PeoplePopulation and economic density in the coastal zone is greater than

other areas of the earth’s surface.

Source: Nicholls and Small, 2003, Journal of Coastal Research

Current Exposure by Elevationbased on today’s conditions in 84 developing countries

Source: Dagsputa et al (2007) World Bank Report (2009) Climatic Change

Coastal PopulationSix global estimates

Source: Litcher et al., in review, Journal of Coastal Research

0

200

400

600

800

0 2 4 6 8 10

Po

pu

lati

on

(m

illi

on

s)

Elevation and mean sea level (m)

GTOPO30 GRUMP GTOPO30 Landscan

GLOBE GRUMP GLOBE Landscan

Isciences GRUMP Isciences Landscan

?

Coastal Trends

• Population

– Growing coastal population (and economy)

– Urbanisation

• Subsiding cities, especially in deltas

• Climate change and sea-level rise

• A reactive approach to adaptation

What is Sea-Level Rise?

Climate-induced Sea-Level Rise

Rising temperatures lead to:

• Thermal expansion of seawater;

• Melting of land-based ice

– Small glaciers (e.g., Rockies, Alaska)

– Greenland ice sheet

– West Antarctic ice sheet

Global Sea-Level Rise (SLR)(Source: IPCC, 2007)

Projections

IPCC AR4

Observations

Global mean-sea level:

Observations and projectionsSource: Nicholls and Cazenave (2010) Science

Red Bar: Rahmstorf (2007) Science

Blue Bar: Vermeer and Rahmstorf (2009) PNAS

Green Bar: Grinsted et al (2009) Clim. Dyn.

Global Sea-Level Rise(Source: IPCC, 2007)

?

?

?

Measured Sea-Level Change(or relative sea-level change)

Source: Nicholls (2010) Book on “Understanding Sea-Level Rise and Variability”

Subsiding Coastal Megacities(maximum subsidence during the 20th Century)

Istanbul

Lagos

Lima

Buenos Aires Rio de Janeiro

MadrasKarachi

Jakarta (0.5 m)

Calcutta ?

BombayBangkok (2 m)

Manila (1 m)

Shanghai (3 m)

Osaka (3 m)

Tokyo (5 m)

Seoul

Tianjin (2 m)Dhaka ?

New York

Los Angeles

Source: Nicholls (1995) GeoJournal

What Are The Impacts of Sea-Level Rise?

Physical Impacts of Sea-Level RiseStudies of migration focus strongly on land loss – mainly inundation

Episodic disasters may be just as important – e.g. Katrina and New Orleans

NATURAL SYSTEM EFFECT INTERACTING FACTORSCLIMATE NON-CLIMATE

1. Inundation,

flood and

storm damage

a. Surge

(flooding from the

sea)

Wave/storm climate,

Erosion,

Sediment supply.

Sediment supply,

Flood management,

Erosion,

Land reclamation

b. Backwater

effect (flooding

from rivers)

Run-off. Catchment management and land

use.

2. Wetland loss (and change) CO2 fertilisation of

biomass production,

Sediment supply,

Migration space

Sediment supply,

Migration space,

Land reclamation (i.e., direct

destruction).

3. Erosion (of ‘soft’ morphology) Sediment supply,

Wave/storm climate.

Sediment supply.

4. Saltwater

Intrusion

a. Surface

Waters

Run-off. Catchment management (over-

extraction),

Land use.

b. Ground-water Rainfall. Land use,

Aquifer use (over-pumping).

5. Higher water tables/ impeded

drainage

Rainfall,

Run-off.

Land use,

Aquifer use,

Catchment management.


Socio-Economic Impacts of SLRCoastal Socio-

economic

Sector

Sea-level rise physical impact

Inundation,

etc.

Wetland loss Erosion Saltwater

intrusion

Higher water

tables/

etc.

Freshwater

ResourcesX x - X X

Agriculture and

forestryX x - X X

Fisheries and

AquacultureX X x X -

Health X X - X xRecreation and

tourismX X X - -

Biodiversity X X X X XSettlements/

infrastructureX - X X X

X = strong; x= weak; - = negligible or not established.


Submergence Due to SubsidenceBangkok Area

(a) 1981 (b) 2002Source: Phien-Wej et al (2006) Engineering Geology

Population Displacement in Deltasunder current relative sea-level trends, including subsdience, constant

population and no adaptation to 2050

Indicative population potentially displaced:

Extreme > 1 million;

High 1 million to 50,000;

Medium 50,000 to 5,000

(Total population of 8.7 million people by 2050)Source: Ericson et al. (2006) Global and Planetary Change

Threatened Coastal Areasto 40-cm of climate-induced SLR by the 2080s

Source: Nicholls et al. (1999); see also Nicholls (2004) Global Environmental Change

People at Risk of FloodingDIVA global results – A1B socio-economic scenario

Low SLR – 0.5 m rise; High SLR – 2 m by 2100, respectively

0

50

100

150

200

250

300

2000 2020 2040 2060 2080 2100

Pe

op

le f

loo

de

d (

mil

lio

ns/ye

ar)

High SLR No Adapt

Low SLR No Adapt

High SLR Adapt

Low SLR Adapt

People at Risk of FloodingDIVA global results – A1B socio-economic scenario

Low SLR – 0.5 m rise; High SLR – 2 m by 2100, respectively

0,1

5

250

2000 2020 2040 2060 2080 2100

Pe

op

le f

loo

de

d (

mil

lio

ns/ye

ar)

High SLR No Adapt

Low SLR No Adapt

High SLR Adapt

Low SLR Adapt

Port City Locations>1 million population in 2005 -- 136 locations

Key global results for the 100-year flood plain

• 40 million people

• 0.6% of global population

• (10% of port city population)

• US $3000 billion of assets

• 5% of global GDP

Port Cities

• USA 17 locations

• China 14 locations

• Brazil 10 locations

Source: Nicholls et al., 2008, OECD Report

Aggregated Population Exposure in the Port Cities

Influence of different change factors: 2005 to 2070s

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

Current Situation/Baseline with storm enhancement

factor only

with sea-level rise only with human induced

subsidence only

All Factors

Factors

Ex

po

se

d p

op

ula

tio

n (

00

0)

Current population

Projected population

Exposed Population 2005Top 20

Exposed Population 2070sTop 20

What Can We Do About Sea-Level Rise?

Mitigation – source control

Adaptation – change behaviour

Mitigation ScenariosThe Commitment to Sea-Level Rise

(Hadley Coupled Ocean-Atmosphere Model 2 Simulations)

Time (years)

0.00

0.25

0.50

0.75

1.00

1.25

1950 2000 2050 2100 2150 2200 2250

Unmitigated Emissions

Stabilize at S750 in 2250

Stabilize at S550 in 2150

Ris

e (m

)

Source: Nicholls and Lowe (2004) Global Environmental Change

Planned Adaptation to SLR


Many Adaptation Options are AvailableP – Protection; A – Accommodation; R – Retreat.

Migration is a form of retreat

NATURAL SYSTEM EFFECT POSSIBLE ADAPTATION RESPONSES

1. Inundation,

flood and storm

damage

a. Surge Dikes/surge barriers [P],

Building codes/floodwise buildings [A],

Land use planning/hazard delineation [A/R].b. Backwater

effect

2. Wetland loss (and change) Land use planning [A/R],

Managed realignment/ forbid hard defences [R],

Nourishment/sediment management [P].

3. Erosion (of ‘soft’ morphology) Coast defences [P],

Nourishment [P],

Building setbacks [R].

4. Saltwater

Intrusion

a. Surface Waters Saltwater intrusion barriers [P],

Change water abstraction [A/R].

b. Ground-water Freshwater injection [P],

Change water abstraction [A/R].

5. Rising water tables/ impeded

drainage

Upgrade drainage systems [P],

Polders [P],

Change land use [A],

Land use planning/hazard delineation [A/R].


Fraction of Coast ProtectedSensitivity Analysis on Protection Costs

FUND analysis (for the ATLANTIS Project)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

2000 2025 2050 2075 2100 2125 2150 2175 2200 2225 2250 2275 2300

fracti

on

1x

5x

10x

20x

100x

linear

non-linear

Source: Nicholls, Tol and Vafeidis (2008) Climatic Change

Concluding Remarks (1)

• Coastal areas contain large and growing concentrations of people and assets (with a net coastward migration today).

• Hence, coastal areas are changing rapidly due to human agency.

• This includes human-induced subsidence in many densely-populated deltas.

• Climate-induced sea-level rise is inevitable –the uncertainty is the magnitude of the change.


• The worst-case (do nothing) impacts are dramatic, but actual impacts depend on

– Relative sea-level rise

– Change in exposure

– Application and success of adaptation

• Effects on human migration will be a product of all these dimensions.

• In some cases, migration (a retreat) will be the best option.


• Mitigation of climate and subsidence will make the problem more manageable, with adaptation to the residual risk.

• To adapt to dynamic coastal risks, proactive assessment is required including:– defining all the relevant drivers,

– the potential impacts,

– the potential adaptation responses,

– selection of sustainable adaptation pathways (linked to wider development goals).

The Way Forward?TE2100 Project (London), Delta Commission (the Netherlands) and

the Economics of Adaptation to Climate Change (World Bank)

Key Features:

• Strategic long-term view

• Include high-end scenarios

• What are our choices?

Climate Change, Sea-Level Rise, and Coastal Migration

Prof. Robert J. Nicholls

School of Civil Engineering and the Environment and the Tyndall Centre for Climate Change Research

University of Southampton

Southampton SO17 1BJ

United KingdomEmail: [email protected]

Climate Change and Security

Trondheim 21-24 June 2010

climate change, sea-level rise, and coastal …...source: nicholls (2010) book on “understanding...

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