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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.
Source: Nicholls (2010) Book on “Understanding Sea-Level Rise and Variability”
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.
Source: Nicholls (2010) Book on “Understanding Sea-Level Rise and Variability”
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
Source: Nicholls (2010) Book on “Understanding Sea-Level Rise and Variability”
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].
Source: Nicholls (2010) Book on “Understanding Sea-Level Rise and Variability”
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.
Concluding Remarks (2)
• 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.
Concluding Remarks (3)
• 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