Title

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NCSP Workshop for Pacific Island Countries on the
Preparation of Second National Communications,
16-19 July 2007, Apia, Samoa
Developing Sea Level Rise Scenarios
Presented by Xianfu Lu (NCSP, UNDP-GEF) 18
July

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In the next 40 minutes or so

• Sea level rise scenarios within the context of
  VA/climate risk assessment
  
• Observed sea level change
• Constructing sea level rise scenarios
• Data sources
• Representing and communicating uncertainties

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• Sea level rise scenarios within the context of
  climate risk assessment in the coastal zone

Sea level is a key feature defining the coastal
system, and sea level rise is a principal impact
of projected global warming.
(Source adapted from R. Nicholls et al., 2007)
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• Observed sea level change

Several factors of varying time and space scales
contribute to observed local relative sea level
change.

• Globally (at decadal and longer time scales)
• Thermal expansion
• Exchange of water between ocean and other
  reservoir
  
• Regionally
• Changes in ocean circulation
• Changes in atmospheric pressure
• Locally
• Vertical land movement tectonics subsistence
  and sendimentation

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• Observed sea level change (continued)

Measurements of present-day sea level change
rely on two different techniques.

• Tide gauge
• Measures sea level variations with respect to the
  land where it lies (including contributions from
  all scales)
  
• Satellite altimetry
• Measures sea level change with respect to the
  centre of the Earths mass (not including local
  factor of land motions)

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• Observed sea level change (continued)

(Source adapted from N. Bindoff et al., 2007)
Global average sea level rose at an average rate
of 1.7 1.2 to 2.2 over the 20th century, 1.8
1.3 to 2.3 mm per year over 1961 to 2003. The
rate was faster over 1993 to 2003 about 3.1 2.4
to 3.8 mm per year.
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• Observed sea level change (continued)

(Source adapted from N. Bindoff et al., 2007)
There is large regional variations in observed
sea level changes the highest magnitude of sea
level rise in the western Pacific and eastern
Indian oceans sea level falling in the eastern
Pacific and Western Indian oceans.
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• Observed sea level change (continued)

In the Pacific Islands, there are only a few
tide gauge stations with sufficient lengths of
records to allow for rigorous trend analysis.
Using datasets from the only 4 locations on the
Pacific Island with sea-level records extending
back to before 1950, the average sea level rise
(relative to the earths crust) is 1.6 mm/year.
Using datasets from the 22 locations on the Paci
fic Islands with record lengths greater than 25
years, the average rate of relative sea level
change is 0.7 mm/year.
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• Observed sea level change (continued)

(Source adapted from N. Bindoff et al., 2007)
There is increasing interannual variability in
sea level in the Pacific Islands since the 1970s,
consistent with the increase in frequency,
persistence and intensity of ENSO events since
the 1970s.
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• Constructing sea level rise scenarios

Typically, coastal zone VA assessments use
GLOBAL projections of sea level rise.
(Source PNGs Initial National Communication to
the UNFCCC, page 48)
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• Constructing sea level rise scenarios (continued)

But, there are major deficiencies in applying
global projections to regional or local VA
assessments

• There are regional variations in the rates of
  oceanic thermal expansion, and in the changes of
  region-specific oceanic and atmospheric
  circulations

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• Constructing sea level rise scenarios (continued)

(Source adapted from G. Meehl et al., 2007)
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• Constructing sea level rise scenarios (continued)

But, there are major deficiencies in applying
global projections to regional or local VA
assessments

• There are regional variations in the rates of
  oceanic thermal expansion, and in the changes of
  region-specific oceanic and atmospheric
  circulations

• Smaller than global average SLR in the Southern
  Ocean
  
• Larger than global average SLR in the Arctic
• A narrow band of pronounced SLR stretching across
  the southern Atlantic and Indian Oceans, and
  discernible in the Southern Pacific
  
• For zonal average, there are maxima of SLR
  between 30-45oS and 30-45oN

(Source adapted from G. Meehl et al., 2007)
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• Constructing sea level rise scenarios (continued)

But, there are major deficiencies in applying
global projections to regional or local VA
assessments

• Vertical land movements, isostatic, tectonics,
  subsistence and sendimentation also contribute to
  local relative sea level change.

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• Constructing sea level rise scenarios (continued)

Historical sea level data and their relative
trends
(Source adapted from P. Hall, 2006)
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• Constructing sea level rise scenarios (continued)

Therefore, to be more applicable for adaptation
planning, sea level change scenarios needs to
account for contributions from global, regional,
and local factors. And, new methods and data ar
e increasingly become available to support the
development of such scenarios.
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• Constructing sea level rise scenarios (continued)

• Global and regional components of climate change
  related sea level rise can be derived from
  Atmosphere-ocean Coupled General Circulation
  Model (AOGCM) simulations.
• Observational records can be used to derive local
  contributions to sea level rise.

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• Constructing sea level rise scenarios (continued)

Modeling tools are now made available to
facilitate the construction of location-specific
sea level change scenarios, accounting for all
three components. The sea level scenario genera
tor within the SimCLIM system is such an example.
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• Constructing sea level rise scenarios (continued)

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4. Data sources

• To construct place-based relative sea level
  scenarios,
  
• Quality controlled observed sea level records of
  sufficient length and
  
• GCM simulations of sea level change due to
  thermal expansion, changes in ocean density and
  atmospheric circulation
  
• Are needed.

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4. Data sources (continued)

• For observed sea level records, consult
• Permanent Services for Mean Sea Level (PSMSL)
  (http//www.pol.ac.uk/psmsl/psmsl_individual_stati
  ons.html)
  

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4. Data sources (continued)
The geographic coverage of the PSMSL stations
have improved over time

1950s
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4. Data sources (continued)
The geographic coverage of the PSMSL stations
have improved over time

1960s
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4. Data sources (continued)
The geographic coverage of the PSMSL stations
have improved over time

1970s
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4. Data sources (continued)
The geographic coverage of the PSMSL stations
have improved over time

1980s
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4. Data sources (continued)
The geographic coverage of the PSMSL stations
have improved over time

1990s
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4. Data sources (continued)

• For observed sea level records, consult
• Permanent Services for Mean Sea Level (PSMSL)
  (http//www.pol.ac.uk/psmsl/psmsl_individual_stati
  ons.html)
  
• National Tidal Centre (http//www.bom.gov.au/ocean
  ography/projects/ntc/ntc.shtml)
  
• South Pacific Sea Level and Climate Monitoring
  Project (SPSLCMP) (http//www.bom.gov.au/pacificse
  alevel)
  

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4. Data sources (continued)
The SPSLCMP supports a Sea level and climate moni
toring Network of 12 SEAFRAME stations In 12 cou
ntries in the South Pacific.
(Source adapted from P. Hall, 2006)
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4. Data sources (continued)

• For observed sea level records, consult
• Permanent Services for Mean Sea Level (PSMSL)
  (http//www.pol.ac.uk/psmsl/psmsl_individual_stati
  ons.html)
  
• National Tidal Centre (http//www.bom.gov.au/ocean
  ography/projects/ntc/ntc.shtml)
  
• South Pacific Sea Level and Climate Monitoring
  Project (SPSLCMP) (http//www.bom.gov.au/pacificse
  alevel)
  
• NOAA Topex/Poseidon analyses (http//ibis.grdl.noa
  a.gov/SAT/hist/index.html)
  

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4. Data sources (continued)

• For observed sea level records, consult
• Permanent Services for Mean Sea Level (PSMSL)
  (http//www.pol.ac.uk/psmsl/psmsl_individual_stati
  ons.html)
  
• National Tidal Centre (http//www.bom.gov.au/ocean
  ography/projects/ntc/ntc.shtml)
  
• South Pacific Sea Level and Climate Monitoring
  Project (SPSLCMP) (http//www.bom.gov.au/pacificse
  alevel)
  
• NOAA Topex/Poseidon analyses (http//ibis.grdl.noa
  a.gov/SAT/hist/index.html)
  
• Reconstruction of sea level records
• Combining the near global coverage sea level
  field from satellite altimeter data with the
  longer but spatially sparse tide-gauge records

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4. Data sources (continued)
Reconstructed global average sea level for the
period 1950 to 2000
(Source J. Church et al., 2003)
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4. Data sources (continued)
Correlation between observed and reconstructed
sea level, 1993-2000
(Source J. Church et al., 2003)
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4. Data sources (continued)
Observed (blue) and reconstructed (red) sea level
change in the South Pacific
(Source J. Church et al., 2003)
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5. Representing and communicating uncertainties

• There is no single best guess sea level
  scenario.
  
• Efforts should be made to represent the wide
  range of uncertainties associated with local
  relative sea level change scenarios.
  
• Global emissions scenarios (?global temperature
  change? thermal expansion)
  
• GCMs (? regional changes in sea level due to
  ocean density and circulation)
  
• Sea level observations (?local contributions)

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5. Representing and communicating uncertainties
(continued)
Projected global average sea level rise due to
thermal expansion with respect to 1980-1999 under
different SRES emissions scenarios and simulated
by different GCMs
(Source G. Meehl et al., 2007)
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5. Representing and communicating uncertainties
(continued)
Normalised sea level change for the 21st century
as simulated by different GCMs
(Source J. Church et al., 2001)
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5. Representing and communicating uncertainties
(continued)

• Probabilistic scenarios could be developed using
  available information and are, arguably, more
  helpful for adaptation planning
  
• But as a minimal, a range of sea level
  scenarios, rather than a single best-guess,
  should be developed
  
• Uncertainties and caveats associated with the sea
  level scenarios should be explicitly
  communicated and
  
• Clear guidance on the interpretation and
  application be provided

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Thank you for your attention and patience!