Summary Day Two
Tuesday 4 April 2000
Report on Morning Session
(by John Campbell)
What is our current understanding/capability?
In terms of the present state of the art it was evident that the high
tech approach used in the South Pacific Sea Level and Climate Monitoring
Project had proved highly reliable and that accuracy could be maintained
down to around 1mm. In addition the real time display capabilities have
many practical applications aside from their long-term climate change
detection role, in such areas as meteorological and tsunami prediction,
warning and other studies. For example, models had enabled the
simulation of the recent tsunamis in Papua New Guinea and Vanuatu. The
objective of the tsunami modelling was to identify areas where there is
some exposure to the hazard. It may also be used for warning purposes
although only for locations at some distance from the point of origin of
the tsunami. It was also shown that the data collected had potential for
use in improving understanding of fisheries in the Pacific. The method
of asymptotic trend evaluation (ATE) has been employed to generate
precise long term trends, but a longer data record (30 years) than
currently is available will be needed. At present it is premature to
make reliable estimates.
Using tide gauges it is possible to estimate that in the 19th and 20th
centuries sea level has risen at a rate of 1.2 + 0.1 mm/yr. Using
satellite altimeter data from the last 15 years a rate of sea level rise
of 2.4 + 1.5 mm/yr is obtained.
It was observed several times that it is important that the distinction
between relative and absolute sea level change is made clear. In
essence, for the purposes of international negotiations about climate
change and detecting the effects of humanity on sea level, absolute sea
level must be measured. On the other hand, when planning to adapt to
climate change in any given location it is the relative sea level which
must be considered.
A method for conducting sensitivity analyses of atoll ground water was
presented. The value of this approach was that it was not dependent
upon scenarios in order to drive the impact assessment, whilst
nevertheless allowing for the identification of sensitive locations or
activities.
What do we still need to know and/or be able to do?
As noted, in order to precisely detect trends in sea-level change a 30
year data record is required. It is important then that monitoring be
continued. Evaluating the links between fisheries production and
environmental data such as that collected in the project also requires a
longer record than currently is available (20-30 years).
It was observed from the floor that a major difficulty for island states
in climate change negotiations is the lack of hard "facts" to support
their case for bringing about a more rapid rate of mitigation.
Unfortunately, the data cannot yet tell us if there is sea level rise,
or if there is an anthropogenic component to it. This is somewhat
counter to what might be expected from the modelling of sea level
change. It is anticipated that the Third Assessment Report of the IPCC
may contain some stronger justification for identification of trends
than was included in the Second Assessment Report.
It was also noted that there are some important gaps in the monitoring
network established in the region, including the French territories and
Easter Island.
There was a problem in comparisons between satellite altimetry data and
that yielded by the sea level gauges, with the former showing more rapid
rates of sea level change.
It was noted by some speakers from the floor that it is important that
we do not lose sight of the importance of noise, in that it is the
variability in environmental conditions that will most likely cause
impacts for human communities, rather than the long term trends. There
is a need for the development of approaches to projecting changes in
variability, as well as to mean conditions.
(Tuesday, 4th April 2000 - Session Number 4)
By John Luick
C.K Shum:
* Highlighted the role of Pacific Basin in studies of global Sea Level
Rise
* Reviewed sources of error in satellite altimeter (water vapour,
Post-Glacial Rebound model) and mentioned, on top of GPS and Doris,
VLBI and satellite laser ranging.
* Sea level changes were contrasted between tide gauges and altimeters,
and also Pacific basin versus global. Globally tg and T/P are in good
agreement but in the Pacific basin the agreement is not as close.
Q: How to correct for tides?
A: Global tide model
Q: What about gravity?
A: T/P at high orbit, hence not a problem, unlike GEOSAT
Q: Is there an inconsistency in the error bars?
A: The error bars are "formal" and not necessarily representative of
true uncertainty.
Raino Heino:
* Presented long time series of global, land, and ocean temperatures
which appear consistent, in that all show recent increase
* Precipitation however is less coherent
* A distinction was drawn between actual and apparent, but false,
"climate change", illustrated by the effect on anemometers and rain
gauges of adjacent structures and improved instruments
* Stressed importance of good metadata
Bill Mitchell:
* Noted importance of going back to hourly, as opposed to monthly or
annual, means in computing sea level trends
* Presented analyses of Pacific tide gauges of more than 25 years data,
finding trends lower than Topex/Poseidou and IPCC results
* A map of recent trends in Pacific showed both negative and positive
trends
Q: Do you have any evidence of who is utilizing your data?
A: A scan through various international agencies would find a wide range
of end-users
Chris de Freitas:
* Place his work in the context of a region which has sparse data
* Pointed out deficiencies of GCM's at regional level and at predicting
future rainfall
* Described an approach based on assessment of potential impacts and
sensitivity, with a focus on processes such as the hydrogeological
system
* Approach is based on a water balance, precipitation, evaporation, etc.
* Approach is sensitive to rainfall and energy availability (solar input
etc..)
* Identified regions in Pacific of greatest sensitivity. These can form
a basis for vulnerability assessment
* Noted that the approach can be used by non-specialists
Q: What forms of data and computer requirements are there?
A: This uses a minimum data set - since a larger data set does not
exist. As for computer technology specialist, consultants can be hired
if required.
SESSION DISCUSSION
Q: Bill Mitchell, are we seeing an increase in climate or sea level
variability?
A: Yes, some people are claiming to observe greater variability but it
is difficult to measure
Q: How does Chris de Freitas' tool complement other systems?
A: This is intended as a practical management tool that predicts
potential vulnerability
COMMENT
A British study found that storm surge return periods were reduced both
by rising mean sea level and by increased extreme weather activity.
Both the mean and variability are important.
Q: (to Chris de Freitas): Is your tool applicable to specific
locations?
A: Yes
Q: (to Bill Mitchell): The model predictions combined with data - is
this a better approach?
A: Local and regional effects must always be considered.
AFTERNOON SESSION (FROM AFTER LUNCH)
By Mahendra Kumar
Climate Monitoring and continuous GPS Positioning of Tide gauges
Series of papers outlining the use of GPS systems at tide gauges for
better calibration and validation of sea surface heights estimated using
satellite altimetry.
Michael Bevis
It may also be possible to monitor total water column amounts using this
in conjunction with a suitable meteorological sensor. This may assist in
better understanding of ENSO, given the impacts of PW on ENSO.
The need for absolute sea-level measurement - W D Scherer
The presentation highlighted the need for absolute sea level
measurements for a closer examination of the connection between climate
change, climate variation and sea level rise. Such measurements are
important also for comparisons from satellite based and in-situ
measurements. Calibration of satellite derived data is important and
hence the need for geocentric reference frame.
The speaker showed some results from continental land masses such as US
and Australia, but the technique is not suitable for islands such as in
the Pacific.
In the Pacific, it is possible to use continuous GPS technique, situated
near tide gauges to get movements for vertical land movements. This
will provide the necessary relative SLR from which to get ASLR.
Requirements in the Pacific for ASLR monitoring
Need
* Long term SLR
* Satellite altimeter calibrations.
* Ocean models available ...
* Impacts
Pacific: Meter with of GPS and sea-frame stations of 11 groups, 7 do
not have continuous GPS receivers.
Requirements
* Of GPS receivers
* Reference marks
* Terrestrial test sites
* Analysis centres
* Reference frame
* Resource requirements
* GPS at tide gauge stations
* Communications & data transfer
* Terrestrial connections
* Episodic absolute gravity
* Link to PC GIAP
Recommendation
* Importance of SLR monitoring
* Cooperation with relevant organisations
* Collaboration with PCGiAS
Discussion
SOPAC: Focal Point for these GPS activities
Need for continuous GPS can also measure up
Opportunity for research & application
Linkages
Distinguish between tectonic geological effects and climatological
effects
Data to be available on public domain
Chalapan
* position of benchmark for long-term SLR monitoring
* position of tidal gauges (national interests v. scientific
desirability)
* is it necessary to invest in ASLR measurements? Isn't RSLR good
enough?
SOPAC
Need for a more comprehensive approach.
Kiribati
Tool - research - understanding uncertainties in climate change
Tonga
Application of geology in meteorology
Kiribati
* Expensive technology
* Need to build human capacity and utilise these
Climate shifts in the South Pacific By Jim Salinger
The observation of ENSO like feature in the climate system, operating
between the scales of 10-30 years was identified. This is relatively
more important in the extratropics, unlike the ENSO which is equatorial
over central and eastern Pacific. This is part of the feature known as
Interdecadal Pacific Oscillation (IPO).
Hadly Centre - sea surface temperature database
NIWA - island surface temperature base
* Island surface temp. have increased by 05-0.8'C = Conclustion 1
Interdecadal Powerful Oscillation (IPO)
* ENSO like feature on time scales of 1-3 decades
* Tightly coupled ocean and atmosphere phenomenon 1922-46, 1978-98. IPO
1947-1976 - IPO
Climate Shift
Climate shifts every 20-30 years.
20th Century occurred around late 40's and 70's
IPO changes expression of ENSO
IPO modulates ENSO
IPO weakens ENSO relationship.
Conclusions
* IPO climate shift every 20-30 years
* Shifts by changes in mean T and rainfall
* IPO modulates response to ENSO between phases and SPCE shift
* Operates on a background of global warming
Physcial basis of IPO mechanism not known
ARM Programme
Bill Clements - described the USDOE funded ARM Programme which was
created as part of US Global Change Research Programme to help better
understand atmosphericradiative and cloud processes.
Objective: Improve data inputs to GCM
Atmosphere radiation and cloud measurements, through better field
measurements.
Currently 2 stations at Manus, PNG and Nauru.
Described the Nauru'99 campaign, using research ships, aircraft and
instrument buoys.
All data available from Programme is available for researchers and
others interested.
Constraint
Budgeting for more stations
Ackerman
Understanding physics of the atmosphere, in particular radiation budget
of the tropical Pacific.
Two things
* natural climate variability - not well understood
* effects of human activities
Stations provide measurements of solar radiation and other parameters
such as temp, dew point, wind speed, cloud amount and height.
Try to make models good enough to understand the differences.
* Understand tropical radiation budget - efforts of clouds links to ENSO
* Ratio of diffuse to sky
Long term goal
Surface radiation budget
* Calibration of satellite measurements
* Effects of clouds
Application to PICs
* SLR important, changes rainfall equally important
* RF may be sensitive to El Nino/La Nina frequency
* Better modelling
* Improvements in links between local and regional efforts
Discussions
Kiribati - SPCZ shifts may affect vulnerability of areas
Eileen Shea - use of traditional knowledge & anecdotal evidence
important.
(Tuesday, 4th April 2000 - Science Session Number 5)
By Greg Musiela
CONTENT
1. Dr. Mike Bevis - University of Hawaii, USA - "Climate Monitoring and
Continuos GPS Positioning of Tide Gauges"
2. Dr. Wolfgang Scherer - NTF, Australia - "Need for Absolute Sea Level
Measurements"
3. Dr. Ramesh Govind - AUSLIG, Australia - "The Geodetic Component for
Avsolute Sea Level Monitoring"
PRESENTATIONS
Dr. Mike Bevis - University of Hawaii, USA - "Climate Monitoring and
Continuos GPS Positioning of Tide Gauges"
Better understanding of climate and sea level change requires
continuously operating GPS (CGPS) receivers established at tide gauges.
The CGPS station can be referenced to the International Terrestrial
Reference Frame (ITRF).
Leveling ties between the CGPS antenna and the tide gauge and the tide
gauge benchmarks enable the transformation of a sea level time series
into a global height system based on the ITRF ellipsoid.
An immediate application of this capability is calibration and
validation of sea surface heights estimated using satellite altimetry.
Identification and removal from a long relative sea level time series
that components due to vertical land movement underlying the tide
gauge. This technique is essential to determinate more accurately a
long term sea level rise, since over 50 year time scales absolute
vertical velocities of the sea and land surfaces are of a similar order
of magnitude (1mm/year). However, vertical land movement is not
critical for sea level rise over short time series with some exceptions
such as Vanuatu and Solomon Islands. An example of contemporary
emergence relative to sea level by 1-9mm/year in the Baltic basin was
also presented.
In addition, by deploying suitable meteorological sensors at the tide
gauge CGPS station, it si possible to monitor total column integrated
water vapor above each station in the network. Recent analysis of such
datasets demonstrated the impact of the ENSO thus complimenting
available observations to study of Pacific climate change. Examples
representing water vapor and SST were provided for Kwajalein and Guam.
An application of episodic GPS measurements with time span > 3 years was
presented to estimate postglacial rebound in Patagonia.
Recommendations for deployment of CGPS station at tide gauges were
suggested as follows:
* Geodetic dual frequency GPS receiver with well understood antenna such
as Dorne-Margolin Choke Ring
* Follow IGS standards for CGPS station
* Include met sensor package if possible
* Perform leveling ties between GPS antenna and TG BMs point
* Prioritize TG land marks founded on rock outcrop and within good sky
view
* On-line CGPS stations can join IGS global network
Recommendations for multiple use of CGPS stations were suggested as
follows:
* CGPS positioning of TGs to measure vertical motion of he crust and the
transformation RSL recorded by TG into absolute sea level change
* GPS water vapor meteorology with an initial emphasis on WV climatology
* CGPS can contribute to national spatial reference systems supporting:
* Control surveying
* WGS-84 coordinates for airports
* Hydrographic surveying
* EEZ mapping
* Geocoding of satellite imaggery
* Commercial exploration activity
* Crustal motion geodesy
Dr. Wolfgang Scherer - NTF, Australia - "Need for Absolute Sea Level
Measurements"
Land movement can introduce a significant amount of spatial variability
into a long sea level trend.
In order to examine the connection between climate change, climate
variation and sea level rise, absolute sea level must be determined.
It is possible to estimate the "noise" into sea level records by land
movement using CGPS techniques.
In addition, the need of obtaining absolute rather than relative sea
level data arises from inter-comparing and joining together satellite
and in situ observations.
Satellite altimetry derived sea level variations and trends, as well as
calibration and validation of satellite altimetry data, are referenced
to a geocentric reference frame and therefore, require absolute sea
level data from the gauges for their comparison.
An example of studies around the continental land mass of the USA was
presented showing regions of different land movement exhibiting
subsidence as well as postglacial rebound.
Presentation concluded that CGPS and the long term trends of sea level
will provide an assessment of absolute sea level. This will allow the
close examination of the influence of the climate system on sea level
trends.
Dr. Ramesh Govind - AUSLIG, Australia - "The Geodetic Component for
Absolute Sea Level Monitoring"
Dr. Govind provided two major results:
* A complete inventory of all operational CGPS stations and their
coordinating agencies in the South Pacific region
* Proposal for a major geodetic program proposed by the developmental
task force of the PCGIAP for cooperative interactions with the present
coordinating agencies and establish the geodetic component at identified
tide gauge sites.
DAY 2 : COMMON THEMES & ISSUES
(Prepared by Chalapan Kaluwin)
1. reinforce importance/value of in -situ measurements (sea level as
prime example)
2. reinforce need for sustained measurement for long-term monitoring
3. the need for short term data on climate variability and sea level
rise for planning purposes for atoll countries
* need to address accessibility and usefulness/usability of
scientific/research results for national policy making.
* Opportunities to integrate some physical data monitoring programs
(also Sea WIFS) e.g. SEAFRAME Topex-Posseidon with data on fisheries
(information on tuna & ENSO links as example)
* More generally: the conference illustrates these are both
opportunities and (scientific/technical) challenges associated
integrating climate information (like info on ENSO) to support important
policy & economic development issues.
* Future regional climate framework/strategy should facilitate/evidence
(regional) capabilities to describe, understand and respond to the
implications of climate variability & change for the overall well-being
of the region e.g. Samoa's interest in the economic consequences of
climate change for tuna/economic development in the region.
* I.e. interpretation of scientific results in the context of
information needs identified by policy makers (users) should be a
component of future regional framework
* Reinforce that the time is here to focus on the integration of various
data & research from different discipline AND integrating scientific
research with policy.
* Look for opportunities to recapitulate on opportunities to leverage
existing (or new) technologies for multiple purposes e.g. adding ''wx''
sensors to GPS stations and adding GPS to existing tide gauges (though
there are real costs here)
* Discussions of some differences in perspective between precise
measurements for long-term monitoring of sea level rise (associated with
climate change) vs. measuring variations to support local decision
making - for future strategy needs both.
* Some atoll nations ( Tuvalu) commented on the need for monitoring and
understanding the short term variability (as "noise") as important for
their policy development in addressing their economic sectors
* Possible significance of GIS & technology
* Common reference maps for diverse data application
* Importance in telecommunications infrastructure in PICs to support &
analyse with the case of GPS, better internet connections required.
* Transfer of appropriate technology (scientific-solar appliance) into
the region
* Importance of sharing data research results openly easily specific
example of continuously operating GPS Network.
* With technologies like GPS NEED TO RECOGNISE that different
applications present different criteria AND that national needs might
not (always) coincide with interests, needs of broad scientific
communities (GPS as tool to reduce uncertainty in climate changes) --
has implications for who pays what.
* Suggests a need to think big and consider climate needs in the context
of an integrated system that addresses a number of needs/issues. NOTE:
may help leverage financial resources from various sources.
* need for value of translating information about changes in variability
("Jims Factor-"IPO & ENSO) and changes in extreme events (to support
emergency management needs_
* The importance of selecting a/the mix of observational systems that
are appropriate to the problem being addressed (or the policy-relevant
information desired) was highlighted.
* Value/importance of incorporating traditional knowledge in scientific
analysis pushing the record back.
* Salinger reinforced the value/importance of sustained observations
* Challenges & opportunities of developing an understanding and
appreciation for new scientific insights (like IPO- Jim's factor) and
learning to integrate into decision making
* Better understanding of SPCZ, ITCZ, Warm pool Influence and impacts on
the regional climate.
* Value of including education and enrichment components to research
program ARMS use e.g.
* Ackerman's talk reinforced the absence of information at a regional
scale
* Need to get a better handle on how natural variability changes and the
role of human influence, especially on oceans and sea level rise
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