Understanding Sea Level Rise and Variability

A WCRP (World Climate Research Programme) workshop in support of the WCRP's strategy 2005-2015 and a WCRP contribution to the GEOSS (Global Earth Observation System of Systems)

Introduction

Following discussions at JSC 25 in Moscow and subsequent discussions as part of the COPES Task Force, a proposal to hold a sea-level workshop to bring together all relevant WCRP science with a view to identifying uncertainties and research and observational activities for narrowing these uncertainties was approved the XXVI^th session of Joint Scientific Committee for the World Climate Research Programme, Guayaquil, Equador, March 2005.  The Workshop would require contributions from WCRP projects and activities (CLIVAR, ocean thermal expansion; CliC, glacier and ice sheet contributions; GEWEX, terrestrial water storage; WGCM, coupled climate modelling).  In addition, contributions of experts from IGBP, the ESSP GWSP, and other relevant groups would also be valuable. 

Workshop Objectives

Given the present and projected future rates of global sea-level rise, and the associated variability ranging from long timescales (i.e., decades to centuries, e.g., due to climate change) to short timescales (i.e., hourly to daily, e.g., due to storm surges):

• Identify the factors contributing to the observed sea level rise and variability, as well as that projected in the future.
• Organize a systematic attack on the error budget: 
  • Identify the major sources of uncertainty for each, 
  • What can be done to reduce each of these uncertainties? 

• In order to reduce the error budget, identify associated requirements for:
  • New and/or augmented research,
  • New and/or augmented technical development, and
  • The collection of sustained, systematic observations.

GEOSS Implementation

Consistent with the mission of GEOSS – to improve monitoring of the state of the Earth, increase understanding of Earth processes, and enhance prediction of the behavior of the Earth system – this workshop was also being conducted in support of the GEOSS 10-Year Implementation Plan.  As such, this workshop would help develop international scientific consensus for those sustained observations required to address sea-level rise and its variability, especially as needed by the GEOSS activities focused on Climate and Hazards.

Expected Outcome

The major output from the workshop would be a WCRP report summarizing the current state of the science, an outline of future research requirements for improving our understanding of sea-level rise and variability and a description of the observational requirements (both experimental and sustained systematic observations).  A careful consideration of uncertainties will be included.  The report would contain sections on requirements for improving present estimates and future projections of:

• sea-level rise and variability,
• ocean thermal expansion,
• non-polar glacier contributions,
• ice sheet contributions,
• vertical motion due to glacial isostatic adjustments and tectonic motions,
• terrestrial (including anthropogenic) water storage contributions,
• changes in the frequency/intensity of extremes sea level events and waves

The report would also address the extent to which current programs adequately cover the requirements and what additional efforts may be necessary.  The report will consider traditional observational techniques (e.g. tide gauges), as well as recent observational techniques (e.g. radar and laser altimetry, satellite gravimetry). 
The full report would be accompanied by a summary report which would briefly present the case for future research and observational programs. 

The report would be different from the forthcoming IPCC Assessment Report in that it would not contain projections of future changes.  It would focus on science and observational requirements, including uncertainties identified during the workshop and by IPCC.  The starting point for the workshop would be the current IPCC uncertainties, and the Report would focus on how the uncertainties could be reduced for any future IPCC Assessment Reports.

Final Outcome