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Reducing Uncertainties in Local Sea Level Projections for Developing Climate Change Mitigation Strategies


Presentation by Hans-Peter Plag and Norman Miller
To be presented on May 30, 2008 at AGU Spring Meeting, Fort Lauderdale, Florida, USA

Copyright 2008, Hans-Peter Plag

ABSTRACT
Reducing uncertainties of local sea level projections for developing climate-change mitigation strategies
Plag, H.-P., hpplag@unr.edu, Nevada Bureau of Mines and Geology and Seismological Laboratory, University of Nevada, Reno, Reno, NV , United States
* Miller, N. L., nlmiller@Berkeley.edu, Climate Science Department and Geography Department, Berkeley National Laboratory & University of California, Berkeley, Berkeley, CA 94720, United States

Changes in Local Sea Level (LSL) may be one of the major climate change impacts requiring expensive coastal protection measures or severe adaptation strategies. In many countries, decision makers are increasingly facing decisions of whether to burden national economies with costs for coastal protection, or to risk major disasters. The decision to rebuild (e.g. New Orleans) or abandon cities or island nations (e.g. Maldives) under incrreasing risk of being devastated by a combination of storm surge and rising LSL requires an understanding of the uncertainties. Today's planning decisions will have long term implications for mitigating the potential of a slowly developing LSL rise disaster. Informed decisions will only be possible if predictions of the range of future LSL rise are made available with reliable uncertainties. State-of-the-science Earth system models cannot reliably predict climate-induced changes in LSL, hence policy- makers lack needed tools for determining best mitigation strategies. Local secular changes in LSL are the result of a location-dependent mix of various factors, including steric changes, ocean and atmospheric circulation changes, mass exchange of the ocean with terrestrial water storage and the cryosphere, and the vertical motion of the land. A major uncertainty is contributed by the uncertain response of large ice sheets on Greenland and Antarctica to climate change. Therefore, Probability Density Functions (PDF) attached to the IPCC predictions for global temperature changes over the next 100 years cannot be translated easily into PDFs for global sea level changes, and even less so for any LSL changes. We will present an observation-based approach for the prediction and probabilities of LSL changes for a wide range of scenarios needed to assess plausible future LSL trajectories at any given location. Identifying the major contributions to the uncertainties and determining their weight with respect to the overall PDF for LSL changes will help to pinpoint steps to reduce these uncertainties. Quantifying LSL change PDFs and providing this information to regional policy-makers will help to develop comprehensive strategies that will be better understood and accepted.

This presentation has the following main parts:
  • Introduction: Basic Terms and Concepts
  • Global Versus Local Sea Level Changes
  • Plausible Forcing Scenarios and Range of Predictions
  • Main Uncertainties‏
  • How to Address these Uncertainties for Policymakers?