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Please see EPA's Climate Change site for current information on climate change and global warming. EPA no longer updates EPA's Global Warming Site, but is maintaining this archive for historical purposes. Thank you for visiting the archive of EPA's Global Warming Site.
The Risk of Sea Level Rise
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The Risk of Sea Level Rise: A Delphic Monte Carlo Analysis in which Twenty Researchers Specify Subjective Probability Distributions for Model Coefficients within their Respective Areas of Expertise (1996, 861 kb pdf), by James G. Titus and Vijay Narayanan, was originally published in Climatic Change 33: 151-212, 1996. The report's Abstract is available below.
For additional reports focused on the implications of rising sea level, go to the Global Warming Site's Sea Level Rise Reports section.
PDF files are in Adobe Acrobat 4.0 (*.pdf) format; the required Reader is available at no cost from Adobe Systems. 
AbstractThe United Nations Framework Convention on Climate Change requires nations to implement measures for adapting to rising sea level and other effects of changing climate. To decide upon an appropriate response, coastal planners and engineers must weigh the cost of these measures against the likely cost of failing to prepare, which depends on the probability of the sea rising a particular amount.
This study estimates such a probability distribution, using models employed by previous assessments, as well as the subjective assessments of twenty climate and glaciology reviewers about the values of particular model coefficients. The reviewer assumptions imply a 50 percent chance that the average global temperature will rise 2°C degrees, as well as a 5 percent chance that temperatures will rise 4.7°C by 2100. The resulting impact of climate change on sea level has a 50 percent chance of exceeding 34 cm and a 1% chance of exceeding one meter by the year 2100, as well as a 3 percent chance of a 2 meter rise and a 1 percent chance of a 4 meter rise by the year 2200.
The models and assumptions employed by this study suggest that greenhouse gases have contributed 0.5 mm/yr to sea level over the last century. Tidal gauges suggest that sea level is rising about 1.8 mm/yr worldwide, and 2.5-3.0 mm/yr along most of the U.S. Coast. It is reasonable to expect that sea level in most locations will continue to rise more rapidly than the contribution from climate change alone.
We provide a set of 'normalized' projections, which express the extent to which climate change is likely to accelerate the rate of sea level rise. Those projections suggest that there is a 65 percent chance that sea level will rise 1 mm/yr more rapidly in the next 30 years than it has been rising in the last century. Assuming that nonclimatic factors do not change, there is a 50 percent chance that global sea level will rise 45 cm, and a 1 percent chance of a 112 cm rise by the year 2100; the corresponding estimates for New York City are 55 and 122 cm.
Climate change impact assessments concerning agriculture, forests, water resources, and other noncoastal resources should also employ probability-based projections of regional climate change. Results from general circulation models usually provide neither the most likely scenario nor the full range of possible outcomes; probabilistic projections do convey this information. Moreover, probabilistic projections can make use of all the available knowledge, including the views of skeptics; the opinions of those who study ice cores, fossils, and other empirical evidence; and the insights of climate modelers, which may be as useful as the model results themselves.
The Risk of Sea Level Rise: A Delphic Monte Carlo Analysis in which Twenty Researchers Specify Subjective Probability Distributions for Model Coefficients within their Respective Areas of Expertise (1996, 861 kb pdf), by James G. Titus and Vijay Narayanan, was originally published in Climatic Change 33: 151-212, 1996. The opinions expressed in this paper do not necessarily reflect the views of the U.S. Environmental Protection Agency or any other agency of the United States Government. For a report that does reflect EPA's official opinion on the same issues, see The Probability of Sea Level Rise (1995). Please send comments to James G. Titus, Strategic Studies Staff, U.S. Environmental Protection Agency, Washington, D.C. 20460.
If you would like a hard copy of this report, please fill out the contact us form (and please include the title of the report and relevant mailing information in your request).
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