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NOAA Sea-Level Rise Report Issued – Dec 2012

This is a busy time of year for the sciences with the annual American Geophysical Union’s and the international Conference of Parties meetings occurring simultaneously.  NOAA has issued a number of reports in recent days, none of which are overflowing with good news.  Today, NOAA released their Global Sea Level Rise Scenarios for the United States National Climate Assessment.  It was produced in response to a request from the U.S. National Climate Assessment Development and Advisory Committee and consists of a review and synthesis of recent scientific publications examining global sea level change.

Why is this report important?  “More than 8 million people in the US live in areas at risk of coastal flooding. Along the Atlantic Coast alone, almost 60 percent of the land that is within a metre of sea level is planned for further development, with inadequate information on the potential rates and amount of sea level rise.”  The public, policymakers and planners need to know what to expect with respect to sea-level rise this century: where should development occur or be restricted and why?

The report is based on four plausible scenarios.  Scenario 1 is simply a linear extrapolation of the historical sea-level rise (SLR) rate out to 2100.  Scenario 2 is based only on projected ocean warming.  Scenario 3 builds on 2 by adding recent ice sheet loss (land-based).  Scenario 4 reflects ocean warming and the maximum plausible contribution of ice sheet loss and glacial melting.  Scenario 1 is appropriate for communities which can assume high risk or for short-term projects.  Scenario 4, in contrast, is meant for places which can’t accept risk.

Here are the scenario SLR values by 2100:

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Note that these values are not predictions, but are projections.  That is, NOAA isn’t saying that if X and Y happen, then the Intermediate-High scenario is a prediction.  The scenarios present a framework for policymakers and the public to use to make decisions.

Here is a time series graph of historical and projected SLR:

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The range of potential SLR shown in the table and figure above might lead some to conclude that ‘high confidence” in that range is misplaced by NOAA.  This is a gross misinterpretation of what is presented.  The level of uncertainty, which will always exist, is actually useful to policymakers.  Given this range of projections, people can leverage local and regional knowledge to come to better decisions than they would without this range.  Something quantified is better than a big shrug when planning, after all.

With the governors of New York, New Jersey, and Connecticut requesting $80 Billion to clean up and rebuild (better) after Hurricane Sandy, future projections of sea-level rise can obviously provide guidance regarding what and how to rebuild in addition to where to rebuild.  Policy development and planning will have to take these and other projections into heavier account this century than they did last century.  An estimate of how many billions of dollars can potentially be saved by incorporating this information would also be useful.

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