By Andrew Brett Einhorn 

Executive Summary

The Intergovernmental Panel on Climate Change (IPCC) predicted in their last report (2001) that global temperatures would increase between 1.4-5.8 degrees Celsius by the year 2100 due to human emissions of greenhouse gases. New predictions (2001) by the IPCC show a rise in sea levels of 9-88 cm (3.5-35in) due to warmer temperatures by 2100 with a most likely increase of 38-55 cm (15-22 in) and a central value of 48 cm (19 in).  These projections have left many coastal planners and developers wondering how severe the impact of these changes will be and what steps to take to protect shorelines and coastal cities.  With over 95,000 miles of coastline, 3.4 million square miles of ocean within its territories, and 53% of the population living on or near the coast (within 20 miles), the Unites States could suffer tremendous losses should sea levels continue rising.

This paper focuses on the effects of accelerated sea level rise (SLR) due to anthropogenically-induced climate change in a literature review of previous attempts to quantify the projected economic effects the continental United States will incur.  Analyses involved estimating the cost of engineering projects needed to protect ecological systems, coastal developments, and shorelines from damages associated with elevated sea levels.

Over the past 100 years, the global mean sea level rose between 10-25 cm at a rate of 1-2.5 mm each year. Currently, 1500 homes are lost in the US each year due to coastal erosion, a value of $530 million dollars. Predictions generally state that elevated sea level rise would begin drastically impacting coastal areas around the middle of this century.  Increased flooding, erosion rates, and storm surge heights would all contribute to higher casualty, property, and ecosystem losses.

In 1991, the cost of protecting the continental United States from damages associated with a 100cm elevation in sea level was estimated to be between 100 and 379 billion dollars.  Downward revisions of these estimates have since been the trend. In 1995, Frankhauser predicted it would cost the continental United States $81.5 billion from a 100 cm rise in sea level. The following year, a new methodology was introduced that depreciated the worth of coastal structures needing protection. The approach lowered protection cost estimates from previous efforts, hypothesizing a cost range between 8 and 10 billion dollars for a 100cm rise.

Protection costs will more likely represent earlier estimates given the high cost of raising rail lines, bulkheads, and bridge, tunnel, and subway entrances around the country at low elevations.  Additional costs will include building enormous storm surge barriers spanning the width of city harbors to protect coastal urban centers from storm-induced flooding.