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Wiry we did this report
The sea is rising. Tidal gauge measurements from around the world confirm this fact. In
the last 100 years, global sea level has risen about 7 Inches (IPCC bost estimate).
Along much of the U.S. coast, sea level rise has been greater - 10 to 12 inches in the
last century. Over the last 15 years, concerns that the rate of sea level rise may
accelerate led coastal decision makers to seriously consider how to respond to this
A series of reports have projected future rates of tea level rise, likely environmental
and economic impacts, and possible response strategies. In 1962, EPA first began to
project sea level rise, and first published estimates in 1983 in Projecting Future Sea
Lovel Rise. Between 1984 and 1989, EPA conducted the first assessments of potential
response strategies for New Jersey, Maryland, Charleston, the Delaware River Basin,
Galveston, and San Francisco. Since the publication of the 1989 EPA Report to
Congress, the Agency has actively participated in the IPCC assessment process.
Other agencies and organizations have also studied this issue. In 1987, the National
Research Council (Committee on Engineering Implications of Changes in Relative
Mean Sea Lovel) issued a report that concluded "The risk of accelerated mean sea
levol rise is sufficiently established to warrant consideration in the planning and design
of coastal facilities." The report recommended that appropriate statistical techniques
be applied to develop a probability distribution associated with son level rise through
the year 2100 and that all updated projections include such information." In addition,
the report noted that while it may be some time before exact estimates of sea level rise
are available, the risks associated with a substantial rise should not be disregarded.
Many decisions that the Federal, state, local and private sectors are making today
regarding investments in coastal structures are sensitive to local sea lovel nae. For
example, barriers have been built to protect coastal cities from flooding during storm
surges. Engineers design these structures to deal with storms of specified design
magnitude. The safety factors of these structures will be reduced as sea level risas.
Maintaining the desired level of safety requires an explicit consideration of the
probability distribution of sea lovel nae.
Statutory requirements have also resulted in institutional needs for sea level rise
probability information. For escample, the Coastal Zone Management Act requires states
to plan for accelerated sea level rise from a changing climate. Similarly, the Water
Resources Development Act of 1985 requires the Army Corps of Engineers to
determine how to address acoplerated sea level rise. Congress requires FEMA to
assess the implications of sea level rise tor the Flood Insurance Program. At the state
lovel, various State Beach Management Acts require the type of probability Information
contained in the EPA report. In addition, ongoing plans to address land loss in states
such as Louisiana, South Carolina, and Maine, already recognize accelerated sea level
niso as a factor that could alter the best response policy.
The cost of preparing for sea level rise may be small compared to the eventual costs if
the sea rises more than allowed for in the initial project design. This is likely to be true
for structures which are ill-suited for retrofitting. For example, coastal buildings such as
beachfront hotels and shopping centers would be vulnerable to a rise in sea level. A
one foot rise in sea level may put the entire investment in the development in jeopardy.
The prudent design might Include an extra foot of elevation or a horizontal setback to
safeguard against expensive reconstruction. Similarly, when offshore oil-drilling
platforms are being built, engineers now add an extra moter to platform height as an
insurance policy to protect against sea level rise. They don't know for sure that sea
level is going to rise by a mater, they do know, however, that it's much cheaper to build
the platform ono meter higher than to risk losing the whole platform.
The purpose of the EPA report is to provide this information to decision makers. It does
this by translating information from the IPCC and others into a form that is more directly
usable to coastal decision makers. That is, the EPA report contains probability-based
projections which can be added to other local information (e.g., tide-gauge.
measurements) to estimate future sea level rise at a particular location. For example, in
Boston, MA, there is a 50 percent chance that sea level will rise 22 inches by the year
2100, a 10 percent chance of a 34 inch rise, and a 1 percent change of a 48 inch rise.
The EPA report also allows decision makers to determine when a specified amount of
sea level rise is likely happen. For example, in Washington DC, there is a 1 percent
chance of a one foot rise in sea level by 2025, a 45 percent chance by 2050 and a greater than 90 percent chance by 2100.
Finally, estimates of sea level rise vary substantially by locality. For example, by 2100 there is a 50 percent chance that the sea will rise: by 13 Inches in Los Angeles, CA; by 20 inches in Miami Beach, FL; by 27 inches in Atlantic City, NJ; by 38 inches in
Galveston, TX; and by 55 inches in Grand Isle, LA This information can help coastal
zone managers and others make better informed and more cost-effective decisions to
protect coastal areas and structuras, personal property, and coastal wetlands.
EPA results and consistency with IPCC estimates
I would like to note the good agreement and general consistency between the EPA and
probabilities associated with various increases in soa lovel, whereas the IPCC report provides a lower, upper and best estimate, not in the overall fining of sea level rise.
The EPA report estimates a 50% chance of sea levels rising 18 inches (45 cm) by the year 2100. The best estimate by the IPCC is for 19 inches (49 am). IPCC also reports a high" estimate of a 34 inch (86 am) rise. The EPA report attaches probabilities of
10% and 1%, respectively, to its estimates of a 29 and 44 inch (75 cm and 112 am)
rise, bounding the IPCC high estimate. We are in close agreement with IPCC's "lowa
estimate of an 8 inch (20 cm) rise, for which we estimate a "high likelihood" probability
Both the IPCC and the EPA reports note that the latest central estimates of sna levol
rise are lower than previous estimates, primarily due to lower estimates of global
temperature change. We should also keep in mind that the range of uncertainty which
surrounds those estimates is narrower. The science is improving, increasing our confidence in estimates of future sea level riso.
I would like to stress that there are significant impacts oven with these newer estimates.
For example, a one-foot rise in sea level in 2100 would result in the following impacts to
Along developed estuarine shores such as the Chesapeake Bay, most beaches
would be replaced by bulkheads;
Along ocean shores such as the Outer Banks, beaches would require
nourishment and/or beach homes would be lost; and