will continue to rise over the next century and beyond; (3) climate models are getting better over time and are important for understanding future potential climate changes; (4) there is a growing consensus that human-induced climate change is a reality, and (5) the uncertainties surrounding our projections of sea level rise are narrowing. The EPA report is the product of good science and increases our confidence in the estimates of sea level rise.

Increasing sea level poses significant risks to our environment. The 1989 EPA Report to Congress, The Potential Effects of Global Climate Change on the United States, concluded that a rise in sea level would inundate wetlands and lowlands, accelerate coastal erosion, exacerbate coastal flooding, threaten coastal structures, and increase the salinity of rivers, bays and aquifers. This can result in loss of habitat for fish, migratory birds and other species and lost recreational opportunities for humans. Some of these effects are potentially catastrophic and irreversible. A sea level rise corresponding to the IPCC's latest best estimate and EPA's 50 percent estimate for the year 2100 could:

Drown approximately 15 to 60 percent of our coastal wetlands, depending on whether they could migrate inland or whether levees and bulkheads block their migration. With current sea level trends already threatening the wetlands of

Louisiana, any additional sea level rise caused by climate change will

exacerbate the problem.

Inundate more than 5,000 square miles (an area the size of Connecticut) of dryland in the U.S. if no protective actions are taken. Areas at highest risk from sea level rise are areas currently experiencing rapid erosion rates and with very low geographic relief, such as parts of the U.S. Atlantic and Gulf coasts.

An even smaller rise in sea level of about one foot would generally cause beaches to erode:

It's also a fact that a large and growing proportion of the nation's population, facilities, and development is located along the coasts. Coastal development decisions are being made everyday - decisions which are sensitive to sea level rise. Farsighted policymaking requires planning for the future. That's what the recent EPA report is all about — helping coastal planners, engineers, and government agencies carry out their

responsibilities to protect the future of the coastal environment for the American public.

Why 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 best 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 problem.

A series of reports have projected future rates of sea 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 Level 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 1988 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 Level) issued a report that concluded "The risk of accelerated mean sea level 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 sea 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 level rise. 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 rises. Maintaining the desired level of safety requires an explicit consideration of the probability distribution of sea level rise.

Statutory requirements have also resulted in institutional needs for sea level rise probability information. For example, 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 accelerated sea level rise. Congress requires FEMA to assess the implications of sea level rise for the Flood Insurance Program. At the state level, 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 rise 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 beach-front 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 meter 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 meter; they do know, however, that it's much cheaper to build the platform one 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.