Federal Report: Rising Seas and Climate Change Threaten Coasts, as Local Governments Shoulder Much of the Preparedness Burden

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A new report on climate change impacts, adaptation and vulnerability in coastal areas of the U.S. warns that coping with sea level rise and coastal disruption "will be a challenge for coastal economies that contributed $8.3 trillion to the GDP in 2011." It says that local governments will have to shoulder much of the burden of "making the critical, basic land-use and public investment decisions and ...working with community stakeholder groups to implement adaptive measures on the ground."

The report, Coastal Impacts, Adaptation and Vulnerability: A Technical Input to the 2012 National Climate Assessment, says that "[i]mpacts on coastal systems are among the most costly and most certain consequences of a warming climate." It continues:

"The warming atmosphere is expected to accelerate sea-level rise as a result of the decline of glaciers and ice sheets and the thermal expansion of sea water. As mean sea level rises, coastal shorelines will retreat and low-lying areas will tend to be inundated more frequently, if not permanently, by the advancing sea. As atmospheric temperature increases and rainfall patterns change, soil moisture and runoff to the coast are likely to be altered. An increase in the intensity of climatic extremes such as storms and heat spells, coupled with other impacts of climate change and the effects of human development, could affect the sustainability of many existing coastal communities and natural resources."

Nearly 60 authors, led by Virginia Burkett of the U.S. Geological Survey and Margaret Davidson of the National Oceanic and Atmospheric Administration, wrote the report and submitted it the ongoing National Climate Assessment of the U.S. Global Change Research Program, an interagency initiative that coordinates research on climate change in the Federal Government. The report will be published soon by Island Press.

The coastal study is part of a large body of information that is being distilled into a single assessment report that will be submitted by the USGCRP to the Congress and President in late 2013. The draft of the main National Climate Assessment, including a brief chapter on coastal impacts, will be released for public comment in December or early January.

Sea Level Rise

The report says that global sea level rose 1.7 millimeters/year (0.07 inches/year) during the 20th century -- but that rate has nearly doubled to over 3 millimeters/year (0.12 inches/year) over the last 20 years. It projects that under intermediate scenarios, sea level would rise 0.5-1.2 meters (20-47 inches) by 2100. Under the highest scenario, sea-level could rise to 2.0 meters (79 inches) by 2100.

"Considering also low-lying coastal wetlands, every state along the Atlantic and Gulf Coast from New Jersey to Texas has at least 1000 square kilometers that could be submerged by a 1 meter rise in sea level, except for the three states with relatively short coastlines: Delaware, Mississippi, and Alabama," the report says. "Some regions such as Louisiana and the Chesapeake Bay will experience greater relative rise due to factors such as land subsidence, gravitational redistribution of ice-sheet meltwater, ocean circulation changes, and regional ocean thermostatic effects. Other regions undergoing land uplift, such as Alaska, will experience lesser sea-level rise."

Above: Sea Level Rise Animation from the Florida Center for Environmental Studies (CES)

Impact of Sea Level Rise and Climate Change on Coastal Areas

In addition to assessing the pervasive impacts on coastal natural resources (some of which are summarized in the table below), the study summarizes the social vulnerabilities and impacts. The researchers warn that as sea levels rise and climate changes, "coastal cities and low-lying areas will be increasingly exposed to erosion, inundation, and flooding," with the greatest impacts in low-lying coastal areas of the Gulf of Mexico, mid-Atlantic states, northern Alaska, Hawaii, and island territories.

There is a lot in harm's way. "Since 1980, roughly half of the nation’s new residential building permits were issued in coastal counties, which substantially increases vulnerability and risk of loss and adds to already populated and densely developed metropolitan areas," says the report. According to the summary of a Sea Rise Summit held in June 2012 in Boca Raton, Florida, 4.9 million people in the U.S. live below an elevation of 4 feet -- and 2.4 million of them are in Florida. "Storm surge flooding and sea-level rise pose significant threats to public and private infrastructure that provides energy, sewage treatment, clean water, and transportation of people and goods," conclude the authors of Coastal Impacts, Adaptation and Vulnerability. "These factors increase threats to public health, safety, and employment in the coastal zone."

Above: Examples of impacts of climate change and human exacerbating factors on coastal ecosystems. Source: Coastal Impacts, Adaptation and Vulnerability: A Technical Input to the 2012 National Climate Assessment, October 2012.

The Threat to Coastal Alaska

Above: Kivalina, Alaska. The community in November 2011 was hit by a Bering Sea "Super Storm" that the National Weather Service characterized as an "extremely dangerous and life-threatening storm of an epic magnitude rarely experienced.” The town subseqently voted to to relocate its school to higher ground.

According to the report on Coastal Impacts, Adaptation and Vulnerability:

"Portions of the north and west coast of Alaska are seeing dramatic increases in the rate of coastal erosion and flooding due to sea ice loss and permafrost melting. As a consequence, several coastal communities are planning to relocate to safer locations. Relocation is a difficult decision that is likely to become more common in the future for many coastal regions."


Impacts on Military Readiness

Above: Hurricane Isabel Storm Surge at Langley Air Force Base, Hampton, Virginia, 18 September 2003. Langley AFB has a mean elevation of 3 feet, with “high” points at 10-11 feet. A 4 foot increase in sea level would inundate 40-50% of the base. Photo source: U.S. Air Force, Tech. Sgt. Ben Bloker. For information on the vulnerability of the base, see Langley Air Force Base: Vulnerable to Sea Level Rise, March 2010, Oak Ridge National Laboratory.

The researchers find that "[c]limate-related changes in global and regional temperatures, precipitation patterns, and sea level, as well as increasing coastal storm extremes and extended polar ice melt seasons, can impact Department of Defense (DoD) coastal installations and associated military readiness in numerous ways." Among the consequences highlighted by the report are:

  • "Diminished capacity to sustain troop combat operational readiness if training and testing opportunities are reduced at coastal military installations;
  • Compromised readiness, especially during extreme climatic events, of military personnel, facilities, and materiel assets for global power projection via combat service support, which is dependent, in part, on secure and properly functioning coastal installations and, in some cases, supporting civil transportation infrastructure; and
  • Increased costs, inefficiencies, and response time for military operations in the coastal zone due to loss or degradation of natural resources and infrastructure at coastal installations as a result of sea-level rise or changes in the intensity of climate extremes"

Preparing for and Coping With Climate Change (Adaptation)

The study summarizes the state of coastal preparedness for rising sea levels and other climate change impacts along the coasts; and obstacles to improved preparedness. Despite the serious threat posed by sea-level rise, the report says "no coordinated, interagency process exists in the U.S. for identifying agreed upon global mean sea-level rise projections for the purpose of coastal planning, policy, or management, even though this is a critical first step in assessing coastal impacts and vulnerabilities." The authors observe that climate preparedness is increasingly recognized as essential, but that adaptation planning is proceeding around the country in an ad hoc manner and "adaptation strategies are not generally mainstreamed into the policy apparatus of governments or the development plans of the private sector."

The report says that the Department of Defense is starting to consider the emerging impacts of climate change, but that it requires additional "actionable climate information and projections at mission-relevant temporal and spatial scales." The authors add that "[a]lthough state and federal governments play a major role in facilitating adaptation planning, most coastal adaptation will be implemented at the local level."

Punta Gorda, Florida: Preparing for Sea Level Rise and Climate Disruption

Above: Aerial image of destroyed homes in Punta Gorda, Florida, following hurricane Charley on 16 August 2004 (photo source: FEMA/Andrea Booher). Five years later, a City of Punta Gordon Adaptation Plan (November 2009) was completed. "The City of Punta Gorda is currently experiencing climate change," said the plan that identified 246 pioritized climate change adaptation options for the city.

Online Resources

Burkett, V.R. and Davidson, M.A. [Eds.]. (2012). Coastal Impacts, Adaptation and Vulnerability: A Technical Input to the 2012 National Climate Assessment. Cooperative Report to the 2013 National Climate Assessment., pp. 150.

Risk and Response: Sea Level Rise Summit. The Future of Florida and the Coast. Summit Summary. 20-22 June 2012, Boca Raton, Florida.

WWF Climate Change Blog:

U.S. National Oceanic and Atmospheric Administration:

Climate Central > Surging Seas

StormSmart Coasts. "The StormSmart Coasts Network is a web resource dedicated to helping decision makers in coastal communities address the challenges of storms, flooding, sea level rise, and climate change. More than just a website, this network of state and local sites gives coastal decision makers a definitive place to find and share the best resilience-related resources available, and provides tools for collaboration."


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