The Impact Of Sea Level Rise

With the rapid growth of knowledge in climate change, especially in sea level rise, its science and impacts, it is hardly surprising that the relationship between sea level rise and its impact on our environment, policies and building practices have attracted considerable attention in recent years. The policymakers, authorities and governing bodies acknowledge that increased sea levels will have significant medium to long-term social, economic and environmental impacts. In an attempt to provide an integrated view of climate change, Synthesis Report (IPCC, 2007) is produced which summarises observed changes in climate and their effects on natural and human systems, regardless of their causes, assesses the causes of the observed changes, presents projections of future climate change and related impacts under different scenarios. Further report discusses adaptation and mitigation options over the next few decades and their interactions with sustainable development, assesses the relationship between adaptation and mitigation on a more conceptual basis and takes a longer-term perspective.

Science of sea level rise

From geological perspective, evidence show that the Earth’s climate has changed through the Earth’s geological history, spanning more than 3 billion years. From the abundant literature on the sea level rise, it has been observed that ocean levels have always fluctuated with changes in global temperatures, supported by different studies. During ice ages when the earth was 5°C colder than today; the sea level often was more than 100 meters below the present level (Dony et al., 1962; Kennet, 1982; Oldale, 1985). The sea level was approximately 20 feet higher than the current sea level in last interglacial period when the average temperature was about 1°C warmer than today (Mercer, 1968). Today, no fewer than 13 studies of global-mean sea level (MSL) change over various periods during the last 100 years concluded that MSL has been rising (IPCC, 1990, Ch. 9, Table 9.1 pp. 263). It appears that two primary processes contribute to sea level rise (SLR): thermal expansion of the oceans and the loss of land-based ice due to increased melting (Bindoff et al., 2007). Global average sea level has risen since 1961 at an average rate of 1.8 [1.3 to 2.3] mm/yr and since 1993 at 3.1 [2.4 to 3.8] mm/yr, with contributions from thermal expansion, melting glaciers and ice caps, and the polar ice sheets (IPCC, 2007). However, whether the faster rate for 1993 to 2003 reflects decadal variation or an increase in the longer-term trend is unclear (IPCC, 2007).

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According to IPCC (2007) special report on Emissions Scenarios (SRES) A1B scenario, the steric sea level changes relative to the global mean (the local part) in different ocean basins are attributed to differential heating and salinity changes of various ocean layers and associated physical processes. As a result of these changes, water tends to move from the ocean interior to continental shelves (Yin et al., 2010)

Impacts of sea level rise on environment

Sea level rise (SLR) has direct impact on environment. Increase in temperatures at global level as well as regional level has affected many marine systems (IPPC Report, 1997). A rise in sea level would inundate wetlands and lowlands, accelerate coastal erosion, exacerbate coastal flooding, threaten coastal structures, raise water tables, and increase the salinity of rivers, bays and aquifers (Barth and Titus, 1984). The literature confirms that indirect effects of sea level rise, as well as the potential impact of extreme events, may be more significant than direct effects in the future. Regarding human settlements, Scott (1996) expresses the view that the impacts of sea-level rise and extreme events are likely to be experienced indirectly through effects on other sectors – for instance changes in water supply, agricultural productivity (Brinkman, 1995) and human migration. In addition to that, intensity and frequency change will be associated with oceans (Venugopalan, 1996; Nicholls et al, 1996), which will ultimately play a dominant part in the internal dynamics of human demography.

Literature also explains the severity of global warming leading to sea level rise. Two global coupled climate models show that even if the concentrations of greenhouse gases in the atmosphere had been stabilized in the year 2000, we are already committed to further global warming of about another half degree and an additional 320% sea level rise caused by thermal expansion by the end of the 21st century. Projected weakening of the meridional overturning circulation in the North Atlantic Ocean does not lead to a net cooling in Europe. At any given point in time, even if concentrations are stabilized, there is a commitment to future climate changes that will be greater than those we have already observed (Meehl, et al., 2005).

Many terrestrial, freshwater, and marine systems are already being affected by regional increases in temperatures (IPCC, 2007). The most rapid changes have been seen in parts of the Polar Regions where 2-3°C increases in temperature have occurred in the last 50 years. Concomitant changes in precipitation, ocean biogeochemistry, sea level, and extreme weather events are generating global concerns about the most effective strategies for conserving biological diversity as climate changes. Further concerns that societies may not be able to stabilize greenhouse gases at a level that will result in only a 2°C increase in global temperatures above preindustrial levels (Anderson & Bows 2008) are leading to a growing realization that governments should develop contingency plans for 4°C increases in temperature. Biological diversity at all levels of organization is affected directly and indirectly by climate change and by adaptation and mitigation measures.

Although the SLR pattern is very important, it suffers from an insufficient amount of study to date and was simply attributed to natural geological processes. With the recent progress in this field (Gregory et al. 2001; Levermann et al. 2005; Landerer et al. 2007) a better understanding of the SLR patterns in past, present, and future climates, and their underlying mechanisms, have been identified (Yin, et al., 2010). The acceleration is distinct from decadal variations in global sea level that have been reported in previous studies. Increased rates in the tropical and southern oceans primarily account for the acceleration. The timing of the global acceleration corresponds to similar sea level trend changes associated with upper ocean heat content and ice melt (Merrifield, et al., 2009).

Impacts of sea level rise on policies

The release of IPCC Third Assessment Report (TAR) motivated researchers to expand the ranges of approaches and methods in use, and of the characterisations of future conditions required by those methods to undertake informed decision making in an environment of uncertainty through assessments of climate change impacts, adaptation and vulnerability (CCIAV) (Carter et al., 2007). Their range of application in assessments has since been significantly expanded and aims to understand and manage as much of the full range of uncertainty, extending from emissions through to vulnerability (Ahmad et al., 2001). The most commonly used standard assessment approach such as ‘impact approach’ aims to evaluate the likely impacts of climate change under a given scenario and to assess the need for adaptation and/or mitigation to reduce any resulting vulnerability to climate risks (Carter et al., 2007). However, other approaches such as adaptation – and vulnerability- based approaches, integrated assessment and risk management are increasingly being incorporated into mainstream approaches to decision-making, resulting into incorporation of wider objectives such as stakeholder involvement, capacity-building, prioritisation and costing of adaptation measures, interrelationships between vulnerability and adaptation assessments and to integrate national development priorities and adaptation options into existing or future sustainable development plans (SBI, 2001; COP, 2005).

While, based upon research, the common response to sea level rise is to understand impacts and relate them to the categories of future characterisations which should be comprehensive, capable to capture the various aspects of the socio-economic/biophysical system it aims to represent and would indicate details with which any single element is characterised. From many characterisations of the future, most commonly used in CCIAV and other studies was found to be Scenarios and Projection. A scenario is a coherent, internally consistent, and plausible description of a possible future state of the world (Nakicenovic et al., 2000; Raskin et al., 2005). Scenarios are not predictions or forecasts, but are alternative images without ascribed likelihoods of how the future might unfold. They may be qualitative, quantitative, or both. An overarching logic often related several components of a scenario (Carter et al., 2007). Currently, two basic approaches are used to support climate adaptation policy on a regional and local scale, the predictive top-down approach and the resilience bottom-up approach (Dessai and Sluijs, 2008).

Further studying the adaptation-based approaches risk management and integrated assessment approaches are found to be effective. Risk management examines the adaptive capacity and adaptation measures required to improve the resilience or robustness of a system exposed to climate change (Smit and Wandel, 2006). Risk-management approach can also be linked directly to mitigation analysis (Nakicenovic et al., 2007).

Over the past 15-20 years, the scientific assessment of climate change impacts has improved considerable with regard to incorporating the human dimensions (e.g., IPCC, 1997; IPCC 2001a; NRC, 1999; Rayner and Malone, 1998; Wynne, 1987). At the same time, as mentioned in Moser (2005), various 23 studies support the fact, attention to the uncertainties, unknowns, and potential surprises in the science of climate change and in impact assessments have grown considerably. Moser, S (2005) emphasis the need of assessments to be taken seriously embedded with local realities and constraints to affect individual decision-makers and communal responses to climate change. Moser (2005) is an excellent study aimed at understanding coastal zone policies and their histories, the challenges and realities of costal policy-making and management, perceptions and understanding of climate change driven sea-level rise and coastal impacts.

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In other studies, Nicholls and Tol (2006) explored the potential impacts of sea-level rise using complementary impact and economic analysis methods at the global scale. In all future scenarios such as emission scenarios and socio-economic scenarios, they found that the exposure and hence the impact potential due to increased flooding by sea-level rise increases significantly compared to the base year (1990). The most vulnerable future worlds to sea-level rise appear to be which reflects differences in the socio-economic situation, rather than the magnitude of sea-level rise. However, future worlds which experience larger rises in sea-level than considered now, more extreme events, a reactive rather than proactive approach to adaptation, where GDP growth is slower or more unequal than, in the future remains a concern.

As climate change threatens to cause the largest refugee crisis in human history (Biermann and Boas, 2010), the situation calls for new governance for the protection and voluntary resettlement of climate refugees-defined as people who have to leave their habitats because of sudden or gradual alterations in their natural environment related to one of three impacts of climate change: sea – level rise, extreme weather events, and drought and water scarcity.

Despite the threat of rising sea levels, the drive to develop Florida’s coastline continues, reported by Mark Schrope, 2010. In his report, he refers to the retreat from submerging lands was relatively uncomplicated with low numbers and a simple lifestyle about 8,000 years ago when there were Native Americans living on land that now lies beneath the Gulf of Mexico (Balsillie et. al., 2004). Further he adds, that vulnerability, combined with its highly concentrated costal population, means that Florida will be a case study for other states and the world for in case of what would happen if you don’t prepare for sea level, especially in lack of legislative and public attention to the issues.

Impact of sea level rise on building practices

Anticipated climate changes will greatly amplify risks to coastal populations. Globally, approximately 400 people live within 20 m of sea level and within 20 km of a coast (Small et al., 2000). By the end of the century, increases in SLR of two to five times the present rates could lead to inundation of low-lying coastal regions, more frequent flooding episodes, and worsening beach erosion (IPCC, 1996a and IPCC, 1996b). Many developed nations have experienced a four-decade rush to the shore, with concomitant beachfront development and exponentially increasing total values for beachfront real estate, infrastructure and buildings and that this unprecedented accelerating coastal development has unfortunately coincided with a century of accelerating global sea level rise means that the prediction of the future rate of shoreline retreat has become a major societal priority (Pilkey and Cooper, 2004). Highly developed coastlines with a large population and considerable private property and infrastructure are potentially at risk from inundation and flooding as well illustrated by three urban case study sites, lower Manhattan, Coney Island, and Rockaway Beach, in Gornitz et al. (2001) study. The greater frequency of severe flooding episodes may lead to abandonment of lower floors, as in Venice, or ultimately of entire buildings Gornitz et al. (2001). Thus zoning and land use policies would need to be established to enable an orderly and equitable pullback from the most vulnerable areas. This could be accomplished by a number of mechanisms such as designation of construction setback lines, removal of buildings or hard structures in imminent danger of collapse and acquisition of empty inland space so that beaches and wetland could be rolled out. To support dense local populations in low-lying sectors of Bangkok, structural measures that have already been undertaken to reduce the rates of coastal erosion which includes building storage dams, constructing barrages, diverting channels and dykes, as well as planning future measures such as the development of pumping stations (Vitoolpanyakij, 2009).

The implementation of improved warning and forecasting methods and the adoption of some land-use planning measures would reduce both current and future vulnerability such as altering the design standard of a physical defence such as realigned channel or a defence wall, altering the effectiveness of building codes based on designing against specified return period events, altering the area exposed to a potential hazard, and/or introducing hazards previously not experienced in an area (Yohe, 2007).

Conclusion

The issue of global sea level rise has aroused much interest because of its great practical and scientific importance, especially its major impact on most coastal regions. Bird (1993), Warrick et al. (1993) and Nichollas and Leatherman (1994) have well documented serious consequences of even a few mm/yr increase of sea level. Moreover, sea level rise is a unique indicator of global climate change, potentially providing a means for evaluating climate models via their hindcasts and forecasts (Douglas, 1997).

Most literature calls for further research and rightly mentioned by Titus (1989) demands better estimates of future sea level rise, improved assessments of the impacts of global warming on coastal environments, improved ocean modelling that will be necessary for better projections of surface air temperatures which would require a substantial increase in the resources allocated for monitoring and modelling local, regional and global climate change. Other climatic variables such as winds, waves and storms should also be taken in consideration and sea-level rise should not be considered in isolation.