Estimating Sea-Level Allowances for Atlantic Canada using the Fifth Assessment Report of the IPCC

Abstract

Sea-level allowances at 22 tide-gauge sites along the east coast of Canada are determined based on projections of regional sea-level rise for the Representative Concentration Pathway 8.5 (RCP8.5) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) and on the statistics of historical tides and storm surges (storm tides). The allowances, which may be used for coastal infrastructure planning, increase with time during the twenty-first century through a combination of mean sea-level rise and the increased uncertainty of future projections with time. The allowances show significant spatial variation, mainly a consequence of strong regionally varying relative sea-level change as a result of glacial isostatic adjustment (GIA). A methodology is described for replacement of the GIA component of the AR5 projection with global positioning system (GPS) measurements of vertical crustal motion; this significantly decreases allowances in regions where the uncertainty of the GIA models is large. For RCP8.5 with GPS data incorporated and for the 1995–2100 period, the sea-level allowances range from about 0.5?m along the north shore of the Gulf of St. Lawrence to more than 1?m along the coast of Nova Scotia and southern Newfoundland.     

Allowances for evolving coastal flood risk under uncertain local sea-level rise

Estimates of future flood hazards made under the assumption of stationary mean sea level are biased low due to sea-level rise (SLR). However, adjustments to flood return levels made assuming fixed increases of sea level are also inadequate when applied to sea level that is rising over time at an uncertain rate. SLR allowances—the height adjustment from historic flood levels that maintain under uncertainty the annual expected probability of flooding—are typically estimated independently of individual decision-makers’ preferences, such as time horizon, risk tolerance, and confidence in SLR projections. We provide a framework of SLR allowances that employs complete probability distributions of local SLR and a range of user-defined flood risk management preferences. Given non-stationary and uncertain sea-level rise, these metrics provide estimates of flood protection heights and offsets for different planning horizons in coastal areas. We illustrate the calculation of various allowance types for a set of long-duration tide gauges along U.S. coastlines.     

An assessment of the physical impacts of sea-level rise and coastal adaptation: a case study of the eastern coast of Ghana

Sea-level rise is a major coastal issue in the 21st century because many of the world??s built assets are located in the coastal zone. Coastal erosion and flooding are serious threats along the coast of Ghana, particularly, the eastern coast where the Volta delta is located. Past human interventions, climate change and the resultant rise in sea-levels, increased storm intensity and torrential rainfall have been blamed for these problems. Accelerated sea-level rise and storm surge pose serious threat to coastal habitat, bio-diversity and socio-economic activities in the coastal zone of Ghana and elsewhere. There is the need for an holistic assessment of the impacts of sea-level rise on the coast zone in order to formulate appropriate adaptation policies and strategies to mitigate the possible effects. Using the eastern coast of Ghana as a case study, this paper assesses the physical impacts of accelerated sea level rise and storm surge on the coastal environment. It evaluates adaptation policies and plans that could be implemented to accommodate the present and any future impacts. Field investigation and Geographic Information System (GIS) are among the methods used for the assessment. The outcome of the assessment has provided comprehensive knowledge of the potential impacts of accelerated sea-level rise and storm surge on the eastern coast. It has facilitated identification of management units, the appraisal of alternate adaptation policies and the selection of the best policy options based upon the local conditions and environmental sustainability. Among other things, this paper reveals that the eastern coast of Ghana is highly vulnerable to accelerated sea-level rise and therefore, requires sustainable adaptation policies and plans to manage the potential impacts. It recommends that various accommodation policies, which enable areas to be occupied for longer before eventual retreat, could be adapted to accommodate vulnerable settlements in the eastern coast of Ghana.     

Estimates of twenty-first century sea-level changes for Norway

In this work we establish a framework for estimating future regional sea-level changes for Norway. Following recently published works, we consider how different physical processes drive non-uniform sea-level changes by accounting for spatial variations in (1) ocean density and circulation (2) ice and ocean mass changes and associated gravitational effects on sea level and (3) vertical land motion arising from past surface loading change and associated gravitational effects on sea level. An important component of past and present sea-level change in Norway is glacial isostatic adjustment. Central to our study, therefore, is a reassessment of vertical land motion using a far larger set of new observations from a permanent GNSS network. Our twenty-first century sea-level estimates are split into two parts. Firstly, we show regional projections largely based on findings from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4) and dependent on the emission scenarios A2, A1B and B1. These indicate that twenty-first century relative sea-level changes in Norway will vary between ?0.2 to 0.3 m (1-sigma ± 0.13 m). Secondly, we explore a high-end scenario, in which a global atmospheric temperature rise of up to 6 °C and emerging collapse for some areas of the Antarctic ice sheets are assumed. Using this approach twenty-first century relative sea-level changes in Norway are found to vary between 0.25 and 0.85 m (min/max ± 0.45 m). We attach no likelihood to any of our projections owing to the lack of understanding of some of the processes that cause sea-level change.     

Exploring high-end scenarios for local sea level rise to develop flood protection strategies for a low-lying delta—the Netherlands as an example

Sea level rise, especially combined with possible changes in storm surges and increased river discharge resulting from climate change, poses a major threat in low-lying river deltas. In this study we focus on a specific example of such a delta: the Netherlands. To evaluate whether the country’s flood protection strategy is capable of coping with future climate conditions, an assessment of low-probability/high-impact scenarios is conducted, focusing mainly on sea level rise. We develop a plausible high-end scenario of 0.55 to 1.15 m global mean sea level rise, and 0.40 to 1.05 m rise on the coast of the Netherlands by 2100 (excluding land subsidence), and more than three times these local values by 2200. Together with projections for changes in storm surge height and peak river discharge, these scenarios depict a complex, enhanced flood risk for the Dutch delta.     

Comment on “Storm surge frequency reduction in Venice under climate change” by Troccoli et al.

Troccoli et al. (Climatic Change, published online 14th May, DOI: 10.1007/s10584-011-0093-x), analysed different projections from global climate models in order to assess the frequency of storm surges in Venice during the 21st century under a climate change context. They concluded that the frequency of storm surges would decrease by about 30%, and that this reduction would compensate the expected mean sea level rise. Their final statement was that “the frequency of extreme tides in Venice might largely remain unaltered”. Although we agree in the expected reduction of storm surges, we strongly disagree in their final conclusion. First, because the impact of storm surges not only depends on the number of extreme surge events, but also on their intensity, that was not explicitely addressed. Second, because their estimates of mean sea level change for the 21st century are largely underestimated, as they miss some of the components driving sea level variability. Using state-of-the-art estimates for the thermosteric, mass and tidal contributions we show that the flooding events in Venice are expected to dramatically increase in a climate change scenario.     

Developing coastal adaptation to climate change in the New York City infrastructure-shed: process, approach, tools, and strategies

While current rates of sea level rise and associated coastal flooding in the New York City region appear to be manageable by stakeholders responsible for communications, energy, transportation, and water infrastructure, projections for sea level rise and associated flooding in the future, especially those associated with rapid icemelt of the Greenland and West Antarctic Icesheets, may be outside the range of current capacity because extreme events might cause flooding beyond today??s planning and preparedness regimes. This paper describes the comprehensive process, approach, and tools for adaptation developed by the New York City Panel on Climate Change (NPCC) in conjunction with the region??s stakeholders who manage its critical infrastructure, much of which lies near the coast. It presents the adaptation framework and the sea-level rise and storm projections related to coastal risks developed through the stakeholder process. Climate change adaptation planning in New York City is characterized by a multi-jurisdictional stakeholder?Cscientist process, state-of-the-art scientific projections and mapping, and development of adaptation strategies based on a risk-management approach.     

Modelling the combined impacts of sea-level rise and land subsidence on storm tides induced flooding of the Huangpu River in Shanghai, China

This paper presents a scenario-based study that investigates the interaction between sea-level rise and land subsidence on the storm tides induced fluvial flooding in the Huangpu river floodplain. Two projections of relative sea level rise (RSLR) were presented (2030 and 2050). Water level projections at the gauging stations for different return periods were generated using a simplified algebraic summation of the eustatic sea-level rise, land subsidence and storm tide level. Frequency analysis with relative sea level rise taken into account shows that land subsidence contributes to the majority of the RSLR (between 60 % and 70 %). Furthermore, a 1D/2D coupled flood inundation model (FloodMap) was used to predict the river flow and flood inundation, after calibration using the August 1997 flood event. Numerical simulation with projected RSLR suggests that, the combined impact of eustatic sea-level rise and land subsidence would be a significantly reduced flood return period for a given water level, thus effective degradation of the current flood defences. In the absence of adaptation measures, storm flooding will cause up to 40 % more inundation, particularly in the upstream of the river.     

Mental models of sea-level change: A mixed methods analysis on the Severn Estuary,UK

Global average sea levels are expected to rise by up to a metre by the end of the century. This long-term rise will combine with shorter-term changes in sea level (e.g. high tides, storm surges) to increase risks of flooding and erosion in vulnerable coastal areas. As communities become increasingly exposed to these risks, understanding their beliefs and responses becomes more important. While studies have explored public responses to climate change, less research has focused on perceptions of the specific risks associated with sea-level change. This paper presents the results of a mental models study that addressed this knowledge gap by exploring expert and public perceptions of sea-level change on the Severn Estuary, a threatened coastal environment in the southwest of the United Kingdom. A model was developed from the literature and expert interviews (N = 11), and compared with public perceptions elicited via interviews (N = 20) and a quantitative survey (N = 359). Whilst we find a high degree of consistency between expert and public understandings, there are important differences that have implications for how sea level risks are interpreted and for what are perceived as appropriate mitigation and adaptation practices. We also find a number of potential barriers to engaging with the issue: individuals express low concern about sea-level change in relation to other matters; they feel detached from the issue, seeing it as something that will happen in future to other people; and many perceive that neither the causes of nor responses to sea-level change are their responsibility. We point to areas upon which future risk communications should therefore concentrate.     

Estimating sea-level extremes under conditions of uncertain sea-level rise

Estimation of expected extremes, using combinations of observations and model simulations, is common practice. Many techniques assume that the background statistics are stationary and that the resulting estimates may be used satisfactorily for any time in the future. We are now however in a period of climate change, during which both average values and statistical distributions may change in time. The situation is further complicated by the considerable uncertainty which accompanies the projections of such future change. Any useful technique for the assessment of future risk should combine our knowledge of the present, our best estimate of how the world will change, and the uncertainty in both. A method of combining observations of present sea-level extremes with the (uncertain) projections of sea-level rise during the 21st century is described, using Australian data as an example. The technique makes the assumption that the change of flooding extremes during the 21st century will be dominated by the rise in mean sea level and that the effect of changes in the variability about the mean will be relatively small. The results give engineers, planners and policymakers a way of estimating the probability that a given sea level will be exceeded during any prescribed period during the present century.     

Simulations of Hurricane Katrina (2005) under sea level and climate conditions for 1900

Global warming may result in substantial sea level rise and more intense hurricanes over the next century, leading to more severe coastal flooding. Here, observed climate and sea level trends over the last century (c. 1900s to 2000s) are used to provide insight regarding future coastal inundation trends. The actual impacts of Hurricane Katrina (2005) in New Orleans are compared with the impacts of a similar hypothetical hurricane occurring c. 1900. Estimated regional sea level rise since 1900 of 0.75 m, which contains a dominant land subsidence contribution (0.57 m), serves as a ‘prototype’ for future climate-change induced sea level rise in other regions. Landform conditions c. 1900 were estimated by changing frictional resistance based on expected additional wetlands at lower sea levels. Surge simulations suggest that flood elevations would have been 15 to 60 % lower c. 1900 than the conditions observed in 2005. This drastic change suggests that significantly more flood damage occurred in 2005 than would have occurred if sea level and climate conditions had been like those c. 1900. We further show that, in New Orleans, sea level rise dominates surge-induced flooding changes, not only by increasing mean sea level, but also by leading to decreased wetland area. Together, these effects enable larger surges. Projecting forward, future global sea level changes of the magnitude examined here are expected to lead to increased flooding in coastal regions, even if the storm climate is unchanged. Such flooding increases in densely populated areas would presumably lead to more widespread destruction.     

Assessing climate change impacts,sea level rise and storm surge risk in port cities: a case study on Copenhagen

This study illustrates a methodology to assess the economic impacts of climate change at a city scale and benefits of adaptation, taking the case of sea level rise and storm surge risk in the city of Copenhagen, capital of Denmark. The approach is a simplified catastrophe risk assessment, to calculate the direct costs of storm surges under scenarios of sea level rise, coupled to an economic input–output (IO) model. The output is a risk assessment of the direct and indirect economic impacts of storm surge under climate change, including, for example, production and job losses and reconstruction duration, and the benefits of investment in upgraded sea defences. The simplified catastrophe risk assessment entails a statistical analysis of storm surge characteristics, geographical-information analysis of population and asset exposure combined with aggregated vulnerability information. For the city of Copenhagen, it is found that in absence of adaptation, sea level rise would significantly increase flood risks. Results call for the introduction of adaptation in long-term urban planning, as one part of a comprehensive strategy to manage the implications of climate change in the city. Mitigation policies can also aid adaptation by limiting the pace of future sea level rise.     

Greenland��s contribution to global sea-level rise by the end of the 21st century

The Greenland ice sheet holds enough water to raise the global sea level with ??7 m. Over the last few decades, observations manifest a substantial increase of the mass loss of this ice sheet. Both enhanced melting and increase of the dynamical discharge, associated with calving at the outlet-glacier fronts, are contributing to the mass imbalance. Using a dynamical and thermodynamical ice-sheet model, and taking into account speed up of outlet glaciers, we estimate Greenland??s contribution to the 21st-century global sea-level rise and the uncertainty of this estimate. Boundary fields of temperature and precipitation extracted from coupled climate-model projections used for the IPCC Fourth Assessment Report, are applied to the ice-sheet model. We implement a simple parameterization for increased flow of outlet glaciers, which decreases the bias of the modeled present-day surface height. It also allows for taking into account the observed recent increase in dynamical discharge, and it can be used for future projections associated with outlet-glacier speed up. Greenland contributes 0?C17?cm to global sea-level rise by the end of the 21st century. This range includes the uncertainties in climate-model projections, the uncertainty associated with scenarios of greenhouse-gas emissions, as well as the uncertainties in future outlet-glacier discharge. In addition, the range takes into account the uncertainty of the ice-sheet model and its boundary fields.     

Spatial variations of sea-level rise and impacts: An application of DIVA

Due to complexities of creating sea-level rise scenarios, impacts of climate-induced sea-level rise are often produced from a limited number of models assuming a global uniform rise in sea level. A greater number of models, including those with a pattern reflecting regional variations would help to assure reliability and a range of projections, indicating where models agree and disagree. This paper determines how nine new patterned-scaled sea-level rise scenarios (plus the uniform and patterned ensemble mean rises) influence global and regional coastal impacts (wetland loss, dry land loss due to erosion and the expected number of people flooded per year by extreme sea levels). The DIVA coastal impacts model was used under an A1B scenario, and assumed defences were not upgraded as conditions evolved. For seven out of nine climate models, impacts occurred at a proportional rate to global sea-level rise. For the remaining two models, higher than average rise in sea level was projected in northern latitudes or around populated coasts thus skewing global impact projections compared with the ensemble global mean. Regional variability in impacts were compared using the ensemble mean uniform and patterned scenarios: The largest relative difference in impacts occurred around the Mediterranean coast, and the largest absolute differences around low-lying populated coasts, such as south, south-east and east Asia. Uniform projections of sea-level rise impacts remain a useful method to determine global impacts, but improved regional scale models of sea-level rise, particularly around semi-enclosed seas and densely populated low-lying coasts will provide improved regional impact projections and a characterisation of their uncertainties.     

Monitoring sea level changes

Future sea level rise arouses concern because of potentially deleterious impacts to coastal regions. These will stem not only from the loss of land through inundation and erosion, but also from increased frequency of storm floods, with a rising base level, even with no change in storm climatology, and from saltwater intrusion and greater amounts of waterlogging. Current sea level trends are important in formulating an accurate baseline for future projections. Sea level, furthermore, is an important parameter which integrates a number of oceanic and atmospheric processes. The ocean surface demonstrates considerable variability on diurnal, seasonal, and interannual time scales, induced by winds, storm waves, coastal upwelling, and geostrophic currents. Secular trends in sea level arise from changes in global mean temperature and also from crustal deformation on local to regional scales. The challenge facing researchers is how best to extract the climate signal from this noise.This paper re-examines recent estimates of sea level rise, discusses causes of variability in the sea level records, and describes methods employed to filter out some of these contaminating signals. Evidence for trends in long-term sea level records and in extreme events is investigated. Application of satellite geodesy to sea level research is briefly reviewed.     

An updated assessment of the risks from climate change based on research published since the IPCC Fourth Assessment Report

The IPCC Fourth Assessment Report (AR4) published in 2007 presents the most complete and authoritative assessment of the status of scientific knowledge on all aspects of climate change. This paper presents an updated assessment of the risks from anthropogenic climate change, based on a comprehensive review of the pertinent scientific literature published since finalisation of the AR4. Many risks are now assessed as stronger than in the AR4, including the risk of large sea-level rise already in the current century, the amplification of global warming due to biological and geological carbon-cycle feedbacks, a large magnitude of “committed warming” currently concealed by a strong aerosol mask, substantial increases in climate variability and extreme weather events, and the risks to marine ecosystems from climate change and ocean acidification. Some topics remain the subject of intense scientific debate, such as past and future changes in tropical cyclone activity and the risk of large-scale Amazon forest dieback. The rise in greenhouse gas emissions and concentrations has accelerated recently, and it is expected to accelerate further in the absence of targeted policy interventions. Taken together, these findings point to an increased urgency of implementing mitigation policies as well as comprehensive and equitable adaptation policies.     

Significance of nitrogen dioxide absorption in estimating aerosol optical depth and size distributions

Abstract

Changes to the Beaufort Sea shoreline occur due to the impact of storms and rising relative sea level. During the open‐water season (June to October), storm winds predominantly from the north‐west generate waves and storm surges which are effective in eroding thawing ice‐rich cliffs and causing overwash of gravel beaches. Climate change is expected to be enhanced in Arctic regions relative to the global mean and include accelerated sea‐level rise, more frequent extreme storm winds, more frequent and extreme storm surge flooding, decreased sea‐ice extent, more frequent and higher waves, and increased temperatures. We investigate historical records of wind speeds and directions, water levels, sea‐ice extent and temperature to identify variability in past forcing and use the Canadian Global Coupled Model ensembles 1 and 2 (CGCM1 and CGCM2) climate modelling results to develop a scenario forcing future change of Beaufort Sea shorelines. This scenario and future return periods of peak storm wind speeds and water levels likely indicate increased forcing of coastal change during the next century resulting in increased rates of cliff erosion and beach migration, and more extreme flooding.     

Increasing flood risk and wetland losses due to global sea-level rise: regional and global analyses

To develop improved estimates of (1) flooding due to storm surges, and (2) wetland losses due to accelerated sea-level rise, the work of Hoozemans et al. (1993) is extended to a dynamic analysis. It considers the effects of several simultaneously changing factors, including: (1) global sea-level rise and subsidence; (2) increasing coastal population; and (3) improving standards of flood defence (using GNP/capita as an “ability-to-pay” parameter). The global sea-level rise scenarios are derived from two General Circulation Model (GCM) experiments of the Hadley Centre: (1) the HadCM2 greenhouse gas only ensemble experiment and (2) the more recent HadCM3 greenhouse gas only experiment. In all cases there is a global rise in sea level of about 38 cm from 1990 to the 2080s. No other climate change is considered. Relative to an evolving reference scenario without sea-level rise, this analysis suggests that the number of people flooded by storm surge in a typical year will be more than five times higher due to sea-level rise by the 2080s. Many of these people will experience annual or more frequent flooding, suggesting that the increase in flood frequency will be more than nuisance level and some response (increased protection, migration, etc.) will be required. In absolute terms, the areas most vulnerable to flooding are the southern Mediterranean, Africa, and most particularly, South and South-east Asia where there is a concentration of low-lying populated deltas. However, the Caribbean, the Indian Ocean islands and the Pacific Ocean small islands may experience the largest relative increase in flood risk. By the 2080s, sea-level rise could cause the loss of up to 22% of the world's coastal wetlands. When combined with other losses due to direct human action, up to 70% of the world's coastal wetlands could be lost by the 2080s, although there is considerable uncertainty. Therefore, sea-level rise would reinforce other adverse trends of wetland loss. The largest losses due to sea-level rise will be around the Mediterranean and Baltic and to a lesser extent on the Atlantic coast of Central and North America and the smaller islands of the Caribbean. Collectively, these results show that a relatively small global rise in sea level could have significant adverse impacts if there is no adaptive response. Given the “commitment to sea-level rise” irrespective of any realistic future emissions policy, there is a need to start strategic planning of appropriate responses now. Given that coastal flooding and wetland loss are already important problems, such planning could have immediate benefits.     

The economic impact of extreme sea-level rise: Ice sheet vulnerability and the social cost of carbon dioxide

The possibility of extreme sea-level rise is one of the commonly cited reasons for concern about climate change. Major increases in sea level would likely be driven by the melting or collapse of major ice sheets. This possibility has implications for the social cost of carbon dioxide, which is a key policy value as well as a useful summary measure of damage caused by greenhouse gas emissions.This paper extends earlier work on the importance of low-probability, high-impact events for the social cost of carbon dioxide to incorporate the possibility of extreme sea-level rise.To estimate its impact, an integrated assessment model is used, which allows a probabilistic assessment of climate change damages based on the linkages between the economic and climate systems. In the model, the generic discontinuity damage is replaced with the possibility of large-scale damage from factors that are taken to be correlated with temperature rise and, crucially for this paper, explicit consideration of extreme sea-level rise.Estimates of the amount of increase in the social cost of carbon dioxide that can be expected from incorporating extreme sea-level rise show that the increase is significant, though not especially large in percentage terms.The paper contributes to the literature of how to represent uncertain climate impacts in integrated assessment models and the associated estimation of the social cost of carbon dioxide.     

Voluntary citizen participation in carbon allowance markets: the role of norm-based motivation

The results from a semi-experimental study of Swedish students’ stated willingness to purchase emission allowances for carbon dioxide are presented. Drawing heavily on recent developments in the literature on integrating norm-motivated behaviour into neoclassical consumer theory, it is assumed that individuals have a preference for maintaining a self-image as a responsible (and thus norm-compliant) person. The results indicate that students’ willingness to purchase carbon allowances is determined by both price and the presence of norms: those who feel personally responsible for contributing to reducing climate damages also appear more inclined to buy allowances. The empirical findings are consistent with the notion that a person's beliefs about others’ stated willingness to purchase carbon allowances imply improvements in their own self-image and ultimately behavioural change. This suggests that information campaigns that attempt to influence beliefs about others’ intentions could promote ‘green’ consumer behaviour in the carbon allowance market. Such (stated) behaviour also appears to be influenced by a person's awareness of the problem of climate change and their beliefs about their own ability to contribute to solving it.

Policy relevance

Although there is a concern that public goods such as reduced climate change may be under-provided in the free market, individual concern for the environment occasionally has profound impacts on consumer choice and voluntary action. This research suggests that information campaigns that attempt to influence beliefs about others’ intentions could promote ‘green’ consumer behaviour in carbon allowance markets. Publicly-provided information about the impacts of climate change and the ways in which these damages stem from individual choices could also induce this type of behaviour.