D.J. Rasmussen, PhD

Storm surge barriers, levees, and other coastal flood defense megaprojects are currently being proposed as strategies to protect several US cities against coastal storms and rising sea levels. However, social conflict and other political factors add a layer of complexity that casts doubt on their status as practical climate adaptation options. The specific mechanisms responsible for some projects not progressing beyond initial planning stages remains unclear. In this study, we examined the… Show more

Storm surge barriers, levees, and other coastal flood defense megaprojects are currently being proposed as strategies to protect several US cities against coastal storms and rising sea levels. However, social conflict and other political factors add a layer of complexity that casts doubt on their status as practical climate adaptation options. The specific mechanisms responsible for some projects not progressing beyond initial planning stages remains unclear. In this study, we examined the outcome of two USACE storm surge barrier proposals to explore the political reasons why some coastal flood protection megaprojects break ground in the US, while others do not. Using original archive research, we concluded that storm surge barriers are politically challenging climate adaptation options because of modern environmental laws that provide avenues for expression of oppositional views within the decision process and the allure of alternative options that are more aesthetically pleasing and cheaper and faster to implement. To better allocate public resources and utilize the expertise of USACE, future flood protection megaprojects should first achieve broad support from the public, nongovernmental organizations (NGOs), and elected officials before beginning serious planning. This support could be achieved through new innovative designs that simultaneously address adverse environmental impacts and provide cobenefits (e.g., recreation). New designs should be studied to better understand the level of protection offered and their associated reliability so that USACE has confidence in their use. Show less

Estimates of changes in the frequency or height of contemporary extreme sea levels (ESLs)
under various climate change scenarios are often used by climate and sea level scientists to
help communicate the physical basis for societal concern regarding sea level rise. Changes
in ESLs (i.e., the hazard) are often represented using various metrics and indicators that,
when anchored to salient impacts on human systems and the natural environment, provide
useful information to policy… Show more

Estimates of changes in the frequency or height of contemporary extreme sea levels (ESLs)
under various climate change scenarios are often used by climate and sea level scientists to
help communicate the physical basis for societal concern regarding sea level rise. Changes
in ESLs (i.e., the hazard) are often represented using various metrics and indicators that,
when anchored to salient impacts on human systems and the natural environment, provide
useful information to policy makers, stakeholders, and the general public. While changes
in hazards are often anchored to impacts at local scales, aggregate global summary metrics
generally lack the context of local exposure and vulnerability that facilitates translating hazards into impacts. Contextualizing changes in hazards is also needed when communicating
the timing of when projected ESL frequencies cross critical thresholds, such as the year in
which ESLs higher than the design height benchmark of protective infrastructure (e.g., the
100-year water level) are expected to occur within the lifetime of that infrastructure. We
present specific examples demonstrating the need for such contextualization using a simple
flood exposure model, local sea level rise projections, and population exposure estimates
for 414 global cities. We suggest regional and global climate assessment reports integrate
global, regional, and local perspectives on coastal risk to address hazard, vulnerability and
exposure simultaneously Show less

The Paris agreement focused global climate mitigation policy on limiting global warming to 1.5 or 2 °C above pre-industrial levels. Consequently, projections of hazards and risk are increasingly framed in terms of global warming levels rather than emission scenarios. Here, we use a multimethod approach to describe changes in extreme sea levels driven by changes in mean sea level associated with a wide range of global warming levels, from 1.5 to 5 °C, and for a large number of locations… Show more

The Paris agreement focused global climate mitigation policy on limiting global warming to 1.5 or 2 °C above pre-industrial levels. Consequently, projections of hazards and risk are increasingly framed in terms of global warming levels rather than emission scenarios. Here, we use a multimethod approach to describe changes in extreme sea levels driven by changes in mean sea level associated with a wide range of global warming levels, from 1.5 to 5 °C, and for a large number of locations, providing uniform coverage over most of the world’s coastlines. We estimate that by 2100 ~50% of the 7,000+ locations considered will experience the present-day 100-yr extreme-sea-level event at least once a year, even under 1.5 °C of warming, and often well before the end of the century. The tropics appear more sensitive than the Northern high latitudes, where some locations do not see this frequency change even for the highest global warming levels. Show less

Major U.S. cities like New York, Boston, Norfolk, and Houston are investigating the use of storm surge barriers, levees, and other coastal flood protection megaprojects to limit damages from coastal storms and sea-level rise. Determining the feasibility of such public works projects is largely dominated by technocratic and engineering-driven frameworks (for example, benefit-cost analysis). However, experience with similar public infrastructure and natural hazard preparedness projects suggests… Show more

Major U.S. cities like New York, Boston, Norfolk, and Houston are investigating the use of storm surge barriers, levees, and other coastal flood protection megaprojects to limit damages from coastal storms and sea-level rise. Determining the feasibility of such public works projects is largely dominated by technocratic and engineering-driven frameworks (for example, benefit-cost analysis). However, experience with similar public infrastructure and natural hazard preparedness projects suggests that social conflict and politics have been crucial in their conception, design, and implementation. In this review, we highlight the role of interest mobilization, political leadership, stakeholder participation, and legal challenges as a result of environmental protection laws in both creating and overcoming political obstacles. Better understanding the social and political factors that enable or hinder the implementation of storm surge barriers, levees, and other coastal flood protection megaprojects could encourage strategies and policies that are less likely to result in deadlocks, delays, or failure, thus saving valuable time and planning resources. Show less

Analyses of how Antarctica will respond to a warming planet embody large uncertainties that increase with time. As such, future projections of sea level rise are strongly dependent upon expert judgment about how much and how quickly Antarctica will melt. This uncertainty complicates any decisions regarding how high to build flood protections in order to reduce coastal flood damages from rising sea levels. Generally, the higher the structure, the greater the margin of safety afforded. If the… Show more

Analyses of how Antarctica will respond to a warming planet embody large uncertainties that increase with time. As such, future projections of sea level rise are strongly dependent upon expert judgment about how much and how quickly Antarctica will melt. This uncertainty complicates any decisions regarding how high to build flood protections in order to reduce coastal flood damages from rising sea levels. Generally, the higher the structure, the greater the margin of safety afforded. If the prescribed margin of safety does not properly account for sea level rise and its uncertainties, the effectiveness of the flood protection will decrease over time. This could potentially waste money and put lives and properties at a greater risk. We create a decision-making approach for flood protection designers that allows them to calculate the height of various flood protection strategies based on their risk tolerance with respect to future Antarctic melt. This framework is compatible with existing decision making protocols such as those used by the U.S. Army Corps of Engineers. We find that projections of flood frequencies and the design of strategies to reduce damages are sensitive to views of how much and how quickly Antarctica will melt Show less

Uncertainties in Representative Concentration Pathway (RCP) scenarios and Antarctic Ice
Sheet (AIS) melt propagate into uncertainties in projected mean sea-level (MSL) changes
and extreme sea-level (ESL) events. Here we quantify the impact of RCP scenarios and AIS
contributions on 21st-century ESL changes at tide-gauge sites across the globe using
extreme-value statistics. We find that even under RCP2.6, almost half of the sites could be
exposed annually to a present-day 100-year… Show more

Uncertainties in Representative Concentration Pathway (RCP) scenarios and Antarctic Ice
Sheet (AIS) melt propagate into uncertainties in projected mean sea-level (MSL) changes
and extreme sea-level (ESL) events. Here we quantify the impact of RCP scenarios and AIS
contributions on 21st-century ESL changes at tide-gauge sites across the globe using
extreme-value statistics. We find that even under RCP2.6, almost half of the sites could be
exposed annually to a present-day 100-year ESL event by 2050. Most tropical sites face large
increases in ESL events earlier and for scenarios with smaller MSL changes than extratropical
sites. Strong emission reductions lower the probability of large ESL changes but due to AIS
uncertainties, cannot fully eliminate the probability that large increases in frequencies of ESL
events will occur. Under RCP8.5 and rapid AIS mass loss, many tropical sites, including low lying islands face a MSL rise by 2100 that exceeds the present-day 100-year event level. Show less

Sea-level rise (SLR) is magnifying the frequency and severity of extreme sea levels (ESLs) that can
cause coastal flooding. The rate and amount of global mean sea-level (GMSL) rise is a function of the
trajectory of global mean surface temperature (GMST). Therefore, temperature stabilization targets
(e.g. 1.5 ◦C and 2.0 ◦C of warming above pre-industrial levels, as from the Paris Agreement) have
important implications for coastal flood risk. Here, we assess, in a global network of… Show more

Sea-level rise (SLR) is magnifying the frequency and severity of extreme sea levels (ESLs) that can
cause coastal flooding. The rate and amount of global mean sea-level (GMSL) rise is a function of the
trajectory of global mean surface temperature (GMST). Therefore, temperature stabilization targets
(e.g. 1.5 ◦C and 2.0 ◦C of warming above pre-industrial levels, as from the Paris Agreement) have
important implications for coastal flood risk. Here, we assess, in a global network of tide gauges, the
differences in the expected frequencies of ESLs between scenarios that stabilize GMST warming at
1.5 ◦C, 2.0 ◦C, and 2.5 ◦C above pre-industrial levels. We employ probabilistic, localized SLR
projections and long-term hourly tide gauge records to estimate the expected frequencies of historical
and future ESLs for the 21st and 22nd centuries. By 2100, under 1.5 ◦C, 2.0 ◦C, and 2.5 ◦C GMST
stabilization, the median GMSL is projected to rise 48 cm (90% probability of 28–82 cm), 56 cm
(28–96 cm), and 58 cm (37–93 cm), respectively. As an independent comparison, a semi-empirical sea
level model calibrated to temperature and GMSL over the past two millennia estimates median GMSL
rise within 7–8 cm of these projections. By 2150, relative to the 2.0 ◦C scenario and based on median
sea level projections, GMST stabilization of 1.5 ◦C spares the inundation of lands currently home to
about 5 million people, including 60 000 individuals currently residing in Small Island Developing
States. We quantify projected changes to the expected frequency of historical 10-, 100-, and 500-year
ESL events using frequency amplification factors that incorporate uncertainty in both local SLR and
historical return periods of ESLs. Show less

Estimates of climate change damage are central to the design of climate policies. Here, we develop a flexible architecture for computing damages that integrates climate science, econometric analyses, and process models. We use this approach to construct spatially explicit, probabilistic, and empirically derived estimates of economic damage in the United States from climate change. The combined value of market and nonmarket damage across analyzed sectors—agriculture, crime, coastal storms… Show more

Estimates of climate change damage are central to the design of climate policies. Here, we develop a flexible architecture for computing damages that integrates climate science, econometric analyses, and process models. We use this approach to construct spatially explicit, probabilistic, and empirically derived estimates of economic damage in the United States from climate change. The combined value of market and nonmarket damage across analyzed sectors—agriculture, crime, coastal storms, energy, human mortality, and labor—increases quadratically in global mean temperature, costing roughly 1.2% of gross domestic product per +1°C on average. Importantly, risk is distributed unequally across locations, generating a large transfer of value northward and westward that increases economic inequality. By the late 21st century, the poorest third of counties are projected to experience damages between 2 and 20% of county income (90% chance) under business-as-usual emissions (Representative Concentration Pathway 8.5). Show less

The United States faces a range of economic risks from global climate change — from increased flooding and storm damage, to climate-driven changes in crop yields and labor productivity, to heat-related strains on energy and public health systems. The American Climate Prospectus (ACP) provides a groundbreaking new analysis of these and other climate risks by region of the country and sector of the economy. By linking state-of-the-art climate models with econometric research of human responses to… Show more

The United States faces a range of economic risks from global climate change — from increased flooding and storm damage, to climate-driven changes in crop yields and labor productivity, to heat-related strains on energy and public health systems. The American Climate Prospectus (ACP) provides a groundbreaking new analysis of these and other climate risks by region of the country and sector of the economy. By linking state-of-the-art climate models with econometric research of human responses to climate variability and cutting edge private sector risk assessment tools, the ACP offers decision-makers a data driven assessment of the specific risks they face.

The ACP is the result of an independent assessment of the economic risks of climate change commissioned by the Risky Business Project (http://riskybusiness.org). In conducting this assessment, RHG convened a research team, co-led by climate scientist Dr. Robert Kopp of Rutgers University and economist Dr. Solomon Hsiang of the University of California, Berkeley, and partnered with Risk Management Solutions (http://www.rms.com). , the world’s largest catastrophe-modeling company for insurance, reinsurance, and investment-management companies. The team’s research methodology and draft work was reviewed by an Expert Review Panel (ERP) composed of leading climate scientists and economists, acknowledged within the report.

The ACP was released on June 24, 2014 alongside a Risky Business Summary (http://riskybusiness.org), and can be downloaded at the American Climate Prospectus site (http://climateprospectus.org). Show less