The transient sensitivity of sea level rise

Author(s):  
Aslak Grinsted ◽  
Jens Hesselbjerg Christensen

<p>We are warming our planet, and sea levels are rising as oceans expand and ice on land melts. This instigates a threat to coastal communities and ecosystems, and there is an urgent need for sea level predictions encompassing all known uncertainties to plan for it. Comprehensive assessments have concluded that sea level is unlikely to rise by more than about 1.1m this century but with further increase beyond 2100. However, some studies conclude that considerably greater sea level rise could be realised and an expert elicitation assign a substantially higher likelihood to this scenario. Here, we show that models used to assess future sea level in AR5 & SROCC have a lower sea level sensitivity than inferred from observations. By analyzing mean rate of change in sea level (not sea level itself), we identify a near linear relationship with global mean surface temperature in both model projections, and in observations. The model projections fall below expectations from the more recent observational period. This comparison suggests that the likely range of sea level projections in IPCC AR5 and SROCC would be too low.</p>


2020 ◽  
Author(s):  
Matthew Bilskie ◽  
Diana Del Angel ◽  
David Yoskowitz ◽  
Scott Hagen

Abstract A growing concern of coastal communities is an increase in flood risk and non-monetary consequences as a result of climate-induced impacts such as sea level rise (SLR). While previous studies have outlined the importance of quantifying future flood risk, most have focused on broad aggregations of monetary loss using bathtub SLR-type models. Here we quantify, for the first time at the multi-state scale, actual impacts to coastal communities at the census block level using a dynamic, high-resolution, biogeophysical modeling framework that accounts for future sea-levels and coastal landscapes. We demonstrate that future SLR can increase the number of damaged residential buildings by 600%, the population of displaced people by 500% and the need for shelter assistance of up to 460% from present-day conditions. An exponential increase in flood damage associated with increasing sea level deems it essential for stakeholders to plan for plausible future conditions rather than the current reality.



Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 181-186
Author(s):  
Aslak Grinsted ◽  
Jens Hesselbjerg Christensen

Abstract. Recent assessments from the Intergovernmental Panel on Climate Change (IPCC) imply that global mean sea level is unlikely to rise more than about 1.1 m within this century but will increase further beyond 2100. Even within the most intensive future anthropogenic greenhouse gas emission scenarios, higher levels are assessed to be unlikely. However, some studies conclude that considerably greater sea level rise could be realized, and a number of experts assign a substantially higher likelihood of such a future. To understand this discrepancy, it would be useful to have scenario-independent metrics that can be compared between different approaches. The concept of a transient climate sensitivity has proven to be useful to compare the global mean temperature response of climate models to specific radiative forcing scenarios. Here, we introduce a similar metric for sea level response. By analyzing the mean rate of change in sea level (not sea level itself), we identify a nearly linear relationship with global mean surface temperature (and therefore accumulated carbon dioxide emissions) both in model projections and in observations on a century scale. This motivates us to define the “transient sea level sensitivity” as the increase in the sea level rate associated with a given warming in units of meters per century per kelvin. We find that future projections estimated on climate model responses fall below extrapolation based on recent observational records. This comparison suggests that the likely upper level of sea level projections in recent IPCC reports would be too low.



2020 ◽  
Author(s):  
Aslak Grinsted ◽  
Jens Hesselbjerg Christensen

Abstract. Recent assessments from the Intergovernmental Panel on Climate Change implies that global mean sea level is unlikely to rise more than about 1.1 m within this century, but with further increase beyond 2100, even within the most intensive future anthropogenic carbon dioxide emission scenarios. However, some studies conclude that considerably greater sea level rise could be realized, and experts assign a substantially higher likelihood of such a future. To understand this discrepancy, it would be useful to have scenario independent metrics that can be compared between different approaches. The concept of a transient climate response has proven to be useful to compare the response of climate models. Here, we introduce a similar metric for sea level science. By analyzing mean rate of change in sea level (not sea level itself), we identify a near linear relationship with global mean surface temperature (and therefore accumulated carbon dioxide emissions) in both model projections, and in observations on a century time scale. This motivates us to define the Transient Sea Level Sensitivity as the increase in the sea level rate associated with a given warming in units of m/century/K. We find that model projections fall below extrapolation based on recent observational records. This comparison indicates that the likely upper level of sea level projections in recent IPCC reports would be too low.



2021 ◽  
Author(s):  
Svetlana Jevrejeva ◽  
Hindumathi Palanisamy ◽  
Luke Jackson

<p>Most of the excess energy stored in the climate system is taken up by the oceans leading to thermal expansion and sea level rise. Future sea level projections allow decision-makers to assess coastal risk, develop climate resilient communities and plan vital infrastructure in low- elevation coastal zones. Confidence in these projections depends on the ability of climate models to simulate the various components of future sea level rise. In this study we estimate the contribution from thermal expansion to sea level rise using the simulations of global mean thermosteric sea level from 15 available models in the Coupled Model Intercomparison Project Phase (CMIP) 6. We calculate a global mean thermosteric sea level rise of 18.8 cm [12.8 - 23.6 cm, 90% range] and 26.8 cm [18.6 - 34.6 cm, 90% range] for the period 2081–2100, relative to 1995-2014 for SSP245 and SSP585 scenarios respectively. In a comparison with a 20 model ensemble from CMIP5, the CMIP6 ensemble mean of future global mean thermosteric sea level rise (2014-2100) is higher for both scenarios and shows a larger variance. By contrast, for the period 1901-1990, global mean thermosteric sea level from CMIP6 has half the variance of that from CMIP5. Over the period 1940-2005, the rate of CMIP6 ensemble mean of global mean thermosteric sea level rise is 0.2 ± 0.1 mm yr<sup>-1</sup>, which is less than half of the observed rate (0.5 ± 0.02 mm yr<sup>-1</sup>). At a multi-decadal timescale, there is an offset of ~10 cm per century between observed/modelled thermosteric sea level over the historical period and modelled thermosteric sea level over this century for the same rate of change of global temperature. We further discuss the difference in global mean thermosteric sea level sensitivity to the changes in global surface temperature over the historical and future periods.</p><p> </p>



Author(s):  
Karen Akerlof ◽  
Michelle Covi ◽  
Elizabeth Rohring

Three quarters of the world’s large cities are located on coasts. As climate change causes oceans to warm and expand, and triggers vast influxes of water from melting ice sheets and glaciers, by the end of the 21st century, as many as 650 million people globally may be below sea levels or subject to recurrent flooding. Human beings have always faced threats from coastal storms and flooding, but never have so many of us and so much of our societal infrastructure been in harm’s way. With entire nations facing forced emigration, international online media are framing sea level rise as a human rights concern. Yet sea level rise suffers from generally low media attention and salience as a public issue. Coastal communities tasked with developing adaptation strategies are approaching engagement through new forms of risk visualization and models of environmental decision making. As a subfield of climate communication that addresses a variety of other anthropogenic and natural phenomena, sea level rise communication also calls upon the less politicized field of natural hazards risk communication. This review explores media analyses, audience research, and evaluation of communication outreach and engagement, finding many remaining gaps in our understanding of sea level rise communication.



2016 ◽  
Vol 5 (1) ◽  
Author(s):  
A. Parker

AbstractContrary to what is claimed by reconstructions of the Global Mean Sea Level (GMSL) indicating accelerating sea level rates of rise over the twentieth-century, the actual measurements at the tide gauges show the sea levels have not risen nor accelerated that much. The most recent estimation by Hay et al [



Author(s):  
Timu Gallien ◽  
Marie-Pierre Delisle

Coastal flooding is a significant humanitarian and socioeconomic hazard (e.g., Nicholls, 2010). Global mean sea levels are expected to rise over the coming century and mean higher high water (MHHW) and mean high water (MHW), peak levels that drive coastal flooding, show upward trends in many locations (Mawdsley et al., 2015). Significant coastal flooding will occur by 2050 (e.g., Tebaldi et al., 2012; Sweet and Park, 2014). Wave overtopping is primary driver of coastal flooding. Low-lying urbanized sand spits, backed by an estuary are particularly vulnerable to sea level rise. Recent field observations suggest distinct feedbacks between wave overtopping, beach groundwater levels and backshore vulnerability.



2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Benjamin H. Strauss ◽  
Philip M. Orton ◽  
Klaus Bittermann ◽  
Maya K. Buchanan ◽  
Daniel M. Gilford ◽  
...  

AbstractIn 2012, Hurricane Sandy hit the East Coast of the United States, creating widespread coastal flooding and over $60 billion in reported economic damage. The potential influence of climate change on the storm itself has been debated, but sea level rise driven by anthropogenic climate change more clearly contributed to damages. To quantify this effect, here we simulate water levels and damage both as they occurred and as they would have occurred across a range of lower sea levels corresponding to different estimates of attributable sea level rise. We find that approximately $8.1B ($4.7B–$14.0B, 5th–95th percentiles) of Sandy’s damages are attributable to climate-mediated anthropogenic sea level rise, as is extension of the flood area to affect 71 (40–131) thousand additional people. The same general approach demonstrated here may be applied to impact assessments for other past and future coastal storms.



Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1142
Author(s):  
Juliano Calil ◽  
Geraldine Fauville ◽  
Anna Carolina Muller Queiroz ◽  
Kelly L. Leo ◽  
Alyssa G. Newton Mann ◽  
...  

As coastal communities around the globe contend with the impacts of climate change including coastal hazards such as sea level rise and more frequent coastal storms, educating stakeholders and the general public has become essential in order to adapt to and mitigate these risks. Communicating SLR and other coastal risks is not a simple task. First, SLR is a phenomenon that is abstract as it is physically distant from many people; second, the rise of the sea is a slow and temporally distant process which makes this issue psychologically distant from our everyday life. Virtual reality (VR) simulations may offer a way to overcome some of these challenges, enabling users to learn key principles related to climate change and coastal risks in an immersive, interactive, and safe learning environment. This article first presents the literature on environmental issues communication and engagement; second, it introduces VR technology evolution and expands the discussion on VR application for environmental literacy. We then provide an account of how three coastal communities have used VR experiences developed by multidisciplinary teams—including residents—to support communication and community outreach focused on SLR and discuss their implications.



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