Abstract
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. By 2150, relative to a 2.0 °C scenario, the reduction in the frequency amplification of the historical 100 year ESL event arising from a 1.5 °C GMST stabilization is greatest in the eastern United States, with ESL event frequency amplification being reduced by about half at most tide gauges. In general, smaller reductions are projected for Small Island Developing States.
Highlights
Extreme sea levels (ESLs) are defined as the combined height of the astronomical tide and storm surge and mean sea level
global mean sea-level (GMSL) rise The GMSL projections for each global mean surface temperature (GMST) target from the K14 and Semi-empirical sea level (SESL) method are shown in figure 1 and are tabulated along with the component contributions in table 1
We find small decreases or no change in ESL event frequency from achieving a 1.5 ◦C GMST stabilization over a 2.0 ◦C GMST stabilization at most tide gauges located in Small Island Developing States (SIDS), as local Sea-level rise (SLR) projections in these areas are similar between GMST scenarios
Summary
Extreme sea levels (ESLs) are defined as the combined height of the astronomical tide and storm surge (i.e. the storm tide) and mean sea level. Rising mean sea levels are already magnifying the frequency and severity of ESLs that lead to coastal floods (Buchanan et al 2017, Sweet and Park 2014) and, by the end of the century, coastal flooding may be among the costliest impacts of climate change in some regions (Hsiang et al 2017, Diaz 2016, Hinkel et al 2014). Schaeffer et al (2012) found that a 2.0 ◦C GMST stabilization would lead to a GMSL rise (relative to 2000) of 0.8 m by 2100 and >2.5 m by 2300, but if the GMST increase were held below 1.5 ◦C, GMSL rise at the end of the 23rd century would be limited to ∼1.5 m These findings suggest that selection of climate policy goals could have critical long-term consequences for the impacts of future SLR and coastal floods (Clark et al 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
