The extreme scenario would mean roughly 10 to 12 feet of sea-level rise by 2100, depending on location, for all coastal states but Alaska — a significant departure above the global average projection (just over 8 feet).
The National Climate Assessment pointed out that, “These ranges do not, however, capture the full range of physically plausible global average sea-level rise over the 21st century,” and that sea levels could rise as much as 8.2 feet (2.5m) by the end of the century if rapid loss of Antarctic ice occurred.
coastline (outside of Alaska) by or about (±5 years) 2080, 2060, 2040, and 2030 under the Interagency Low, Intermediate-Low, Intermediate, and Intermediate-High GMSL scenarios, respectively.71 Figure 12.5d, which shows the decade in which the frequency of such moderate level flooding will increase 25-fold under the Interagency Intermediate Scenario, highlights that the mid- and Southeast Atlantic, western Gulf of Mexico, California, and the Island States and Territories are most susceptible to rapid changes in potentially damaging flood frequencies.
Climate Change Cause by Human and Affect the System Globally
Similarly, during the mid-Pliocene warm period, about 3 million years ago, the global mean temperature was about 1.8°–3.6°C (3.2°–6.5°F) above the preindustrial level.24 Estimates of GMSL are less well constrained than during the Last Interglacial, due to the smaller number of local geological sea-level reconstruction and the possibility of significant vertical land motion over millions of years.20 Some reconstructions place mid-Pliocene GMSL at about 10–30 meters (about 30–100 feet) higher than today.25 Sea levels this high would require a significantly reduced Antarctic ice sheet, highlighting the risk of significant Antarctic ice sheet loss under such levels of warming (Figure 12.2a).
Projected increase of the 100-year ESL from changes in climate extremes, the high tide water level, as well as from SLR contributions from Antarctica, land-water, Greenland, glaciers, dynamic sea level (DSL), glacial isostatic adjustment (GIA), and steric-effects (a, b); variance (in m2) in components (c, d) and fraction of components’ variance in global ESL change (e, f); under RCP4.5 (a, c, e) and RCP8.5 (b, d, f).
The impacts of extreme sea levels in the future will also vary around the Australian coastline because of regional variations in mean sea level rise, tidal amplitude, coastal geomorphology, and the particular weather systems that drive storm surges and wave characteristics in those regions.