Title: Coastal flood implications of 1.5 °C, 2.0 °C, and 2.5 °C temperature stabilization targets in the 21st and 22nd century,
Abstract: Sea-level rise (SLR) is magnifying the frequency and severity of 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 differences in
the return periods of coastal floods at a global network of tide gauges 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 construct estimates of
the return levels of current and future flood heights for the 21st and 22nd
centuries. By 2100, under 1.5 °C, 2.0 °C, and 2.5 °C GMST
stabilization, median GMSL is projected to rise 47 cm with a very likely range
of 28-82 cm (90% probability), 55 cm (very likely 30-94 cm), and 58 cm (very
likely 36-93 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 will rise within < 13% of these projections. By 2150,
relative to the 2.0 °C scenario, GMST stabilization of 1.5 °C
inundates roughly 5 million fewer inhabitants that currently occupy lands,
including 40,000 fewer individuals currently residing in Small Island
Developing States. Relative to a 2.0 °C scenario, the reduction in the
amplification of the frequency of the 100-yr flood arising from a 1.5 °C
GMST stabilization is greatest in the eastern United States and in Europe, with
flood frequency amplification being reduced by about half.