evaluation of the CDE estimation performance
throughout the years from 2030 to 2100.
2 THE SEA LEVEL RISE EFFECT
GLOBALLY
Enhanced greenhouse effects on earth environment
have brought the global climate change. Thermal
expansion of sea water, resulting from temperature
increment of the ocean upper layer, is defined as the
main source of SLR (Woodworth, 2017; Shannon et
al., 2019). SLR is anticipated to have a tremendous
impact on human activity near coastal regions. In fact,
inundation of low-lying coastal areas is a direct
outcome of SLR and constitutes a long-term problem
having been under consideration in a variety of fields
(Pickering et al., 2017; IPCC, 2021).
The ocean thermal expansion and the melting of
glaciers, ice-sheets cause SLR that demonstrates a
timescale of 100–200 years, which is related to the
continuance of CO2 in the atmosphere and therefore
the radiative forcing time span. In accordance with
the model of (Jevrejeva et al., 2012), SLR of 0.57–
1.10 m by 2100 has been predicted. In effect,
simulation indicates that sea level will keep at rising
for many centuries after stabilization of radiative
forcing, finally outstretching between 1.84 and 5.48
m above sea level by 2500 concerning all scenarios,
apart from the RCP3PD low emission scenario. The
work (Hinkel et al., 2014) evaluates on a global
scale the coastal flood damage and adaptation costs
under 21
st
century SLR. Devoid of adaptation, it is
expected that 0.2–4.6% of the world’s population
will be flooded annually by 2100 within 25–123 cm
of a global mean SLR. Moreover, concerning coastal
sea level changes and the associated risks of
flooding and erosion, wind waves are a key factor.
The work (Melet et al., 2020) is based on empirical
formulations, different estimates of beach slopes and
an ensemble of global wave models, to propose a
first‐order estimate of the correlation significance of
the input of atmospheric climate directed wave setup
changes to 20‐year mean projected coastal sea level
changes at global scale.
Thereafter, the challenge for coastal regions
globally is the projection of SLR and its effects into
the future. The Intergovernmental Panel on Climate
Change (IPCC) is seriously concerned with the latter,
but also governments individually are simultaneously
trying to estimate future SLR projections for their
own regions. Future climate projections are attainable
through global climate models. In these models,
uncertainties and assumptions regarding future
greenhouse gas emissions (i.e., Representative
Concentration Pathways-RCPs) are contained whilst
the factors that will influence global climate,
including ice melt and consequently SLR, are
modeled (Griggs and Reguero, 2021). Nowadays, all
predictions for the next few decades, generally agree,
but projections in concern with the end-of-century
vary between models. In fact, RCPs play a substantial
role, with growingly broader uncertainties and ranges
in estimations by 2100. By the newest estimates, the
values for the end-of-century (2100) range from a low
of ~50 cm to as high as ~310 cm, independence of
greenhouse gas emission scenarios and various proba-
bilities, mainly regarding the extent of Greenland and
Antarctica ice melt (De Conto et al, 2016).
Virtually definitely, global mean sea level
(GMSL) will keep up rising over the 21st century
coming after the continued warming of the climate
system (IPCC, 2021). The SLR will carry on with
over the centuries and millennia following emissions
stopping, which is related to continuing ocean heat
growth and the slow adjustment of the ice sheets. By
2100, GMSL is projected to increase per 0.28–0.55
m under SSP1-1.9 and per 0.63–1.02 m under SSP5-
8.5 relative to the 1995–2014 average (IPCC, 2021),
where SSP represents a shared socio-economic
pathway. Concerning the scenarios of higher CO2
emissions, sea level projections for 2100 and beyond
are strongly debatable, which is linked with the ice-
sheet responses to warming. In the case of a low
probability, hard plot and a high CO2 emissions
scenario, ice-sheet processes, that are characterized
by deep unpredictability, could bring GMSL rise up
to about 5 m by 2150.
Considering the long-term commitment,
uncertainty in relation to the timetable of
outstretching different GMSL rise levels is an
important contemplation for adaptation planning.
Regional sea level changes differ from global
estimates. This happens due to alterations in ocean
density and circulation, in atmospheric pressure as
well as in Earth Gravity, in Earth Rotation and in
viscoelastic solid-Earth deformation with regards to
mass redistributions such as ice melting and
groundwater extractions (Gregory et al., 2019;
Toilim et al., 2020). In fact, SLR tends to increase at
lower latitudes and decrease at higher latitudes.
Due to the great uncertainty issues and the
complex factors that have to be considered in
simulation models, future climate projections and in
specific SLR projections, would need an alternative
way of estimating. Here lies the usability of the CDE
estimator which is proposed in the current work. The