Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 137

socio-economic development of coastal zones and the vulnerability of
these zones to climate change. As far as the long-term future is
concerned, that is to say in the next 50 years and up to the horizon of
2100, there is the question of knowing toward what kind of climate
the Earth is evolving. First, it is necessary to turn to the socio-
economic scenarios that have been developed by the
Intergovernmental Panel on Climate Change (IPCC) and called SRES
scenarios [SRE 00]. The temporal trajectories for atmospheric
concentrations of greenhouse gas resulting from a given SRES
scenario are imposed as external forcing on the atmosphere-ocean
coupled general circulation models that allow projections of the future
climate to be made. Following the AR4 report - the IPCC's fourth
evaluation report - scenarios for the concentration trajectories, called
RCP for Representative Concentration Pathways [MOS 10], are used;
these serve as forcing conditions for the socio-economic and climate
scenarios. Each RCP scenario corresponds to a given total radiative
forcing value for greenhouse gas emissions in 2100. Thus,
the scenario RCP8.5 corresponds to a radiative forcing of 8.5 W/m 2 at
the end of the 21st Century and represents the scenario where the
volume of the emissions is higher during this century. Scenario
RCP2.6 represents the development of measures for mitigation that
reach the objective of not exceeding an increase in global average
temperature higher than 2ºC, compared to the pre-industrial era. The
RCP scenarios produce data essential for climate scenarios, but for the
study of vulnerability, impacts and adaptation, socio-economic
scenarios are also needed. The studies carried out on the possible
trajectories for socio-economic development up to the end of the
century [MOS 10] have enabled five scenarios, called SSP for Shared
Socio-economic Pathways, to be defined.
Scenario SSP1 corresponds to a situation where the global
population is lowest and where the global GDP is highest; it is called
“sustainable world” since it reflects a world that succeeded in making
a transition toward sustainable development, addresses environmental
questions, encourages innovation and technological development and
avoids intensive consumption of natural resources, in particular fossil
fuels. SSP3, called “fragmented world”, reflects a world where the