Climate change impacts and vulnerability in Europe 2016

Introduction
collaboration between integrated assessment
modellers, climate modellers, terrestrial ecosystem
modellers and emissions inventory experts — are
called representative concentration pathways (RCPs).
The RCPs provide a consistent set of trajectories for
future atmospheric composition and land-use change
up to the year 2100.
The four RCPs are named from RCP2.6 to RCP8.5
according to their approximate radiative forcing level
in the year 2100. Extended concentration pathways
(ECPs) extend the RCPs up to 2300 based on simple
extension rules. All ECPs, including the highest, ECP8.5,
assume that very low (or even negative) emission levels
are reached by 2250 at the latest (Moss et al., 2010;
van Vuuren et al., 2011). Minor differences in radiative
forcing between the 'name' of an RCP and the values
shown in Figure 1.1 (left) are due to different definitions
of forcing (e.g. instantaneous, stratospherically
adjusted, fixed sea surface, or effective radiative
forcing) (Sherwood et al., 2015), how models implement
the various radiatively active species (e.g. prescribed
aerosol optical depth vs. prescribed aerosol
precursor emissions), and uncertainties in converting
concentrations to radiative forcing (Collins et al., 2013,
Section 12.3).
There are two key 'technical' differences between the
SRES scenarios and the RCP scenarios. One relates
to the unit applied for specifying greenhouse gas
'emissions' and the other to the link between and
socio-economic development. In the case of SRES,
each scenario provides a trajectory of anthropogenic
greenhouse gas emissions coupled with an underlying
storyline of socio-economic development. In contrast,
the RCPs are scenarios of radiative forcing, which
is determined not only by direct anthropogenic
greenhouse gas emissions but also by the future
development of the global carbon cycle and other
processes. Moreover, the process of RCP development
has been separated from the socio-economic storyline
development, which means that the different RCPs are
not directly associated with a particular socio‐economic
scenario (see Section 1.2.2 for details on the
development of socio-economic scenarios alongside
the RCPs).
The key 'political' difference between the RCP and
SRES scenarios is that the RCPs cover the full range
of stabilisation, mitigation and baseline emissions
scenarios available in the scientific literature, whereas
all SRES scenarios are no-climate-policy scenarios.
Therefore, the range of temperature projections
between the highest and lowest RCP is larger than that
between the highest and lowest SRES scenario (see
Figure 1.1, right). Note that the highest RCP (RCP8.5) is
less extreme than the highest SRES emissions scenario
(A1FI), whereas the lowest RCP (RCP2.6), which requires
ambitious mitigation policies, lies far below the range of
the SRES scenarios (see Figure 1.1, left). As a result, the
range of projected increases in global temperature for
RCPs is smaller than the range of projections for SRES
scenarios. Owing to the differences between RCP and
SRES scenarios, the projections for global temperature
increase during the 21st century in the IPCC AR5 (0.3 to
4.8 °C, based on the RCPs) (IPCC, 2013) and in the
IPCC AR4 (1.1 to 6.4 °C, based on the SRES scenarios)
(IPCC, 2007b) are not directly comparable. Further
information on global temperature change projected
for different RCPs is available in Section 3.2.2.
Figure 1.1
Relationship between SRES scenarios and RCPs
Rediative forcing relative to pre-industrial (W m -2 )
10
8
6
4
2
SRES (TAR)
A1B
A1T
A1FI
A2
B1
B2
RCP (AR5)
RCP8.5
RCP6.0
RCP4.5
RCP2.6
Mean surface temperature change (°C)
SRES CMIP3
AR4 AR5
A1B
A1T
A1FI
A2
B1
B2
RCP CMIP5
RCP8.5
RCP6.0
RCP4.5
RCP2.6
0
0
2000 2010 2040 2060 2080 2100 2000s 2010s 2040s 2060s 2080s 2100s
4
3
2
1
Note:
Source:
Projected radiative forcing (left) and global mean surface temperature change (right) over the 21st century using the Special Report on
Emissions Scenarios (SRES) and representative concentration pathway (RCP) scenarios.
IPCC, 2014a (Figure 1.4). © 2014 Intergovernmental Panel on Climate Change. Reproduced with permission.
38 Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report