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representative of the three most likely emission pathways: two medium stabilization scen-
arios (RCP4.5/RCP6); and one business as usual baseline emission scenarios (RCP8.5). A
RCP was also included to illustrate what could be achieved if every mitigation strategy
was employed (RCP2.6). This pathway is also referred to as RCP3PD, a name that em-
phasizes the radiative forcing trajectory as it first goes to a peak forcing level of 3 W/m
2
followed by a decline, the PD representing peak then decline (see
Figure 15
). This shows
that emissions would initially increase producing a radiative forcing of 3 W/m
2
and then
there would be huge cut backs in emissions so that by the year 2100 a radiative forcing of
only 2.6 W/ m
2
was achieved. What is rarely mentioned about this RCP is that it assumes
negative emissions from 2070 onwards, which means that not only does the world have to
cease producing any carbon emissions by 2070 but that after this date we will actively be
taking carbon dioxide and other GHGs out of the atmosphere, which is an immense under-
taking.
Table 2
. Defining Representative Concentration Pathway used in the IPCC 2013 report
Representative Concentration Pathway (RCP)
Description
RCP8.5
Stabilization without overshoot pathway to 6 W/m
2
(~850
ppm CO
2
eq) at stabilization after 2100
RCP6
Stabilization without overshoot pathway to 4.5 W/m
2
(~650 ppm CO2 eq) at stabilization after 2100
RCP4.5
Peak in radiative forcing at ~3 W/m
2
(~490 ppm CO
2
eq)
before 2100 and then decline to 2.6 W/m
2
by 2100 (~420
ppm CO
2
eq).
RCP2.6 (also called RCP3PD)
