Page 76 - Managing Global Warming

48 Managing Global Warming

may be numerically coherent, GGR at that scale is implausible. Nevertheless, at lower
levels, GGR can be a balancing factor that provides flexibility in generating plausible
portfolios of policy options. Thus, if the combination of ZEE/REC/CIR falls short, it
can be brought back on target by the addition of some GGR. This is explored in
Section 2.5.

2.5 Applying plausibility

For a portfolio of interdependent policy options to be plausible, it is not sufficient that
each of its components be plausible, their combination must also be plausible. For
example, aggressive policies to retire FF energy are dependent on either there being
an adequate amount of ZEE to take its place, or commensurate reductions in TFC. In
this section, the policy levers are examined to assess their plausible ranges and deter-
mine the mix that would deliver the UNFCCC temperature targets.
There are eleven policy-driven variables that are mathematically but not necessar-
ily politically independent. Their plausibility ranges are examined in four groups
(Table 2.2). The suggestions given in the following paragraphs for the ranges of plaus-
ible values are indicative and not prescriptive.
As noted, if the timely scaling of GGR and ZEE to their required levels is implau-
sible, then the combination of policy options from which they flow is also implausible,
irrespective of the plausibility of the individual policy components (scenario energy
charts marked with a Θ are implausible policy portfolios).

Table 2.2 List of calculator variables

Driver Variable
FF emissions l Year of peak emissions
Level at which emissions eventually stabilize (Gt
l
(C)/yr)
Years taken from peak emissions to reach
l
stabilization level
Reduction in energy consumption l Target percentage reduction in TFC from its peak
(REC) l Year REC starts
l Years taken from start to reach REC target
FF carbon intensity (CIR) l Target incremental percentage reduction in carbon
intensity
l Year CIR starts
l Years taken from CIR start to reach target level
GGR l Year GGR starts
Years taken from GGR start to reach calculated
l
level