Page 25 - Managing Global Warming

20 Managing Global Warming

alternative policy scenarios; they are not intended to be forecasts or predictions. A full
explanation of the eleven policy variables is given in Section 2.5.
The calculator assumes that all transitions follow standard S-curve trajectories.
The S-curve coefficients are calculated dynamically to generate smooth paths over
the relevant periods.
The charts in Fig. 2.1 illustrate the calculator outputs. Each scenario is represented
by two charts for energy consumption and emissions, respectively, each covering the
period 2014–2100 (actual data for 2014). The energy chart shows the annual global
TFC divided between FF energy and ZEE. The ZEE Index is the ratio of the slope
of the imputed linear growth of ZEE from all sources from 2015 to 2100 to the slope
of its growth during the base period 2004–14. The ZEE Index is a measure of the
rate at which the development of ZEE must be accelerated to meet energy demand
during the balance of the century. For example, a ZEE Index of 10 means that in every
year from 2015 onwards, ZEE will need to grow by 10 times the average annual
amount it grew in the base period. The actual growth of ZEE is unlikely to be linear,
but for the purposes of assessing the policy implications of the incremental demand
for ZEE, the ratio of the imputed linear growth rates is an adequate indicator. Energy
charts overwritten with a Θ represent implausible policy portfolios (see discussion in
Section 2.5).
The emissions chart shows annual (primary axis) and cumulative (secondary axis)
emissions, including net emissions after GGR. The long-dashed line is the carbon
budget for the chosen temperature target; the short-dashed line shows the trajectory
of cumulative emissions converging to the carbon budget by 2100. Total emissions
are shown by the solid white line with the slanted brick area being net emissions after
GGR (horizontal bricks).
The UNFCCC use a fuzzy temperature increase target of “well below 2°C above
preindustrial levels and pursuing efforts to limit it to 1.5°C.” In this chapter 1.5°C and
2°C are used as outer boundaries, and 1.8°C is the value within these boundaries
used to define “well below 2°C.” Fig. 2.1 illustrates the IPCC’s RCP2.6 scenario with
some help from GGR. Here the temperature increase is 1.8°C, emissions fall to 40% of
their 2010 value by 2050 and then reduce to zero by 2100, and GGR is deployed from
2050 [1]. In this scenario, GGR must grow to 9.7Gt(C)/yr. Cumulative emissions
overshoot the carbon budget in 2043, reaching an excess of 11% in 2071 before being
brought back on target by 2100. The ZEE Index is 15.
This analysis focuses throughout on energy consumption rather than primary
production (TPES) or energy generation. Climate change has meant that sources
of energy are under scrutiny creating an emerging consensus largely to abandon
conventional FF energy in favor of various forms of renewable energy and nuclear.
This requires that future energy policy not be predetermined by the historical reli-
ance on FF. Accordingly, the future energy source profile that emerges from this
analysis is based on end-user consumption and not on prior assumptions about pri-
mary energy sources. This treatment also accounts for transformation and other
losses intrinsic to the current global energy economy in which most production
of electricity wastes about two-thirds of the primary energy consumed in its
manufacture [6].