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Greenhouse gas removal and zero emissions energy production 59

2.6 Policy implications

Using the worst plausible values for all the input parameters, there is no amount of
GGR that will deliver even the 2°C target if it does not start before 2050. If the
GGR starts in 2025 this target is achievable but only if GGR grows to an annual
amount of 11.4Gt(C)/yr within 46 years, or if it starts in 2030, growing to
14.7Gt(C)/yr within 59 years (Scenario 9). These amounts of GGR might become
plausible in the future if sufficient investment is made in the appropriate technologies.
This corresponds to more than 50Gt(CO 2 )/yr, a mass of material about double the
combined total of current global mining of all fuel and mineral resources [23].In
the absence of a credible plan to deliver GGR at this scale, for now at least, it must
be considered implausible. This scenario also implies a ZEE Index of 12, illustrating
the challenge of simultaneously scaling GGR and ZEE technologies.
Using the best plausible values for all the input variables, with no GGR, the cumu-
lative emissions by 2100 fall 34 Gt(C) short of the 1.8°C target with a ZEE Index of
11 (Scenario 10). This shows that we have within our reach the possibility of keeping
global warming to well below 2°C without recourse to GGR albeit with only a little
headroom. However, in scenarios where the transition from FF to ZEE is rapid and
deep, the contribution achievable from REC and CIR is minimal. Even excluding
any benefit from REC and CIR, reducing emissions to zero by 2057 still keeps
cumulative emissions within the 1.8°C carbon budget without any help from GGR,
and the 1.5°C target requires less than 2Gt(C)/yr of GGR by mid-century
(Scenario 11). The ZEE Index remains at a challenging 14.
Demonstrably there exist multiple combinations of input values compatible with
the Paris Agreement. In the following paragraphs, a few of these will be examined
by reference to increasing levels of GGR.

2.6.1 Zero GGR

Zero GGR requires that the available carbon budget be rationed to cover the elimina-
tion of FF. For example, to meet the 1.8°C target, emissions would need to peak by
2018 and reduce to zero within 40 years (the minimum plausible period for a reduction
to zero emissions) (Scenario 12). This requires that the almost flatlining of emissions
for 2013–15 proves to be the peak, rather than, as recent data suggest [13], another
soon-to-be corrected anomaly of which there have been many in the past 250 years.
The ZEE Index is 14.
The 2°C target could be reached in the same time span but this higher temperature
target would allow emissions to settle at 2Gt(C)/yr rather than be totally eliminated.
This relaxes very slightly the demand for ZEE with the Index reducing to 13
(Scenario 13).
There is no plausible scenario, even with reductions in energy demand and
improvements in carbon intensity that would deliver either 1.5°C or 1.8°C with resid-
ual emissions at 2Gt(C)/yr or more.
It is apparent that GGR can only be avoided if FF emissions have already peaked or
will do so imminently, and are subject to rapid reduction to almost zero. When FF is