Sustainability and policy - Climate Change: Biological and Human Aspects - page 477

Table8.3 PotentialB-a-Ucarbonemissionsagainstmaximumlikelypossiblesavingsfortheyear2025.Non-fossil
energyincludesrenewableenergiesandission(henceishigherthantheestimatesforsolelynon-nuclearrenewables
giveninTable8.2)

Human-related CO 2 emissions/savings, in GtC year − 1

Carbon source or sink 2000 2025 B-a-U 2025 with savings

Total human activity 8 14 (savings not realised) 14 GtC

Decline in deforestation and some reforestation - 0 Save ≈ 2GtC

Improvement in energy efficiency - 0 Save ≈ 20%

Offset with non-fossil energy - 0 Save ≈ 2.2%

To t a l 8 14 7 (low)-8.5 (high)

pronounced current urban thermal islands.) However, we still have at least decades to
go before the first commercial fusion reactor. ITER has to prove itself theoretically
and then a fully commercial reactor needs to be designed and produced along with a
fusion epicycle plant to produce fuel and process waste. Fusion is therefore unlikely to
make a significant contribution to meeting global energy before the mid-21st century.
It is, though, a worthy long-term goal and an option that arguably we cannot afford
to ignore.

8.2.6 Overallprospectsforfossilcarbonsavingsto2025

Such are the errors of estimation it is not worthwhile presenting an overall picture
for potential carbon dioxide emissions for the present (taken here as 2000) and those
possible for the near future (taken as 2025) to greater than one or two significant
figures. Table 8.3 below depicts the overall current and near-future carbon scenarios
with the latter considered both in a B-a-U way (i.e. continuing as we did in the 1990s
without adopting any greenhouse strategies) and what might realistically be done with
greenhouse measures. Note the total carbon emissions include all those associated
with human activity and so include fossil fuels, cement manufacture and land-use
change.
The second and third columns of Table 8.3 tie in with many of the IPCC SRESs.
In part this is a cheat on my part because most of the IPCC's scenarios do not
diversify until the second quarter of the 21st century onward: after then, things not
only get difficult to summarise but the outcomes and scenarios are so varied that any
attempt to include them would have limited meaning. However, although calculated
independently, the final column of savings happens to approximate broadly the IPCC's
B1 SRES optimistic scenario, especially the high with-savings total. The low with-
savings total also ties in with the extreme low-fossil SRESs. Although this scenario
could in theory be realised, it would be foolish to assume that it will occur in practice,
for the global political and economic will for this needs to be considerable.
It should be noted that the non-fossil contribution includes elements of both renew-
able energies and nuclear fission. It may be possible to invest solely in non-nuclear
renewable energy but as some of this would be new unproven technology (or estab-
lished technology operating in untried circumstances), individual nations' policy-
makers have to decide whether to go down the nuclear route. Globally speaking,