Some global economics 235450 550 650 750
Eventual CO 2 stabilisation level (ppm)Percentage reduction relative to baseline00.51.01.52.02.53.03.54.04.5 Scenarios:
A1BA1TA1FIA2B1
B2Figure 9.4Global average GDP reduction in 2050 (relative to the baseline
scenarios) for alternative stabilisation targets (see Chapter 10) and six SRES
scenarios as baselines.
cheap fossil fuels are replaced by other energy sources that, at least in
the short term, are likely to be more expensive. Some detail is provided
in the next chapter of the profile of reductions in emissions that are
required to stabilise carbon dioxide concentrations in the atmosphere
at different levels over the next one or two hundred years. Figure 9.4
presents estimates from six economic models of the cost to the world’s
economy in the year 2050 of these reductions. As might be expected,
the cost is substantially dependent on the target level of carbon dioxide
concentration stabilisation. It is also dependent on the baseline scenario
that is assumed. With typical levels of economic growth being between
two and four per cent per annum, the cost of achieving reductions to
meet any of the stabilisation levels in the figure, even that at 450 ppm,
is less than one year’s economic growth over fifty years.
However, it should be noted that, even if the carbon dioxide con-
centration is stabilised at 450 or 500 ppm, remembering that the effect
of increases in the other greenhouse gases also has to be included (see
Chapter 10, page 259), the world will have been committed to a sig-
nificant degree of climate change (close to equivalent to doubling of
atmospheric carbon dioxide concentration), bringing with it substantial
costs and demands for adaptation. What is being mitigated is further and
even more damaging climate change.
Although the economic studies I have mentioned have attempted
to take into account many of the relevant factors, they are bound to be
surrounded by substantial uncertainty. For instance, they have mostly