Environmental Engineering Reference
In-Depth Information
The shaded region in the figure corresponds to the likely range, which
is defined as the 67% confidence interval or ± one standard error.
CHAPTER 6
Figure 6.1 and associated discussion in text:
The very long-term warming in Figure 6.1 was computed on the basis
of the CO
2
concentrations at 1,000, 5,000 and 10,000 years in the LTMIP
ensemble of carbon-cycle models (Archer et al., 2009). The minimum,
median, and maximum climate sensitivity from Table 3.1 was applied to
each member of the ensemble in order to produce the range of estimated
warming. Only ensemble members that included sediment dissolution feed-
back were used in the calculation, but the ensemble includes simulations
with and without climate feedback on carbon uptake. Because the climate
feedback invariably increases the long-term CO
2
value, the no-feedback
case defines the lower end of the estimated warming, corresponding to a
case in which the climate feedback on uptake is negligible. The upper end
of the warming is underestimated in this calculation, because the climate
feedback should increase when a climate sensitivity higher than that used
in the carbon-cycle model is applied, but this effect was not taken into ac-
count because there was no reliable methodology for doing so within the
ensemble of published results. The LTMIP ensemble states results for 1,000
GtC and 5,000 GtC cumulative emissions. Temperatures for intermediate
values of cumulative emissions were obtained by interpolating log(CO
2
)
linearly in the cumulative emissions, based on the geochemical principles
laid out in Caldeira and Kasting (1993).
