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 CO2 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 feedback 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 CO2 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 account 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(CO2) linearly in the cumulative emissions, based on the geochemical principles laid out in Caldeira and Kasting (1993).



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