Environmental Engineering Reference
In-Depth Information
level of cumulative CO
2
emissions do not result in stable CO
2
concentra-
tions, but rather in CO
2
concentrations that peak at some value and then
decrease slowly when emissions fall below the level of persistent natural
carbon sinks (see Figure 3.7). For rates of emission reduction of the order
of 1-4% per year, and even if CO
2
emissions become close to zero, the de-
crease in atmospheric concentrations may, however, occur very slowly over
FIGURE 3.7 Illustrative emissions scenarios with cumulative emissions from 1750 to 2100 totaling 1,000 GtC
(3,700 GtC). For all scenarios, the year-2100 temperature change and CO
2
concentration do not depend on
the shape of the emissions scenario, but rather on the total cumulative emitted. These scenarios were con-
structed such that total cumulative carbon emissions were the same for each scenario, the rate of emissions
decline varied from 1.5 to 4. 5% per year relative to the peak emissions, and emissions were constrained to
reach zero at the year 2100. CO
2
concentrations and temperature changes shown here were simulated by
the UVic ESCM. Source: Weaver et al. (2001) and Eby et al. (2009).
