Environmental Engineering Reference
In-Depth Information
FIGURE 2.3 (a) Illustrative atmospheric CO
2
stabilization scenarios for 1,000, 750, 550, and 450 ppmv;
SP1000 (red), SP750 (blue), SP550 (green) and SP450 (black), from Meehl et al. (2007). (b) Compatible an-
nual emissions calculated by three models, the Hadley simple model (solid), the UVIC EMIC (dashed), and
the BERN2.5CC EMIC (triangles) for the three stabilization scenarios. Panel (b) shows emissions required for
stabilization without accounting for the impact of climate on the carbon cycle, while panel (c) included the
climate impact on the carbon cycle, showing that emission reductions in excess of 80% (relative to peak val-
ues) are required for stabilization of carbon dioxide concentrations at any of these target concentrations.
suggested that slow reductions in emissions could lead to eventual stabili-
zation of climate (e.g., Wigley et al., 1996). But recent studies using more
detailed models of key feedbacks in the ocean, biosphere, and cryosphere,
have underscored that although a quasi-equilibrium may be reached for a
limited time in some models for some scenarios, stabilizing radiative forcing
at a given concentration does not lead to a stable climate in the long run.
Cumulative emitted carbon can more readily be linked to climate stabiliza-
