Geoscience Reference
In-Depth Information
CSM1.4-carbon model have been selected to illus-
trate the long-term inl uence of anthropogenic car-
bon emissions on ocean acidii cation and climate
( Fig. 14.4 ). In the i rst scenario ('Hist' case), emis-
sions are hypothetically set to zero in 2000. In the
other two scenarios, emissions follow the SRES B1
(low 'B1_c' case) and SRES A2 (high 'A2_c' case)
path until 2100, when emissions are instantaneously
set to zero. Setting emissions immediately to zero in
2000 or 2100 is not realistic, but it allows the quantii -
cation of the long-term impact of previous greenhouse
gas emissions. The three scenarios roughly span the
range of 21st century carbon emissions from base-
line and mitigation scenarios (Fig. 14.2A). The 'Hist'
case obviously features lower emissions (397 Gt C)
than any of the mitigation scenarios. Cumulative
emissions in the 'B1_c' case (1360 Gt C) are some-
what smaller than to those from the highest mitiga-
tion scenario and the lowest baseline scenario
shown in Figs 14.1 and 14.2 and emissions in the
'A2_c' case (2210 Gt C) are close to those of the most
extreme baseline scenario.
While projected atmospheric CO 2 and surface
saturation in 2100 is similar for the Bern2.5CC
(A)
(B)
30
850
25
750
20
650
15
550
10
450
5
350
0
250
(C)
(D)
3.5
3
3.2
2.9
2
2.6
1
2.3
2.0
0
1.7
1900
2000
2100
2200
2800
2400
2500
1900
2000
2100
2200
2300
2400
2500
Year
Year
A2_c
B1_c
Hist
Figure 14.4 Long-term impact of 21st century carbon emissions. (A) Carbon emissions, (B) atmospheric CO 2 , (C) global-mean surface air-temperature change,
and (D) global average saturation state of surface waters with respect to aragonite (Ω a ) for three illustrative emissions commitment scenarios evaluated with the
NCAR CSM1.4-carbon model (Frölicher and Joos 2010). In the high 'A2_c' case and the low 'B1_c' case, 21st century emissions follow the SRES A2 and SRES B1
business-as-usual scenario, respectively. Emissions are set to zero in both cases after 2100. In the 'Hist' case, emissions are stopped in the year 2000.
 
Search WWH ::




Custom Search