Geography Reference
In-Depth Information
Table 2.2
Description of RCPs
RCPs
Description
Publication-IA Model
CP8.5
Rising radiative forcing pathway leading
to 8.5 W/m
2
MESSAGE (Riahi et al.
2007
)
in 2100
RCP6
Stabilization without overshoot pathway
to 6 W/m
2
AIM (Y. Hijioka
2008
)
at stabilization
RCP4.5
Stabilization without overshoot pathway
4.5 W/m
2
GCAM (Smith and Wigley
2006
)
at stabilization after 2100
Peak in radiative forcing at *3 W/m
2
before 2100 and decline
RCP2.6
IMAGE (Van Vuuren et al.
2006
)
The RCP4.5 scenario is a stabilization scenario in which the total radiative
forcing is stabilized shortly after 2100, without overshooting the long-run radiative
forcing target level (Liu et al.
2005a
,
b
). RCP4.5 includes long-term, global
emissions of greenhouse gases, short-lived species, and land use-land cover in a
global economic framework which stabilizes the radiative forcing at 4.5 Watts per
square meter (W/m
2
), approximately 650 ppm CO
2
-equivalent in the year 2100
without ever exceeding that value. The defining characteristics of this scenario are
enumerated in Moss' papers (Moss et al.
2008
; Moss et al.
2010
). RCP 4.5 was
updated from earlier GCAM scenarios to incorporate the historical emissions and
land cover information and follows a cost-minimizing pathway to reach the target
radiative forcing. The necessity to limit emissions in order to reach this target leads
to the changes in the energy system, including shifts to electricity, lower emissions
energy technologies and the deployment of carbon capture and geologic storage
technology. In addition, the RCP4.5 emission price is also applicable to the land
use emissions. The simulated future emissions and land use were downscaled from
the regional scale to the grid scale to facilitate the transfer to climate models.
While there are many alternative pathways to achieve a radiative forcing level of
4.5 W/m
2
, the application of the RCP4.5 provides a common platform for climate
models to explore the response of the climate system to stabilizing the anthro-
pogenic components of radiative forcing. Therefore, the RCP4.5 scenario is used
in this study, under which the land use change is simulated with GCAM. Besides,
the GTAP-AEZ model, which is similar to GCAM, is also used to analyze the land
use structure in AEZs, and the results obtained with the two models were finally
compared.
2.3.4 Results and Analysis
The results indicate that the land use area in different AEZs, which are obtained with
the GCAM model and the GTAP-AEZ model, are generally consistent. The pasture
land areas simulated with the two models differ most greatly, but are still generally
consistent in different AEZs. Besides, the results obtained with the GTAP-AEZ
model and the GCAM model both show that the grassland is approximately equally
