An Empirical Approach toward the SLCF reduction targets in Asia for the Mid-term Climate Change Mitigation
Although importance of co-control of SLCFs together with the emission reduction of CO 2 has attracted much attention for the mid-term climate change mitigation, their contribution to radiative forcing (RF) are rather complex, and chemical-climate model analysis for the future scenario tends to give black box for the contribution of each species. In order to deliver a more straightforward message on the effect of the reduction of SLCFs to policymakers, we propose "top-down" reduction targets of
... duction targets of CH 4 and tropospheric O 3 in reference to the historical levels of their RF. Although the RF increase due to the increasing CO 2 concentration is inevitable in mid-term future (ca. 0.80 W m -2 in 2040), the RF of CH 4 and O 3 is expected to decrease from 0.48 to 0.41, 0.34, 0.27, and 0.22 W m -2 , and from 0.40 to 0.29, 0.23, 0.19, and 0.15 W m -2 , respectively, if their atmospheric concentrations decrease from the level of 2010 to those of 1980, 1970, 1960 and 1950, according to the IPCC 2013 database. Consequently, the sum of -ΔRF x (CH 4 ) and -ΔRF x (O 3 ) (the difference of RF between the target year of x and 2010 as the base year) are 0.18, 0.31, 0.42 and 0.51 W m -2 in 1980, 1970, 1960 and 1950, respectively. This indicates that the increase of ΔRF 2040 (CO 2 ) can be compensated by of 23 to 64%, and the policy target can be selected from the combination of different target years for CH 4 and O 3 . With these global reduction ratio the necessary reductions in CH 4 , NO x, and NMVOC in Asia was estimated and compared with the GAINS model-based cost-beneficial reduction amount proposed by the Solution Report prepared under UN Environment Asia pacific Office. The comparison suggests that the reduction of O 3 to the 1970 level is promising if the emissions of NO x and NMVOC from other parts of the world are reduced coherently, but further efforts would be necessary for the reduction of CH 4 emissions to realize the 1970 concentration level.