16 4
a
b
Fig. 4.10 Transient climate response to cumulative CO 2 emissions, in units of Gt C. Both panels
show rise in GMST relative to an 1861–1880 baseline (ΔT) from CMIP5 GCMs as a function of
cumulative CO 2 emissions for RCP 2.6, 4.5, 6.0, and 8.5. (a) Rise in GMST found using our
Empirical Model of Global Climate (EM-GC) for the four RCP scenarios, run using the IPCC
( 2013 ) best estimate for ΔRF due to tropospheric aerosols between 1750 and 2011 of −0.9 W m−^2
and OHC based on the average of six data records shown in Fig. 2.8. The computed cumulative
CO 2 emissions are based on our summation of data archived in files that drove the various RCP
scenarios; (b) same as (a), except the rise in GMST from our EM-GC is displayed as a function of
the cumulative CO 2 emissions associated with the CMIP5 GCMs, which are lower than the CO 2
emissions that drove the RCP scenarios. See Methods for further information
4 Implementation