1654.5 (Thomson et al. 2011 ), RCP 6.0 (Masui et al. 2011 ), and RCP 8.5 (Riahi et al.
2011 ). Each of these four runs used the IPCC (2013) best estimate for radiative forc-
ing of climate due to tropospheric aerosols of −0.9 W m−^2 in year 2011 (AerRF 2011 ),
as well as ocean heat content (OHC) based on the average of six data records shown
in Fig. 2.8. As discussed in Chap. 2 , projections of ΔT are sensitive to AerRF 2011
(Fig. 2.9) and insensitive to OHC (Fig. 2.10).
Values of ΔT from the CMIP GCMs and our EM-GC shown in Fig. 4.10 are dis-
played as a function of cumulative CO 2 emissions from land use, fossil fuel combus-
tion, cement manufacturing, and flaring since 1870 (ΣCO 2 EMISS). Prior to this point,
we have displayed CO 2 emissions using units of Gt CO2, because this is most appro-
priate for the Paris Climate Agreement. In Figs. 4.10 and 4.11, however, ΣCO 2 EMISS
is displayed using Gt C because most of the discussion of TCRE in the peer-reviewed
literature (Allen et al. 2009 ; Rogelj et al. 2016b) and in IPCC ( 2013 ) uses Gt C. The
distinction between these two units is described by footnote 13 of Chap. 1.
Fig. 4.11 Transient climate response to cumulative CO 2 emissions, RCP 8.5. Simulations of the
rise in GMST relative to an 1861–1880 baseline (ΔT) found using our EM-GC plotted versus
cumulative CO 2 emission, in units of Gt C. Paris Climate Agreement target and upper limit of 1.5
and 2.0 °C warming are denoted by the dotted and dashed lines, respectively. The EM-GC projec-
tions (red, white, and blue colors) represent the probability that the future value of ΔT will rise to
the indicated level, considering only acceptable fits to the climate record (i.e., χ^2 ≤ 2). The light
grey, dark grey, and black curves represent the 95, 66, and 50 % probabilities of either the Paris
target (intersection of dotted horizontal lines with the respective curve) or upper limit (intersection
of dashed line with curves) being achieved (see text). See Methods as well as Chap. 2 for further
information
4.4 Emission Metrics