a
b
c
Fig. 2.9 Observed and EM-GC simulated global warming, 1860–2015 as well as global warming
projected to 2060. (a) Top rung of a typical ladder plot, comparing EM-GC modeled (red) and
CRU observed (black) ΔT, as well as three of the terms that drive ΔTHUMAN (Eq. 2.4) computed for
the AerRF 2011 = −0.4 W m−^2 , the IPCC ( 2013 ) upper limit of the likely range for ΔRF due to
anthropogenic, tropospheric aerosols. The projection of ΔT to 2060 uses the indicated value of λ.
The gold circles at 2060 are placed at the Paris target (1.5 °C) and upper limit (2.0 °C); (b) same
as (a), except calculations conducted for AerRF 2011 = −0.9 W m−^2 , the IPCC ( 2013 ) best estimate
of ΔRF due to aerosols. Here, the contribution to ΔT from ENSO is also shown, so that the con-
nection of anomalous warm conditions in 2015 to projected ΔT can be better visualized. The
contribution of ENSO to ΔT is only shown once, since it is similar for all three simulations; (c)
same as (a), except for AerRF 2011 = −1.5 W m−^2 , the IPCC ( 2013 ) lower limit of the likely range
for ΔRF due to anthropogenic, tropospheric aerosols. All calculations used the mean value of OHC
computed from the six datasets shown in Fig. 2.8