87Studies of tropospheric aerosol ΔRF are unable, at present time, to definitely rule
out any of these possibilities.
One clear message that emerges from Figs. 2.15 and 2.16 is that to achieve the
goal of the Paris Climate Agreement, emissions of GHGs must fall significantly
below those used to drive RCP 8.5. The range of ΔT 2100 shown in Fig. 2.16b is
1.6–4.7 °C. Climate catastrophe (rapid rise of sea level, large shifts in patterns of
drought and flooding, loss of habitat, etc.) will almost certainly occur by end of this
a
b
RCP 4.5
RCP 8.5
Fe
edback
Pa
rameter
(W
m
-2oC
-1)
AerRF 2011 (Wm–2)
Fig. 2.15 Projected rise in GMST, year 2060, as a function of climate feedback and aerosol radia-
tive forcing. Values of ΔT relative to the pre-industrial baseline found using the EM-GC frame-
work, for all combinations of model parameters λ and AerRF 2011 that provide an acceptable fit to
the climate record, defined here as yielding a value of χ^2 ≤ 2. Projections of ΔT are shown only for
AerRF 2011 between the IPCC ( 2013 ) limits of −1.9 and −0.1 W m−^2. The color bar denotes ΔT 2060
found by considering only the ΔTHUMAN term in Eq. 2.2 for the future. All simulations used OHC
from the average of six data records shown in Fig. 2.8 and the aerosol ΔRF time series are based
on scaling parameters along the middle road of Fig. 2.21. (a) GHG and aerosol ΔRF based on RCP
4.5 (Thomson et al. 2011 ); (b) GHG and aerosol ΔRF based on RCP 8.5 (Riahi et al. 2011 ). The
minimum and maximum values of ΔT 2060 are recorded on each panel
2.5 Future Temperature Projections