Paris Climate Agreement Beacon of Hope

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allow physical variables within the troposphere to respond to perturbations, except
for those ocean and sea ice variables. For computations of RF, all surface and tropo-
spheric conditions are kept fixed. Quoting Box 8.1 of IPCC ( 2013 ), “the calculation
of ERF requires longer simulations with more complex models than the calculation
of RF, but the inclusion of the additional rapid adjustments makes ERF a better
indicator of the eventual global mean temperature response, especially for aero-
sols”. We have used a mixture of ΔRF and ΔERF values for Fig. 1.4 because this is
all that is available from Chap. 8 of IPCC ( 2013 ). Table 1.3 provides numerical
estimates of the value, uncertainty, and origin of the data used in Fig. 1.4. All uncer-
tainties represent 5–95 % confidence intervals and are given as a range, rather than
a plus and minus value, since some are asymmetric about the mean.
Figure 1.5 shows a profile of the change in temperature over the time period
1959–2012, based on radiosonde observations collected in the latitude range 30°S
to 30°N (Sherwood and Nishant 2015 ). Data reflect the Iterative Universal Kriging

Table 1.3 ΔRF values used in Fig. 1.4

Term

ΔRF

(W m−2)

Range of ΔRF

(W m−2)

Origin within Chap. 8 of

IPCC ( 2013 )

CO 2 1.82 1.63–2.01 Table 8.2, RF

CH 4 0.48 0.43–0.53 Table 8.2, RF

N 2 O 0.17 0.14–0.20 Table 8.2, RF

ODSa 0.33 0.297–0.363 Table 8.2, RF

Other F-Gasesb 0.03 0.027–0.033 Table 8.2, RF

Tropospheric O 3 0.4 0.2–0.6 Table 8.6, RF

Stratospheric O 3 −0.05 −0.15 to 0.05 Table 8.6, RF

Stratospheric H 2 Oc 0.07 0.02–0.12 Table 8.6, RF

Contrails and Contrail-Induced

Cirrus

0.05 0.02–0.15 Table 8.6, ERF

Surface Reflectivity: Land Use

Change

−0.15 −0.25 to −0.05 Table 8.6, RF

Surface Refl.: Black Carbon on

Snow

0.04 0.02–0.09 Table 8.6, RF

Aerosol Direct Effect −0.45 −0.95 to 0.05 Table 8.6, ERF
Aerosol-Cloud Interaction −0.45 −1.2 to 0.0 Table 8.6, ERF
Total Anthropogenic 2.3 1.1–3.3 Table 8.6, ERF
Solar Irradiance 0.05 0.0–0.10 Table 8.6, RF
aThe definition of Ozone Depleting Substances used in Chap. 8 of IPCC ( 2013 ) combines the RF
of climate due to CFC-11, CFC-12, CFC-13, CFC-113, CFC-114, CFC-115, HCFC-141b, HCFC-
142b, CH 3 CCl 3 , CCl 4 , Halon-1211, and Halon-1301. The IPCC ( 2013 ) definition appears to
neglect Halon-1202, Halon-2402, CH 3 Cl, and CH 3 Br. The ΔRF of these four compounds is quite
small, less than 0.002 W m−2, so Fig. 1.4 would look identical had these four gases been considered
bThis term considers the RF of climate due to HFCs, PFCs, SF 6 , and a few other long-lived fluori-
nated species. The IPCC ( 2013 ) definition combines the RF of climate due to HFC-23, HFC-32,
HFC-125, HFC-134a, HFC-143a, HFC-152a, CF 4 , C 2 F 6 , SF 6 , SO 2 F 6 , and NF 3
cThis term represents the RF of climate due to the increase in stratospheric H 2 O driven by rising
levels of tropospheric CH 4. It does not include radiative effects of changes in stratospheric H 2 O that
occur in response to global warming (Solomon et al. 2010 )

1.3 Methods

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