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participants is made up of the huge corresponding database, ready to be
simulated by atmosphere-ocean coupled general circulation models.
These models comply both locally and globally with the fundamental
principle of heat conservation: there can be no “missing heat” and, in the
end, their global behavior complies with that of the elementary energy
balance models. Supplying the flows of radiative forcing therefore equates to
supplying an entire part of the model, corresponding to the sum of
present
in
the
linearized
model
Q
=
α
u
+
α
u
+
α
u
1
1
2
2
3
3
(see section 4.1).
I
(
s
)
s
x
=
α
u
+
α
u
+
α
u
λ
x
G
1
1
2
2
3
3
G
Under examination, the “historic” forcing in Figure 9.1 appears to
effectively consist of three components:
1) A basis of anthropogenic growth, approximately exponential over the
historic period, corresponding to the term
α
11 ;
u
results in small and barely visible
oscillations for periods of 11 years, caused by solar cycles. The relative
weakness of the coefficient
2) The solar contribution
α
2 u
2
makes the slow variations of TSI
α
2
undiscernible;
3) The negatives peaks associated with volcanic eruptions.
In reality, the label “history” at the top of Figure 9.1 is no more justified
than the alleged determination of radiative forcing by observations (see
section 5.8: AR5 8.3). Only the observations in the strictest sense are
historic: concentrations of GHGs, TSI, AOD, etc. The assumed radiative
forcing is not.
So what degrees of freedom are left to the participants of the CMIP? The
inertias and thermal exchanges are determined by the laws of physics:
thermodynamics and fluid mechanics. Therefore, this essentially leaves the
(distributed) coefficient of climate feedback
G , where the clouds play the
central role, through their properties of radiation, emission, absorption and
reflection. Above all, prior to this, the mechanisms governing the genesis of
cloud formations. According to the IPCC, “there is very high confidence that
the uncertainties in cloud processes explain much of the spread in modelled
climate sensitivity” (AR5, Chapter 9, p. 3). It is even the only possible
λ
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