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world’s oceans occurs in the upper 700 m (Sect. 5.2.2.1 of IPCC 2007 ). This multi-
plication is carried out because ocean heat export in the model must represent the
entire water column. As stated above, a 6 year lag is assumed between perturbation
and response (Schwartz 2012 ). Next, OHC is divided by 3.3 × 10^14 m^2 , the surface
area of the world’s oceans. Finally, a value for κ is derived so that the change in
OHC over the period of time covered by a particular data set (i.e., the average time
derivative) is matched, rather than attempting to model the ups and downs of any
particular OHC record. Since the ups and downs of the various records are uncor-
related, it is more likely these variations reflect measurement noise rather than true
signal.
2.2.1.2 Model Outputs
In addition to the regression coefficients, two additional parameters are found by the
EM-GC: the climate sensitivity parameter (γ in Eq. 2.2) and the ocean heat uptake
efficiency coefficient (κ in Eq. 2.3). As described in Sect. 2.5, values of γ and κ
inferred from the prior climate record are used to obtain projections of ΔT, assum-
ing γ and κ remain constant in time. In this section, some context for the numerical
Fig. 2.8 Ocean Heat Content (OHC) versus time from six sources (colored, as indicated). The
black solid line is the average of the six measurements used in most of the EM-GC calculations.
See Methods for further information
2 Forecasting Global Warming