Figure 13.7: Pattern correlations
between the decadal ensemble mean temperature (Northern Hemisphere only) from
the HadCM2 experiment forced with a 0.5%/yr increase in greenhouse gas concentrations
(Gd) and: the scaled ensemble mean pattern (solid line); the four scaled individual
ensemble member patterns – average coefficient (dashed line); and the scaled
ensemble mean pattern derived from the HadCM2 experiment forced with a 1%/yr increase
in greenhouse gas concentrations (Ga) (dotted line). The correlations increase
with time as the pattern of greenhouse gas response (the “signal”) increasingly
dominates the random effects of internal climate variability (the “noise”).
The shaded area shows the spread of correlations between the pairs of the individual
members of the Gd ensemble; these correlations are lower than those between the
realised and scaled patterns above, indicating that the scaled pattern is not
due to internal climate variability. (Source: Mitchell et al., 1999.)
