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.)
