Fig. 2: Relationship between spreads in projection and historical temperature pattern.
From: Emergent constraints on future projections of the western North Pacific Subtropical High
T1 in (a) and T2 in (b) (K2) measure how the sea surface temperature (SST) patterns in gray boxes in Fig. 1c, d are simulated in a model’s historical climate, respectively (see Eqs. (2) and (3)). T1 and T2 well explain the first and second principal components (PC1 and PC2), respectively, the two leading uncertainty modes of projected changes in the western North Pacific Subtropical High, with high correlation coefficients (ρ) statistically significant at the 1% level under Student t-test. Bold gray fitting line is obtained by the least square method while thin red line is an observational correction based on Eq. (5). Gray dashed curves denote the 95% confidence range of the linear regression. T1 and T2 indices from five observational SST datasets (HadISSTv1.1, ERSSTv5, ICOADS, COBE-SST2, and HadSST3; vertical thin dashed lines) are used to constrain the values of PCs. Mean of the five observational results yield the optimal constraint (red dashed line).
