Western Indian Ocean coral temperature reconstruction. (a) Coral composite temperature reconstruction scaled to large-scale western Indian Ocean SST (WIO coral; thick magenta line: annual mean of 5-core average, thin lines: 95% CL; dashed magenta line: annual mean of 3-core average). The WIO coral reconstruction has been scaled to the standard deviation of HadSST37,8 averaged over 50°E-70°E, 10°N-10°S (thick blue line: annual mean; thin lines: 95% CL; see supplementary methods); base period: 1961–1990. The WIO coral temperature reconstruction is consistent with MOHMAT419 (thick green line) averaged over 50°E-70°E, 10°N-10°S. (b) Reconstruction skill statistics of the WIO coral SST against HadSST37,8 are calculated for the 5 (Rsq, magenta), 3 and 2 core composites (Rsq, magenta, reduction of error, RE, blue; coeefficient of efficiency, CE, green). Calibration period: 1950–1995; Validation period: 1908–1913, 1922–1939.