Intensified decadal variability in tropical climate during the late 19th century

To evaluate and extend the record of decadal climate variability, we present a synthesis of 23 coral oxygen isotope records from the tropical Indo-Pacific that extends back to A.D. 1850. Principal components analysis (PCA) on detrended records reveals a leading pattern of variance with significant interannual (3-5 year) and decadal (9-14 year) variability. The temporal evolution and spatial pattern of this variability closely resembles the El Nino/Southern Oscillation (ENSO) pattern across both time scales, suggesting that this decadal tropical variability is fundamentally related to ENSO. The 19th century experienced stronger decadal tropical climate variability, compared to the 20th. Decadal variability in the tropical oceans thus remains underestimated by analysis of direct observations.