Strontium to calcium ratio and oxygen isotopic coral records can exaggerate past decadal tropical climate variability

Abstract Geochemical tracers measured in corals are a key archive for reconstructing past variations in tropical climate and provide unique information on the complex nature of global climate dynamics. However, reconstructions from many tropical corals contain much greater decadal to centennial climate variability than evident from models or instrumental records, suggesting either biases in climate models or enhanced preindustrial climate variability. Using a method to distinguish climate from non-climate variations, on a recently compiled coral dataset covering the tropics and subtropics, we show that records from single corals contain a strongly autocorrelated non-climate noise component. This noise inflates the variance of reconstructed temperature by a factor of two to seven across a large range of timescales, implying that past studies may have exaggerated decadal to centennial temperature variations.