Correction to “Late 20th century warming and freshening in the central tropical Pacific”

Abstract

We present corrections to uncertainty estimates of late 20th century (1972-1998) coral-based sea-surface temperature (SST) and salinity (SSS) trends from Palmyra, Fanning and Christmas Islands of the central tropical Pacific reported in Nurhati et al. [2009] (Geophysical Research Letters, 36, L21606, doi:10.1029/2009GL040270). In our original paper we had assigned relatively large error bars to coral Sr/Ca-based warming trends observed at all three islands, rendering those trends statistically insignificant with respect to the large errors. However, those large uncertainties originate from large errors associated with quantifying absolute SST at any given point, whereas the uncertainties for SST trends should reflect errors in quantifying relative changes, which are much lower. Late 20th century warming trends of 0.94–1.65∞C at the three islands are statistically significant with the corrected error ranges of ±0.19–0.37∞C (1σ; originally ±5.73–6.57∞C). Freshening trends inferred from coral-based oxygen isotopic composition of seawater (δ18OSW) of −0.32‰ and −0.12‰ (1σ) at Palmyra and Fanning, respectively, are associated with corrected error ranges of ±0.07‰ and ±0.08‰ (1σ; originally ±0.08‰ for both), respectively. Christmas experienced an insignificant +0.03 ± 0.11‰ (1σ; originally also ±0.11‰) trend in δ18OSW over this period. With the new, lower uncertainty estimates, the coral-based SST and SSS trends are statistically significant, thereby strengthening Nurhati et al.'s (2009) conclusions that robust warming and freshening have occurred in the central tropical Pacific over the late 20th century. Our detailed uncertainty calculations presented below will be of value to the paleoclimate community, as the correct calculation of absolute errors and relative errors represents a key component of paleoclimatic reconstruction.