Climatic trends and interdecadal variability from south‐central Pacific coral records

We study climate variability over interdecadal time scales from δ13C and δ18O records, measured in a Porites lutea coral core drilled in the Moorea lagoon. Previously, we demonstrated that the annual δ18O variations reflect those in sea‐surface temperature (SST), while the annual δ13C variations record primarily cloud‐cover changes. We apply two distinct spectral analysis methods to the δ13C and δ18O time series from 1853 to 1989. Our analysis of the δ18O record shows a secular warming trend and a 35‐year oscillation in temperatures over the last 137 years. A trend and a 34‐year cycle are also found in the δ13C record. The latter trend may be caused by either anthropogenic effects or a cloud‐cover increase in this region of the Pacific Ocean, while the interdecadal oscillation appears to be related to changes in cloud cover, as well as in precipitation.