We study climate variability over interdecadal time scales from 5•3C and 5•SO records, measured in a Porites lutea coral core drilled in the Mootea lagoon. Previously , we demonstrated that the annual 5•SO variations reflect those in sea-surface temperature (SST), while the annual 5•3C variations record primarily cloud-cover changes. We apply two distinct spectral analysis methods to the 5•3C and 5•sO time series from 1853 to 1989. Our analysis of the 5•SO 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 5•3C 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.