Determining the position of the SPCZ over longer timescales in the past (pre-20th century) has been studied using coral records of the southwest Pacific. Linsley et al. (2006) reconstructed sea-surface temperature and sea surface salinity in the southwest Pacific starting circa 1600CE by measuring the oxygen isotopic composition of four Porites coral records from Rarotonga and two from Fiji. Coral isotope measurements provide information on both sea surface temperature and sea surface salinity, so they can indicate times of increased or decreased temperature and/or precipitation associated with changes in the position of the SPCZ. Their coral oxygen isotope index indicated an eastward shift of the decadal mean position of the SPCZ since the mid 1800s. A shift of the SPCZ in this direction suggests there were more La Niña-like or cold-phase conditions in the Pacific, during this period, often called the Little Ice Age. Additional paleoclimate studies are still needed in order to test the reliability of these coral results.