FIGURE 4: Interdecadal variability in ENSO since 1880. 2.86-5 year bandpass filtered coral δ18O and environmental variables. The local SST record is the 1°square reconstruction from the GISST2.3 dataset from the UK Met. Office; the NINO3.4 record is from the OS SST reconstruction of Kaplan et al., 1998. Gaussian bandpass filter from Analyseries software, Paillard et al., 1996.
FOSSIL CORAL:
The δ18O record from a 2,650 year old Laing Island coral is compared with the record from the modern Laing Island coral in Figure 5. In both cases, seasonal data (thin line) has been smoothed by a 9 poit binomial, filter (thick line) to help reveal interannual and longer timescale variability. Seasonality and interannual-interdecadal variability are evident in the fossil coral. Use of a bandpass filter to focus on the ENSO frequercy band (Figure 6) indicates that ENSO-style variability existed 2,650 years ago, but that it was, on average, weaker than that which occurred over the past century. In addition, the fossil record displays similar interdecadal modulation of ENSO variability to that in the modern record.
