Climate Science

El Niño's Past and Future

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Science  08 Dec 2006:
Vol. 314, Issue 5805, pp. 1517
DOI: 10.1126/science.314.5805.1517a

The El Niño-Southern Oscillation (ENSO) causes large annual changes in tropical Pacific sea surface temperatures and leads to climate anomalies across the world. Researchers have sought a better understanding of the impact of global warming on ENSO phenomena. However, the limited temporal resolution of the few existing proxies for ENSO events has hindered reconstructions of ENSO variability in the past.

Koutavas et al. take an important step toward creating a more detailed paleo-ENSO record by performing oxygen-isotope analyses on single foraminifera and then combining those results with a Holocene sea surface temperature record of the eastern equatorial Pacific. They find that the variability in oxygen-isotope composition of individual forams increased since the mid-Holocene, indicating that ENSO events became more frequent or more intense over that interval. Additionally, opposing temperature variations in the eastern and western Pacific were consistent with a shift in the position of the Intertropical Convergence Zone (ITCZ). Because global warming is expected to shift the ITCZ position even further, there very well could be accompanying changes in ENSO phenomena. — HJS

Geology 34, 993 (2006).

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