Quat. Sci. Rev. 30, 3716–3727 (2011)

Marine sediment analyses suggest that over the past 400,000 years, the hydrological cycle over the Western Pacific warm pool was controlled by local incoming solar radiation.

Kazuyo Tachikawa and colleagues at Aix-Marseille University, France, determined the geochemistry of marine sediments and associated fossils in a core collected from the northern coast of Papua New Guinea. Using the abundance of elements typically found in the rocks of the island, they reconstructed river run-off, and hence precipitation, over the past four glacial–interglacial cycles. Somewhat surprisingly, precipitation intensity was seemingly unrelated to the glacial cycles. Instead, changes in rainfall were closely linked with the precession of the Earth's orbit, which strongly influences insolation in the tropics on a 23,000-year cycle.

Records in other parts of the warm pool that do show glacial–interglacial shifts in precipitation could reflect the effects of glacial reduction of sea level, which eliminated the shallow seas that serve as a moisture source to the neighbouring islands.