First author

The western Pacific warm pool, one of the open ocean's largest bodies of warm water, wields significant influence over Earth's climate. Even though scientists understand the key part that the warm pool plays in the El Niño/Southern Oscillation (ENSO), they do not know the extent to which it influences global climate change — past and present. Graduate student Jud Partin and his adviser at Georgia Institute of Technology, Atlanta, turned to stalagmites from Borneo to create a tropical climate history (page 452). Partin spoke to Nature about how this new approach revealed complex climate controls.

Did you set out to be a spelunking scientist?

No, I consider myself a lucky graduate student who enjoys the fieldwork — even though it is demanding. Other people have been using stalagmites as a proxy for past climate records, but we were the first to use ones from remote areas in the ENSO-affected west Pacific. To sample the stalagmites, we hiked 20 kilometres with 32-kilogram packs to get to a remote part of the Gunung Buda National Park in Borneo.

Why use stalagmites rather than sediments or coral reefs to understand climate change?

Our mission was to create high-resolution records of the history of the tropical Pacific climate. Stalagmites provide decadal resolution within a 30,000-year record. We can absolutely date stalagmites using the radioactive decay rate of uranium, and we can determine the past rainfall amounts by measuring oxygen isotopes. Sediment cores are difficult to date accurately, which obscures climatic cause and effect. Corals provide monthly resolution, but an individual coral is usually only several hundred years old, and those pre-dating 1800 AD are extremely rare.

How can you use absolute dates to a scientific advantage?

Absolute dating allows a direct comparison of climate records from all over the world. This helps scientists to determine the sequence of events during abrupt climate changes in the past. Armed with precise dating from other stalagmites around the world, we can next ask: does the western tropical Pacific act as an amplifier or as a trigger of global climate variability?

What was the biggest surprise the stalagmite data revealed?

Some people think that the tropical Pacific is slave to the climate influence from higher latitudes. We found, however, that it is more complex because the tropical Pacific can also act independently — responding to changes in solar input.