The band of rainfall happens at what is called the inter-tropical convergence zone. There, just north of the equator, trade winds from the northern and southern hemispheres collide, at the same time heat pours into the atmosphere from the tropical sun.

The new study presents surprising evidence that the inter-tropical convergence zone hugged the equator some three and a half centuries ago during Earth's little ice age, which lasted from 1400 to 1850.

The authors analysed the record of rainfall in lake and lagoon sediments from four Pacific islands at or near the equator.

These findings were published in the July issue of Nature Geoscience.