Scientists suspect this phenomenon connects to global climate - but exactly how - remains a question.

Now a big piece of the puzzle has fallen into place - with a study showing that the amount of dust entering the equatorial Pacific spikes sharply during repeated ice ages - then declines when climate warms.

Researchers at the Earth Institute at Columbia University say it cements the theory that atmospheric moisture - and thus dust - move in close step with temperature on a global scale.

The team says that the finding could advance the idea that seeding oceans with iron-rich dust may mitigate global warming.

The study appears in the February 28 edition of Science Express - the advance online edition of the leading journal Science.