The mystery event in 1257 was so large its chemical signature is recorded in the ice of both the Arctic and the Antarctic.
European medieval texts talk of a sudden cooling of the climate, and of failed harvests.
Little remains of the original mountain structure - just a huge crater lake.
The team has tied sulphur and dust traces in the polar ice to a swathe of data gathered in the Lombok region itself, including radiocarbon dates, the type and spread of ejected rock and ash, tree-rings, and even local chronicles that recall the fall of the Lombok Kingdom sometime in the 13th Century.
Prof Clive Oppenheimer, from Cambridge University, UK, told the BBC that the evidence is very strong and compelling.
The team's studies on Lombok indicate that as much 40 cubic kilometres (10 cubic miles) of rock and ash could have been hurled from the volcano, and that the finest material in the eruption plume would likely have climbed 40km (25 miles) or more into the sky.
It would have had to be this big in order for material to be carried across the entire globe in the quantities seen in the Greenland and Antarctic ice layers.
The impact on the climate would have been significant.
Medieval texts describe atrocious weather the following summer in 1258. It was cold, and the rain was unrelenting, leading to flooding.
The research is published in the PNAS journal.
--ANI (Posted on 01-10-2013)