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When Mount Agung last erupted in 1963, more than 1,600 people were killed, dozens of villages were destroyed and tens of thousands were left homeless.

After spewing lava and thick black smoke for days, the eruption – the first in 120 years – was powerful enough to cool the planet by a staggering 1C.

Should that happen again, the pollution shooting from its chasm would block out the sun, sending temperatures plummeting to a similar degree.

Now, 54 years on, scientist believe the volcano is building up to another eruption that could cause cooling effects on a global scale.

Natural disaster researcher Dr Simon Day, of University College London, said evidence shows Mount Agung is capable of "large and strongly explosive eruptions”.

(Image: GETTY)

Speaking exclusively to Daily Star Online, Dr Day said the 1963 eruption released Earth-cooling “aerosols” that reflected sunlight away from Earth.

He said: “The 1963 eruption was notable for producing a large amount of SO2 rich aerosol.

“This was sufficient to produce an observable cooling of the climate for a year or so by about 1 degree centigrade averaged across the globe.”

“Otherwise, the primary hazard from that eruption was due to pyroclastic [lava] flows on the flanks of the volcano.

“The present evacuation zone is based largely on the extent of those pyroclastic flows.”

(Image: GETTY) (Image: GETTY)

In order for the “aerosols” to spread globally, the eruption must be “explosive” enough to propel them into the upper atmosphere, according to experts.

“You need a big enough eruption to get it high enough,” US volcanologist Janine Krippner said earlier this year.

“You also need the right kind of gases.”

But Indonesia’s volcano monitor, the National Board for Disaster Management (NBDM), said a “strong, explosive eruption” is becoming more likely as magma has now reached near the surface of the volcano.

The NBDM are warning that 3km tall Mount Agung volcano could unleash the eruption at “any time”.

More than 100,000 people living with a 10km radius of the summit have been ordered to evacuate the area immediately.

Bali’s main international airport, Ngurah Rai, has been closed, leaving around 60,000 travellers stranded on the Indonesian holiday island.

More than 400 flights were grounded by airlines concerned about the safety of their passengers.