Many could become destitute in the two continents as staple foods more than double in price by 2050 as a result of extreme temperatures, floods and droughts.

Experts said that rising temperatures will also have a drastic effect on access to basic foodstuffs, with potentially dire consequences for the poor, 'The Observer' reported.

A US government-funded study of the fertile Lower Mekong basin in Asia, which includes Vietnam, Cambodia, Thailand and Laos, states that temperatures there could rise twice as much as previously expected, devastating food supplies for the 100 million people expected to live there by 2050.

"We've found that this region is going to experience climate extremes in temperature and rainfall beyond anything that we expected", said Jeremy Carew-Reid, author of the Climate Change Adaptation and Impact Study for the Lower Mekong.

"Food production will have to rise 60 per cent by 2050 just to keep pace with expected global population increase and changing demand. Climate change comes on top of that," Frank Rijsberman, head of the world's 15 international CGIAR crop research centres, which study food insecurity, said.

The impending threat of global warming was discussed at two major food security summits being held in Ireland, organised by UN World Food Programme, the CGIAR Research Programme on Climate Change and the Mary Robinson Climate Justice foundation.

"We are entering an uncertain and risky period. Climate change is the game changer that increases exposure to high and volatile food prices, and increases the vulnerability of the hungry poor, especially those living in conflict zones or areas of marginal agricultural productivity.

"We must act quickly to protect the world's poorest people," Ertharin Cousin, the UN's World Food Programme director, said.