Nearly a third of the world's land surface may be at risk of extreme drought by the end of the century, wreaking havoc on farmland and water resources and leading to mass migrations of "environmental refugees," climate experts warned on Tuesday.

Predictions based on historical trends in rainfall and surface temperatures dating back to the 1950s reveal that regions blighted by moderate droughts are set to double by the end of the century, with tentative data suggesting areas struck by extreme droughts may soar from 1 per cent today to 30 per cent in 2100.

The most striking impact is expected in parts of southern Europe, North Africa, western Eurasia and the United States, whilst regions of Central Africa, East Asia and the high northern latitudes are due to experience wetter climates.

Researchers at the UK Met Office's Hadley Centre announced the findings at a "climate clinic" meeting of scientists.

"This is something we need to take extremely seriously. Even if droughts get only half as bad as we predict they will have a tremendous impact," said Vicky Pope, head of the centre's climate prediction programme.

Widespread droughts would bring turmoil to poorer countries where a lack of clean water already poses a health threat and farmers struggle to make parched soils productive.

Experts expressed alarm at the findings and fear a rise in droughts will force many people to search for more fertile land, leading to mass migrations of environmental refugees.

The Hadley Centre scientists, led by Eleanor Burke, looked at climate records from 1952 to 1998 and used them to define typical drought conditions for the latter half of the 20th century.

Using a climate model, they showed that in the last decade of the 20th century droughts were nearly 25 per cent more widespread than in the previous 40 years.

When the scientists altered the model to remove the warming effect of greenhouse gas emissions from human activity, they found that droughts barely changed.

"It's clear the increase in drought we've seen in the past decade or so has in part been down to human activity," said Pope.

The scientists next used the model to predict how droughts were likely to change in the coming century, assuming greenhouse gas emissions continue on an upward trend. "It amounts to a doubling of droughts," said Pope.

Uncertainties in the model mean the prediction may overstate the threat of droughts, but until further studies are done it will be impossible to know by how much, she added.

The study is due to be published at the end of the month in the Journal of Hydrometeorology.

Source: China Daily