According to a leading German climate study institute climate change will increase the number of people at risk of absolute water scarcity by 40 per cent this century.
Ten people in 100 will have less than 500 cubic metres of water available a year, up from one to two people today, should Earth warm by three degrees Celsius above pre-industrial levels and populations grow.
Bloomberg newsagency reports that assessment was made by the Potsdam Institute for Climate Impact Research (PIK).
According to PIK, which cited its and other analysts, the global average is about 1200 cubic metres, and much greater in industrialised nations.
“Water scarcity is a major threat for human development as for instance food security in many regions depends on irrigation,” said Professor Qiuhong Tang of the Chinese Academy of Sciences, who co-wrote the study.
“Agriculture is the main water user worldwide,” Professor Tang said.
As the world warms, the southern United States, Mediterranean, Middle East and southern China probably will see lower water availability as southern India, western China and parts of East Africa may experience substantial increases, PIK said.
About 1.3 billion of Earth’s seven billion people already live in water-scarce regions, PIK said in October.
With greenhouse gas emissions at a record, the United Nations said the world is on track to surpass a two-degree Celsius temperature increase by 2100.
Such a rise would raise sea levels and trigger more violent storms.
More precipitation “may cause water-logging, flooding and malfunctioning or failure of water-related infrastructure,” Professor Tang said.
“So the overall risks are growing.”
Research institutes from around the world conducted the study based on an analysis of 11 global hydrological models, PIK said.
