Climate change is likely to put 40 per cent more people worldwide at risk of absolute water scarcity, but parts of India and China may actually see increase in availability of water, a new study has found.
Today, between one and two people out of a hundred live in countries with absolute water scarcity, researchers said.
Population growth and climate change combined would increase this to about ten in a hundred at roughly 3 degrees global warming, they said.
Climate change due to unabated greenhouse-gas emissions within our century is likely to put 40 per cent more people at risk of absolute water scarcity than would be without climate change, according to a study published in the journal Proceedings of the National Academy of Sciences.
"The steepest increase of global water scarcity might happen between 2 and 3 degrees global warming above pre-industrial levels, and this is something to be experienced within the next few decades unless emissions get cut soon," said lead-author Jacob Schewe of the Potsdam Institute for Climate Impact Research.
"It is well-known that water scarcity increases, but our study is the first to quantify the relative share that climate change has in that, compared to - and adding to - the increase that is simply due to population growth," said Schewe.
Absolute water scarcity is defined as less than 500 cubic meters available per year and person - a level requiring extremely efficient water use techniques and management in order to be sufficient, which in many countries are not in place.
For a comparison, the global average water consumption per person and year is roughly 1200 cubic meters, and significantly more in many industrialised countries.
As climate change is not uniform across the world, the regional differences of its impacts on water availability are huge, researchers said.
For example, the Mediterranean, Middle East, the southern US, and southern China will very probably see a pronounced decrease of available water, according to the study.
Southern India, western China and parts of Eastern Africa might see substantial increases, it found.
The study is based on a comprehensive set of eleven global hydrological models, forced by five global climate models - a simulation ensemble of unprecedented size which was produced in collaboration by many research groups from around the world.
