Washington: A new study has found that global warming resulting from unabated greenhouse-gas emissions is likelier to put 40 percent more people at risk of absolute water scarcity within the century than would be without it.
Lead-author Jacob Schewe of the Potsdam Institute for Climate Impact Research said that 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.
Today, between one and two people out of a hundred live in countries with absolute water scarcity. Population growth and climate change combined would increase this to about ten in a hundred at roughly 3 degrees global warming.
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.
Co-author Qiuhong Tang of the Chinese Academy of Sciences said that water scarcity is a major threat for human development, as for instance food security in many regions depends on irrigation - agriculture is the main water user worldwide.
Moreover, many industrial production processes require large amounts of water, so a lack thereof in some regions hampers economical development.
This 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.
Hence, the findings synthesize the current knowledge about climate change impacts on water availability. The cooperative ISI-MIP process systematically compares the results of the various computer simulations to see where they agree and where they don`t.
The results quoted above represent the multi-model average, so some of the models indicated even greater increases of water scarcity.
The multi-model assessment is unique in that it gives us a good measure of uncertainties in future impacts of climate change, which in turn allows us to understand which findings are most robust, co-author Pavel Kabat of the International Institute for Applied Systems Analysis said.
From a risk management perspective, it becomes very clear that, if human-made climate change continues, we are putting at risk the very basis of life for millions of people, even according to the more optimistic scenarios and models, Kabat added.
The study will be published in a special issue of the Proceedings of the National Academy of Sciences.