Global Warming to Leave Another 500 Million or More Plagued by Water Scarcity

Global warming, even if limited to 2 degrees Celsius above pre-industrial levels, could subject some 500 million people to increased water scarcity -- a number that would rise by 50 percent if greenhouse gas emissions are not cut soon.

These were the findings of a series of new studies carried out by researchers from the Postdam Institute for Climate Research (PIK), which found that a mean global warming of 2 degrees Celsius -- a target set by the international community -- will expose an additional 8 percent of the world's population to new or increased water scarcity. An rise of 3.5 degrees Celsius, which the researchers say is likely if national emissions remain at currently pledged levels, would affect 5 percent, and an increase of 5 degrees Celsius a total of 13 percent of humanity.

Most vulnerable, according to the study, are parts of Asia and North Africa, the Mediterranean and Middle East.

"If population growth continues, by the end of our century under a business-as-usual scenario these figures would equate to well over one billion lives touched," Dieter Gerten, lead author of one of the studies, said in a statement. "And this is on top of the more than one billion people already living in water-scarce regions today."

In terms of the planet's green cover, the scientists identified even greater changes.

By systematically comparing impact models, researchers found that the area at risk of ecosystem transformation is projected to double should temperatures rise 3-to 4 degrees Celsius. An increase of 5 degrees, which they say is likely to occur in the next century if trends continue, would put nearly all ecosystems at risk of significant change.

"So despite the uncertainties, the findings clearly demonstrate that there is a large difference in the risk of global ecosystem change under a scenario of no climate change mitigation compared to one of ambitious mitigation," Sebastian Ostberg, lead author of the third study, explained.

Those regions most at risk should global warming continue unabated are the grasslands of Eastern India, shrublands of the Tibetan Plateau, the forests of Northern Canada, the Amazonian rainforest and the savannas of Ethiopia and Somalia.

Of the studies' findings, Hans Joachim Schellnhuber, one of the co-authors and director of PIK, said: "Now this is not a question of ducks and daisies, but of our unique natural heritage, the very basis of life. Therefore, greenhouse-gas emissions have to be reduced substantially, and soon."