A new study projects that hundreds of millions of people will soon live in regions at an increased risk of water scarcity, even if the average global temperature rise is limited to 2 degrees Celsius, the cap cited in several U.N. agreements.
Published today in the journal Environmental Research Letters, the paper predicts that an additional 8 percent of the world's current population, or 486 million people, will be forced to cope with new or exacerbated water scarcity even if international agreements succeed in halting global mean temperature rise at 2 C.
However, if temperatures were to rise 3.5 C over preindustrial levels -- the likely trajectory under current international pledges to cut emissions, the study states -- the population forced to live in areas with greater water strain would increase to 11 percent, or 668 million people.
Lead author Dieter Gerten of the Potsdam Institute for Climate Impact Research in Germany said that in areas like southern Europe, which suffered from a severe drought in 2012, he's afraid people are unaware that "things can be more dramatic in the future than they have been."
"That is something that the climate models more or less consistently show: that the events of the past decade or so are just harbingers of things that might happen in the future if climate warming would go on," Gerten said.
Growing populations will compound scarcity
Defining water scarcity as the annual availability of less than 1,000 cubic meters of water per person, an international group of researchers analyzed 152 climate scenarios produced by 19 climate models, noting the climatic changes for a range of global average temperature increases between 1.5 C and 5 C.
The models showed that the Middle East, some parts of southern Europe, Northern Africa and portions of the American Southwest are especially vulnerable in the coming years if emissions levels continue to increase.
These areas are already generally accepted to be at risk of water shortage in a warming world, raising U.N. concerns about potential conflicts in the coming years. According to a recent report by the Worldwatch Institute, 1.2 billion people, or about a fifth of the world population, already live in areas of physical water scarcity (ClimateWire, March 22).
A projected decrease in precipitation is the main reason behind the growth of water scarcity in these regions, although higher temperatures that lead to increased water evaporation also play a role, Gerten said.
He noted that his study does not take population growth into account, a factor that could significantly worsen global water risk.
"If one superimposes the expected population growth in the future, well over 1 billion more people than today will be living in water-scarce regions," he said. "Every person more on planet Earth needs a certain amount of water, and if population grows and water resources decline, then the problems multiply in those countries."
Daniel Morris, a fellow with Resources for the Future's Center for Climate and Electricity Policy, said there was "nothing terribly surprising" about the results of the study but noted that the research provides a "better understanding of some of the sensitivities with the climate system and how much things can change with just a very small comparative change in global temperature."
Morris added that although the issue of water scarcity in the Middle East is nothing new, he was concerned about the looming vulnerabilities in Pakistan and northwestern India highlighted in the new study.
"Water scarcity could layer on top of animosities that already exist in this area," he said.
Is the energy sector threatening U.S. supplies?
Animosities over dwindling water supplies already rage in the United States, where agriculture, municipalities and the energy sector compete for limited resources.
In the Austin, Texas, area, for example, downstream rice farmers have been cut off for the second year in a row as the man-made reservoirs overseen by the Lower Colorado River Authority (LCRA) sit at 32 percent capacity as a result of one of the longest droughts in Texas history (ClimateWire, Aug. 22).
This week, the LCRA board considered cutting off water supplies to Matagorda Bay, which many consider an important wildlife refuge, prompting objections from several environmental groups.
But in addition to wildlife, rice farmers and the city of Austin, the area's energy sector also depends on large quantities of water from the LCRA's reservoirs. The South Texas Nuclear Operating Co. in Matagorda uses 40,000 acre-feet of the LCRA's water each year, more than several of the region's smaller cities.
A new report by Synapse Energy Economics Inc., backed by the environmental think tank the Civil Society Institute, advocates for U.S. policymakers to drastically reduce their support of power sources like coal, nuclear and natural gas in favor of less water-intensive power sources like wind and solar.
According to the report, thermoelectric plants withdraw more water than any other U.S. sector at 41 percent.
"On an average day, water withdrawals across the nation amount to an estimated 85 billion gallons for coal plants, 45 billion gallons for nuclear plants, and 7 billion gallons for natural gas plants," it states. "Significant amounts of water are also required for fossil fuel extraction, refining and processing, and transportation."
Moreover, the authors argue, declining availability of water resources due to climate change could threaten the reliability of these power sources.
"The same technologies that reduce water needs ... also reduce greenhouse gas emissions," said Frank Ackerman, an environmental economist with Synapse and co-author of the report. "The solutions we need for the climate crisis and the solutions that we need for the water crisis turn out to be the same."