new method to make better use of vast amounts of data related to global
geography, population and climate may help determine the relative
importance of population increases vs. climate change.
several recent studies suggest that much of the world is likely to
experience freshwater shortages as the population increases and
temperatures rise, determining the relative impact of each has been
difficult. An Oak Ridge National Laboratory paper published in Computers
& Geosciences outlines a process that might help.
work establishes a new method to couple geographic information system
data with global climate outputs and statistical analysis,” said ORNL’s
Esther Parish, lead author. Using this technique, researchers can now
conduct assessments that will provide information critical to
policymakers and stakeholders.
tool provides a simple method to integrate disparate climate and
population data sources and develop preliminary per capita water
availability projections at a global scale,” said Parish, a member of
the Department of Energy laboratory’s Environmental Sciences Division.
and co-authors Evan Kodra, Karsten Steinhaeuser and Auroop Ganguly
began working on this approach at ORNL in the summer of 2009. At that
time, it was unusual to integrate population, climate and water data
into one model. Although just a first step, the toolkit, which has been
made freely available, may be further developed for more involved
results of the study point to areas potentially vulnerable to water
shortages, Parish cautioned that this set of calculations is based on
just one set of ensembles from one climate model with static population
growth rates applied on a per country basis.
water stress, researchers are referring to per capita freshwater
availability of less than 450,000 gallons per person per year, but the
ways society chooses to store and allocate water will determine whether
an actual shortage exits. For example, water can be allocated for
industry, agriculture or residential use, or any combination of the
this study, the team used ORNL’s high-resolution Global LandScan
population distribution dataset in combination with population growth
projections from the Intergovernmental Panel on Climate Change. This
allowed them to estimate changes in freshwater demand by 2025, 2050 and
2100. The researchers also used the Community Climate System Model 3 to
estimate future freshwater availability during those same time periods.
Researchers then combined freshwater supply and demand projections to
yield estimates of per capita water availability around the world.
Given the number of variables, the process can quickly become unwieldy.
the interrelationship between human populations and water availability
is greatly complicated by the uncertainties associated with climate
change projections and population storylines,” said Parish, who added
that for this exploratory study population growth appears to have a
greater impact than temperature.
test the new tool, Parish and colleagues plugged in four IPCC
greenhouse gas emissions scenarios – from low to high – along with
global population projections to arrive at different potential
scenarios. None paint a promising picture for freshwater availability.
study suggests that by 2100, 56 to 75% of the world’s population could
be vulnerable to significant freshwater security threats. In areas like
the Great Lakes region, freshwater may be easier to replenish than
portions of Florida and the Southwest, but people in most areas of the
country will face challenges.
worst case combination of per capita freshwater availability indicate
that many major U.S. cities may experience some degree of water stress
by the year 2100,” Parish said.
addition, the feedback between population shifts and water resources
scarcity may exacerbate the situation. Thus, as pointed out in other
recent studies, the projected water scarcity in parts of Central and
South America may have ramifications for population movement and hence
water scarcity in the United States.
we have not considered migration as part of this paper, these are
precisely the directions we believe require further research,” Ganguly
researchers noted that while this paper outlines a proof of concept
that lends some preliminary insight to the relative importance of
climate change vs. population, output from multiple climate models must
be incorporated in future research.
investigating multiple models, we may be able to quantify—or at least
qualify—uncertainty in how different climate change scenarios could
affect water availability,” Parish said. “Given that population growth
is likely to be an even bigger factor in water availability than climate
change, it will also be critical to reassess areas of concern with
regional- or state-level population growth scenarios.”
added: “Our understanding of multiple stressors on natural resources as
well as dynamically coupled natural and human systems is critical to
address emerging concerns like urban sustainability.”
and Ganguly, both formerly of ORNL, are employed by Northeastern
University while Steinhaeuser, also formerly of ORNL, is employed by the
University of Minnesota.
for this project was provided initially by the Laboratory Directed
Research and Development program and, later, by the National Science
Source: Oak Ridge National Laboratory