2. Purpose Statement
The purpose of this research paper is to examine the link between climate change
and drought conditions in the Southwestern United States, to include the states of Texas,
Oklahoma, New Mexico and Arizona. Understanding how drought conditions may worsen
with changes to precipitation and temperatures is useful in developing drought mitigation
plans designed to lessen the impact of prolonged droughts on individuals and communities.
The term drought is difficult to define. For the purposes of this paper, drought will be
broken down into several categories as outlined by the National Climatic Data Center
(2011): meteorological drought occurs when a pattern of dry weather dominates an area;
hydrological drought typically occurs when low levels in the water supply become
noticeable; and agricultural drought occurs when crops are impacted due to dry conditions.
The quantitative research method will be employed to gather statistical data from a
number of databases and other resources to establish a correlation between changes in
precipitation and temperature levels, and the severity and duration of drought in the
Southwest.
Problem Statement
This study will examine the relationship between climate change and drought
conditions in the Southwest United States, so that we may better understand the future
impact rising temperatures and decreasing precipitation will have on the severity and
duration of drought in this region.
Three questions that will help guide this research are as follows: how have drought
conditions in the Southwest changed from the previous century? How are rising
temperatures and falling precipitation levels affecting the duration and severity of drought?
What will future drought conditions look like as climactic patterns continue to change?
Theoretical Framework
Susan Hassol (2009) examines the impact of global climate change on the various
regions of the United States. She states that recent rises in temperatures in the Southwest
3. have been among the worst and most rapid in the United States, and goes on to say that
future climate change projections indicate warming in the region will continue with much
large increases seen in under higher emissions scenarios. Hassol further concludes that
summertime temperatures in the Southwest will continue to rise, resulting in more severe
droughts.
MacDonald (2010) examined the effects of drought in the southwestern United
States, and the potential effects this region may experience if there is an increase in the
severity and frequency of drought conditions. MacDonald also found that climate models
indicate the 21st century will be more arid, thus resulting in longer and more severe
droughts in the Southwest. He goes on to conclude that the Southwest is unlikely to
experience prolonged periods of moist conditions similar to that of the 20th century due to
an increase in global temperatures.
Seager et al. (2007) examines nineteen varying climate change models to conclude
that Southwestern North America (including the Southwest United States) is on track to
become increasing dry and arid. Additionally, Seager et al. states "the levels of aridity of the
recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new
climatology of the American Southwest within a time frame of years to decades" (p. 1181).
Seager and Vecchi (2010), after analyzing 15 coupled climate models, conclude that
the climate of Southwestern North America (including those states located in the Southwest
United States) will dry throughout the 21st century as a consequence of rising greenhouse
gases. They go on to explain that this regional drying is part of a series of larger climatic
changes including a drying of the subtropics; the pole-ward expansion of subtropical dry
zones; and a reduction in winter-season precipitation levels due to a shift in winter storm
tracks. They conclude that it is unlikely the Southwest will experience moist conditions such
as was seen in the 20th century, and further warn that dry conditions in the region could
intensify even more in the event of La Niña-like conditions.
4. Strzepek, Yohe, Neumann, and Boehlert (2010) analyzed the effects of climate
change on the frequency and severity of drought across the United States by applying two
separate indices to twenty-two IPCC (Intergovernmental Panel on Climate Change)
circulation models under three differing emissions scenarios. Results from the study indicate
that the frequency and severity of drought in the United States will vary by region, with the
Southwestern states being particularly hard hit. They also found that climate change is
likely to increase the length of drought conditions, causing otherwise mild droughts to
become severe or even extreme.
Hypothesis
Climate change increases drought conditions in the Southwestern United States.
Significance of Study
Current drought conditions in the Southwest United States provides a preview of
what the region may experience as global temperatures continue to rise due to climate
change. The effects of severe and prolonged drought conditions have a detrimental impact
on agricultural output; lead to water supply problems; increase the likelihood of severe
fires; cause erosion issues due to changes in precipitation patterns; and negatively impact
native plant and animal species.
Understanding the likelihood for future droughts, as well as how severe those
droughts may be, can help ease its impacts by allowing individuals and governments to take
appropriate actions prior to the onset of drought (NOAA, 2001).
5. Research Design and Implementation
The units of analysis for this research projec t are climate change, drought, and
Southwestern United States.
Theoretical definitions.
Climate Change. Climate change is defined by the U.S. Environmental Protection
Agency [EPA] (2011) as referring to any significant changes in climate, such as
temperature, precipitation or wind that lasts for a prolonged or extended period of time.
Additionally, the causes of climate change as stated by the EPA (2011) are due to a number
of different variables including natural factors, natural processes and human act ivities.
Drought. The term drought incorporates several definitions depending on the type
of drought being discussed. This paper will depict drought as a combination of the following
terms as defined by the National Oceanic and Atmospheric Administration's National
Climatic Data Center (2011), and will differentiate between the terms as necessary:
Meteorological drought. Occurs when a pattern of dry weather dominates an area.
Hydrological drought. Typically occurs after prolonged instances of meteorological
drought, when low levels in the water supply (groundwater, reservoirs, streams and rivers)
become noticeable.
Agricultural drought. Occurs when crops are impacted due to dry conditions.
Southwest United States. There are many different definitions regarding the
boundaries of this region, depending upon which government agency is being cited. For the
purposes of this paper, Southwestern United States will refer to the following states as
established by the U.S. Fish and Wildlife Service (2011): Texas, Oklahoma, New Mexico,
and Arizona.
Relation between Variables
Drought is the result of dry conditions that last an extended period of time (NOAA,
2011). As climate change includes significant alterations in temperature and precipitation
(EPA, 2011), it can be theorized that as the climate continues to warm, the severity of the
6. drought conditions -- especially in drought prone regions such as the Southwestern United
States (Williams, 2011) -- will become significantly worse.
Methodology
This study will use the quantitative research methodology to prove the validity of the
hypothesis. Data and statistical information will be collected from a number of databases
including the U.S. Drought Monitor; the Drought Impact Reporter; the National Oceanic and
Atmospheric Administration's National Climatic Data Center; the National Drought Mitigation
Center; and the Climate Center for the Southwest. The data collected will include average
annual precipitation levels; mean annual temperatures; and historical and current drought
conditions.
Data Analysis
Data analysis will focus on establishing a correlation between drought
duration/severity and changes to temperature and precipitation levels in the region. For
near term drought forecasting, the Palmer Drought Index will be used to calculate the
probabilities of drought intensity based on historical weather data. Long-term drought
predications will be made by analyzing data presented by the U.S. Global Change Research
Program.
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