tions or predicting changes. A wide range of global-temperature-change
predictions exists, but they generally fall in the 0.5 to 6.0°C range. The
Intergovernmental Panel on Climate Change (IPCC) predicts a 1.4 to 5.8°C
temperature increase by 2100 relative to 1990 (IPCC 2001).
Complex interactions between systems, actions, and counteractions of the
carbon cycle and other processes make it difficult to determine exactly how
atmospheric warming will affect the Earth’s ecosystem. On the basis of our
current understanding of climate and weather, a rise in temperature worldwide and changes in temperature distribution, spatially and temporally,
will change weather and climate over large areas of the Earth. Higher
temperatures will produce more evaporation from the oceans, resulting in
increased rainfall somewhere. Higher temperatures over land will increase
evaporation of soil moisture, raise dry-soil temperatures, and melt ice. All
of these factors will combine to change the weather patterns of a particular region in both frequency and intensity of events. These variations in
weather pattern can, over time, sum to changes in regional climates in many
parts of the world (Watson et al. 2000). For example, locations of grasslands,
forests, and deserts may shift because of evolving climates.
Sea-level rise as a direct response to global warming has been an issue
that has captured considerable public attention, although there are many
other equally important possibilities that must be assessed, particularly in
considering environmental security. On the basis of scientific analysis to
date, the range of sea-level rise is predicted to be between -1 and +6 meters
(King 2000), not a particularly informative range to use in assessing impacts.
However, the factors that enter into this calculation are well defined. First,
warm water occupies a larger volume than cold water, so as ocean surface
temperatures warm because of contact with the warmer air, the volume of
the ocean will increase, resulting in a rise in sea level. The more difficult
factor to calculate is the depth change attributable to warmer air temperatures occurring in regions with snow and ice cover. Uncertainty about
whether and how much ice will melt under different warming predictions
accounts for the wide range in the sea-level-rise estimates. Using the IPCC
(1992) warming estimate as a basis for temperature rise, Houghton (1994)
predicts a 50-cm sea-level rise by the year 2100. The most detailed statistical analysis of sea rise predicts a 35-cm rise by 2100 as the most likely result,
with a 10% chance of sea rise reaching 65 cm, and a 1% chance of a 1-m
rise (Titus and Narayanan 1995). This rise, coupled with natural land
subsidence in some lowland regions, could have large impacts in several
critical areas of the world, such as Bangladesh and Egypt (Houghton 1994).
There is scientific certainty that changes in weather will affect water and
forest resources, food production, human health, weather events like floods
and other “natural disasters,” and coastal processes, all of which have peace
and security implications. The nature of these impacts is more difficult to
predict than sea-level rise. To realistically predict the impacts of global
climate change, models of future water, food, health, and disturbance
conditions need to be driven by projected climate scenarios. Table 15.1
15. Using Models for Environmental Security
293
predictions exists, but they generally fall in the 0.5 to 6.0°C range. The
Intergovernmental Panel on Climate Change (IPCC) predicts a 1.4 to 5.8°C
temperature increase by 2100 relative to 1990 (IPCC 2001).
Complex interactions between systems, actions, and counteractions of the
carbon cycle and other processes make it difficult to determine exactly how
atmospheric warming will affect the Earth’s ecosystem. On the basis of our
current understanding of climate and weather, a rise in temperature worldwide and changes in temperature distribution, spatially and temporally,
will change weather and climate over large areas of the Earth. Higher
temperatures will produce more evaporation from the oceans, resulting in
increased rainfall somewhere. Higher temperatures over land will increase
evaporation of soil moisture, raise dry-soil temperatures, and melt ice. All
of these factors will combine to change the weather patterns of a particular region in both frequency and intensity of events. These variations in
weather pattern can, over time, sum to changes in regional climates in many
parts of the world (Watson et al. 2000). For example, locations of grasslands,
forests, and deserts may shift because of evolving climates.
Sea-level rise as a direct response to global warming has been an issue
that has captured considerable public attention, although there are many
other equally important possibilities that must be assessed, particularly in
considering environmental security. On the basis of scientific analysis to
date, the range of sea-level rise is predicted to be between -1 and +6 meters
(King 2000), not a particularly informative range to use in assessing impacts.
However, the factors that enter into this calculation are well defined. First,
warm water occupies a larger volume than cold water, so as ocean surface
temperatures warm because of contact with the warmer air, the volume of
the ocean will increase, resulting in a rise in sea level. The more difficult
factor to calculate is the depth change attributable to warmer air temperatures occurring in regions with snow and ice cover. Uncertainty about
whether and how much ice will melt under different warming predictions
accounts for the wide range in the sea-level-rise estimates. Using the IPCC
(1992) warming estimate as a basis for temperature rise, Houghton (1994)
predicts a 50-cm sea-level rise by the year 2100. The most detailed statistical analysis of sea rise predicts a 35-cm rise by 2100 as the most likely result,
with a 10% chance of sea rise reaching 65 cm, and a 1% chance of a 1-m
rise (Titus and Narayanan 1995). This rise, coupled with natural land
subsidence in some lowland regions, could have large impacts in several
critical areas of the world, such as Bangladesh and Egypt (Houghton 1994).
There is scientific certainty that changes in weather will affect water and
forest resources, food production, human health, weather events like floods
and other “natural disasters,” and coastal processes, all of which have peace
and security implications. The nature of these impacts is more difficult to
predict than sea-level rise. To realistically predict the impacts of global
climate change, models of future water, food, health, and disturbance
conditions need to be driven by projected climate scenarios. Table 15.1
15. Using Models for Environmental Security
293