Conserving Freshwater and Coastal Resources in a Changing Climate

Climate Change Overview
CHAPTER
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The Earth’s climate has changed, is changing, and
will continue to change during the twenty-first
century. Average global air and ocean temperatures
have warmed, precipitation has increased in some
areas while droughts have flourished in others, and
intense weather events occur more frequently (Alley,
2007). The broadly accepted consensus among scientists
is that these changes are occurring at a rate and to
an extent significantly exacerbated by human activities,
specifically the combustion of fossil fuels and changes
in land-use, and that these changes are projected to
continue. This global phenomenon presents a new and
different threat to the conservation of the Earth’s biodiversity.
Natural concentrations of heat-trapping gases, such
as carbon dioxide (CO2) and methane (CH4), occur in
our atmosphere. These gases absorb infrared radiation
and limit its escape from Earth, much like the trapping
of heat within a greenhouse, maintaining the planet’s
surface temperature to make life as we know it possible
(Schneider, 2002). However, human actions are leading
to an accelerated change in our planet’s climate. For the
past two centuries, the burning of fossil fuels such as
coal, oil, and natural gas has propelled industrialization,
has heated and lighted our buildings, powered our businesses
and factories, and fueled our transportation. This
burning of fossil fuels has also released greenhouse gases
in quantities resulting in atmospheric concentration
of these gases beyond any in recorded history.
Current Global Impacts of Climate Change
The Intergovernmental Panel on Climate Change has
reported that global average surface temperature has
warmed by 1.3°F (0.74° C) over the past century. During
this period, sea level is estimated to have risen 0.17 mm/
year and the rate of rise is increasing. Since the 1970’s,
the world has seen droughts of increased severity
and length that spread across wider geographic areas.
Subsequent observations of changed wind patterns and
decreased snow pack and snow cover have also been
made. The frequency of heavy precipitation events has
increased (Alley, 2007).
Models, Scenarios, and Mitigation
These trends are expected to continue. Scientists from
around the world have produced projections of the effects
of climate change based on sophisticated climate
models. Various models exist, the most complex of
which are known as general circulation models (GCMs).
These models analyze climate events by dividing the
surface of the Earth into a grid composed of threedimensional
cells that measure a few degrees of latitude
and longitude per side (Schneider, 2002). These models
are useful in analyzing climatic events on a global
scale; unfortunately, the basic unit is roughly the size
of a small country such as Belgium, making regional
projections more difficult. The accuracy of modeling
technology continues to improve and regional accuracy
can be enhanced by aggregating outputs from a number
of different models (Environmental Protection Agency
[EPA], n.d.).
Climate modelers use various future greenhouse
gas emissions scenarios to create a range of outputs.
These scenarios are based upon the different possible
levels of human-induced greenhouse gas emission
levels due to varying expectations of population change,
development, and, most importantly, an increase or
reduction in emissions.
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Conserving Freshwater and Coastal Resources in a Changing Climate