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Proposed Costco Wholesale Redwood City GDF Expansion 7.A. - Page 146
<br /> Air Quality/Climate Change Analysis
<br /> Page 11
<br /> Global Climate Change (Greenhouse Gases)
<br /> Unlike emissions of criteria and toxic air pollutants, which have local or regional impacts,
<br /> emissions of greenhouse gases (GHGs) that contribute to global climate change have broader
<br /> impact. Global climate change is a process whereby GHGs accumulating in the atmosphere
<br /> contribute to changes in the planet's weather patterns. Although there is disagreement as to the
<br /> rate of global climate change and the extent of impacts attributable to human activities, most in
<br /> the scientific community agree that there is a direct link between increased GHG emissions and
<br /> long-term global temperature increases. The principal GHGs of concern with respect to global
<br /> climate change are carbon dioxide (COZ), methane (CH4), nitrous oxide (N20), and fluorinated
<br /> compounds. These gases allow sunlight to pass through the atmosphere, but trap a portion of
<br /> the planet's heat from escaping back out into space.
<br /> Potential implications of global warming include rising sea levels due to melting of glaciers and
<br /> polar ice caps, and adverse impacts to water supply, water quality, agriculture, forestry, and
<br /> habitats. In addition, global warming may increase electricity demand for cooling, decrease the
<br /> availability of hydroelectric power, and affect regional air quality and public health. Like most
<br /> criteria and toxic air pollutants, much of the GHG emissions come from motor vehicles. GHG
<br /> emissions can be reduced to some degree by improved coordination of land use and
<br /> transportation planning on the city, county, and subregional level, and other measures to reduce
<br /> automobile use. Energy conservation measures also can contribute to reductions in GHG
<br /> emissions.
<br /> Emissions of GHGs contributing to global climate change are attributable in large part to human
<br /> activities associated with the transportation, electricity generation, commercial/residential,
<br /> industry, and agriculture sectors. In California, the transportation, electricity generation, and
<br /> industry sectors are responsible for over 80 percent of GHG emissions (CARB, 2008, page 13).
<br /> Emissions of carbon dioxide (CO2) are byproducts of fossil fuel combustion. Methane (CH4), a
<br /> potent GHG, is largely associated with agricultural practices and landfills. Nitrous oxide (N20),
<br /> an even more potent GHG, is also largely attributable to agricultural practices and soil
<br /> management. Carbon dioxide sinks include vegetation and the ocean, which absorb COZ
<br /> through sequestration and dissolution (BAAQMD, 2011 b, page C-18).
<br /> Over the period from 2002-2004, emission sources in California emitted an annual average of
<br /> 469 million metric tons of GHGs, expressed as COZ equivalent, or COZe. Carbon dioxide is
<br /> used as a unit of ineasurement for GHGs to account for the difference in the potential to retain
<br /> infrared radiation in the atmosphere (contributing to the greenhouse effect) for different GHGs.
<br /> This potential, known as the global warming potential (GWP) of a GHG, is dependent on the
<br /> lifetime, or persistence, of the gas molecule in the atmosphere. Based on information from the
<br /> Intergovernmental Panel on Climate Change (IPCC) Second Assessment Report, CH4 has 21
<br /> times the 100-year GWP of CO2, and N20 has 310 times the 100-year GWP of COZ (The
<br /> Climate Registry—TCR, 2008, page 168). Expressing emissions in COZe accounts for the
<br /> contributions of all GHG emissions to long-term climate change as a single measurement
<br /> equivalent to the effect that would occur if only COZ was being emitted.
<br /> The California Climate Change Scoping Plan establishes a GHG emissions target level of 427
<br /> million metric tons COZe, which must be met in 2020. This will require a reduction of 169 million
<br /> metric tons COZe, or approximately a 30 percent reduction from the state's projected "business
<br /> as usual" 2020 GHG emissions forecast of 596 million metric tons COZe (CARB, 2008, page
<br /> 12).
<br /> 7/30/2012
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