gases such as hydrochlorofluorocarbon-22, a refrigerant fluid, such lifetimes can be reasonably determined (for CH4 it is about 12 years, for N2O about 110 years and for HCFC-22 about 12 years). A lifetime for CO2 cannot be defined (IPCC, 2007).
Pages 4.F-3, 4 OSEC-174 [See page 5-329 for the original comment] REVISE the text in five locations of pages 4.F-3 and 4.F-4 to add the term “metric” in the discussion of global, U.S., state and regional GHG inventory estimates, as follows:
Worldwide emissions of GHGs in 2004 were 30 billion metric tons of CO2e per year (UNFCCC, 2012).
In 2009, the United States emitted about 6.7 billion metric tons of CO2e or about 21 metric tons per year per person. Of the four major sectors nationwide -- residential, commercial, industrial, and transportation -- transportation accounts for the highest fraction of GHG emissions (approximately 33 percent); these emissions are entirely generated from direct fossil fuel combustion (U.S. EPA, 2011).
In 2004, California emitted approximately 550 million metric tons of CO2e, or about 6 percent of the U.S. emissions.
In the San Francisco Bay Area, the transportation sector and industrial/commercial sector represent the largest sources of GHG emissions, accounting for 36.4 percent each of the Bay Area’s 95.8 million metric tons of CO2e in 2007.
Page 4.F-6 OSEC-176 [See page 5-329 for the original comment] ADD the following text after the two bullet points regarding the endangerment finding:
In making the endangerment finding, the Administrator considered how elevated concentrations of the well-mixed greenhouse gases and associated climate change affect public health by evaluating the risks associated with changes in air quality, increases in temperatures, changes in extreme weather events, increases in food- and water-borne pathogens, and changes in aeroallergens. It was determined that the evidence concerning adverse air quality impacts provides strong and clear support for an endangerment finding. Increases in ambient ozone are expected to occur over broad areas of the country, and they are expected to increase serious adverse health effects in large population areas that are and may continue to be in nonattainment. (Federal Register, Volume 74 No. 239, 2009).
Page 4.F-18 OSEC-182 [See page 5-329 for the original comment] REVISE Table 4.F-2 to reflect the recalculations and add the missing parenthesis bracket as follows: