Many chemicals in the atmosphere act as greenhouse gases because they absorb infrared radiation and trap heat in the atmosphere. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide and ozone. Some human activities also generate greenhouse gases such as electricity and natural gas consumption, vehicle travel, manufacturing and agricultural practices.
PAG staff conducted GHG community and government operation inventories for eastern Pima County (which includes Tucson), the City of Tucson, as well as several of the smaller jurisdictions within eastern Pima County. The results of the various inventories revealed similar trends and emission sources. Energy use and transportation were the major sources of GHG emissions in each jurisdiction and emission increases tracked population growth.
Eastern Pima County GHG Emissions Inventory Summary
From 1990 to 2008, GHG emissions in eastern Pima County increased by 47 percent, which closely tracks the region's 51 percent population growth over this same period. In 2008, the County produced 14.9 million metric tons of GHG emissions, showing little change from the 2007 level. Almost two-thirds of the GHG emissions can be attributed to energy use by the residential, commercial and industrial (RCI) sectors. Of these energy use emissions, 90 percent are generated by electricity consumption.
The remaining third of the emissions are from transportation, 99 percent of which is produced by private and commercial vehicle use.
Eastern Pima County's GHG Emission Trends: 1990 - 2008
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Eastern Pima County's 2008 GHG Emissions by Sector
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City of Tucson GHG Emissions Inventory Summary
From 1990 to 2008, Tucson’s emissions grew by 28 percent with a concurrent 34 percent rise in population. In 2008, the City generated 6.9 million metric tons of CO2e, slightly less than half of the County’s emissions, and a 5 percent decline from the 2007 level. As in the County inventory, RCI energy use (63 percent) and transportation (34 percent) were the major sources of GHG emissions.
City of Tucson's GHG Emission Trends: 1990 - 2008
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County and City per capita GHG emissions remained low compared to national averages. According to EPA, U.S. per capita 2008 GHG emissions were 22.9 metric tons, while PAG’s results showed County and City per capita emissions were 15 and 13 metric tons, respectively. |