Greenhouse Gas (GHG) - Several gases that absorb and emit radiation which trap heat near the earth's surface. Most can be naturally occurring and human generated.
Regional GHG Inventories and Trends
Many chemicals in the atmosphere act as greenhouse gases (GHG) because they absorb infrared radiation and trap heat. Naturally occurring GHG include water vapor, carbon dioxide, methane, nitrous oxide and ozone. In addition, some human activities, such as electricity and natural gas consumption, vehicle travel, manufacturing and agricultural practices also produce GHG including carbon dioxide, methane, nitrous oxide and fluorinated gases.
When accessing the amount of human- generated GHG, carbon dioxide equivalents (CO2e), a weighted value, is usually used. This allows the various gases to be compared based upon the relative global warming potential and their persistence in the atmosphere.
PAG conducts GHG inventories for various communities and government operations in eastern Pima County. Community inventories include GHG emissions from electricity and natural gas use, vehicle travel and waste disposal and locomotive, aircraft and industrial activities, as applicable. Results from the various community inventories show a similar trend: energy use and transportation are responsible for most GHG emissions and trends generally track population growth.
Government operations’ inventories include emissions produced by energy used in government buildings, water delivery and wastewater treatment and streetlights; vehicle emissions from government fleets and employee commuting, and from waste disposal. The results from the government inventories indicate that the energy used in buildings and in water handling are the major sources of governments’ GHG emissions.