In the recent years, studies have increasingly shown that anthropogenic climate change is occurring on a global level (IPCC 2007). Main drivers of climate change are greenhouse gases, including carbon dioxide (CO2), methane (CH4), ozone (O3), nitrous oxide (N2O), and other halocarbons. These greenhouse gases have long lifetimes in the atmosphere and can disrupt the energy balance of the climate system if concentrations exceed previously observed ranges. With increasing concentration of greenhouse gases, the average global temperature is predicted to increase by several degrees by the end of the century (IPCC 2007). This increase of energy in the climate system may activate positive feedback systems that can amplify natural systems such as stronger and more frequent natural disasters, redistribution of natural resources, coastal erosion, and water scarcity.
One way to address and better understand greenhouse gas emissions is to track where and how these gases are emitted. Through the United Nations Framework Convention on Climate Change (UNFCCC), national emission inventory emerged as a tool to track anthropic greenhouse gas sources. IPCC created a methodology framework used to aggregate emissions from several main categories, including energy, forestry, agriculture, livestock, industrial processes, and product use (IPCC 2006). Though this framework can work on a national or state level, it does not help pinpoint geographical locations where emission is the highest.
Local emissions inventory can be completed on a city or metropolitan level to drive better policy decisions. Having a local greenhouse gas inventory can also help evaluate the effectiveness of previous strategies and identify new methods for greenhouse gas reduction. However, with a smaller scope, establishing a boundary for emission calculation can be difficult and often inconsistent between different local emissions inventory. The Cities for Climate Protection (CCP) established by International Council for Local Environmental Initiatives (ICLEI) created a standardized framework for greenhouse gas inventory on a local level.
In addition to driving policy decisions, a greenhouse gas inventory also has benefits in other areas of local government management. Efficiency increase can help reduce the amount of fossil fuel combustion and in turn improve the air quality of the surrounding area. The action plan also makes business sense because it can help reduce long term cost from lowered energy consumption. Furthermore, these benefits can attract community attention and improve awareness education in schools and neighborhoods.