Top-down and bottom-up approaches to greenhouse gas inventory methods—a comparison between national- and forest-scale reporting methods

Abstract

Federal agencies are mandated to measure, manage, and reduce greenhouse gas (GHG) emissions. The General Services Administration (GSA) Carbon Footprint Tool (CFT) is an online tool built to utilize measured GHG inventories to help Forest Service units streamline reporting and make informed decisions about operational efficiency. In fiscal year 2013, the Forest Service Sustainable Operations GHG Tracking Team completed GHG inventories of three Forest Service units to compare top-down (national) and bottom-up (local) inventory reporting approaches. In this report, the Track to Zero Team (formerly the GHG Tracking Team) and Sustainability Science Team summarize the top-down and bottom-up approaches to GHG inventories collected and data input into the GSA CFT for the three pilot units: the Northern Research Station Institute for Applied Ecosystem Studies, (Rhinelander, Wisconsin, location), the Stevensville Ranger District (Bitterroot National Forest, Stevensville, Montana), and the Tongass National Forest (Alaska). Because both top-down and bottom-up reporting methods and the scale of the three pilot units differ significantly enough to preclude quantitative analysis, this report will use qualitative analysis to compare (1) sources and methods of obtaining information, (2) ease of data access to GHG inventories, (3) level of accuracy of data within the inventories, (4) confidence in data accuracy, and (5) level of data aggregation. By conducting these pilots and comparing the top-down results from the national GHG inventory with the bottom-up or local results, we will identify methods to improve the accuracy of local GHG inventorying and tracking, strengthen the connection between local and national GHG inventories, and promote information sharing.