The National Academy of Sciences is helping facilitate the increased involvement of scientists in answering questions related to climate, energy, and environmental change. The goal is both to advance scientific understanding of global climate and other environmental and disaster-related phenomena, and consider the implications for both fundamental scientific understanding and national security.This particular study will review current methods and propose improved methods for estimating and verifying greenhouse gas emissions at different spatial (e.g., national, regional, global) and temporal (e.g., annual, decadal) scales. The greenhouse gases to be considered are carbon dioxide, chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), nitrous oxide, methane, and perfluorinated hydrocarbons (PFCs). Emissions of soot and sulfur compounds along with precursors of tropospheric ozone may also be considered. The results would be useful for a variety of applications, including carbon trading, setting emissions reduction targets, and monitoring and verifying international treaties on climate change.The approximate start date is October 1, 2008.A report will be issued at the end of the project.(June 8, 2009) A letter report on the Orbiting Carbon Observatory will be issued in summer 2009, preparatory to issuance of the final report.