Global warming, as a result of increasing C02 and other greenhouse gases in the atmosphere, has been hypothesized for many years. The precise role of land use in this scenario, though widely recognized as important, remains largely unknown. One compelling question is "How will the balance of carbon in the terrestrial ecosystem change in response to a variety of land use practices?" We describe a study in which methodology is being developed to help narrow this uncertainty for a major terrestrial carbon pool, the temperate forests of the Pacific Northwest region of the United States. In this study we are further developing a carbon storage model that responds to forest harvesting, the dominant usage of land in the region. By linking the carbon model to satellite imagery and a climate simulation model, we are estimating the current amount of carbon stored in the forests of the Pacific Northwest. The archive of LANDSAT Multispectral Scanner (MSS) images permits a twenty year historical perspective of land use changes in the region. With these data we are assessing the recent historical impacts of regional land use on forest carbon stores.