Global Change refers to large-scale change in the Earth's biological, geological, hydrological, and atmospheric systems, whether of natural or human origin. Agriculture is both vulnerable to environmental change and is affecting some factors (e.g. greenhouse gas emission) that contribute to these changes. The formation of the Global Change National Program in 1998 was driven by a need to resolve uncertainty concerning the effects of large-scale environmental change, including changes in climate, composition of the atmosphere and increasing UV-B radiation, on agriculture and food security. There was a need to define the extent that agriculture contributes to large-scale environmental change, and to develop technologies for mitigating undesirable impacts of environmental change or accommodating change via adaptation. During 2002, a new cycle of research was initiated to address these issues. During May 2002, a NP 204 Planning Workshop was held in Denver, Colorado to better coordinate the efforts of ARS scientists working on aspects of Global Change. Because of the strong interdisciplinary nature of global change research, workshop participants recognized the need for periodic reviews of the state-of-the-art of global change research of relevance to agriculture. A unique feature of the Global Change National Program is the inclusion of a synthesis and analysis effort.

Short-term environmental changes at regional scales, such as seasonal drought and late freezes, have long been recognized as primary causes of variation in crop yield and livestock productivity. Addressing the likelihood that agricultural and other terrestrial ecosystems will also be affected by long-term global-scale changes, such as human impacts on the Earth's atmosphere and energy balance is now deemed necessary. At the same time, we must investigate the potential for agriculture to play a role in mitigating the factors driving environmental change, for instance by sequestering carbon.

This Accomplishment Report summarizes selected accomplishments that have resulted from the research developed to address the objectives of the 2002 Global Change Research Action Plan. These accomplishments are categorized in this report by the Program’s major components:

• Carbon and Carbon Cycle
• Trace Gases
• Agricultural Ecosystem Impacts
• Changes in Weather and the Water Cycle at Farm, Ranch, and Regional Scales

The success of the Global Change National Program in meeting goals established in its Action Plan will be assessed by a panel of outside experts. An Executive Summary of their assessment report will be published on the ARS website during 2008 and will provide a basis on which to begin planning for the next 5-year research cycle of global change topics. For the next 5-year research cycle the Global Change National Program will be merged with the Air Quality Research Program and the Soil Resource Management Research Program to form the Soil and Air Resource Management National Program.

The immediate and expected impacts of global change have become urgent concerns of citizens from all nations. The ARS Global Change Program’s vision is for a productive and profitable future for American agriculture based on a research program that correctly anticipates changes and provides the tools for producers to adapt to them. The research accomplishments reported by this report were conducted to make this vision a reality for the U.S. and the world.