The Famine Early Warning Systems Network (FEWS NET) is a decision support system sponsored by the Office of Food for Peace of the U.S. Agency for International Development (USAID), which distributes around two billion dollars of food aid to 40+ countries each year. FEWS NET identifies the times and places where aid is required by the most food insecure populations of the developing world. USGS has been a FEWS NET implementing partner since the beginning, contributing expertise in satellite remote sensing, modeling, GIS, and climate analyses. Drought and famine in the Horn of Africa point up the vulnerability to climate shocks of people living with poverty, conflict, and weak institutions. This is especially so for pastoralist and subsistence farming livelihoods, which are highly climate-sensitive. Consequently, climate monitoring is as important to famine early warning as tracking market food prices and nutrition/mortality surveys. FEWS NET has been monito ring growing conditions since its inception in 1985. Because station networks are sparse in the countries of concern, FEWS NET has a tradition of reliance on satellite remote sensing of vegetation and rainfall. During the 1990s, seasonal forecasts were integrated into preparation of 3-6 month food security outlooks, and in the 2000s the importance of climate change has been recognized through detailed analyses of observed climate trends, diagnostic ocean-atmosphere studies, and interpretations of GCM scenarios. The case of the Horn of Africa in 2010-2011 demonstrates how FEWS NET's understanding of livelihoods and climate (locally and globally) made possible early warning months before the crisis, and enabled pre-positioning of food and supplies in the region. In spite of these efforts, conditions overwhelmed the capacity of humanitarian organizations to provide food aid, driving home the lesson that long term disaster reduction lies with political stability, development, and climate change adaptation, rather than emergency response.