Drought is one of the likely consequences of climate change in many regions of the world. Together with an increased demand for water resources to supply the world's growing population, it represents a potentially disastrous threat to water supplies, agriculture and food production, leading to famine and environmental degradation. Yet predicting drought is fraught with difficulty. The aim of this book is to provide a review of the historical occurrence of global drought, particularly during the twentieth century and assess the likely potential changes over the twenty-first century under climate change. This includes documentation of the occurrence and impacts of major twentieth century drought events and analysis of the contributing climatic and environmental factors that act to force, prolong and dissipate drought. Contemporary drought is placed in the context of climate variability since the last ice age, including the many severe and lengthy drought events that contributed to the demise of great civilizations, the disappearance of lakes and rivers, and the conversion of forests to deserts. The authors discuss the developing field of drought monitoring and seasonal forecasting and describe how this is vital for identifying emerging droughts and for providing timely warning to help reduce the impacts. The book provides a broad overview of large scale drought, from historic events such as the US Dust Bowl and African Sahel, and places this in the context of climate variability and change. The work is soundly based on detailed research that has looked at drought occurrence over the twentieth century, global drought monitoring, modeling and seasonal prediction, and future projections from climate models.