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"Dendrochronologists have shown that tree-ring data produce a remarkably accurate history of droughts and other climate changes. Combined with reliable drought indices and historical descriptions of climate conditions, dendrochronology - the technique of dating events and environmental change by relying on characteristic patterns of tree-ring growth - can provide a climate perspective on important events such as large-scale human migration and even the rise and fall of entire civilizations."

essays in this book reflect pioneering efforts to study the global movement of ideas and institutions. They deal with topics of significant contemporary importance: initiatives to address the AIDS epidemic in East Africa; to protect the peoples and ecosystems of the Amazon; to advance the "truth and reconciliation" process in South Africa and in other areas of great conflict; to promote "civil society" in Eastern Europe and Central Asia; to advocate for environmental protection in the United States, Great Britain, Germany, and Japan; and to spread Rotary Clubs and encourage "social entrepreneurship" throughout the world. These essays highlight a wide range of research, paying close attention to the realities of particular situations and to current thinking about general processes.

In the first study of its kind, researchers have linked a natural global climate cycle to periodic increases in warfare. The arrival of El Niño, which every three to seven years boosts temperatures and cuts rainfall, doubles the risk of civil wars across 90 affected tropical countries, and may help account for a fifth of worldwide conflicts during the past half-century, say the authors. The paper, written by an interdisciplinary team at Columbia University's Earth Institute, appears in the current issue of the leading scientific journal Nature.

In what is starting to become a familiar theme, researchers have speculated on what types of observational data from distant planetary systems might indicate the presence of an alien civilization, in this case asteroid mining - but end up concluding that most of the effects of such activity would be difficult to distinguish from natural phenomena.

Purdue University civil engineers are working with the Indiana Department of Transportation (INDOT) to perfect the use of recycled concrete for highway construction, a strategy that could reduce material costs by as much as 20 percent.