Human migration and social change are closely linked to changes in Earth's climate. Climate shifts have both
helped to foster the rise of civilizations and contributed to their demises. Over the last few decades, proxy records
(tree rings, sediment cores, mineral deposits, etc.) of ancient climates and past climate shifts have become
available. Studies of these records show that past periods of significant climate change often correspond to periods
of social change across remote parts of the globe. While no universally accepted definition for civilization exists,
here civilizations are defined as societies that rely on permanent infrastructure (i.e. cities, granaries and irrigation
systems) and intensive cultivation of crops for their survival, meaning that they cannot respond to climate change
simply by moving to where the weather is better nor can they readily switch to different food sources.
Human migration and social change are closely linked to changes in Earth's climate. Climate shifts have both
helped to foster the rise of civilizations and contributed to their demises. Over the last few decades, proxy records
(tree rings, sediment cores, mineral deposits, etc.) of ancient climates and past climate shifts have become
available. Studies of these records show that past periods of significant climate change often correspond to periods
of social change across remote parts of the globe. While no universally accepted definition for civilization exists,
here civilizations are defined as societies that rely on permanent infrastructure (i.e. cities, granaries and irrigation
systems) and intensive cultivation of crops for their survival, meaning that they cannot respond to climate change
simply by moving to where the weather is better nor can they readily switch to different food sources.