... climate changes. Many glacial advances and retreats have occurred during the last billion years of Earth history. Large, important glaciations occurred during the late Proterozoic (between about800 and 600 million years ago), during the Pennsylvanian and Permian (between about 350 and 250 million years ago), and the late Neogene to Quaternary (the last 4 million years). Somewhat less extensive glaciations occurred during ... These ice cores are a unique record of what has happened to the weather, for the last hundred thousand years. Oxygen Isotopes analysed in the ice showed that during...

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