The world's climate have changed naturally throughout history. For example, much of Europe and parts of Africa where covered by ice 100,000 years during the last ICC age which ended 10,000 ers ago.In recent times, scientists have become concerned that human activities, such as burning fossil fuels, are producing green house gases such as carbon dioxide, and these are causing global warming. The effects include ocean currents altering, ice sheets melting, sea levels rising by 3mm a year, and more severe weather, such as cyclones and floods becoming more common.

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