Burning fossil fuels contributes most to global oxygen drop. It is estimated that the world’s oxygen concentration will drop from its current level of 20.946 percent to 20.825 percent as the annual atmospheric oxygen consumption increases sharply to 100 billion tonnes by 2100.

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Burning fossil fuels contributes most to global oxygen drop. It is estimated that the world’s oxygen concentration will drop from its current level of 20.946 percent to 20.825 percent as the annual atmospheric oxygen consumption increases sharply to 100 billion tonnes by 2100.