Methane is a natural part of our world, but human activities over the past two centuries have increased its concentration in the atmosphere from a base global average of 722 ppb in 1750 to a global average of 1,823 ppb in 2015…On some days methane concentration above 2,000 ppb extends for 50 kilometres near the coal mines. We have not encountered any other landscape with elevated readings extending for kilometres, with the exception of days when there are bushfires.

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