Climate change and atmospheric oxygen
Current climate change is slowly reducing the amount of oxygen in the air.
Billions of tonnes of carbon have been released from fossil fuels - coal, oil, and gas.
The carbon joins up with atmospheric oxygen when it burns.
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Each carbon atom joins with two oxygen atoms to make carbon dioxide.
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Several scientific organisations measure the gases in the air.
One major set of measurements are from a laboratory in Hawaii.
This is all extra evidence that extra carbon dioxide in the air comes from burning fossil fuels.