Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded 300 parts per million. Today, carbon dioxide levels have exceeded 410 parts per million.
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Between 400,000 years ago until 1950, the levels of carbon dioxide in the atmosphere never exceeded (answer here options: 100, 200, 300, 400 ) parts per million. Today, carbon dioxide levels have exceeded (answer here Options: 300, 410, 500, 550) parts per million.
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