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Carbon dioxide (CO2) level in the Earth’s atmosphere

Dear Tom,
I just heard that carbon dioxide reached a record high amount in the atmosphere. What is that amount and what does it mean for our weather?
Sandra Oliff, Omaha, Nebraska
Dear Sandra,
You are correct that the carbon dioxide (CO2) level in the Earth’s atmosphere reached a concentration of 415 parts per million (meaning 415 molecules of CO2exist in the atmosphere out of every 1,000,000 molecules). The concentration has increased from 400 parts per million in 2013, and the increase continues. CO2 is a “greenhouse gas” in the sense that it retards the escape of heat from the Earth’s surface into space and thus it is responsible (along with some other gases in the atmosphere) for keeping the atmosphere warmer that it would otherwise be. The problem is that as atmospheric CO2 content continues to increase, the Earth’s atmosphere itself is warming.

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