When Americans celebrated the first Earth Day on April 22, 1970, the planet's atmosphere was markedly different than it is today. Nearly 50 years ago, scientists measured Earth's levels of carbon ...
Update April 21, 2023: Earth's atmospheric carbon dioxide levels averaged over 417 ppm in 2022, and even recently reached a daily reading of over 424 ppm. When this story first published in 2019, CO2 ...
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