A graph of carbon dioxide levels in the atmosphere from the year 1000 to the present shows that CO2 has risen steadily since the 1800s due to human activities of fossil fuel burning and land use changes, and the upward trend is accelerating. The measurements are from two sources: air trapped inside ice cores, and direct measurements of the atmosphere (taken from the Hawaiian peak Mauna Loa) since the late 1950s. (Figure courtesy of Scott Doney, Woods Hole Oceanographic Institution)[back]
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