For the first time in human history, atmospheric carbon dioxide levels passed 400 parts per million (ppm) of carbon dioxide at the historic Mauna Loa Observatory in Hawaii. This is the same location where Scripps Institution of Oceanography researcher Charles David Keeling first established the “Keeling Curve,” a famous graph showing that atmospheric carbon dioxide concentrations are increasing rapidly in the atmosphere. CO2 was around 280 ppm before the Industrial Revolution, when humans first began releasing large amounts of CO2 to the atmosphere by burning fossil fuels. On May 9, the reading was a startling 400.08 ppm for a 24-hour period. But without the help of the oceans, this number would already be much higher.