During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm repeatedly. Daily levels of CO2 can vary due to weather, and there are seasonal trends as well.
U.S. Antarctic Program
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Funded by the U.S. Government's National Science Foundation (NSF), the United States Antarctic Program (USAP) supports scientific research in Antarctica and the Southern Ocean. The USAP carries forward the Nation's goal of supporting the Antarctic Treaty, fostering cooperative research with other nations, protecting the Antarctic environment, and conserving living resources.
