Percentage of fossil fuel CO₂ emissions that remain in the atmosphere, about 55%. Carbon dioxide mixing ratio measurements have been taken in Hawaii since 1958 by the research group of Charles David Keeling (1928-2005), a project initiated with support from Roger Revelle at Scripps Oceanographic Institute and Harry Wexler at the U. S. Weather Service. These data demonstrated that atmospheric carbon dioxide gas concentrations were increasing in the atmosphere and not just being absorbed by the ocean and plants. Atmospheric carbon dioxide gas phase concentration is lower during the spring when plants take up carbon dioxide and higher in the winter when the majority of plants are conserving energy, growing slower, and fallen plants are decaying and thus causing a rising fluctuation of carbon dioxide.