The rate of growth in carbon dioxide concentrations in the atmosphere has accelerated since the beginnings of the Keeling Curve.  The rate has gone from about 0.75 parts per million (ppm)/yr in 1959 to about 2.25ppm/yr today. The attached graphic is from the Intergovernmental Panel on Climate Change Fifth Assessment Report and is based on data gathered by the Scripps CO2 Group and NOAA. The lower image shows the growth rate versus time, which has consistently stayed in positive territory since the late 1950s. No surprise here, because Mauna Loa record shows a clear rise from year to year. But this plot also shows that the growth rate (while staying positive) does vary quite a bit from year to year, something that is less evident in the Mauna Loa record. These variations are due to a combination of natural and human factors.