This dataset is sourced from the US Government’s Earth System Research Laboratory (ESRL), Global Monitoring Division (GMD). The study under discussion comprises the Mauna Loa Annual Mean Growth Rate series from 1959 through 2017.
The annual mean rate of growth of CO2 in a given year is the difference in concentration between the end of December and the start of January of that year. If used as an average for the globe, it would represent the sum of all CO2 added to, and removed from, the atmosphere during the year by human activities and by natural processes. There is a small amount of month-to-month variability in the CO2 concentration that may be caused by anomalies of the winds or weather systems arriving at Mauna Loa. This variability would not be representative of the underlying trend for the northern hemisphere which Mauna Loa is intended to represent. Therefore, it is the final estimation for the annual mean growth rate of the previous year in March, by using the average of the most recent November-February months, corrected for the average seasonal cycle, as the trend value for January 1. The estimate for the annual mean growth rate (based on the Mauna Loa data) is obtained by subtracting the same four-month average centered on the previous January 1. Preliminary values for the previous year are calculated in January and in February.
The estimated uncertainty in the Mauna Loa annual mean growth rate is 0.11 ppm/yr (where ppm represents parts per million). This estimate is based on the standard deviation of the differences between monthly mean values measured independently by the Scripps Institution of Oceanography and by National Oceanic and Atmospheric Administration (NOAA)/ESRL. The annual growth rate measured at Mauna is not the same as the global growth rate, but it is quite similar. One standard deviation of the annual differences Mauna Loa Observatory (MLO) minus global is 0.26 ppm/year.