With the northern hemisphere having moved into fall, the annual cyclical upswing in atmospheric CO2 has begun. Key numbers relating to the National Oceanic and Atmospheric Administration (NOAA)’s release of the October 2013 mean monthly CO2 concentration are as follows:
- October 2013 = 396.66 ppm, +2.55 ppm year-on-year
- Twelve Month Average = 396.1 ppm, +2.69 ppm year-on-year
- Twelve month average over pre–industrial level = +41.5%
Atmospheric CO2 concentration is the world’s leading risk indicator. Every month, the National Oceanic and Atmospheric Administration (NOAA), a U.S. government federal agency, releases data on the concentration of atmospheric CO2 as measured by the Mauna Loa Observatory in Hawaii. The official NOAA CO2 data source can be found here.
This is the longest continuous monthly measurement of CO2 and dates back to March 1958, when 315.71 parts per million (ppm) of CO2 was recorded. The Intergovernmental Panel on Climate Change (IPCC) uses the year 1750 as the pre-industrialisation reference point, at which date the atmospheric concentration of CO2 was approximately 280 ppm according to ice core measurements.
Atmospheric CO2 displays annual seasonality: concentrations decline from the spring during the growing phase of terrestrial vegetation and rise in the autumn as vegetation dies and decomposes. The cycle is dominated by the northern hemisphere growing season since the northern hemisphere contains over 65% of the globe’s land mass. The cyclical pattern can be seen in the following chart (red line). The black line is the adjustment for seasonality.
Risk and Well-Being 