Statistical and Spectral Analysis of the Carbon Dioxide Variations in Terrestrial Environment

We analyse annual mean and annual growth rate measurements of the global CO2 abundances taken from the NOAA General Monitoring Laboratory (GML). The annual CO2 variations are shown to be best described by a parabolic fit with concavity up, in contrast to a linear trend often attributed to fossil-fuel emissions. Global CO2 abundance variations were shown to correlate (r = 0.60) with variations of the Global Mean Sea Level (GMSL), Oceanic Nina Index/El Nino Southern Oscillations (ONI/ENSO) (r = 0.24) and global terrestrial temperature (r = 0.82). De-trended CO2 variations show much stronger correlation with ONI/ENSO (r = 0.79). Morlet wavelet spectral analysis of CO2 abundances reveals significant periods of 21.4, 9, and 3.7 years. Similar periods appear in GMSL (21.4 and 8.5 years), ONI/ENSO (21.4, shared 21.4-year period indicates influence from cyclic variations in solar magnetic activity (double solar cycle). The 9-year CO2 oscillation, together with the strong correlation of detrended CO2 with ONI/ENSO, links to ENSO variations spanning 4.5 - 12 years. The spectral analysis with Morlet’s wavelet of the variations of CO2 abundances reveals the natural periods of 21.4, 9 and 3.7 years. The similar periods are derived for the variations of GMSL (21.4, and 8.5 years), ONI/ENSO index (21.4, 12 and 4.5 years) and the GLB terrestrial temperature (21.4, 8.36 and 3.75 years). The presence of a common period of 21.4 years indicates that all the datasets are affected by cyclic variations of the solar magnetic activity in a double solar cycle. The measured CO2 oscillations with a period of 9 years combined with the correlation of the de-trended CO2 abundances can be linked to the ONI/ENSO variations ranging within the periods of 4.5 and 12 years. Cross-correlation analysis shows a time lag of approximately one year in variations of the global CO2 abundance relative to the global terrestrial temperature. Wavelet coherence analysis confirms a time lag of 1.2 - 1.8 years for the global CO2 abundance to fall behind the temperature during most temporal intervals. These results indicate that global CO2 variations follow temperature variations rather than driving them.