Here is the atmospheric CO2 concentration measured weekly at the Mauna Loa Observatory for the period 29 March 1958 to 28 April 2018. The Observatory is at Latitude 19.54° North, Longitude 155.57° West, Elevation 3397 metres. It is on the northern slope of Mauna Loa, an active volcano on the island of Hawai’i in the mid-North Pacific Ocean.

Polynomial fit to adjoining data strings has been used to calculate missing values in the CO2 concentration time series. The series shows the regular seasonal variation superimposed on an upward trend which gradually increases from a rate of 0.8 ppm per annum for first 12 months to 2.1 ppm per annum for the last 12 months.

The amplitude of the seasonal variation for the six years March 1958 to March 1964 was 6.4 ppm while for the six years April 2012 to April 2018, it was 8.0 ppm. The difference is statistically significant as the probability of the seasonal variations being equal was less than 5%. Thus both the rate of change in the CO2 concentration and the amplitude of the seasonal variation increased for the 60 years of measurement.

Here is the 52 week increment in the CO2 concentration after application of a low pass filter to reduce the high frequency noise and make the medium term events more obvious. The maxima in the series correspond to the occurrence of El Nino events and their coincident atmospheric temperature maxima. The filter was a simple three point moving average with weights (0.2929, 0.4142, 0.2929).

The correlation confirms the earlier proposition that the temperature level determines the rate of change of CO2 concentration seen in the monthly data for Mauna Loa Observatory, Macquarie Island station and Mt Waliguan Observatory.

Here is the amplitude spectrum for the 52 week increments in the CO2 concentration. In the light of the earlier findings this can be taken as a proxy to represent the temperature level corrected for seasonal variation:

Unfortunately this was not ideal as there were breaks in the time series that have had to be filled by interpolated values. The 3084 data points were padded with values of zero at each end to give the Fourier amplitudes for 4096 data points. Once again the greatest maximum was at a wavelength of 1303 days (42.8 months) and is considered to be the heat source for the El Nino event.

Other local amplitude maxima were at wavelengths of:-

27.18 days attributed to the Moon’s draconic period of 27.32 days,

29.17 days attributed to the Moon’s synodic period of 29.53 days,

55.6 days attributed to twice the Moon’s draconic period of 54.6 days,

82.2 days attributed to three times the Moon’s draconic period of 81.9 days,

114.2 days attributed to the synodic period of Mercury of 115.9 days,

225.8 days attributed to the sidereal period for Venus of 224.7 days,

367.6 days attributed to the sidereal period for Earth of 365.26 days,

398 days attributed to the synodic period for Jupiter of 399 days,

573 days attributed to the synodic period for Venus of 583.94 days merged with the synodic period of Mercury and Venus of 579 days,

699 days attributed to the sidereal period for Mars of 687 days,

796 days attributed to the synodic period for Mars of 779.9 days merged with the synodic period of Jupiter and the Moon of 797.8 days,

1147 days attributed to the synodic period of Mercury and Venus of 1158.8 days.

These may also relate to the periodicities resulting from the Short-term orbital forcing described in Cionco, R. G., and Soon,W. W.-H.[8]

It is notable that both the synodic and draconic periods of the Moon are apparent in the weekly series. An explanation for the synodic period is that each New Moon reduces the incoming Sun’s radiation to the Earth and its atmosphere as it passes between the Sun and the Earth. Similar temperature minima must occur when Mercury and/or Venus pass between the Sun and the Earth. The draconic period is when the Moon passes across the Earth’s elliptic relative to the Sun and thus has the greatest influence on the irradiation of the Earth.

As a number of the spectral maxima approximately correspond with orbital periods of the Moon and the planets, the results are interpreted as showing that the Sun’s irradiance of the Earth is modulated by the movement of the Moon and planets. This must cause corresponding changes in the Earth’s atmospheric temperature which, in turn, cause changes in the climate.