Each year, the minimal value for carbon dioxide levels in the atmosphere for a particular year is observed in the Northern Hemisphere's early autumn, usually in September. The Mauna Loa Observatory reports weekly year to year increases for each week of the current year compared to the same week in the previous year.

This year, in 2019, as is pretty much the case for the entire 21st century, these minima are uniformly higher than the carbon dioxide minima going back to 1958, when the Mauna Loa carbon dioxide observatory first went into operation. Weekly data is available on line, however, only going back to the week of May 25, 1975, when the reading was 332.98 ppm.

For many years now, I have kept spreadsheets of the data for annual, monthly, and weekly Mauna Loa observatory data with which I can do calculations.

In the weekly case, the week ending May 12, 2019 set the all time record for such readings: 415.39 ppm.

These readings, as I often remark vary in a sinusoidal fashion, where the sine wave is imposed on a monotonically increasing more or less linear axis, not exactly linear in the sense that the slope of the line is actually rising slowly while we all wait with unwarranted patience for the bourgeois wind/solar/electric car nirvana that has not come, is not here and will not come.

This graphic from the Mauna Loa website shows this behavior:



Here is the data for the week beginning on September 15, 2019

Up-to-date weekly average CO2 at Mauna Loa

Week beginning on September 15, 2019: 408.50 ppm
Weekly value from 1 year ago: 405.67 ppm
Weekly value from 10 years ago: 384.59 ppm...

...The operative point is that this reading is only 0.09 ppm lower than last week's reading, which was, 408.59 ppm. This suggests, if one is experienced with working with such data, that this is most likely the annual September minimum reading. For the rest of this year, and through May of 2020 the readings will be rising. We will surely see next May readings around 418 ppm, if not higher.