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Sun Oct 13, 2019, 12:11 PM

I was mistaken about the timing and magnitude of the 2019 Mauna Loa CO2 minimum.

On September 22 I wrote the following in a post in this section:

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.

However, I was wrong, because the next two weeks at Mauna Loa showed values lower than 408.50 ppm. It actually took place this year during the week ending 09/29/19, when the reading was: 407.97

The most recent data point is the week ending October 6, 2019 is a follows:

Up-to-date weekly average CO2 at Mauna Loa
Week beginning on October 6, 2019: 408.39 ppm
Weekly value from 1 year ago: 405.50 ppm
Weekly value from 10 years ago: 384.06 ppm
Last updated: October 13, 2019

From here on out, until May, 2020, the values for each week will exceed the number reported on September 29 of this year.

Previous weekly data annual lows took place as follows over the last 5 years:

9/9/18: 405.39 ppm

9/24/17: 402.77ppm

9/25/16: 400.72ppm

9/27/2015: 397.2 ppm

9/14/2014: 394.79 ppm

No one alive today will ever see a measurement at Mauna Loa lower than 400 ppm again.

In 2000, the weekly data annual low took place on September 10, 2000: 367.08 ppm.

In 1980, the weekly data annual low took place on September 4, 1980, 339.87 ppm.

In 1975, the first year the weekly data was reported, the weekly data annual low took place on August 31, 1975 when it was 329.24 ppm.

The movement to late September is most probably a function of a warmer and longer summer in the Northern Hemisphere, during which the annual minimums take place.

The annual maxima show up in early May. We may expect that the 2020 maximum should approach or exceed 418 ppm.

I apologize for jumping the gun. It's possible that next year we'll see, for the first time ever, the minimum appearing in October.

Have a nice afternoon.

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