It's not a bug it's a feature
Conner in the comments asks about what some people, not me, Eli hastens to add, would call a Plimer
"The raw data from Mauna Loa is 'edited' by an operator who deletes what is considered poor data. Some 82% of the raw data is "edited" leaving just 18% of the raw data measurements for statistical analysis. With such savage editing of raw data, whatever trend one wants can be shown."and inquires WTF (sort of the right tude for WUWT).
Eli and Rattus Norvegicus try to be helpful, but after Capital Climate shows that this has become a rich source of denial delight, Ethon, who was getting quite hungry, decided to fly over to the Mauna Loa Observatory (MLO) and check it out. Ethon is quite fond of high aeries even if they are on scenic Pacific Islands and you have to burn a lot of liver to get there, but he does like to check it out before he goes, and lo, the big bird found a nice intro from a high school student who spent time doing science in 1994, Eleanor Foltz, who, some people, not Eli, he hastens to add, would say obviously knows more about the subject than Ian Plimer
It is well known that MLO nighttime downslope winds and daytime upslope winds do not relate well to free tropospheric wind flow in the region of the Mauna Loa massive. The regular downslope winds bring nocturnal upper level air to the observatory site that allows MLO to make background atmospheric composition measurements most days of the year.While measurement of the CO2 mixing ratio in the free troposphere is possible almost every day at MLO, one has to monitor the winds and other conditions to be sure that it is being measured. The figure to the left shows the number of days during which measurements could be made for a given number of hours. In any particular hour, not every measurement is accepted for a variety of reasons. This being the government, there is a web page which actually even a bird can find. Now, some people, not me, Eli hastens to add, might believe Ian Plimer's research was slipshod. The NOAA web page carefully explains how measurements are made and how and why readings are accepted or rejected. In addition to the meteorology (wind direction and such) this includes
- The standard deviation of minute to minute averages should be less than 0.30 ppm within a given hour.
- The hourly average should differ from the preceding hour by less than 0.25 ppm.
- In keeping with the requirement that CO2 in background air should be steady, we apply a general “outlier rejection” step, in which we fit a curve to the preliminary daily means for each day calculated from the hours surviving step 1 and 2, and not including times with upslope winds. Aell hourly averages that are further than two standard deviations, calculated for evry day, away from the fitted curve ("outliers") are rejected. This step is iterated until no more rejections occur.
Anyone who wants to look at the hourly data since 1974 is welcome. Stuff they toss is flagged.