Measurement Note: An Adjustment to the Record


On Nov. 5, 2015, we made an adjustment to the Scripps Mauna Loa CO2 record that has the effect of increasing concentrations we have reported since April 2015 by 0.4 parts per million (ppm).  We made the adjustment after comparing our short-term calibration gases with the long-term calibration gases, concentrations of which have been determined manometrically.  Comparing short- and long-term calibration gases is a normal part of the strategy for maintaining reliable long-term measurements.  The adjustment increases the likelihood that concentrations will remain above 400 ppm permanently after 2015.

– Ralph Keeling

3 thoughts on “Measurement Note: An Adjustment to the Record”

  1. Can you please tell us when were the last two previous adjustments were made to the measurements and what were their impacts?
    I am specifically talking about adjustments similar to the one made on 5th November 2015.

  2. Is there any data that permits determination of whether the 10-YEAR MEAN FOR co2 sampled at Mauna Loa is statistically the same as the same 10-yr mean for CO2 sampled at Antarctica during the same period.. It does not seem a trivial matter to accurately compare samples of non-ideal gases obtained at different altitudes, temperature and water vapor content. (I realize the data is always for mole fraction in dry air.) I am always a bit suspicious of comparisons between samples that are not comparable without a lot of corrections.

    The goal is global determination of CO2. Unless CO2 is known to be everywhere the same, and of course we know it isn’t, it seems the Mauna Loa data is only good for telling us how CO2 is changing with time near Mauna Loa. Are we to assume it is changing the same amount with time in Antarctica? I understand that there was agreement between core samples and air samples for samples that overlapped in time. But were these core and air samples collected at the same or different locations? What was/were the location(s)?

    For core samples going back hundreds of thousands of years, how is the data corrected for CO2 diffusion? Is the diffusion coefficient for CO2 in ice known as a function of temperature and pressure? I doubt it was known by the early core investigators. They surely must have assumed that it is negligible. While the diffusion of gas through a solid would usually be extremely slow, I don’t think it is safe to ignore diffusion of CO2 in ice if we are talking about very old core samples. It seems that in the core data, unless corrected for, diffusion is going to reduce the peak concentration and enhance the valley concentrations.

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