In addition to reporting atmospheric carbon dioxide concentration, the Scripps Institute reports measurements of the concentration of oxygen (O2) in the air. Since carbon dioxide increase comes mainly from burning fossil carbon using atmospheric oxygen, as CO2 goes up, O2 goes down.

What they actually report is the ratio of oxygen to nitrogen in the air. This can be roughly converted to O2 concentration in parts per million by volume (ppmv), but there are some complications which I won’t go into. I’m just going to convert their reported O2/N2 ratio changes (in “permeg”) to O2 change (in ppmv) by a simple ratio, and ignore the complications — after all, this is just a quick look.

Without further ado, here’s what O2 has done since they started monitoring in 1989, through mid-2013 (roughly, it’s the change since about 1985), measured at the Mauna Loa atmospheric observatory in Hawaii:


Just as CO2 shows an annual cycle due to the respiration of land plants, so too does O2. We can remove that annual cycle to define de-seasonalized O2 concentration:


Let’s try something interesting. We’ll remove the linear trend from both O2 and CO2, and scale the O2 so that it “predicts” the CO2 change. For prediction, we’ll use O2 as a proxy for emissions, and suppose that the airborne fraction of the emitted CO2 (the fraction that stays in the atmosphere, rather than being absorbed by the oceans or biosphere) is 46% (a figure I estimated by regressing CO2 increase against O2 decrease). Comparing the observed CO2 change (with the linear trend removed) to the predicted CO2 change (with the linear trend removed), we get this:


I draw two conclusions from this. First, the rate of CO2 increase is accelerating (which we saw in the last post) and the rate of O2 decrease is too. Second, I don’t see any evidence for a change in the airborne fraction, because the observed CO2 change and that “predicted-from-O2” track each other so well.

This is just a cursory look, and there are plenty of complications. Nonetheless, it’s quite clear that the rate of CO2 increase is getting faster, as is the rate of O2 loss. As for those who think the CO2 rise in the atmosphere is from something other than human activity … stupid is as they do.

If you like what you see, feel free to donate at Peaseblossom’s Closet.

17 responses to “Oxygen

  1. So NASA studies shows CO2 studies on the Space Station – where 1000ppm – brings on dull headaches and confusion.

    • http://ehp.niehs.nih.gov/wp-content/uploads/advpub/2015/10/ehp.1510037.acco.pdf — 33 pages.

      24 subjects; CO2 levels 550, 945, and 1400 ppm; 6 days.
      Cognitive assessment using the Strategic Management Simulation (SMS) software to test effectiveness of management-level employees through assessments of higher-order decision making.

      “Cognitive function scores were 15% lower for the moderate
      CO2 day (~945 ppm) and 50% lower on the day with CO2 concentrations around 1400 ppm…. The exposure-response between CO2 and cognitive function is approximately linear across the concentrations used in
      this study.”

  2. Chris O'Neill

    As for those who think the CO2 rise in the atmosphere is from something other than human activity …

    If they want to continue their stupid rhetoric about the CO2 rise being caused by outgassing from the oceans then they will have to say the O2 is being absorbed by the oceans. I wonder how the oceans are supposed to outgas one gas while absorbing another gas at the same time?

  3. Andrew Haines

    Thanks for that Tamino. I agree that the observed and predicted values do track each other well. But I also note that in the 1995-2000 period there are two brief periods where they do not track quite as well. Do you or any readers think these brief periods have any significance? As a layman, aware of a significant El Nino in the middle of that period, it would seem the failure to track quite as well could correspond to changes in the ocean absorption rate? Certainly the observed being lower than predicted in the lead up to the El Nino would be consistent with better than average absorption by cooler surface waters? And the reverse, observed being higher than predicted, would be consistent with worse than average absorption by warmer surface waters?

  4. Does anyone have any idea what’s going on with the divergence around 1998? Is it just noise, or related to something else (e.g., el-nino)?

  5. It appears to me that 400ppm CO2 brings confusion if not dull headaches from some politicians.

  6. Can the difference between the observed and predicted-from-O₂ CO₂ levels be used as a measure of the rate of sequestration of CO₂ from the atmosphere? Could it then be correlated with the ENSO?

  7. Well colour me surprised! I had no idea we knew atmospheric concentrations of oxygen so well. Pretty impressive.

  8. skeptictmac57

    A ‘breathtaking’ analysis.

  9. Nice analysis! The decreasing atmospheric oxygen is a powerful indication that the rise in CO2 is due to an oxidative process: the burning of fossil fuels and the emissions from changes in land use (deforestation: burning and decomposition of biomass). Two comments however:
    1) the O2/N2 scale is relative to a laboratory standard.
    2) taking atmospheric O2 as a proxy for the CO2 emissions is stretching it a bit: Atmospheric O2 decreases because of the burning of fossil fuels and biomass, while it increases when CO2 is taken up by the land biosphere through photosynthesis. Thus the negative trend in atmospheric O2 reflects the CO2 emissions minus the CO2 sink by land plants. The close tracking of the scaled O2 anomaly and the CO2 anomaly is therefore not a confirmation of the approximate constancy of the airborne fraction. Indeed, looking at the global budget equations of the two gases one can actually determine the ocean versus land sinks of atmospheric CO2, a powerful method that has been introduced by Ralph Keeling and his group in the early 1990’s. See e.g. Keeling and Shertz, Nature, 1992, or Keeling et al., Nature, 1998.

  10. Could you take a de-seasonalized look at ESRL’s methane record? I think there’s something interesting happening there.

  11. Well so much for the volcanoes idea… again.

  12. scottdenning156684402

    The most important implication of the O2/N2 record is that it helps us to quantify the contribution of CO2 sinks in the ocean vs land.

    Land processes (combustion, photosynthesis, and biological decomposition) all show a tight stoichiometric ratio of CO2 release to oxygen uptake. Dissolving CO2 into the oceans, by contrast, has very little impact on atmospheric oxygen.

    Comparing the CO2 time series to the O2/N2 time series allows Ralph Keeling and his colleagues to unambiguously partition the relative strengths of land uptake and ocean uptake of fossil fuel CO2. This is an incredibly valuable contribution because land uptake is almost certain to stop over a period of decades or maybe even reverse whereas ocean uptake of CO2 could persist for many centuries.