Weatherdem's Weblog

Bridging climate science, citizens, and policy

December 2011 (Scripps) CO2 Concentrations: 391.80ppm


The Scripps Institution of Oceanography measured an average of 391.80ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory during December 2011.  These readings are from the Scripps’ dataset, not NOAA’s, which was my original data source when this series began.

391.80 is the highest value for December concentrations in recorded history. Last year’s 389.68 was the previous highest value ever recorded.  This December’s reading is 2.12ppm higher than last year’s.  As I’ve written before, this increase is significant.  Of course, more significant is the unending trend toward higher concentrations with time, no matter the month or specific year-over-year value.

The yearly maximum monthly value normally occurs during May. Last year was no different: the 394.34 concentration is the highest value reported both last year and all time.  If we extrapolate last year’s value out in time, it will only be 3 years until Scripp’s reports 400ppm average concentration for a singular month (likely May 2015).

Judging by the year-over-year increases seen per month in the past 10 years, I predict 2012 will not see a monthly concentration below 390ppm.  I had earlier predicted that 2011′s minimum would be ~388ppm.  I overestimated the minimum somewhat since both September’s and October’s measured concentrations were just under 389ppm.

CO2Now has the following graph on their front page:

It shows concentrations in the Scripps dataset going back to 1958.  As I wrote above, concentrations are persistently moving upward.

Given our historical emissions to date and the likelihood that they will continue to grow at an increasing rate in the next 25 years, we will pass a number of “safe” thresholds – for all intents and purposes permanently as far as concerns our species.  It is time to start seriously investigating and discussing what kind of world will exist after CO2 concentrations peak at 850 and 1100ppm.  I don’t believe the IPCC has done this to date.  To remain relevant, I think it will have to do so moving forward.

Cross-posted at SquareState.


2 thoughts on “December 2011 (Scripps) CO2 Concentrations: 391.80ppm

  1. One of the most common criticisms of the so-called Keeling Curve is that it is unduly alarming because pre-industrial CO2 levels were not zero and that the origin of the y-axis is not at zero.

    However, when you take these two factors into account, the situation is in fact much more alarming because it is clear that we are on the near-vertical end of a J curve.

    I therefore agree with you that the IPCC are definitely behind the curve on this one (pun very much intended)…

    • Well stated, Martin.
      I included the following graph in December’s post reporting on November’s CO2 concentrations showing concentrations dating back 10,000 years, which merely extends back into time the data you show via your `J curve` plot.

      To follow up on your comment, the fact that concentrations weren’t zero and thus the origin point isn’t zero doesn’t matter one whit. If it really bothers critics, all they have to do is decide on a reference point from any time in the past, subtract that value from every value in the time series so that the origin point is zero and the data is referenced accordingly. What is the end result of doing that? The same graph somehow magically appears! The J curve remains no matter the reference point chosen!

      Which is one more reason why I don’t waste time on the critics anymore. No amount of data or explanation will ever be enough to convince them. And since I’m interested in actual solutions, that’s what I’m focused on moving forward.

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