CO2 concentration closes in on 400 ppmv. It’s near its annual peak at 397 ppmv, and as usual at this time of year, this is the highest value in the instrumental record.



  1. Yes, this can be confusing because of the various time scales that you might look at the problem. Over historical time (hundreds of years) the record looks like the top graph here:


    Over deep time there is much less certainty, and this graph may be out of date for the best info, but the picture looks something like this:


    In looking at that, it is important to understand how very long the time scale is (hundreds of millions of years.

    Over most of deep time CO2 was much higher than at present, and the earth was ice free, which would raise sea level hundreds of meters. Evolutionary time scales are short compared to this graph and most species are adapted to low CO2.

    In between hundreds of years and hundreds of millions, we can look at the scale of hundreds of thousands of years, which is very interesting. Humanity developed in a period of highly unstable climate:


    Here is an interesting attempt to summarize all of this on one figure, this one a bit more schematic:


    which comes from this interesting article:


    I hope this helps you.

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