Weatherdem's Weblog

Bridging climate science, citizens, and policy

July 2012 CO2 Concentrations: 394.49ppm


The Scripps Institution of Oceanography measured an average of 394.49ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory during July 2012.

394.49ppm is the highest value for July concentrations in recorded history. Last year’s 392.59ppm was the previous highest value ever recorded.  This July’s reading is 1.90ppm higher than last year’s.  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, as seen in the graphs below.

The yearly maximum monthly value normally occurs during May. This year was no different: the 396.78ppm concentration was the highest value reported this year and in recorded history (no proxy data).  If we extrapolate this year’s value out in time, it will only be 2 years until Scripps reports 400ppm average concentration for a singular month (likely May 2014).  Note that I previously wrote that this wouldn’t occur until 2015.  I’ve seen comments on other posts that CO2 measured at Mauna Loa should be higher than anywhere else because of its elevation and specific location.  It is important to understand that this statement exists between confusing and an outright falsehood: CO2 is a well-mixed constituent of the atmosphere.  While point locations might vary between each other (differences between polar and tropical CO2 concentrations vary, for example), the observations at Mauna Loa are very representative of those found across the set of observation stations.  In addition, as the graphs below will help demonstrate, the historical record is very clear: concentrations have done only one thing in the past 50+ years at Mauna Loa: increased.  There has been no plateauing or decrease in that time period.

That being said, it is worth noting here that stations measured 400ppm CO2 concentration for the first time in the Arctic earlier this year.  The Mauna Loa observations represent more well-mixed conditions while sites in the Arctic and elsewhere more accurately measure local and regional concentrations.

Judging by the year-over-year increases seen per month in the past 10 years, I predict 2012 will not see an average monthly concentration below 390ppm.  Last year, I 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.  So far into 2012, my prediction is holding up.


Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in previous Julys: from 1958 through 2012.

This time series chart shows concentrations for the month of July in the Scripps dataset going back to 1958. As I wrote above, concentrations are persistently and inexorably moving upward. Alternatively, we could take a 10,000 year view of CO2 concentrations from ice cores and compare that to the recent Mauna Loa observations:


Figure 2 – Historical CO2 concentrations from ice core proxies (blue and green curves) and direct observations made at Mauna Loa, Hawai’i (red curve).

Or we could take a really, really long view:


Figure 3 – Historical record of CO2 concentrations from ice core proxy data, 2008 observed CO2 concentration value, and 2 potential future concentration values resulting from lower and higher emissions scenarios used in the IPCC’s AR4.

Note that this graph includes values from the past 800,000 years, 2008 observed values (~6-8ppm less than this year’s average value will be) as well as the projected concentrations for 2100 derived from a lower emissions and higher emissions scenarios used by the IPCC.  If our current emissions rate continues unabated, it looks like a tripling of average pre-industrial concentrations will be our future reality (278 *3 = 834).  This graph clearly demonstrates how anomalous today’s CO2 concentration values are.  It further shows how significant projected emission pathways are.  Note that we are on the higher emissions pathway.

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 or any other knowledgeable body has done this to date. To remain relevant, I think institutions who want a credible seat at the climate science-policy table will have to do so moving forward.

As the second and third graphs imply, efforts to pin any future concentration goal to a number like 350ppm or even 450ppm will be insanely difficult: 350ppm more so than 450ppm, obviously. Beyond an education tool, I don’t see the utility in using 350ppm – we simply will not achieve it, or anything close to it, given our history and likelihood that economic growth goals will trump any effort to address CO2 concentrations in the near future.  That is not to say that we should abandon hope or efforts to do something.  On the contrary, this post series is meant to inform those who are most interested in doing something.  With a solid basis in the science, we are well equipped to discuss the policy options.


3 thoughts on “July 2012 CO2 Concentrations: 394.49ppm

  1. I was momentarilly astonished when retired Vicar Philip Foster said to me in an email recently that the Earth is currently CO2-deficient with levels at the lowest they have been for 300 million years (he’s not a Young Earth Creationist clearly). I responded by saying this was simply wrong; and even if he had meant pre-Industrial 180ppm this was simply irrelevant – life is adapted to the way things are now…. In the end, though, as with Monckton, trying to overturn such ideological and/or theological prejudice is like trying to nail custard to the wall…

    • The use of ‘CO2-deficient’ is interesting. It’s in line with the talking point of more CO2 = more plants, I suppose. But I would love to hear someone like Vicar Foster explain what is meant by “deficient”. Would he argue that plants have been CO2-disadvantaged during the past tens of millions of years?

      I will tune in to your blog. Yes, for now, midnight there is 1700 my time. Arizona used to be the same time as here, but now they observe daylight savings time also.

    • Requested edits made.

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