Weatherdem's Weblog

Bridging climate science, citizens, and policy

May 2013 CO2 Concentrations: 399.89 ppm

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During May 2013, the Scripps Institution of Oceanography measured an average of 399.89 ppm CO2 concentration at their Mauna Loa, Hawai’i Observatory.

This value is important.  Why?  Because not only is 399.89 ppm the largest CO2 concentration value for any May in recorded history, it is the largest CO2 concentration value in any calendar month in recorded history.  More on that below.  This year’s May  value is 3.02 ppm higher than May 2012′s!  Month-to-month differences typically range between 1 and 2 ppm.  This jump is clearly well outside of that range.  This is more in line with February’s year-over-year change of 3.37 ppm.  The unending trend toward higher concentrations with time, no matter the month or specific year-over-year value, as seen in the graphs below, is more significant.

Let’s get back to that all-time high concentration value.  The yearly maximum monthly value normally occurs during May. Last year was no different: the 396.78ppm concentration in May 2012 was the highest value reported last year and, prior to the last four months, in recorded history (neglecting proxy data).  I expected May of this year to produce another all-time record value and it clearly did that.  May 2013’s value will hold onto first place until February 2014.  I wrote the following three months ago:

If we extrapolate last year’s maximum value out in time, it will only be 2 years until Scripps reports 400 ppm average concentration for a singular month (likely May 2014; I expect May 2013′s value will be ~398ppm).  Note that I previously wrote that this wouldn’t occur until 2015 – this means CO2 concentrations are another climate variable that is increasing faster than experts predicted just a short couple of years ago.

For the past few months, I stood by that prediction.  But actual concentration increases proved me slightly wrong.  Here is why: the difference in CO2 concentration values between May 2012 and March 2012 was 2.33 ppm (396.78 – 394.45).  If we do the simplest thing and add that same difference to March 2013’s value, we get 399.67 ppm.  That is awfully close to 400 ppm, but less than the 399.93 ppm extrapolation I first performed in February, which ended up being a perfect projection.  It’s also close to the 399.3 ppm extrapolation I calculated in March.  I discussed May 2013′s projection with Sourabh after February’s post.  They predicted 399.5-400 ppm concentration for May 2013.  I predicted NOAA would measure May 2013′s mean concentration near 399.3 ppm, but it turns out Sourabh was closer than I was to the actual value.

 photo co2_widget_brundtland_600_graph_201305_zpsfad83dd1.gif

Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in May from 1958 through 2013. added the `350s` and `400s` to the past two month’s graphics.  I suppose they’re meant to imply concentrations shattered 350 ppm back in the 1980s and are pushing up against 400 ppm now in the 2010s.

How do concentration measurements change in calendar years?  The following two graphs demonstrate this.

 photo CO2_concentration_5y_trend_NOAA_201306_zps66f17f18.png

Figure 2 – Monthly CO2 concentration values (red) from 2009 through 2013 (NOAA).  Monthly CO2 concentration values with seasonal cycle removed (black).  Note the yearly minimum observation occurred seven months ago the yearly maximum value occurred last month.  CO2 concentrations will decrease throughout the rest of 2013, as they do every year after May.

 photo CO2_concentration_50y_trend_NOAA_201306_zps5ba37b14.png

Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory.  The red curve represents the seasonal cycle based on monthly average values.  The black curve represents the data with the seasonal cycle removed to show the long-term trend.  This graph shows the recent and ongoing increase in CO2 concentrations.  Remember that as a greenhouse gas, CO2 increases the radiative forcing of the Earth, which increases the amount of energy in our climate system.

CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  Natural systems are not equipped to remove CO2 emissions quickly from the atmosphere.  Indeed, natural systems will take tens of thousands of years to remove the CO2 we emitted in the course of a couple short centuries.  Human systems do not yet exist that remove CO2 from any medium (air or water).  They are not likely to exist for some time.  So NOAA will extend the right side of the above graphs for years and decades to come.

This month, I want to spend some time on this post’s focus: CO2 concentration values.  Given our species penchant for round numbers, it came as little surprise that the corporate media placed an uncommon amount of attention on a value that has relatively low meaning: daily CO2 concentrations at Mauna Loa surpassed 400 ppm for a day during the month of May.  In fact, both the media and many climate activists made a very big deal about this development.  I think that was largely a waste of time.  Again, the daily value itself didn’t represent any large difference once reached.  The climate system did not automatically kick into a different setting once concentrations passed 400 ppm for a day.  Nothing substantially new occurred that didn’t when concentration were “only” 399 ppm (or 390 ppm or 380 ppm for that matter).

As I state in this series every month, the trend makes much more of a difference than any daily, monthly, or even yearly average value.  And that trend is accelerating upwards at a rate that many didn’t think was possible even 10 years ago.  The effects from last year’s average CO2 concentrations won’t manifest in realizable terms until 30-50 years from now.  I didn’t see anybody pointing out that important detail.  Similarly, I didn’t see any explanation that today’s mean temperatures are largely a result of CO2 concentrations from 30+ years ago.  Perhaps most importantly, climate activists didn’t mention that CO2 concentrations are rising at a rising rate despite decades of their activism.  That fact creates a rather uncomfortable situation because most activists are proponents of doing tomorrow what they did yesterday.  If those actions haven’t had any effect up until now, why the advocacy for the status quo when those same activists try to claim that the status quo is untenable.  If they really believed in their catastrophic climate change claims, shouldn’t they honestly evaluate the effects their actions have had?  And if those actions produced far less meaningful progress than they state is absolutely required for the survival of our species and the planet (grandiose language, I know), why do their strategies and tactics remain largely unchanged?

I write these posts for people who are curious or interested in the state of a key climate variable.  I realized that doomsday language turns a significant portion of my potential audience off from the get-go.  If we are to do something meaningful about climate change, we cannot afford the disengagement and hostility of one-third or more of our fellow global citizens towards climate activism.  I don’t want to simply treat people as empty vessels into which I can pour knowledge.  I want to engage them on ground that is similar between us precisely because I want to do something.  Screaming about 400 ppm mean CO2 concentration for one day and then walking away from the variable until we pass the next perceived meaningful threshold doesn’t strike me as engagement.

The rise in CO2 concentrations will slow down, stop, and reverse when we decide it will.  It depends primarily on the rate at which we emit CO2 into the atmosphere.  We can choose 400 ppm or 450 ppm or almost any other target (350 ppm seems out of reach within the next couple hundred years).  That choice is dependent on the type of policies we decide to implement.  It is our current policy to burn fossil fuels because we think doing so is cheap, although current practices are massively inefficient and done without proper market signals.  We will widely deploy clean sources of energy when they are cheap, the timing of which we control.  We will remove CO2 from the atmosphere if we have cheap and effective technologies and mechanisms to do so, which we also control to some degree.  These future trends depend on today’s innovation and investment in research, development, and deployment.  Today’s carbon markets are not the correct mechanism, as they are aptly demonstrating.  The bottom line is: We will limit future warming and climate effects when we choose to do so.


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