392.92ppm is the highest value for November concentrations in recorded history. Last year’s 390.31ppm was the previous highest value ever recorded. This November’s reading is 2.61ppm 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 in May 2012 was the highest value reported this year and in recorded history (neglecting proxy data). If we extrapolate this year’s maximum 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 – another climate variable that is increasing faster than energy or climate experts predicted.
I’ve seen comments in the skeptic blogosphere that CO2 measured at Mauna Loa should be higher than anywhere else because of its elevation and specific location. This is an effort to challenge the credibility of the dataset. It is important to understand that this statement exists somewhere between correct to purposefully confusing to outright deceitful. CO2 is a well-mixed constituent of the atmosphere. That means that emissions of new CO2 are quickly and pretty evenly distributed in space. While point locations might vary between each other (differences between polar and tropical CO2 concentrations at the same point in time vary the most, for example), the observations at Mauna Loa are very representative of those found across the set of observation stations on the globe. 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 any station you want to discuss: 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 (global) conditions while sites in the Arctic and elsewhere more accurately measure local and regional concentrations. That is why scientists and media reference the Mauna Loa observations most often.
Earlier in the year, I predicted that 2012 would not see an average monthly CO2 concentration below 390ppm. It wasn’t the hardest prediction to make: the trend was going up at a steady rate and based on humanity’s continued reliance on fossil fuels, we weren’t going to break that trend this year. The next prediction to verify is the first month at Mauna Loa during which Scripps records an 400ppm average. After that, the first year during which the minimum concentration is at least 400ppm, which I think will occur within the next 5 years.
Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in November: from 1958 through 2012.
This time series chart shows concentrations for the month of November 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 (10,000 year) 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 into the past:
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’s Fourth Asssessment Report from 2007. Has CO2 varied naturally in this time period? Of course it has. But you can easily see that previous variations were between 180 and 280ppm. In contrast, the concentration has, at no time during the past 800,000 years, risen to the level at which it currently exists. That is important because of the additional radiative forcing that increased CO2 concentrations impart on our climate system. You or I may not detect that warming on any particular day, but we are just starting to feel their long-term impacts.
Moreover, if our current emissions rate continues unabated, it looks like a tripling of average pre-industrial concentrations will be our reality by 2100 (278 *3 = 834). This graph clearly demonstrates how anomalous today’s CO2 concentration values are (much higher than the average recorded over the past 800,000 years). It further shows how significant projected emission pathways are. I will point out that our actual emissions to date are greater than the higher emissions pathway shown above. This reality will be partially addressed in the upcoming 5th Assessment Report (AR5), currently scheduled for public release in 2013-14.
Given our historical emissions to date and the likelihood that they will continue to grow at an increasing rate for at least 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 or 1100ppm. No knowledgeable body, including the IPCC, 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. The AR5 might possibly fill in some of this knowledge gap. I expect most of that work has recently started and will be available to the public around the same time as the AR5 release, which is likely to cause some confusion in the public.
As the second and third graphs imply, efforts to pin any future concentration goal to a number like 350ppm or even 450ppm will be incredibly 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 (as President Obama himself stated recently). That is not to say that we should abandon hope or efforts to do something. On the contrary, this series informs those who are most interested in doing something. With a solid basis in the science, we become well equipped to discuss policy options. I join those who encourage efforts to tie emissions reductions to economic growth through scientific and technological research and innovation. This path is the only credible one moving forward.