Up and up the value goes. The Scripps Institution of Oceanography measured an average of 395.55ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory during January 2013.
395.55ppm is the highest value for January concentrations in recorded history. Last year’s 393.14ppm was the previous highest value ever recorded. This January’s reading is 2.41ppm 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. Last year was no different: the 396.78ppm concentration in May 2012 was the highest value reported last year and in recorded history (neglecting proxy data). Note that January’s value is only 1.23ppm less than May 2012′s. If we extrapolate last 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; 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.
It is worth noting here that stations measured 400ppm CO2 concentration for the first time in the Arctic last year. The Mauna Loa observations are usually closer to globally averaged values than other sites, such as in the Arctic. That is why scientists and media reference the Mauna Loa observations most often.
Figure 1 – Time series of CO2 concentrations measured at Scripp’s Mauna Loa Observatory in January: from 1959 through 2012.
This time series chart shows concentrations for the month of January in the Scripps dataset going back to 1959. As I wrote above, concentrations are persistently and inexorably moving upward. How do concentration measurements change in calendar years? The following two graphs demonstrate this.
Figure 2 – Monthly CO2 concentration values from 2009 through 2013 (NOAA). Note the yearly minimum observation is now in the past and we are three months removed from the yearly maximum value. NOAA is likely to measure this year’s maximum value at ~398ppm.
Figure 3 – 50 year time series of CO2 concentrations at Mauna Loa Observatory. The red curve represents the seasonal cycle. 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 toward the Earth, which eventually increases lower tropospheric temperatures.
We could instead take a 10,000 year view of CO2 concentrations from ice cores and compare that to the recent Mauna Loa observations. This allows us to determine how today’s concentrations compare to geologic conditions:
Figure 4 – 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) through the early 2000s.
Or we could take a really, really long view into the past:
Figure 5 – 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 last graph includes values from the past 800,000 years, 2008 observed values (~8-10ppm 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 Assessment 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 and took thousands of years to move between the two. In contrast, the concentration has, at no time during the past 800,000 years, risen to the level at which it currently exists; nor has the concentration changed so quickly (287ppm to 395ppm in less than two hundred years!). 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). Figure 5 clearly demonstrates how anomalous today’s CO2 concentration values are (much higher than the average, or even the maximum, recorded over the past 800,000 years). It further shows how significant the projected emission pathways are. I will point out that our actual emissions to date are greater than the higher emissions pathway shown above. That means that if we continue to emit CO2 at an increasing rate, end-of-century concentration values would exceed the value shown in Figure 5 (~1100ppm instead of 800). 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 1200ppm. 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 work leading up to AR5 will begin to 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. This could potentially cause some confusion in the public since the AR5 will tell one storyline while more recent research might tell a different storyline.
The fourth and fifth graphs imply that 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 in 2012). 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 action. With a solid basis in the science, we become 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.