February 2013 CO2 Concentrations: 396.80 ppm

During February 2013, the Scripps Institution of Oceanography measured an average of 396.80ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory.

This value is a big deal.  Why?  Because not only is 396.80 ppm the largest CO2 concentration value for any February in recorded history, it is the largest CO2 concentration value in any month in recorded history.  More on that below.  This year’s February value is 3.37 ppm higher than February 2012′s!  Most month-to-month differences are between 1 and 2 ppm.  This jump of 3.37 ppm is very high.  Of course, 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 this moth, in recorded history (neglecting proxy data).  We can expect March, April, and May of this year to produce new record values.  I wrote the following last month:

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.

For the most part, I stand by that prediction.  But actual concentration increases might prove  me wrong.  Here is why: the difference in CO2 concentration values between May 2012 and February 2012 was 3.13 ppm (396.78 – 393.65).  If we do the simplest thing and add that same difference to February’s value, we get 399.93 ppm.  That is awfully close to 400 ppm.  A more robust approach would be to add an average value – say the annual growth rate from the past 3, 5, or 10 years.  Over those time periods, the average differences are 2.31 ppm, 2.08 ppm, and 2.08 ppm.  So it’s probably safe to assume a growth of at least 2 ppm, which is what I did in my original prediction.  396.78 ppm + 2 ppm = 398.78 ppm (2013′s prediction).  398.78 ppm + 2 ppm = 400.78 ppm (2014′s prediction).  But if we use annual averages, we smooth out the large jumps in concentration values (like the 2013-2012 February difference).  There are other calculations that we could do to come up with a range of predictions, but I unfortunately don’t have the time to do them right now.  We will have to be content with waiting until early June to find out how fast concentrations are rising this year.

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 February: 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 two months removed from the yearly maximum value.  NOAA is likely to measure this year’s maximum value between 398ppm and 399ppm.

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 toward the Earth, which eventually increases tropospheric temperatures.

In previous posts on this topic, I show and discuss historical and projected concentrations at this part of the post.  I will skip this for now because there is something about this data that I think provides a different context of the same conversation.  The increase in average annual concentrations in 2012 generated quite a bit of buzz in media outlets this week.  I dismissed the first couple of reports I saw because I’ve spent so much time during the past year writing about the concentrations.  But more media outlets wrote and discussed the same topic as the week went on.  So I think it is a valid story, especially after I saw a graphic that I thought should have been the focus the entire time:

Figure 4 – CO2 concentration (top) and annual average growth rate (bottom). Source: Guardian

The top part of Figure 4 should look familiar – it’s the black line in Figure 3.  The bottom part is the annual change in CO2 concentrations.  If we fit a line to the data, the line would have a positive slope, which means annual changes are increasing with time.  So CO2 concentrations are increasing at an increasing rate – not a good trend with respect to minimizing future warming.  In the 1960s, concentrations increased at less than 1 ppm/year.  In the 2000s, concentrations increased at 2.07 ppm/year.

The greenhouse effect details how these concentrations will affect future temperatures.  The more GHGs in the atmosphere, all else equal, the more radiative forcing the GHGs cause.  More forcing means warmer temperatures as energy is re-radiated back toward the Earth’s surface.  Conditions higher in the atmosphere affects this relationship, which is what my volcano post addressed.  A number of medium-sized volcanoes injected SO2 into the stratosphere (which is above the troposphere – where we live and our weather occurs).  Those SO2 particles reflect incoming solar radiation.  So while we emitted more GHGs into the troposphere, less radiation entered the troposphere in the past 10 years than the previous 10 years.  With less incoming radiation, the GHGs re-emitted less energy toward the surface of the Earth.  This is likely part of the reason why the global temperature trend leveled off in the 2000s after its run-up in previous decades.

This situation is important for the following reason.  Once the SO2 falls out of the atmosphere, the additional incoming radiation will interact with higher GHG concentrations than was present in the late 1990s.  We will likely see a strong surface temperature response sometime in the future.

In my mind, the newsworthy detail is not that CO2 concentrations increased at the second fastest rate on record in 2012.  In climate, year-to-year differences matter less than long-term trends.  In my mind, the decadal concentration increase is what is noteworthy.  If concentrations rise by an average of >3 ppm/year in the 2010s or 2020s, a great deal of future warming and other climate change effects will occur.

It is my opinion that global temperature rise by 2100 will exceed 2C.  This target is primarily politically-driven.  Scientific research doesn’t exist that dictates 2C is “safe”.  Scientific research does exist that projects the likely temperature response to a range of CO2 concentration values.  If we do want to prevent >2C global temperature rise by 2100, we would have to immediately stop emitting CO2 and begin removing CO2 from the atmosphere.  We currently don’t have technologies to do either.

I have more to say about some details in the Guardian article from which I got Figure 4.  That will have to wait for another post.  The Science study the article mentions is worthy of discussion, as is the Guardian’s comment that concentrations continue to increase despite government action.  The article also links to a recent study of GHG reductions by 2020.  I will address these in an upcoming post.

January 2013 CO2 Concentrations: 395.55ppm

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.

Climate Sensitivity and 21st Century Warming

I want to write about shoddy opining today.  I will also write about tribalism and cherry-picking; all are disappointing aspects in today’s climate discussion.  In climate circles, a big kerfuffle erupted in the past week that revolves around minutiae and made worse by disinformation.  The Research Group of Norway released a press release that somebody’s research showed a climate sensitivity of ~1.9°C (1.2-2.9°C was the range around this midpoint value) due to CO2-doubling, which is lower than other published values.

Important Point #1: The work remains un-peer reviewed.  It is part of unpublished PhD work and therefore subject to change.

Moving from that context, what happened next?  The Inter-tubes were ablaze with skeptics cheering the results.  Additionally, groups like Investor’s Business Daily jumped on the “global warming is hooey” bandwagon.  Writers like Andy Revkin provided thoughtful analysis.

Important Point #2: Skeptics view some model results as truthful – those that agree with their worldview.

IBD can, of course, opine all it wants about this topic.  What obligation to their readers do they have to disclose their biases, however?  All the other science results are wrong, except this one with which they agree.  What makes the new results so correct when every other result is so absolutely wrong?  Nothing, as I show below.

Important Point #3: These preliminary results still show a sensitivity to greenhouse gas emissions, not to the sun or any other factor.

For additional context, you should ask how these results differ from other results.  What are IBD and other skeptics crowing about?

Figure 1.  Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) is indicated by the vertical light blue bar. [h/t Skeptical Science]

They’re crowing about a median value of 1.9°C in a range of 1.2-2.9°C.  If you look at Figure 1, neither the median nor the range is drastically different from other estimates.  The range is a little smaller in magnitude than what the IPCC reported in 2007.  Is it surprising that if scientists add 10 more years of observation data to climate models, a sensitivity measurement might shift?  The IPCC AR4 dealt with observations through 2000.  This latest preliminary report used observations through 2010.  What happened in the past 10 years that might shift sensitivity results?  Oh, a number of La Niñas, which are global cooling events.  Without La Niñas, the 2000s would have been warmer, which would have affected the sensitivity measurement differently.  No  mention of this breaks into the opinion piece.

Important Point #4: Climate sensitivity and long-term warming are not the same thing.

The only case in which they are the same thing is if we limit our total emissions so that CO2 concentrations are equal to CO2-doubling.  That is, if CO2 concentrations peak at 540ppm sometime in the future, the globe will likely warm no more than 1.9°C.  Note that analysis’s importance.  It brings us to:

Important Point #5: On our current and projected emissions pathway, we will more than double pre-industrial CO2 concentrations.

Figure 2.  Historical emissions (IEA data – black) compared to IPCC AR4 SRES scenario projections (colored lines).

As I’ve discussed before, our historical emissions continue to track at the top of the range considered by the IPCC in the AR4 (between A2 and A1FI).  Scientists are working on the AR5 as we speak, but the framework for the upcoming report changed.  Instead of emissions, planners built Representative Concentration Pathways (RCPs) for the AR5.  A graph that shows these pathways is below.  This graph uses emissions to bridge between the AR4 and AR5.

Figure 3. Representative Concentration Pathways used in the upcoming AR5 through the year 2100, displayed using yearly emissions estimates.

The top line (red; RCP8.5) corresponds to the A1FI/A2 SRES scenarios.  As Figure 3 shows, our historical emissions most closely match the RCP8.5 pathway.  The concentration for this pathway through 2100 is 1370ppm CO2-eq, which results in an anomalous +8.5W/m^2 forcing.  This forcing is likely to result in 4 to 6.1°C warming by 2100.  A couple of critical points: in this scenario, emissions don’t peak in the 21st century; therefore this scenario projects additional warming in the 2100s.  I want to make absolutely clear this point: our business-as-usual concentration pathway blows past CO2-doubling this century, which means the doubling sensitivity is a moot point.  We should investigate CO2-quadrupliung.  Why?  The peak emissions and concentration, which dictates the peak anomalous forcing, which controls the peak warming we face.

The IBD article contains plenty of skeptic-speak: “Predictions of doom have turned out to be nothing more than madness”, “there are too many unknowns, too many variables”, and “nothing ever proposed would have any impact anyway”.

They do have a point with their first quoted statement.  I avoid catastrophic language because doom has not befallen the vast majority of people on this planet.  Conditions are changing, to be sure, but not drastically.  There are too many unknowns.  Most of the unknowns scientists worked on the last 10 years ended up with the opposite result that IBD assumes: scientists underestimated feedbacks and results.  Events unfolded much more quickly than previously projected.  That will continue in the near future due mainly to our lack of knowledge.  The third point is a classic: we cannot act because others will not act in concert with us.  This flies in the face of a capitalist society’s foundation.  Does IBD really believe that US innovation will not increase our competitiveness or reduce inefficiencies?  Indeed, Tim Worstall’s Forbes piece posited a significant conclusion: climate change becomes cheaper to solve if the sensitivity is lower than previously estimated.  IBD should be cheering for such a result.

Finally, when was the last time you saw the IBD latch onto one financial model and completely discard others?  Where was IBD in 2007 when the financial crisis was about to start and a handful of skeptics warned that the mortgage boom was based on flawed models?  Were they writing opinion pieces like this one?  I don’t think so.  Climate change requires serious policy consideration.  This opinion piece does nothing to materially advance that goal.

December 2012 CO2 Concentrations: 394.39ppm

The Scripps Institution of Oceanography measured an average of 394.39ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory during December 2012.

394.39ppm is the highest value for December concentrations in recorded history. Last year’s 391.79ppm was the previous highest value ever recorded.  This December’s reading is 2.60ppm 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 this year and in recorded history (neglecting proxy data).  Note that December 2012′s value is only 2.39ppm 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 – another climate variable that is increasing faster than energy or climate experts predicted.

It is worth noting here that stations measured 400ppm CO2 concentration for the first time in the Arctic last 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 last year, I predicted that 2012 would not see an average monthly CO2 concentration below 390ppm.  I was correct: September and October 2012 concentration values were the lowest recorded last year (391ppm).  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.  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 December: from 1958 through 2012.

This time series chart shows concentrations for the month of December in the Scripps dataset going back to 1958. 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 2008 through 2013 (NOAA).  Note the yearly minimum observations are now in the past and we are five months removed from the yearly maximum value.

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 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).

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 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).  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 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.  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 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.

November 2012 CO2 Concentrations: 392.92ppm

The Scripps Institution of Oceanography measured an average of 392.92ppm CO2 concentration at their Mauna Loa, Hawai’i’s Observatory during November 2012.

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.