Charts of Atmospheric CO2, Carbon Isotopes, Oxygen and Methane

 I started making charts of atmospheric CO2 in 2009, when the global average CO2 concentration was 386 ppm.  I updated my charts in 2012, at 392 ppm, and in 2017, at 405 ppm, and at the end of 2021, at 418 ppm. 

The monitoring stations are located from the far north, at 82° N in Canada to the South Pole.  Scripps Institute has managed most of these stations since the 1950s, first under the direction of Charles Keeling, and later under his son, Ralph Keeling.  I also included records from a few obsolete legacy stations that were operated by foreign governments.  I standardized my chart displays using cool colors to represent the Northern Hemisphere, and warm colors for the Southern Hemisphere.

The amplitude of the CO2 seasonal cycle varies with latitude, from high amplitude in far northern latitudes to very little amplitude at the South Pole.  The seasonal cycle is driven by seasonal plant growth and decay on lands with temperate climate, which are concentrated in the Northern Hemisphere.  Agriculture, which is also concentrated in the Northern Hemisphere, also contributes to the seasonal cycle.  I took advantage of this for my standard display, overlaying low amplitude over higher amplitude traces, so that all traces can be seen.

In general, CO2 concentration in the atmosphere is growing exponentially, a fact noted by Isaac Asimov in 1959.  In 2009, I made an exponential function, beginning at the pre-industrial CO2 concentration of 280 ppm in 1800, with an eyeball-fit to the data from 1957 to 2009.  Here’s the function, and the chart beginning in 1800, updated with CO2 data through 2021.  This chart has the “hockey stick” impression that characterizes many climate-change charts.

CO₂ concentration, ppm = e^(n*0.001854) + 280, where n = the number of months since Jan. 1800

This function would predict that global CO2 would pass 450 ppm in January, 2032 (ten years from now), and pass 500 ppm in August, 2043.

The exponential function seems to be slightly overstating the rate of CO2 growth since 2009, so I tried an alternate formula for the forecast in coming decades, a second-degree polynomial with a least-squares fit to the global average CO2 from 1974 to 2009.  That formula is CO2 in ppm = 0.000104*x²+0.0897*x+331.66, where x is the number of months from July, 1974.  This formula predicts global CO2 will pass 450 ppm in June, 2034, and pass 500 ppm in July, 2050. 

Certainly, these forecasts are simple extrapolations, and include none of the analysis of policies and economics which should be the basis of forecasting.  But it’s worth noting that my exponential forecast from 13 years ago is pretty much right on the money, overshooting by only one or two parts per million.  The last thirteen years has seen unprecedented growth in renewable energy technologies, but so far without significant impact on the rate of CO2 growth.  Here are the two forecasts on the same chart.

The seasonal cycle can easily be filtered from the data, leaving the long-term trend at each station.  From this, it’s easy to see that the Northern Hemisphere leads the Southern Hemisphere in rising CO2.  About 90% of fossil fuel burning happens in the Northern Hemisphere, and CO2 accumulates in the far north, while dispersing to the south. 

The difference in concentration from the far north to the South Pole has been increasing as larger volumes of fossil fuels are burned each year, from about 3 ppm in the 1980s to over 5 ppm now.  The chart below shows the difference in the one-year time-averaged CO2 concentration measured in Alert, Canada, at latitude 82° North, and the South Pole. 

The amplitude of the seasonal cycle has also been increasing in the far north.  The amplitude of the cycle increased from 15 ppm to 20 ppm since the mid-1970s.  This probably reflects increased agriculture and farm productivity in the Northern Hemisphere as world population has doubled.  Previous work showed that seasonal fossil-fuel use is volumetrically inadequate to produce the change in the atmospheric CO2 seasonal cycle.  https://dougrobbins.blogspot.com/2012/04/modeling-global-co2-cycles.html

Carbon comes in two common naturally occurring isotopes, C¹² and C¹³.  Various processes, including life processes, sort the isotopes, favoring the accumulation of one or the other isotope.  Photosynthesis favors C¹², so everything with carbon derived from plants, including lumber, your mashed potatoes, you, me, and fossil fuels is enriched in C¹².  Scientists use a measure of the C¹³/C¹² ratio written as d¹³C , and called delC13.  As fossil fuels are burned the C¹²-enriched carbon in CO2 changes the ratio of these isotopes in the atmosphere, lowering the value of delC13.  DelC13 continued to fall from 2009 to 2021, reflecting a growing fraction of carbon from fossil fuels in the atmosphere. 

Carbon isotopes in the atmosphere are also affected by the seasonal cycle of plant growth on the temperate land mass of the Northern Hemisphere.  As plants grow during the northern summer, the lighter isotope C¹² is preferentially removed from the atmosphere, and returned during the winter months as plants decay.

After filtering the seasonal cycle, we see that the Northern Hemisphere leads the Southern Hemisphere in falling DelC13.  As an aside, the residual fluctuations in the trend have a strong correlation to the Oceanic Nino Index (ONI), reflecting sea surface temperatures in the Pacific.  https://dougrobbins.blogspot.com/2013/11/carbon-isotopes-in-atmosphere-part-ii.html

Interestingly, if all of the carbon released by fossil fuels stayed in the air, the DelC13 value would be much lower, about -13, instead of -8.5.  The measured dilution of carbon with the isotope signature of fossil fuels provides a way of estimating the volume of all carbon reservoirs exchanging carbon with the atmosphere.  Currently, the reservoirs freely exchanging carbon with the atmosphere have a carbon mass of about 5200 gigatonnes, before accounting for additional carbon in the system from new burning of fossil fuels.  That’s about 6 times the mass of carbon currently in the atmosphere.  https://dougrobbins.blogspot.com/2013/11/how-big-is-carbonsphere.html

Atmospheric oxygen is also influenced by burning of fossil fuels.  Oxygen is consumed, causing atmospheric O2 to fall.  The atmosphere is about 21% oxygen, and the decline is only about 0.08%, so there is no threat to breathing.  Still, the decline can be measured precisely.  The decline in oxygen is reported in units per meg, which is equivalent to ppm in this range of values.

After filtering the seasonal cycle, we see that the Northern Hemisphere leads the Southern Hemisphere in oxygen decline, because most fossil fuels are burned in the Northern Hemisphere.  The total volume of oxygen decline is very close to the expected consumption of oxygen considering the reported volumes of fossil fuels burned and deforestation, as reported in this previous post.  https://dougrobbins.blogspot.com/2019/12/understanding-source-of-rising.html

Atmospheric methane (C4) is also increasing as a result of human emissions.  Methane is a much more powerful greenhouse gas than CO2, but has a shorter lifespan.  CO2 has a half-life of 120 years, while methane has a half-life of about 10 years.  This is why the climate scientists use the parameter GWP (global warming potential) to represent the different strength of various greenhouse gases over an effective time frame.  The GWP of CO2 equals 1, by definition, for all time intervals.  For methane, the warming potential over 20 years (GWP-20) is 84 – 87, and over 100 years is 28 – 36.  Over shorter intervals, methane is an even stronger greenhouse gas.  Currently, methane concentration in the atmosphere is about 1.9 ppm (i.e. 1900 ppb).  In absolute terms, methane warmed the earth by about 0.52 W/m2, compared to 2.11 W/m2 for CO2, for the latest year reported by NOAA, 2020.  All other greenhouse gases combined contributed another 0.55 W/m2.  Methane also has a seasonal cycle in both hemispheres with high values in the summer and low values in the winter, but I don’t know the explanation for the seasonal cycle. 

As the concentrations of CO2 and methane in the air rise, the atmosphere will absorb heat at a faster rate, leading to destructive climate change.  Temperatures and climate change will not stabilize until carbon emissions reach zero.  I will update my charts on carbon emissions when summary data for 2021 is released in the BP Statistical Summary of World Energy in July.  Apart from a small pandemic-related decline in emissions in 2020, the world continues to add CO2 to the atmosphere at an ever-increasing rate.  If the world had acted to reduce emissions three decades ago, simply reducing emissions might have been a reasonable policy.  However, in our current situation, outright elimination of carbon emissions is required to avoid some level of catastrophic consequences. 

Globally, we need to reduce emissions to 50% by 2035, and to zero some time between 2050 and 2070.  I am very pessimistic that we have the public understanding or political will to reach these goals.  As Bill Gates wrote in 2021, "To avoid a climate disaster, we have to get to zero greenhouse gas emissions….The case for zero was, and is, rock solid.  Setting a goal to only reduce our emissions—but not eliminate them—won’t do it.  The only sensible goal is zero.”

References:

CO2, CO2 carbon isotopes, oxygen and methane data, including obsolete CO2 stations

https://scrippsco2.ucsd.edu/data/atmospheric_co2/sampling_stations.html

https://scrippso2.ucsd.edu/data.html

https://gml.noaa.gov/dv/data/

https://data.ess-dive.lbl.gov/view/doi:10.3334/CDIAC/ATG.015

https://www.osti.gov/dataexplorer/biblio/dataset/1409297

https://carbonmapper.org/data/

Isaac Asimov, "No More Ice Ages?" prediction and commentary on global warming,
in Fantasy and Science Fiction, Jan. 1959, republished in Fact & Fancy, 1962 and Asimov on Chemistry, 1974. 

Global Warming Potential

https://www.epa.gov/ghgemissions/understanding-global-warming-potentials#:~:text=Methane%20(CH4)%20is%20estimated,uses%20a%20different%20value.).

GWP-20 for methane = 84 to 87; GWP-100 for methane = 28 to 36 (also reported as 25)

Radiative Forcing for various greenhouse gases

https://gml.noaa.gov/aggi/aggi.html

Understanding the Source of Rising Atmospheric CO2

For the last time, increasing atmospheric CO2 is coming from fossil fuels, and not from volcanoes.

The concentration of CO2 in the atmosphere is rising rapidly.  Before widespread burning of coal, circa 1750, atmospheric CO2 was about 280 parts per million (ppm).  By 1955, global CO2 concentration had risen to 314 ppm.  Average global CO2 levels are now about 412 ppm, and are still rising at about 3 ppm per year. 

Industrial processes are able to change the composition of the earth’s atmosphere because there really isn’t very much atmosphere, and there isn’t very much CO2.  The atmosphere thins rapidly with altitude, so that about half of the atmosphere is less than 3 miles above the earth, and breathable atmosphere extends only about 6 miles above the earth.  Further, there isn’t very much CO2 in the atmosphere – about 400 ppm, or 0.04%.  Nevertheless, that small amount of CO2 is very effective at blocking thermal infrared radiation, which is why changing the CO2 concentration of the atmosphere has already had a significant impact on global climate. 

Figure 1.  There isn’t very much atmosphere, and there really isn't very much CO2.  The pie-slice of CO2 in the second figure is exaggerated three-fold for visibility.

A common myth that circulates on social media is that rising CO2 in the atmosphere is coming from volcanoes.   It isn't.  I already wrote one blog post about the origin of atmospheric CO2.  (https://dougrobbins.blogspot.com/2017/06/volcanic-co2-emissions.html). 

This blog post will present additional evidence that rising CO2 is of human origin.  The evidence is:

• Declining oxygen concentration of the atmosphere
• The quantity of missing oxygen
• The location of declining oxygen concentration by hemisphere
• Volumetric data for fossil fuel emissions, deforestation, and volcanism, compared to volumes of CO2 appearing in the atmosphere
• The location of rising CO2 by hemisphere
• Changing carbon isotopic composition of the atmosphere
• The location of the declining carbon isotope measure (del C13) by hemisphere
• The steady rise of atmospheric CO2, whereas volcanic eruptions are intermittent (although slow emissions from non-eruptive events, mid-ocean ridges and rifts also occur). 

Atmospheric CO2 is now also monitored by two orbiting carbon observatories (OCO), which directly measure CO2 concentrations in the atmosphere and connect rising atmospheric CO2 with points of origin.

The myth that volcanoes are responsible for human-caused atmospheric disruption has been propagated since the 1990s.  The book “Merchants of Doubt” provides a history of claims that volcanoes were responsible for destruction of stratospheric ozone, or for acid rain in the US and Canada.  Those claims were thoroughly debunked long ago.  Nevertheless, articles attributing rising CO2 to volcanoes still appear on climate-change denying websites, (e.g. James Edward Kamis’ 2018 post on ClimateChangeDispatch).

Let’s look at the evidence.

Fossil-Fuel Combustion

When fossil fuels are burned, atmospheric oxygen is converted to CO2.  Consequently, the oxygen concentration in the atmosphere falls.  If we quantify oxygen depletion in the atmosphere, we find that it validates the volumes of fossil fuel consumption reported by inventory methods (BP Statistical Review, CDIAC, EIA, etc.).  The volumes of CO2 determined by either method are approximately twice what is necessary to account for the observed rise in atmospheric CO2.  The remaining CO2 is dispersed into CO2 reservoirs in the oceans and biosphere.  A full accounting of the CO2 flows on earth can be found in the Global Carbon Project or Berkeley Earth websites. 

Simply stated, the depletion of atmospheric oxygen quantifies CO2 emissions from fossil fuels.  This volume of CO2 emssions more than accounts for the rise in atmospheric CO2.  There isn’t any room for a significant contribution from volcanoes without somehow getting rid of the CO2 from the combustion of fossil fuels in some as-of-yet unidentified carbon sink (which is unlikely to exist). 

Depletion of Atmospheric Oxygen

The amount of oxygen in the atmosphere is falling (although not enough to cause trouble for breathing).   Atmospheric oxygen is falling because oxygen is consumed by burning fossil fuels.  This would not occur if the source of rising CO2 was from volcanoes (Figure 2).  As seen in the bulk CO2 and Del C13 charts, there is a strong seasonal signal in the concentration of atmospheric oxygen, related to the growing season in each hemisphere.  The amplitude of the seasonal cycle is somewhat stronger in the Northern Hemisphere, due to the preponderance of temperate land-mass and agriculture. 

Figure 2.  The concentration of atmospheric oxygen is falling, due to combustion of fossil fuels.  The Per Meg (del O2/N2) can be roughly converted to ppm by multiplying by 0.2095, the fractional concentration of oxygen in the atmosphere.  A discussion of the Per Meg (del O2/N2) measure can be found on the Scripps Institute CO2 website FAQs.  The loss of 700 ppm of oxygen is a relatively small change because of the greater abundance of oxygen in the atmosphere as compared to CO2.  The percentage of oxygen in the atmosphere is about 20.95%; the percentage of CO2 in the atmosphere is about 0.04%.

Oxygen Depletion by Hemisphere

Falling oxygen concentrations in the Northern Hemisphere lead falling oxygen in the Southern Hemisphere (Figure 3).  This is because 90% of fossil fuels are being burned in the Northern Hemisphere, consuming oxygen in the Northern Hemisphere.  Atmospheric mixing works to equilibrate oxygen concentrations, but continuing combustion of fossil fuels in the Northern Hemisphere keeps oxygen lower than in the Southern Hemisphere.

Figure 3.  Atmospheric oxygen recorded by Scripps Institute network of atmospheric observatories.   The seasonal cycle at each station was filtered with a 12-month rolling average.  The Northern Hemisphere leads the Southern Hemisphere in falling oxygen.

Oxygen – Carbon Stoichiometry

The number of molecules of oxygen disappearing from the atmosphere is a very close match to the number of carbon atoms burned in fossil fuels and deforestation (Figure 4).  There is a quantitative match, showing that for each atom of carbon burned, one molecule of oxygen disappears from the atmosphere, as C + 02 -> CO2.  The depletion of atmospheric oxygen, in stochiometric balance with human carbon combustion, validates the volume of CO2 released into the atmosphere by burning fossil fuels.  

Figure 4.  Moles of carbon burned by fossil fuels and deforestation annually, compared to atmospheric oxygen depletion in moles.   The close match confirms that volumes of CO2 released from fossil fuels and deforestation are responsible for rising atmospheric CO2.  

Moles of oxygen depletion can be calculated by converting “per meg” to ppm (oxygen/atmosphere) and assuming an initial volume of the total atmosphere of 1.81E+20 moles (various Internet sources).  Notes on the calculation are given in the Appendix, following References.

Volumetric Evidence

CO2 emissions from gas, oil, coal, cement, flaring, and deforestation are now about 40 gt per year, and forecast to go higher.   Estimates and measurements of volcanic CO2 emissions are far smaller than known volumes of CO2 from fossil fuels and deforestation (Figure 5).  Estimated volumes of volcanic CO2 include deep carbon emissions, and passive emissions from continental rifts and mid-ocean ridges.  Volcanic CO2 emissions are only about 1.8% of human CO2 emissions by volume.

Figure 5.  Annual Human CO2 Emissions by type and Volcanic CO2 Emissions, with EIA forecast to 2040.  Estimates of CO2 emissions from volcanic activity have been revised significantly higher since the 1990s, as CO2 emissions from deep volcanic source, continental rifts and mid-ocean ridges have been recognized and quantified.  Still, volcanic CO2 emissions are now estimated at about 700 million tonnes, compared to about 40 gigatonnes of CO2 from fossil fuels and deforestation.

Fraction of CO2 Emissions Which Remain in the Atmosphere

Only about 44% of human CO2 emissions remain in the atmosphere; the rest of the CO2 is absorbed by the oceans or taken up by plants.  Human CO2 emissions are more than twice what is necessary to account for rising atmospheric CO2.  Since volcanic CO2 emissions represent only 1.8% of human CO2 emissions, it is impossible for volcanoes to account for the large volume of CO2 now appearing in the atmosphere.  (Figure 6). 

Figure 6.  If all human CO2 emissions remained in the atmosphere, atmospheric CO2 concentrations would rise about twice as fast as what is observed (red line).  Actual average global CO2 is rising at a rate of about 44% of cumulative human CO2 emissions.  If only volcanic CO2 was entering the atmosphere, atmospheric CO2 would rise only negligibly, offset by the removal of carbon by natural processes.

Difference in CO2 between Northern and Southern Hemispheres, and
Comparison to Net CO2 Emissions from the Northern Hemisphere

About 90% of humans live in the northern hemisphere, and 90% of human CO2 emissions originate in the northern hemisphere.  Atmospheric CO2 concentrations in the northern hemisphere are consistently higher than CO2 concentrations in the southern hemisphere.   The amount of the difference is very close to the net CO2 emissions from fossil fuels in the northern hemisphere (Figure 7).  The close correspondence of net Northern Hemisphere CO2 emissions and the difference between Northern and Southern CO2 concentration is partly a coincidence between the mixing rate between the hemispheres and the reporting period for CO2 emissions.  However, the consistent fit is a clear proof that fossil fuel emissions in the Northern Hemisphere are principally responsible for rising CO2.  The largest volcanic eruptions of the past 60 years have been in the Southern Hemisphere, but these have made no impact on the record of atmospheric CO2.

Figure 7.  Northern and Southern Hemisphere CO2 concentrations, and net fossil-fuel emissions from the Northern Hemisphere.  Major volcanic eruptions, such as Mt. Pinatubo and Mt. Hunter in the Southern Hemisphere in 1991, are not observed as a difference in CO2 observations between the hemispheres. 

Carbon Isotope Ratios in Atmospheric CO2

Natural carbon mostly occurs in two isotopes: C12 and C13.  Plants and all fossil fuels (which derive from plants) are enriched in C12 by biological processes, giving fossil fuel emissions and deforestation a “lighter” isotopic signature (more C12) than the atmosphere.  The measure of carbon isotopic ratios is d C13/C12, typically called “del C13”.  Samples which are relatively enriched in “light” C12 have a negative del C13, while samples that are enriched in “heavy” C13 have a positive del C13.  A technical definition of del C13 is given at the bottom of the article, below the references.

In the 1950s, the atmosphere had a del C13 value of about -7.5, reflecting a higher concentration of C12 than the oceans, which has a del C13 of about zero.  As mentioned above, fossil fuels are enriched in C12 with typical values in the range of -20 to -30.   Biogenic natural gas has been fractionated twice, and may have del C13 values ranging from -40 to -70.  Volcanic emissions have a heavier isotopic signature than the atmosphere, with a del C13 value of about -1 to -4.  

The isotopic composition of the atmosphere is steadily becoming lighter as CO2 concentrations rise.  This is only possible if the additional CO2 is from a source isotopically lighter than the atmosphere, not heavier.  Thus, fossil fuels, and not volcanoes or the oceans, are the source of rising CO2 (Figure 8).

Figure 8.  The Del C13 Carbon Isotopic Record of Atmospheric CO2, recorded by the Scripps Institute.  The record is marked by a strong seasonal cycle in the Northern Hemisphere.  During the Northern Hemisphere growing season C12 is preferentially taken out of the atmosphere by plants, and released back to the atmosphere in winter causing the seasonal cycle in the air.  Overall, the Del C13 index has fallen from -7.5 to -8.5 since 1977, showing an increasing prevalence of light C12 (characteristic of fossil fuels and deforestation) in the atmosphere.

After filtering the seasonal cycle, we see that the Northern Hemisphere leads the Southern Hemisphere in falling Del C13 isotope ratio (Figure 10).  This is because 90% of fossil fuel emissions occur in the Northern Hemisphere. The remaining wavy signal in the Del C13 record correlates to El Nino cycles (Figure 9), with a rapidly falling Del C13 ratio during El Nino events, and a slightly rising Del C13 ratio during La Nina events.  It is unclear whether the El Nino signal in the data is due to fractionation between atmosphere and ocean, changes in the uptake of carbon in the ocean, or related climate events. 

Figure 9.   The Del C13 carbon isotope record in atmospheric CO2, from Scripps Institute atmospheric observatories; the seasonal cycle was filtered with a 12-month rolling average.  Broadly, the Northern Hemisphere leads the Southern Hemisphere in falling Del C13, because 90% of CO2 emissions from fossil fuels occur in the Northern Hemisphere.  The residual long-wavelength signal relates to the El Nino/La Nina cycle. [See an earlier post:
https://dougrobbins.blogspot.com/2013/11/carbon-isotopes-in-atmosphere-part-ii.html ]

Rate of Increase in Global Atmospheric CO2

Atmospheric CO2 is steadily rising around the globe.  Volcanic eruptions are intermittent; the largest eruption (Mt. Pinatubo) and the third-largest eruption (Mt. Hudson) of the past century both occurred in 1991, but there is no perceptible change in the rate of rising atmospheric CO2 (Figure 10).  Likewise, other large volcanic eruptions produced no perceptible impact over the period of detailed CO2 observations [Mount Agung (1963), Mt. St. Helens (1980), El Chichon (1982). Puyehue-Cordón Caulle (2011)].  Slow, *quiet*, emissions of CO2 also occur from non-eruptive events, mid-ocean ridges and onshore rifts, but these have been well quantified over the past 20 years, and do not contribute significant volumes of CO2 to the atmosphere.

Figure 10. Global atmospheric CO2.   This is my version of the Keeling Curve.  Data is from the Scripps Institute network of atmospheric observatories.  Cool colors indicate stations in the Northern Hemisphere. Warm colors show stations in the Southern Hemisphere. Atmospheric CO2 falls in the Northern Hemisphere summer, as carbon is taken up by plants, and rises in winter as the plants decay.  There is a strong seasonal cycle dominated by the Northern Hemisphere due to predominant location of temperate landmass and agriculture in the Northern Hemisphere.  Apart from the seasonal cycle, CO2 has risen steadily from about 314 ppm in 1955 to about 412 ppm today.

Orbiting Carbon Observatories and NASA CO2 Modeling

Two new NASA satellites, OCO2 & OCO3, now provide worldwide continuous CO2 monitoring.  Data gathered by these satellites will provide a detailed identification of the specific sources of CO2 across the entire globe. 

https://www.youtube.com/watch?v=TrQzbXc6LVE

NASA also prepared a supercomputer simulation of atmospheric CO2, based on ground-based and aerial CO2 observations.  A video of the simulation can be seen on YouTube:

https://www.youtube.com/watch?time_continue=33&v=x1SgmFa0r04&feature=emb_logo

The simulation highlights major CO2 sources, in the eastern US, eastern China, industrial centers of central & eastern Europe, oilfields of western Siberia, and wildfires in the Amazon rainforests (Figures 11A and 11B).

Figures 11A and 11B.  Atmospheric CO2 Concentrations from NASA supercomputer simulations for the year 2006.  The location of CO2 sources is apparent from cities, industrial centers, and wildfires.

Conclusion

Rising CO2 concentrations are unquestionably from human sources, as a result of combustion of fossil fuels and deforestation.  There is volumetric, temporal, isotopic, geographic, stoichiometric evidence supporting human sources of rising atmospheric CO2.  There is no evidence that volcanoes make a significant contribution to rising CO2.

References:

Previous Posts on Volcanic and Atmospheric CO2

https://dougrobbins.blogspot.com/2017/06/volcanic-co2-emissions.html

https://dougrobbins.blogspot.com/2016/08/the-keeling-curve-and-global-co2.html

https://dougrobbins.blogspot.com/2013/08/forecast-of-future-carbon-dioxide.html

https://dougrobbins.blogspot.com/2013/05/the-keeling-curve-seasonal-co2-cycles.html

https://dougrobbins.blogspot.com/2012/04/modeling-global-co2-cycles.html

https://dougrobbins.blogspot.com/2012/03/long-term-trends-in-atmospheric-co2.html

https://dougrobbins.blogspot.com/2012/03/seasonal-carbon-isotope-cycles.html

https://dougrobbins.blogspot.com/2012/03/keeling-curve-and-seasonal-carbon.html

Posts on Twitter on Volcanic CO2

https://twitter.com/dougrbbns/status/1128751236012838912

https://twitter.com/dougrbbns/status/1106691152906842117

External References:

Scripps Institute CO2 Home

https://scrippsco2.ucsd.edu/

Scripps Institute O2 Program

http://scrippso2.ucsd.edu/

Boden, et al, 2013, Global and National Fossil-fuel CO2 Emissions, in Global Carbon Atlas

http://www.globalcarbonatlas.org/en/content/fossil-fuel-emissions

http://www.globalcarbonatlas.org/docs/Public_Presentation_of_the_GCA_Paris_EN.pdf

http://www.globalcarbonproject.org/

Burton et al, 2013,  Deep Carbon Emissions from Volcanoes

http://www.minsocam.org/msa/rim/RiMG075/RiMG075_Ch11.pdf

Discussion of CO2 flux from subaerial volcanic eruptions on page 332.

Total CO2 flux from volcanic sources:  637 mT per year, p. 341, table 6.

The eruption of Mt. Pinatubo in 1991 was the largest volcanic eruption since 1912.   That eruption produced ~50 Mt of CO2 (Gerlach et al. 2011).  Individual eruptions are dwarfed by the time-averaged continuous CO2 emissions from global volcanism.  The eruption of Mt. Pinatubo was equivalent to only 5 weeks of global subaerial volcanic emissions. 

The average volume of eruptive CO2 emissions over the past 300 years was only 0.1 cubic kilometers, which suggests an annual rate of about 1 million tonnes of CO2 annually (Crisp, 1984, cited in Burton).

CO2 consumption from continental silicate weathering was 515 Mt/yr, (Gaillardet et al., 1999, cited in Burton).

Metamorphism accounts for the release of about 300 million tonnes of CO2 annually.  (Mörner and Etiope, 2002, Carbon degassing from the lithosphere. Global Planet Change 33:185-203, cited in Burton). 

Lee et al, 2016, Massive and prolonged deep carbon emissions associated with continental rifting,  Nature Geoscience Letters, Jan.18, 2016. 

http://csi.unm.edu/sites/default/files/public/2016_Lee_etal_ngeo.pdf

Paper accounts for additional CO2 emissions from East African Rift, potentially bringing natural world CO2 emissions to 708 mT, an increase of 11% from previous estimates.

Houghton, R.A. 2008. Carbon Flux to the Atmosphere from Land-Use Changes: 1850-2005. In TRENDS: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

http://cdiac.ornl.gov/trends/landuse/houghton/houghton.html

Marland, G., T.A. Boden, and R.J. Andres. 2008. Global, Regional, and National Fossil Fuel CO2 Emissions. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

http://cdiac.ornl.gov/trends/emis/overview

Erik Klemetti, 2015, Volcanic versus Anthropogenic Carbon Dioxide: An Addendum, WIRED website.

https://www.wired.com/2015/04/volcanic-versus-anthropogenic-carbon-dioxide-addendum/

Pre-industrial atmospheric del C13 was about -6.5, and declined following industrialization, in correlation with rising atmospheric CO2.

Individual Volcanic Eruptions

Judy Fierstein, USGS, in Forbes, Ethan Siegel, "How Much CO2 Does a Single Volcano Emit?"

https://www.forbes.com/sites/startswithabang/2017/06/06/how-much-co2-does-a-single-volcano-emit/

Representative del C13 values from volcanism:

https://www.researchgate.net/publication/320194432_Isotopically_delta_C-13_and_delta_O-18_heavy_volcanic_plumes_from_Central_Andean_volcanoes_a_field_study

Del C13 :  -3.2

https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2016GL068499

Del C13: -4.9 to -6.3

https://www.researchgate.net/publication/225535635_First_13C12C_isotopic_characterisation_of_volcanic_plume_CO2

Del C13: Currently  -0.9 to -1.4; 1970s and 1980s ~ -4

http://csi.unm.edu/sites/default/files/public/2016_Lee_etal_ngeo.pdf

Del C13: -6 to -10.  N.B.: These are samples of soil gases in a rift zone with known petroleum generation, and may be contaminated by thermogenic or biogenic CO2 deriving from petroleum sources.  

Faure, 1984, Principles of Isotope Geochemistry
Del C13: -2 to -6. 

Volcanoes and CO2

http://www.volcanocafe.org/volcanoes-and-co2/

http://www.volcanocafe.org/volcanoes-and-co2-continued/

A good discussion of former and current estimates of CO2 emissions from volcanoes and fossil fuels.  Also, a good recap of errors made by certain commentators in creating and propagating the volcanic CO2 myth. 

Naomi Oreskes and Erik Conway, 2010, Merchants of Doubt.

A deeply researched book about right-wing scientists, funded by industry, working outside of their fields of expertise, tried to throw doubt on science that might result in regulations in the interest of public health or environmental protection.  The scientists involved were generally retired, had worked in military science and were given compensation or recognition in return for their efforts.  Among the false narratives they created was the idea that volcanoes were responsible for chlorine damage to stratospheric ozone, and that volcanoes were responsible for acid rain in the US and Canada.  Neither idea is correct.  The idea of blaming volcanoes for man-made atmospheric disruption has now been extended to CO2 and climate change.

Which emits more carbon dioxide: volcanoes or human activities?  Climate.gov.

https://www.climate.gov/news-features/climate-qa/which-emits-more-carbon-dioxide-volcanoes-or-human-activities

The following are examples of deliberately misleading media articles about atmospheric CO2.

Volcano eruption WARNING: Intense volcanic CO2 activity 'drives GLOBAL EXTINCTION'

https://www.express.co.uk/news/science/973192/Volcano-eruption-warning-carbon-dioxide-CO2-extinction-climate-change

Article omits mention of fossil fuels entirely.

J.E. Kamis, 2018, Discovery Of Massive Volcanic CO2 Emissions Puts Damper On Global Warming Theory

https://climatechangedispatch.com/massive-volcano-emissions-warming/

This article contains false claims.  Notably, the article claims that:

“Natural volcanic and man-made CO2 emissions have the exact same and very distinctive carbon isotopic fingerprint.  It is therefore scientifically impossible to distinguish the difference between volcanic CO2 and human-induced CO2 from the burning of fossil fuels (see here).”

The reference provided (https://skepticalscience.com/anthrocarbon-brief.html) directly contradicts the claim!  “In fact the global C13/C12 ratio has declined, which is very strong evidence the source of the CO2 increase has was C12 enriched, ie, derived from photosynthesis.  Therefore it is very strong evidence that it comes from the biosphere or fossil fuels, rather than from volcanoes or oceanic outgassing.”

Appendix

Stoichiometry Calculations
Annual fossil fuel emissions are reported in tonnes of CO2 by CDIAC, the BP Annual Statistical Review of World Energy, and the EIA.  One tonnes of CO2 (1000 kg) contains 22,722 moles of CO2. 

Calculation Notes for atmosphere stoichiometry.  The Scripps pages on units and FAQs are helpful in understanding the use of the “per meg” unit, and conversion to ppm. 

http://scrippso2.ucsd.edu/units-and-terms.html

http://scrippso2.ucsd.edu/faq.html

“Per meg” units of oxygen reported by Scripps can be converted to ppm (oxygen/atmosphere) over small ranges by multiplying by 20.95%, the current oxygen fraction in air.  Parts per million (ppm) of oxygen can then be converted to moles by multiplying by the number of moles in the atmosphere (1.81E+20), from various Internet sources.  https://www.theweatherprediction.com/habyhints3/976/

A Few Words about CO₂ Carbon Isotopes

There are two stable isotopes of carbon, C13 and C12.  C12 is the more abundant isotope; the natural ratio of C12 to C13 is about 99 to 1.  The standard measure of carbon isotopes compares the C12/C13 isotope ratio of the sample in question to the C13/C12 ratio of a standard limestone, according to the expression:

d C13/C12 = ((C13/C12 sample/C13/C12 standard) – 1)*1000.

This expression, commonly termed “del 13”, amplifies small but meaningful differences in the isotopes, which are diagnostic of certain processes and occurrences of carbon.  The standard is a uniform Cretaceous limestone with a d 13 value defined as zero.   Positive values indicate a heavier composition, i.e., a greater concentration of C13 than the standard.  Negative values indicate a lighter composition, i.e., a smaller concentration of C13 than the standard.

Plants fractionate carbon, favoring the lighter isotope C12.  Anything derived from plants, including oil, gas, and coal (and algae, animals and people) carries a light (negative) d C13/C12 signature.  Limestone carries a d C13/C12 ratio near zero.  The atmosphere, in 1977, had a d C13/C12 ratio of about -7.5; it is currently about -8.3, reflecting the influence of fossil fuels.  Oceans have a slightly positive d C13/C12 ratio of dissolved inorganic carbon, although Northern Hemisphere waters show a negative ratio due to the greater use of fossil fuels in the Northern Hemisphere.  Fossil fuel CO₂ emissions and CO₂ emissions from deforestation carry a very light d C13/C12, often in the range of -25 to -28 (although biogenic natural gas, which is fractionated twice, can have del 13 value in the range of -40 to -70).  The distinctive isotopic signature of CO₂ from fossil fuels and deforestation is useful in tracking the movement of carbon through the atmosphere and oceans.  

Carbon Isotopes in the Atmosphere -- Part II

Finding Niño -- Correlating CO2 Carbon Isotopes in the Atmosphere with the El Niño Cycle

Abstract:

Carbon dioxide released by fossil fuels has a lighter isotopic composition than CO2 in the atmosphere.   The distinctive signature of light carbon released from fossil fuels provides a tool for tracking the movement of carbon through the atmosphere.  That same distinctive signature can also be used to measure the exchange of carbon between the atmosphere and carbon reservoirs on the earth’s surface.

Carbon istotope ratios in the air have been measured at monitoring stations around the globe since 1977.  Despite superficial similarity to the bulk CO2 record, isotope records tells a different story, and give deeper insight into the workings of the earth’s carbon systems. 

Part I of this post discussed how we can measure the size of carbon reservoirs exchanging carbon with the atmosphere.  We defined the term "Carbonsphere" representing the sum of all reservoirs freely exchanging carbon with the atmosphere.   We estimated the size of the carbonsphere as 5200 gigatonnes, about seven times the carbon volume of the atmosphere, based on the dilution of light isotopes from fossil fuel emissions.   

In this post, we will examine fluctuations in atmospheric carbon isotopes, and show how these can be correlated to the El Niño/La Niña climate cycle.  A number of mathematical operations on the base carbon isotope data reveal a clear correlation to the El Niño cycle.

 d C13/C12 CO2 isotope fluctuations correlate with the El Niño/La Niña climate cycle.

The El Niño/La Niña cycle controls how the Pacific Ocean exchanges carbon with the atmosphere.  The mechanism is not clear.   Two hypotheses are considered.  First, ocean currents may move carbon from shallow water into the deep ocean during La Niña events.  Or second, ocean temperatures may cause selective absorption and release of carbon isotopes, favoring absorption of light isotopes in cool water, and heavy isotopes in warm water.  The isotope cycles represent the ocean "breathing" -- taking in light isotopes during the cool phase, and exhaling during the warm phase.  Isotope data from dissolved carbon dioxide in the Pacific Ocean would answer the question.

 Carbon isotope data should be monitored throughout the earth’s carbon reservoirs to recognize and quantify the movement of carbon, and to understand the destiny of carbon emitted by burning fossil fuels.

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Carbon Isotopes in the Atmosphere

As described in previous posts, the isotope ratio d C13/C12 is the standard expression of stable carbon isotopes.   The d C13/C12 formula allows recognition of small but meaningful changes in the ratios of carbon isotopes.    In this post, d C13/C12 will be referred to by the expression “del 13”.

Let’s begin by comparing the bulk CO2 record (the “Keeling Curve”) to the del 13 record. 

Figure 1 shows atmospheric CO2, as measured at monitoring stations located from the Arctic Ocean to the South Poel.   The chart shows increasing CO2 concentration in the atmosphere due to fossil fuel emissions.  The record shows a strong seasonal cyclicity resulting from plant growth in the northern hemisphere, as discussed in previous posts.  The chart is color-coded according to the latitude of the monitoring stations.  

Figure 2, location of CO2 and Carbon Isotope Monitoring Stations.

Figure 3 shows the isotopic ratio d C13/C12, otherwise known as “del 13”, in atmospheric CO2.

The del 13 record resembles the Keeling Curve.  There is a strong cyclity in the isotope record resulting from seasonal plant growth and decay in the Northern Hemisphere, as discussed in a previous post. 

In general , the isotope record is a mirror image of the bulk CO2 record.   The long-term bulk CO2 is increasing due to fossil fuel emissions, and the del 13 record is decreasing, reflecting the light isotopic composition of fossil fuels.  The del 13 ratio of fossil fuel emissions is about – 26, compared to the del 13 ratio of the atmosphere, at about – 7.5.   The seasonal cyclicity is likewise a mirror image.  As plants take up carbon in the summer, the concentration of atmospheric CO2 decreases, while the del 13 ratio increases, because the plants preferentially remove light isotopes from the atmosphere. 

Let’s begin the investigation of atmospheric carbon isotopes by removing the seasonal cycle.   For reference, we will first look at the bulk CO2 data, after filtering the seasonal cycles with a one-year rolling average, seen in Figure 4 below.

 Let’s compare the del 13 carbon isotope data, after removing the seasonal cycle with the same technique, shown in Figure 5.

 This is an amazing chart!    There are two surprises immediately apparent in the del 13 chart, in comparison to the bulk CO2 chart.   First, there is a wide separation between the curves on the del 13 chart, whereas the bulk CO2 curves are in a narrow band.   Second, the del 13 chart shows large waves moving through the data, whereas the bulk CO2 curves are smooth and nearly linear.   Let’s explore these two differences.

The del 13 chart shows a wide separation of curves by latitude.  The time required for equilibration between northern and southern hemisphere is much longer in the isotope data than in the bulk CO2 data.   The falling del 13 ratio at the South Pole lags the readings in Alaska by about eight years, while the rising bulk CO2 concentration at the South Pole lags the northernmost readings by only about two years.

Figure 6 shows the 2- year time lag required for the concentration of CO2 at the South Pole to equilibrate with the far northern hemisphere.  

Figure 7 shows the 8-year time lag required for the CO2 del 13 ratio at the South Pole to equilibrate with the far northern hemisphere.

What can account for the difference in the time required for equilibration between bulk carbon and carbon isotopes?   I suggest that light isotopes released in the northern hemisphere by fossil fuels have a long residency time in carbon reservoirs.    The difference in equilibration times shows exchange of carbon between the atmosphere and carbon reservoirs.  These reservoirs are not simply carbon sinks, but are actively exchanging carbon with the atmosphere.   Light carbon from fossil fuels is absorbed by carbon reservoirs near the point of emission; the bulk CO2 concentration of the atmosphere is maintained by the release of heavier carbon from the reservoir back to the atmosphere.

There is a second surprise in the del 13 chart, compared to what we see in the bulk CO2 data.  When we remove the seasonal cycle from the bulk CO2 data, the curves are very smooth, almost linear.   However, when we remove the seasonal cycle from the del 13 data, we see a series of large waves, observed at every monitoring station across the globe.  These are events which were not removed by the seasonal filter.  There are a few events which occurred only in the northern hemisphere, and a few which occurred only in the southern hemisphere. 

There is a remarkable paradox in the del 13 chart.   The paradox lies in the different responses of the atmosphere to perturbations of the carbon isotope ratio.   Following a perturbation in del 13 as a result of fossil fuel emissions in the northern hemisphere, nearly a decade is required for the air at the South Pole to reach to the same level of isotopic composition.   But the waves moving through the del 13 chart occur nearly simultaneously at every monitoring station on earth!   Although the del 13 values do not equilibrate to the same value, this signal is felt around the world with a lag of less than six months.   I would speculate that this indicates two carbon reservoirs; one on land, and the other in the ocean.   The land system locks up carbon in forests and soils, accounting for the long residency time, while the ocean system more readily propagates changes around the globe. 

On that hunch, I plotted measurements of the El Niño – La Niña cycle on the del 13 plot.   Figure 8 shows an apparent correlation of strong El Nino events to periods of rapidly falling del 13. 

Figure 8.  Atmospheric carbon isotopes and El Niño events.

To clarify the wave-like signal in the data, I took the average of all curves, and a linear regression through the average curve.  

Figure 9.   Atmospheric CO2 del 13 ratios, with average curve and linear regression.

I then subtracted the linear fit from the data, to produce a chart of the residual values after removing the linear trend.

Figure 10.  Chart of Residual del 13, after subtraction of linear trend.

We can compare the residual chart with the El Nino events.  El Nino events tend to correspond to negative slopes on the residual chart. 

Figure 11.  Chart of Residual del 13, with El Niño events.

If we recall Part I of this post on carbon isotopes, a relative increase in del 13 corresponds to a larger carbonsphere; relative decreases in del 13 correspond to a smaller carbonsphere.   It is the slope of the residual function that is significant, rather than the peaks and valleys.   Changes in slope indicate a change in conditions.  A positive slope indicates an expanding carbonsphere – fossil fuel emissions are being diluted into a larger volume of carbon reservoirs.  A negative slope indicates a shrinking carbonsphere – fossil fuel emissions are being diluted into a smaller volume of carbon reservoirs. 

So, to complete the transformation of the del 13 data, we now take the derivative, or instantaneous slope of the residual curve.   On this chart, positive values will indicate an expanding carbonsphere, and negative values will indicate a shrinking carbonsphere. 

Figure 12.   Derivative of Residual del 13 data; all curves.

The initial chart is rather noisy.   A better signal to noise ratio can be obtained by taking the average of all curves, to produce the following curve.  Positive values indicate an expanding carbonsphere (the light isotope is being diluted into a larger volume), and negative values indicate a shrinking carbonsphere (the light isotope is being diluted into a smaller volume). 

Figure 13.  Derivative of residual del 13 data, from average of all curves.

La Nina/El Nino

El Niño is an oceanic phenomenon, involving anomalously warm surface waters in the Pacific Ocean.  The warm waters develop off the western coast of South America, and extend westward across the equatorial Pacific Ocean.  El Niño events have profound meteorological impact, and influence weather around the globe.   The opposite of the El Niño event is termed La Niña, and involves anomalously cool Pacific waters.

Figure 14.  Pacific Ocean Temperature Anomalies, showing El Niño and La Niña events;(from  NASA).

                  http://www.elnino.noaa.gov/lanina.html

The National Oceanographic and Atmospheric Administration keeps a record of the strength of the El Nino – La Nina cycle, and expresses that record as the Oceanic Nino Index (ONI).    The data are a time series of three-month average sea surface temperature anomalies.    For the purposes of this blog post, I have reversed the sign of the ONI values, making La Nina events positive, and El Nino events negative.

Figure 15.  Here is the chart of the Oceanic Nino Index (polarity reversed).  

We can superimpose the chart of the Oceanic Niño Index, and the slope of the residual del 13 measurements.   Despite some noise, there is a clear and perceptible correlation between the curves.  

Figure 16.   Averaged derivative of residual del 13 data, and Oceanic Niño Index (from NOAA).

The ONI curve does not match the isotope data, in terms of the timing of events.  There is a brief lag between the ONI curve (representing surface temperature anomalies, and the del 13 data indicating isotopic changes in the atmosphere.  I added a six month lag to the ONI curve, in order to make a better match to the observed isotope data. 

Figure 17.  Average derivative of the residual del 13 data, and ONI curve with a 6 month lag.

We’ve performed a number of transformations of the atmospheric CO2 carbon isotope data, in order to reach the curve that corresponds to the Oceanic Niño Index. 

Figure 18.   Here is a summary slide indicating the transformations. 

The meaning of the correlation is not clear at this time, but it is clearly a significant phenomenon for global climate study.  I can advance two hypotheses. 

Deep Current Hypothesis

My first thought was that La Niña conditions indicated currents which displaced waters of the shallow Pacific Ocean into deeper water.  When La Niña conditions prevail, carbon which is enriched in light isotopes due to fossil fuels is transported and sequestered in the deep ocean.  The shallow water would be replaced by deeper waters, which still carry pre-industrial del 13 ratios (of about -6.5, based on ice core data).   Such a current would expand the Carbonsphere (as discussed in the previous post) and dilute light isotopes from fossil fuels into a larger volume of carbon reservoirs.   El Niño conditions would be stagnant, allowing heat to build up in shallow waters, and light isotopes from fossil fuels to accumulate.  El Niño would shrink the Carbonsphere, relative to La Niña.

CO2 Solubility and Isotope Differentiation Hypothesis

My daughter suggested a different hypothesis to me; one that is more probably correct.  She suggested that temperature changes in the shallow ocean should change the solubility of CO2, and the rate of exchange with the atmosphere.  An extension of that thought is that changes in the temperature of the water may differentiate the carbon isotopes being exchanged with the atmosphere.   Thus, during La Niña events, with cold Pacific water, light isotopes may be better absorbed by the water, raising the del 13 of the atmosphere.   During La Niño events with warm Pacific water, heavy isotopes may be better absorbed by the water, lowering the del 13 of the atmosphere.

NOAA is now conducting research and modeling on sea-air carbon exchange, with a focus on the Pacific Ocean, and the El Nino-La Nina cycle.  However, I have not seen data regarding isotope differentiation through that process.  Figure 19 shows one map from that study.

Figure 19.  Carbon Flux map from NOAA study.  The upper map shows carbon flux in absolute terms; the lower map shows relative variability from the normal pattern.  Positive values (reds) indicate less uptake of CO2 by the ocean from the atmosphere.  The year chosen is a strong La Nina year.  However, the published maps do not address the behavior of carbon isotopes as a function of temperature.  

Carbon isotope data in the waters of the tropical Pacific is needed to resolve the question.  If the current hypothesis is correct, the cool waters of La Niña would be have high, pre-industrial del 13 values of about -6.5 (from ice-core data).   If the isotope differentiation model is correct, La Niña waters would be enriched in light isotopes relative to the atmosphere, lower than -8.2.   This question of interpretation would seem to be easily resolved by additional data.   Physical solubility data and modeling would be helpful, but direct measurements of carbon isotopes in water would be definitive.   The isotope data must target chemical species related to aqueous carbon dioxide – carbonate, bicarbonate, and carbonic acid. 

Further, if the current hypothesis is correct, La Niña is transporting a measurable quantity of atmospheric carbon into the deep ocean.   From that information, the volume of water and quantity of heat carried by the current could also be calculated, providing key data in understanding the pace of global warming on earth.

Isotope data through all of earth’s carbon reservoirs would be helpful in understanding the movement of carbon through those systems, and the destiny of carbon emitted by burning fossil fuels.

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References:
Atmospheric CO2 Carbon Isotope Data:

Keeling, R.F. S.C. Piper, A.F. Bollenbacher, and S.J. Walker. 2010. Monthly atmospheric ¹³C/¹²C isotopic ratios for 11 SIO stations. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

http://cdiac.ornl.gov/trends/co2/iso-sio/iso-sio.html

Global Emissions average isotope data

Boden, T.A., G. Marland, and R.J. Andres. 2013. Global, Regional, and National Fossil-Fuel CO₂ Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2013

http://cdiac.ornl.gov/ndps/db1013_v2012.html

ftp://cdiac.ornl.gov/pub/db1013_v2012/db1013.global.dat

El Nino/La Nina Climate Cycle

http://www.elnino.noaa.gov/lanina.html

Oceanic Nino Index

http://www.nwfsc.noaa.gov/research/divisions/fe/estuarine/oeip/cb-mei.cfm

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml

Data:  http://www.cpc.ncep.noaa.gov/data/indices/oni.ascii.txt

Carbon Flux Models -- NOAA

http://www.pmel.noaa.gov/co2/file/CO2+Flux+Map

http://www.oco.noaa.gov/oceanCarbonUptake.html

http://www.pmel.noaa.gov/co2/story/Surface+CO2+Flux+maps

Interactive mapper:  http://cwcgom.aoml.noaa.gov/erddap/griddap/aomlcarbonfluxes.graph

Previous posts om this site regarding atmospheric CO2:

1)  The Keeling Curve
     http://dougrobbins.blogspot.com/2011/05/keeling-curve.html

2)  The Keeling Curve and Seasonal Carbon Cycles

      http://dougrobbins.blogspot.com/2012/03/keeling-curve-and-seasonal-carbon.html

3)   Seasonal Carbon Isotope Cycles

      http://dougrobbins.blogspot.com/2012/03/seasonal-carbon-isotope-cycles.html

4)   Long-Term Trends in Atmospheric CO2

      http://dougrobbins.blogspot.com/2012/03/long-term-trends-in-atmospheric-co2.html

5)   Modeling Global CO2 Cycles

      http://dougrobbins.blogspot.com/2012/04/modeling-global-co2-cycles.html

6)   The Keeling Curve Summary:  Seasonal CO2 cycles and Global CO2 Distribution
       http://dougrobbins.blogspot.com/2013/05/the-keeling-curve-seasonal-co2-cycles.html

7)   Carbon Isotopes in the Atmosphere, Part I -- How Big is the Carbonsphere?
       http://dougrobbins.blogspot.com/2013/11/how-big-is-carbonsphere.html