CO2 Increase

CO2 in our atmosphere is still increasing. Last year the annual average amount has passed 400 ppmv (part per million by volume) for the first time in a long time — at least a million years.

The reason: we’re burning fossil fuels like oil, coal, natural gas. When we do, it turns that long-buied carbon into carbon dioxide, which ends up in the atmosphere. It’s as simple as that.

Lately, though, more and more are talking about reducing our emissions of CO2. So, how is planet earth doing? We haven’t stopped increasing atmospheric CO2, but is there any sign that at least we’ve slowed down?

Here’s CO2 concentration from the Mauna Loa atmospheric observatory:


Clearly there’s an annual cycle; we can see the planet “breathe” in and out each year. During spring and summer in the northern hemisphere (where most of the land is) plants grow, absorbing CO2 from the atmosphere. During fall and winter they decay, releasing CO2 back into the air.

So, the first thing I’ll do is remove the annual cycle to give a clearer picture of the changes which are not part of that annual cycle of plant growth and decay.


Then I’ll compute yearly averages of such “de-seasonalized” data. We get this:


Yes, it’s still going up. But how fast? I’ll estimate it in two ways. For one, I’ll fit a smooth curve, using a method which simultaneously estimates the rate of change. For an even simpler method, I’ll just take the difference in the amount from one year to the next. Both will give me estimates of how much CO2 is increasing each year, which we can examine for growth rate changes.

The two methods are in excellent agreement (black dots are the year-to-year changes, the red line is the smoothed estimate):


The rate of CO2 growth has been increasing (we knew that) so CO2 concentration has been accelerating. Unfortunately is hasn’t yet shown any sign that the acceleration has stopped.

We can also compute average CO2 over 5-year time spans, and smooth the data on a slower time scale, to get a more “ponderous” estimate of the growth rate. That gives this (again, the red line is the smoothed rate while the black dots are the rates estimated from 5-year averages):


There’s still no sign that we’ve stopped the acceleration of atmospheric CO2, let alone actually decreased the growth rate.

The world is finally waking up to the fact that to avoid climate disaster, we need to reduce CO2 emissions. But it seems not yet to have realized that what we really need to do is stop CO2 increase. The frightening truth is that not only have we failed to stop CO2 growth, we haven’t even slowed it down.

The more frightening truth is that as warming increases, we run the risk of triggering feedbacks in the carbon cycle. Perhaps the biosphere and/or ocean have already lost their capacity to absorb as much of our emissions as they have so far. We might trigger massive melt of the world’s permafrost, which could release massive amounts of carbon quite apart from what we’re digging out of the ground and burning.

If the warming we’ve already brought about, or that soon to come, releases yet more CO2 from sources other than fossil fuels …

If you like what you see, feel free to donate at Peaseblossom’s Closet.


36 responses to “CO2 Increase

  1. I think there is precious little understanding (outside of the scientific community) that carbon dioxide is a long lived gas. The popular and political perception is that once carbon emissions are reduced, the concentration of carbon in the atmosphere will decrease shortly afterwards and we will return to the old normal.

    This misperception is a very dangerous one. Our atmospheric bathtub acts more like one with a plug than one with an empty drain.

    • “I think there is precious little understanding… that carbon dioxide is a long lived gas.”

      Quite possibly, though I suspect a lot of folks haven’t thought about it enough to consider such matters.

    • skeptictmac57

      I agree George, and I have made this point often myself. But it’s even worse than that, since once we start reversing the trend (if we do) then we will also have the whiplash effect of reduced aerosols in the atmosphere that are masking an unknown amount of potential energy input. I have seen research on the estimated effect, but I am not sure that we have a good handle on what the actual number would be. Maybe someone else has seen more definitive research?

      • > Maybe someone else has seen more definitive research?

        >Maybe someone else has seen more definitive research?

        In this article

        Michael Mann estimates about 45ppm CO2e from aerosols if I understand this (quote below) correctly ie 450-405

        >These findings have implications for what we all must do to prevent disaster. An ECS of three degrees C means that if we are to limit global warming to below two degrees C forever, we need to keep CO2 concentrations far below twice preindustrial levels, closer to 450 ppm. Ironically, if the world burns significantly less coal, that would lessen CO2 emissions but also reduce aerosols in the atmosphere that block the sun (such as sulfate particulates), so we would have to limit CO2 to below roughly 405 ppm.

      • skeptictmac57, It’s my understanding that aerosols and land use changes have offset around .9C of GHG warming, about equal to the observed warming we have seen so far.

  2. I don’t think that the world really has woken up to the fact that we need to reduce CO2 emissions. If the Paris agreement signalled a change there then it is hardly noticeable, except in the mutual congratulations from the delegates. Even the global financial crisis and the subsequent anaemic economic growth rates have barely put a dent in the acceleration. Michael Mann thinks we can’t go above 405 ppm CO2, if we are to avoid a 2C rise, and yet we’re already above 400 (latest readings are over 402). Even reductions in emissions won’t meet that particular target.

    By the way, I think you meant “last year”, at the beginning of the second sentence! We can’t have an annual average amount for this year, after only 10 days. :)

    [Response: Right you are]

  3. Reblogged this on Anmerkungen und Beobachtungen and commented:
    Ich denke, dass dies für Viele die Situation noch deutlicher werden lässt.

  4. David B. Benson

    What is required is a significant carbon dioxide decrease. Because just stopping the increase leaves Terra with the same carbon dioxide levels as before in the Pliocene with sea stands around 25 meters higher than now.

  5. thefordprefect

    ” we can see the planet “breathe” in and out each year. During spring and summer in the northern hemisphere (where most of the land is) plants grow, absorbing CO2 from the atmosphere. During fall and winter they decay, releasing CO2 back into the air”
    The planet breathes, plants “breathe” grow and rot.
    However, the max pk to pk CO2 is from stations far north. e.g. Alert – gets less towards equator.
    The autumn and winter temperature will slow the rotting to low levels limiting the release of CO2.
    Are these sufficient to increase the CO2 level to that of NH spring with sub zero temperatures?.
    However as stated, plants breathe – CO2 out in the dark (respire) O2 in the light (photosynthesis). And far north is full of dark in winter and light in summer!
    Could the annual cycle be due to phytoplankton and plants breathing

    • I suspect that “the winter increase in atmospheric CO2 concentration is due to leaves rotting” is a simplistic explanation given by scientists to a nonscientific public (DISCLAIMER: I am not a scientist, and I therefore don’t know what I am blabbering about). I have heard that terrestrial plants and the oceans have taken up about 55% of the human CO2 emissions. If so, this seems to mean that instead of an increase of ~80 ppm from 1960 to the present, we would have seen an increase of ~178 ppm, which would give us a current atmosphere with 498 ppm in the absence of photosynthesis and CO2 dissolving in surface water.

      I do not doubt that rotting plant material contributes some CO2 to the atmosphere in the winter. But I also suspect that the absence of photosynthesis removing human-emitted CO2 also contributes to increased rate of atmospheric CO2 growth in the winter.

      Several other factors are neglected for simplicity: the temperature dependence of plant respiration, the seasonal change in plant respiratory surface area, the temperature dependence of rock weathering, the seasonal covering of rock surface with forms of solid water (snow and ice), the temperature dependence of the equilibrium between atmospheric CO2 and CO2 dissolved in surface water, the seasonal dependence of surface water in liquid form, and so on.

      In summary, I suspect that ”we can see the planet ‘breathe’ in and out each year. During spring and summer in the northern hemisphere (where most of the land is) plants grow, absorbing CO2 from the atmosphere. During fall and winter they decay, releasing CO2 back into the air” is more of a “sound bite” that captures a significant part of the full picture but fails to tell the whole story.

    • I very much doubt the annual cycle could be attributable to phytoplankton. The Southern Hemisphere is where the huge expanses of oceans are. If you look at the difference between CO2 readings in northern and southern regions, the south is pretty steady.

      When you watch the first part of this animation you see the one step at a time, plodding, steady rise of CO2 concentrations measured at the South Pole while the Mauna Loa and other NH recording sites dance about tremendously.

  6. Watching the Mauna Loa CO2 levels will be an interesting exercise over the next decade. Just what will the world do if our “efforts” at reducing emissions don’t work?

  7. Is there a forum where I can find (and pester) carbon flux experts? I’m trying to wrap my head around the scales of various sinks and sources of CO2. For example, all the years of pine tree crops being “sequestered” in A-frame housing, all the indigestible plastics going into landfills, the total additional CO2 volumes from the increased wildfires, and plankton plankton plankton.

  8. David B Benson’s response above has it right. Halting the increase in CO2e outputs is the first of a series of goals, followed by the goal of significantly reducing outputs, followed by the goal of ending those outputs, followed by the goal of recovering the carbon now resident in the atmosphere and oceans that is driving most of AGW.

    Of these, the last one is the only one that matters in terms of stabilizing the climate – the rest are just milestones.

    The urgency of getting to the point of cleansing the atmosphere is not, IMHO, about avoiding a particular global surface air temperature, but about avoiding the acceleration of the 7 non-linear Major Interactive Feedbacks to the point where their outputs offset our efforts at emissions reduction. At present, they are plainly winning that race hands down, as we’re still raising our emissions.

    Consider: a 2014 paper by the eminent Prof Schaefer et al: “The impact of the permafrost carbon feedback on global climate” ( ) warned that a non-linear rise in permafrost carbon output is liable by 2100 to use up much of the carbon budget on which the IPCC ‘pathway’ used at CoP21 was based. In late 2015, PNAS published a paper by NOAA and others: “Cold season emissions dominate the Arctic tundra methane budget” ( showing that permafrost methane outputs, which are 84 times as potent as CO2 over the crucial 20-yr horizon, continue in the winter especially in dry upland tundra. Thus Schaefer et al’s 2014 paper actually seriously understated the rising CO2-equivalent emissions from permafrost.

    And consider: – The equally eminent Prof Ramanathan et al’s 2014 paper “Observational determination of albedo decrease caused by vanishing Arctic sea ice” ( ) used the satellite record since 1979 of arctic sea-ice decline to show its resulting albedo loss whose global warming effect has on average been equal to around 25% of that of anthro-CO2 over the period. – Globally the Albedo Loss Feedback is somewhat larger as the recent minor rise in Antarctic sea ice from raised glacier outputs etc is more than offset by the strong trend of declining global snow cover.

    Given that the White House is likely the best-informed on the rising hazard of any govt on the planet, its conduct on climate since 2001 is clearly bizarre. The latest coup has been of promoting and successfully setting a voluntary global goal of “Net-zero emissions in the 2nd half of the century.” The lack of urgency is palpable.

    With respect I’d thus suggest that the most common and most pernicious form of denial is the Denial of Urgency – and that the media, politics and science shills so elegantly debunked here are actually only providing political cover for that denial of the need of urgent action. It is the White House that sets the targets, such as its Paris ‘pledge’ of 12% off the legal 1990 UN baseline in 10 years time, and it is the President who should be massively criticized for the reckless US climate policy.

    Lewis Cleverdon

  9. Paris COP21 may have nailed the lie that AGW isn’t a problem for mankind. But what has yet to be established in the public or political mind-set is that we have a fight on our hands with the AGW issue. This has long been evident. And the longer we fail to act vigorously, the more difficult that fight becomes. So it’s not over yet.
    Emerging from the emissions data in recent years are some reassuring signs. There is the arrival in the ranks of top emitting countries of more developing economies while the established economies do show signs of emission rates peaking and even declining. (Compare the second & third graphic here which show the top 20 rankings for 2007 and 2013.)
    Yet there is a need for a little caution in, say, celebrating the achievements of the UK in cutting its GHG emissions. The data looks very encouraging at face value (33 page 2014 report here) with 2014 CO2 down 29% on 1990 and GHGs down 36%.
    The UK is (assuming some right-wing government doesn’t decide it isn’t) committed to cutting GHGs to 80% of 1990 levels by 2050 with 5-year milestone targets. All seems well. Such cuts would provide the below-RCP2.6 contribution and, as the 2014 figures show, the milestone targets are so far met.
    Except there is the history of emissions. The UK has a track record. It kicked off AGW. It has higher accumulative emissions even that the USA. Only tiny Luxembourg has outdone the UK in GHGs (due to a very large steel industry shoehorned into a very small country). Simply ‘doing its bit’ isn’t good enough for a country like the UK.
    And the cuts that have been achieved are not all entirely as they seem. Cynics have said the UK CO2 reductions result from exporting our industries plus swapping coal for gas at the power stations. There is a lot of truth in that, certainly before 1990, indeed before 2007.
    The UK’s 29% CO2 reduction 1990-2014 ignores the net import of carbon footprint which was growing to 2007. Since 2007 it has dropped back to roughly 1990 levels but it remains positive and a growing percentage of the UK’s GHG emissions (30% in 1990, 44% in 2013).
    So that 2013 UK CO2 reduction is more like 22% with a third of that (7%) from the swap from coal to gas which is a short-term fix as the gas continues to emit. The remainder of the 22% is down to 9% cuts from using less energy plus a renewables contribution of 6% but beneath the radar is 2% of this from using imported biomass, that is the likes of replacing US coal by buying in US wood chips or adding Egyptian recycled cooking oil to our diesel.
    From my analysis I conclude that the UK has done a lot but has only scratched the surface of the solution. And until the difficulties we face with solving AGW are properly understood, that solution will crucially not be delivered in a timely fashion.

    • It seems unfortunate (I am crying over spilt milk) that the UNFCCC determined to use climate scientists effectively via the IPCC mechanism (a few were muzzled and many were willingly co-opted). A sad example is Richard Somerville, who misrepresents physicians at the beginning of his March 2015 TEDxUCSD talk ( We climate scientists are planetary physicians. We advise, but you decide.

      I cannot believe that Somerville has never heard of quarantines or commitment procedures when the patient presents a danger to others.

      As co-author of the famous “Ski Slope” paper (see Physics Today, October 2011, page 48), Somerville is also well aware that the time for moderate “reasonable” actions to reduce CO2 emissions has passed and gone. (Also see for a 2015 discussion of this point.)

  10. The apparent peaking of emissions from Western nations is nothing more than an attractive deception, caused by the wholesale export of manufacturing industries to Asia. We send them money and they send us stuff — doing our emissions for us in the process. In a global economy, with a global climate, only global emissions matter.

  11. An interesting experiment would be to try the detect the impact of ENSO on CO2.

  12. Wow. Your first chart showing the CO2 rise rate versus time lays right over the UAH satellite temperature record. Pinatubo depression in 92/93, check. Super el nino in 97/98, yes. Step up to new plateau after 98 el nino, yes. It is often said that in skeptical communities that comparing the rise in CO2 with the rise in temperature does not correlate. It does with this first derivative of the data set, the acceleration of the CO2 rate rise.

    • True, because of Henry’s Law: when the temperature rises, the ocean absorbs less of what we emit, leaving more of what we emit in the air. When the temperature falls, the oceans absorb more of what we emit, leaving less of what we emit in the air.

    • You shouldn’t expect the atmospheric CO₂ increase to correlate closely with temperature on short timescales (annual or even decadal). CO₂ is a rate effect, leading to a net radiation imbalance (measured in planet-wide W/m²). Heating, on the other hand, is nearer to an aggregate effect, reflecting the large thermal inertia of the system (which is mostly in the oceans; more like J/m²). So to a first approximation* you’d expect temperature change to correlate with some time integral of the CO₂ increase (J/m² == W/m² x s). It’s not just the ppm CO₂, but for how long.

      (* The thing is much more complex of course — the actual radiation imbalance depends on the temperature increase, and the actual surface heating depends on the rate of transfer of heat to the deeper ocean — but it’s useful to get the first order right.)

  13. Another excellent post Tamino. And for a few reasons, thoughts occur about a possible comparison study of the atmosphere CO2 levels and O2 levels over time. Perhaps readers here can point me to where it has already been done, or perhaps you might consider it Tamino?
    1) Some “sceptics” will claim that the CO2 rise is volcanoes or something else, not us. So the corresponding drop in O2 with CO2 rise is clear evidence that combustion* is the cause (*and/or oxidation of CH4 etc).
    2) I expect that a close examination would show O2 dropping faster than CO2 rises, due to some CO2 getting sequestered out of the atmosphere. Any sign of a trend in the sequestration rate? For example, as the ocean dissolved CO2 level increases, further dissolution should slowdown. Actually, if I remember my Chem lessons, it is the difference between atmosphere and dissolved concentration that matters. And we are certainly adding extra CO2 to the atmosphere faster than it dissolves, so any slowdown in the sequestration rate would be a worry!
    3) You and some of the posters mention feedbacks. At some stage there may well start to be extra non-combustion sources of C02. Any sign in the data of that? For example, any climate related higher ocean surface temperatures (eg El Nino if I understand correctly) may result in some CO2 coming out of solution. Or at the very least, a slower sequestration rate into warmer water.

    • Hi Andrew. This link might be of assistance ( See “6) Declining oxygen concentration”. Further search within Skeptical Science is likely to uncover additional relevant graphs.

      • Andrew Haines

        Thanks Ammonite. That is certainly a very relevant link.

        With regard to my item 1), concerning the anthropogenic source of the CO2 increase, the change in the C13/C12 ratio is certainly good evidence also. “Item 5) Declining C13/C12 ratio” at the Sceptical Science link.

        With regard to my other points, “Item 6) Declining oxygen concentration” is also very relevant. From the size of the “outgassing” arrow on the diagram, compared to the other relevant arrows, it seems that outgassing especially will be difficult to observe/detect…

  14. Lewis,
    I’m not sure whether Schuur greatly underestimated future permafrost carbon emissions. While that study is correct in methane emissions persisting into the cold season, it does not change the overall emissions calculated from that area.

    • Bryant – thanks for your response.
      This from the new study [Zona et al] ‘Results and Discussion’ puts the change in perspective.

      “Our measurements of CH4 emissions from Arctic tundra are more extensive in both time and space than what have been used to develop and test existing models. Annual CH4 emissions rates from noninundated Arctic tundra (<20% surface water; Fig. 2) are comparable to those of inundated environments. Most models map CH4 fluxes to the Arctic landscape using inundation (27), thus dramatically underestimating the emitting area in the Arctic, including during the cold season. The zero curtain interval in fall and winter, and even the period of frozen soils in winter, produce significant, previously underestimated, CH4 emissions (27). Our work provides the basis for parametric representation of these fluxes and highlights the critical importance of driving models with subsurface soil temperature, and not air temperature. "

      The graph at Figure 4 (just below this para) shows aircraft surveys during the 'zero curtain' period giving around a quarter or the CH4 output recorded by the new surface monitoring on which this paper's findings are based.

      Should you want to contact the authors to affirm this I'd be interested to read their response.


  15. > triggering feedbacks in the carbon cycle. Perhaps the biosphere …

    Plankton organisms reproduce in days or weeks, so the relative dominance of populations of different species can change very fast.

    Do we get lucky? More food for more fish and marine mammals and a recovery of some of the damage done to date? Or do we get something like global red tides/toxicity and noxious wind blowing onto the seashores?

  16. Bobcobblog – it could be more clearly put, I’d agree.
    Alex Kirby did a decent article in the excellent (denier-free) site “Climate News Network”:
    that is worth a look. He got some much clearer quotes from those involved.
    Scientists have for some years been accurately measuring Arctic methane emissions and incorporating the results into their climate models. But crucially, the SDSU team says, almost all of these measurements have been obtained during the Arctic’s short summer.
    Its long cold period has been largely “overlooked and ignored,” according to Walter Oechel of SDSU, with most researchers thinking that, because the ground is frozen solid during the cold months, methane emissions practically shut down for the winter.
    “Virtually all the climate models assume there’s no or very little emission of methane when the ground is frozen,” he says. “That assumption is incorrect.”
    “This is extremely relevant for the Arctic ecosystem, as the zero curtain period continues from September until the end of December, lasting as long as or longer than the entire summer season,” said Donatella Zona, the study’s lead author.
    . . . . . . . .
    “These results are the opposite of what modellers have been assuming, which is that the majority of the methane emissions occur during the warm summer months while the cold-season methane contribution is nearly zero.”

    The researchers also found that during the cold season methane emissions were higher at the drier, upland tundra sites than in the wetlands. Upland tundra had previously been assumed to contribute a negligible amount of methane, Zona said.


    • Lewis, that makes sense to me. Ed didn’t see it as being catastrophic, though. Definitely something needing to be watched.

  17. The Mauna Loa curve is the final say on whether we really are diminishing our emission rates, no matter what other (local?) measurement or calculations say.

    What would be interesting is to see how the curve should look if the Paris target of “a 40 percent reduction in global greenhouse gas emissions from 1990 levels by 2030” really is fulfilled, i.e. how would the curve then look and how soon will we see any change at all?

    I guess the target simply means that the rate of change at 2030 will match the rate of change in 1990, which evidently is far from sufficient.

    It would be interesting to see such plot, though.