The correlation between global population and global CO2

Guest  essay by Roger Graves

Predictions of atmospheric CO2 levels at some future time are commonly made, usually with the object of assuring us that beyond a certain point our planet will be fried to a crisp. Most of these predictions are in the form ‘if CO2 levels reach x, the effect will be such-and-such’, without actually indicating why CO2 levels should reach such a value. However, it is possible to make an accurate prediction of future CO2 levels using readily available information.

The graph shown below plots CO2 levels as a function of world population, encompassing the period 1960 to 2015. Note that although each data point represents an individual year in sequential order, time is not explicitly represented on this graph, which merely shows how CO2 levels are related to overall world population.


It is reasonably obvious to the naked eye that CO2 and population seem to move in lockstep. To show this in more analytical terms, we can superimpose a trend line, which is simply a mathematical curve which fits the data. After some experimentation it was found that a trend line consisting of a third-order polynomial provided a very good fit to the data. In statistical terms, the R2 value for this curve is more than 0.999, which indicates that it correlates with the data to an accuracy of better than 99.9%.

One advantage of a trend line is that we can then extend it to make predictions of what the future may hold, which you can see in the chart below. Both axes in this chart have been extended for this purpose.


Of course, the same graph could have been drawn with CO2 levels on the horizontal axis and population on the vertical axis, so that population would be shown as the dependent variable and CO2 as the independent variable. The same correlation between the two would still exist.

The question that now arises is whether population is driving the CO2 level, or CO2 is driving population. There are four possibilities to be considered:

1. There is no connection between the two, the apparent lockstep is just a fluke. Possible, but very unlikely. This possibility can reasonably be ignored.

2. Population causes CO2. This is ‘obvious’ explanation that most people would give. The more people there are on our planet, the more CO2-generating activities there will be, such as electrical power generation, industrial activity, automobiles, cooking fires, and so on.

3. CO2 causes population. Much of the population growth in the foreseeable future will come from sub-Saharan Africa. Population growth in these regions is dependent to a large extent on the food supply, and as we know, crop yields increase with CO2 levels. The greater the food supply, the more children will survive to maturity.

4. The connection between CO2 and population results from some, as yet unspecified, combination of 2 and 3.

My personal view, and this is only an unsupported guess, is that possibility 4 is the most likely.

What conclusions can be drawn from this? First, the population/CO2 curve is a smooth curve. No evidence is shown of any significant decrease in the inexorable rise of either CO2 or population from beginning to end of this curve. We can conclude from this that none of the measures taken by industrialized countries to reduce CO2 output have had any noticeable effect, nor does it appear likely that they will have any significant effect in the foreseeable future.

Second, current UN population projections indicate that we will reach a population of 9 billion by 2038, and 10 billion by 2056, using the medium variant of their three prediction levels. (To follow this further, go to, then download the spreadsheet called Total Population – Both Sexes.) Assuming that the population/CO2 relationship still holds good by then, we can predict a CO2 level of nearly 460 ppm by 2038 and 500 ppm by 2056.

Population growth is a quantity which can be reasonably well predicted for one or two decades into the future. While extrapolating a curve in order to make predictions is always fraught with danger, based on the data so far I am fairly confident that the CO2/population relationship will hold for a few years yet. In the long term of course, your guess is as good as mine, but I think we can reasonably well predict CO2 levels in the range 450-500 ppm by the middle of this century. Whether the world then disappears in a puff of smoke, or enters a new golden age of unsurpassed crop yields, remains to be seen.

Roger Graves is a physicist and mathematician who, much to his chagrin, is not associated with big oil, big coal, or big anything else.


117 thoughts on “The correlation between global population and global CO2

    • Didn’t see a sari tag on this post, but I sure hope he realizes how ridiculous this is.

      • Yes, it’s hard to imagine how this plot could be true. What portion of the CO2 is anthropogenic? It is magical that massive differences in population density (Singapore, Australia or Bangladesh for example.) and the energy efficiency of their production* could “average out” so perfectly! What the graph is saying, is that it doesn’t matter how much a nation pollutes, all that matters is population. But this is counter intuitive because there are of course high population centres with low emissions in the developed and the third worlds! Now we also have the fast growing Asia with both high populations and high CO2 output. Again it is very hard to believe that this graph could be representing reality. If it is, then a whole lot of bets are off about the causes. It immediately made me think about UHI and how it correlates temperature and population (If indirectly).

        *In terms of CO2 emissions.

  1. What about a new option? Option 5: The growth in CO2 and population is mainly related to the growth of industrial economic activity. Industrial economic growth is related to many factors which I think few people would exactly agree on how to “weight” them. But some of the factors are technological growth, growth in access to technology and education, growth in access to vaccinations, cleaner water, genetically enhanced food crops, the spread of free market capitalism, and etc.

    • “””””….. 1. There is no connection between the two, the apparent lockstep is just a fluke. Possible, but very unlikely. This possibility can reasonably be ignored. …..”””””

      Well I see a problem. You deliberately forced these two sets of numbers into the fit that you show. So it is NOT a fluke; you forced it to happen.

      And all of your numbers; population and CO2 are already known numbers.

      You have shown no earthly reason, why this curve would predict what the very next point on the curve might be.

      You can’t even tell if it will go up from the last value or stay the same, or go down.

      You can’t predict ANYTHING about any future numbers.

      Statistics has NO predictive power whatsoever. It is simply idle twiddling with numbers you already have.

      Sort of like Origami with numbers.


      • george – you say that Roger forced the two sets of numbers to fit. But that’s not correct. The population numbers were taken as is, ie. no changes were made to them. The CO2 numbers were similarly taken unchanged. So nothing was done to the numbers to make them fit anything. They were plotted in a standard scatter chart, and they showed a very marked degree of non-scatter. Roger then did a polynomial fit, another standard technique, and obtained a very strong fit. So I think your criticism is very badly directed.

        But there are valid criticisms: Deducing correlation between values where each changes quite smoothly over time in only one direction is dodgy. They might both be increasing for quite separate reasons, and there could still be a 99.9%+ correlation. So let’s do some checking to see whether it holds water:

        1. If the world population had not increased, would the CO2 levels have increased? Answer – yes, but not nearly as much. That’s because economic and technological advances would still have led to greater fossil fuel use [etc], but not as much of an increase because of fewer consumers.
        2. Do the actions which increase CO2 [NB. Not the CO2 itself] lead to greater population? Answer – No. There is a clear link between fossil fuel use [etc] and prosperity, and clear evidence that prosperity leads to a lower birth rate.
        3. If the world population had increased as shown, but there had been no economic or technological progress, would the CO2 levels have increased? Answer – yes, but not nearly as much. That’s because cars, aeroplanes, cement etc would have remained in the hands of the rich, and the rich would have remained few in number.

        I think we can safely conclude that there is indeed a causal link between population and CO2 levels, but that it is not as strong as the article suggests because economic activity and technological advance have been very important factors. So the prediction of the article’s fitted curve is suspect.

        Here is another thought which can hopefully help to clarify: If you were to plot a similar chart of CO2 levels and global food production, you would get a very similar result. That’s because global food production has also advanced steadily over the same period. Does CO2 increase cause food production increase? Yes. Does food production increase cause CO2 increase? No. But it is unsafe to deduce that all of the food production increase is caused by CO2 because there has been great progress in farming methods.

        The situation is a bit less clear than the article portrays it.

      • Mike, and let’s not forget the temps, carbon growthrate connection that you yourself once had plotted out in graph form… I’d like to see one of these cumulative type graphs plotted out with the assumption that it never warmed after 1960. (say we were stuck at 1 ppm per year) What would such a graph look like then?

    • “””””….. After some experimentation it was found that a trend line consisting of a third-order polynomial provided a very good fit to the data. …..”””””

      I believe the author said this, I didn’t.

      Dr Roy Spencer used to give third order polynomial fits to his data; “just for amusement”, as he put it.

      In other words, he didn’t provide ANY Physical basis for the data fitting a third order polynomial, ” after some experimentation.”

      Why not a fifth order ? What is the reason for supposing the physical connection between the two sets of numbers is a third order formula. I dare say you could fit some logarithmic, or exponential formula to the same data, or even the function: y=exp(-1/x^2).

      And if I’m not mistaken, ALL of the trend line fits to scatter plot graphs, we have seen (here) this year have been straight line fits, up until now, even though the data clearly never fitted a straight line even approximately.

      So where all of a sudden does a trend line become a fitted polynomial ??


      • Clyde, I don’t see the relevance of your comment.

        Whether one fits twos sets of regularly occurring (more or less) to a second order, or third order polynomial function or to a logarithmic or exponential function, n matter how good the fit, that does not establish a rational basis for believing that the two sets od data are causally related.

        In this case, we have one set of numbers being periodically measured (presumably) values of atmospheric CO2 abundance. (I found NO reference to the source of those figures, but I’ll assume they are from the Mauna Loa numbers.)
        Then we have another set of numbers, apparently annually determined world human population numbers.

        Now we know that a human person does affect in numerous ways the emission or removal of CO2 to or from the atmosphere.

        So does an astronomical number of other life forms on earth, that do not necessarily vary in lockstep with humanity. Then their are numerous physical processes that take place all over the world, and none of those should be considered to follow human population for any causal reason.

        It seems reasonable to believe that some increment in atmospheric CO2 does not cause another human being to come into existence; or in other words; CO2 in the atmosphere does not cause humans.

        Perhaps we can’t be as sure that humans do not cause atmospheric CO2.

        There is plenty of opinion and belief (even evidence) that in fact humans are responsible for some of the CO2 in the atmosphere.

        Given the diversity of human cultures, and industrialization, it is highly unlikely that any human contribution to CO2 in the atmosphere depends on nothing else besides the number of them, and doesn’t depend in any significant way to the numbers of other living species on earth, that might be expected to create random deviation from strict synchronism with the count of humans.

        So the present author used a third order polynomial. You say that you used a second order one.
        I daresay that one could fit a fourth order or fifth order polynomial just as well.

        But it’s all quite arbitrary, and points to no physical causal reason for the tracking.

        The volume of a sphere fits a third order polynomial in the circumference of the sphere.

        That happens because their is a well defined and understood mathematical reason for those two measures to track each other .

        There’s no such physical reason for the number of CO2 molecules in the atmosphere to track causally the number of humans on the planet, no matter how accurately one can fit the two numbers to some curve.

        But if people want to play around with curve fitting one set of numbers to a completely unrelated set of numbers, well I’m certainly not going to stand in their way.

        All of the various stock market indices, also track quite well over various time intervals to the atmospheric CO2 abundance.

        But people who extrapolate beyond those periods of tracking, invariably get caught in a trap of their own making.

        Specially in the case of fitting known data sets to some curve, extrapolation beyond those fitted regions, traps its own victims.


    • “””””….. Note that although each data point represents an individual year in sequential order, time is not explicitly represented on this graph, …..”””””

      So who is measuring global CO2 abundance as a function of world population; i.e. without any time data ??

      Usually when people make observations or measurements, they do so at some specific epoch of time; namely the time for which they make the observation or measurement.

      So I don’t see how someone is waiting for world population to hit some number, and then making a global CO2 abundance measurement at that time.

      I’m having a hard time seeing how you do this. Data is usually obtained when you read the meter, rather than when the meter reading reaches a certain value.

      Perhaps you can fit the sea level rise to world population by a third order polynomial.


      • George,

        I was taking issue with your comment, “And if I’m not mistaken, ALL of the trend line fits to scatter plot graphs, we have seen (here) this year have been straight line fits, up until now, even though the data clearly never fitted a straight line even approximately.” Your statement is clearly false. That is, you ARE “mistaken.”

        One can always fit a polynomial of a higher order to a scatter plot. The issue is, what is the purpose of the fitting? Generally, if one is only interested in establishing a relationship between two variables such that one can be used to reasonably predict the other variable, then the lowest order that does the job adequately is dictated by Occam’s Razor. However, if one is trying to make a case that a causal relationship exists, then a higher order may be justified if a case can be made that the higher order actually is the relationship that is explained by the physical processes.

        Even spurious correlations may be useful if they can be depended upon to allow predictions. You might choose to rely on a spurious correlation because the independent variable is easier to measure than the one that is actually causally responsible for changes in the dependent variable. Remember the remark, “All models are wrong, but some are useful.”

        Incidentally, time is implicit in the scatter plots. That is, time is common to both; population and CO2 were measured with a common year over a period of years. This is not ‘New Math!’

        Graves was making the case that there probably is a causal relationship between population and CO2, as in a dynamic system with feedback loops. I personally have no argument with that. It seems intuitively obvious to me that humans create CO2, and in the process of making CO2 humans make a safer, more comfortable world that allows the population to increase.

    • I’d say, Yes, option 5. Population and CO2 are both dependent variables, controlled by a single independent variable. That variable is a gently warming climate over the last 20,000 years. It just makes life easier in general and promotes the growth of most living things including the human population. The warming seas accelerate outgassing thus CO2 increases as well. This also fits the historic charts that show CO2 levels vs. temps over the last half-million years (about 5 glaciation cycles).

  2. It certainly looks a bit more logical than anything else. But how far back does the relationship go before the 99.9% correlation breaks down? And what happened when it broke down?

    Thinks – it there is a logical relationship that holds good into the distant past, there should have been a higher population than now when the earlier CO2 levels were higher. This is where the fantasists can take comfort – there was civilization before the (whoever – you name it). All destroyed by Atlantis, and like rubbish.

    But option 5 is probably the correct one, that the increase in CO2 and population are both caused by some other unknown cause – the “Unknown unknown”. As Sir Humphrey said when Bernard asked him what the “unknown unknown” was: “I don’t know – that is the whole point, we don’t know!”

    • So the mathematically “fitted” third order polynomial fits the “data” to 99.9%.

      So what is your Physical Theory that calls for a cubic polynomial connection between these two number sets.

      So what if your “theory” agreed with experimental observations to somewhat better than 0.1% difference. Let’s say for example the “fitted” computed value agrees with the observed experimental value to say one part in 10^8.

      That is somewhat better than your cubic fit.

      Would you say that the observational value supports the theoretical model or not.

      What if I told you that such a theoretical derivation kluged up simply by dicking around with numbers the same way you just did, theoretically derived a fundamental constant of Physics to one part in 10^8, somewhat better than the standard deviation of the very best experimentally measured value.

      And that theoretical derivation was like yours a purely mathematical exercise, with not one jot of real universe data, involved in the whole concoction.

      So with the rise in global population since 1960 why has there not been a commensurate increase in the global mean Temperature, and in fact for the last 18 plus years the Temperature has gone precisely nowhere.

      So would you say (mathematically of course) that global warming is NOT related in any statistically significant way to global population ?? They have often gone in completely opposite directions.


      • One advantage of a trend line is that we can then extend it to make predictions of what the future may hold,

        OH crap , here we go.

        This is just the kind of insane BS that the whole CAGW scam has been based on. Why not fit a fourth order poly, you will get an even better correl. coeff. and it will shoot off even more as you extrapolate your baseless assumptions way outside the actual data.

  3. Taking up BobG’s point, in my last para, “unknown cause” should probably read “unknown causes”.

  4. I would expect the curve to do odd things in the future.

    On the one hand, population is likely to peak at around the 10-12 billion level, while individual energy use will continue to rise.

    But at the same time, CO2 emissions due to energy use will almost certainly have a different profile in the mid-long term.

    So it’s anyone’s guess really.

    • Well when you get some future data, you just refudge the cubic fit polynomial, and then declare that that will let you predict future events as well.

      If one is trying to match cause and effect to try and discover a causal link, you have to have some basic Physics reason to expect say a cubic relationship.

      And I notice that the “data points” are actually sizeable blobs. But the blobs don’t seem to reflect any uncertainty values.

      If the “Trend line” is actually a third order polynomial, then one would expect that curve to be a smooth curve, with a continuous slope and curvature, and no changes in direction.

      The plotted line is clearly monotonically increasing, as one would expect from just four terms, and no point of zero slope or maximum (minimum) value.

      But the blobs are clearly not a monotonic plot. So if plotted as dots the same dimension as the line width, one could see how they meander about the smooth cubic.

      It’s a minor point but the blobs obfuscate the smoothness of the data. (I’ll accept the data; just don’t see why one would hide the meandering.)


    • The eleven billion number is built in to the system, and my guess is that CO2 will indeed follow the population numbers and level off.

      For an enlightening look at the population rise and level off, try

      The level off is explained about 19 minutes in, but the whole presentation is entertaining.

      • Saw this a while back and love his work. Many have falsely dire / Bias view of global health and wealth. Good science.

  5. Well, we obviously have too many people on this great Earth.

    Or maybe the increase in CO2 is driving the increase in food production, which is driving the increase in population (we all gotta eat). Or since we all breathe out CO2, each of us contribute our fair share of CO2 molecules and it is, from your graph, a one-to-one incremental linear relationship.

    The only issue is you should also be able to extrapolate it backward to a world population of 2 and a corresponding CO2 level of 0. Unfortunately the data suggests this doesn’t apply. So with this in mind, I think your graph is nothing more than an incredible coincidence. Sorry.

  6. Interesting. I also think option 4, including natural buffers such as vegitation and oceans. Looking forward to greener deserts and bigger crops.

  7. CO2 is more likely the causitive agent. More CO2 allows for more food and healthier people. Healthier people can live longer and have more children. Population shrunk, or at least slowed during the little ice age.

  8. “current UN population projections indicate that we will reach a population of 9 billion by 2038, and 10 billion by 2056,”

    Looks like Gaia will have to inflict a huge natural disaster on us to keep we uncaring humans in check. A drug resistant virus carried by mosquitoes might do the trick.

    • Hmm maybe. But what was the pop of mansized+ dinosaurs in Triasic,Jurrasic, Cretaceous?

      Also curious about the Caribou,Bison herds of pre-Columbian times any way to see if the massive decline during Colonial times had an effect upon CO2 worldwide?

    • The high level of CO2 which we are now seeing is simply the result of earlier warming cycles which occurred on Earth a very long time ago. CO2 follows heat.

  9. I expect the population/CO2 relationship to change, as population stabilizes and industrialization increases. This means more than 460 PPMV CO2 in 2038 and more than 500 PPMV CO2 in 2056.

    • Industrialization increases are at least partly compensated for by efficiency improvements.

      For example, I haven’t seen a CRT in years, everyone is using flat screens these days. Modern LED flat screens use less power than the LCD ones of just a few years ago which in turn used less power than did the older plasma monitors. As time goes by older monitors are replaced by new, more efficient ones.
      Just as CFL lights have been replacing incandescent bulbs, LED lights are starting to replace CFL.

      Modern appliances use less power to do the same work, compared to a few years ago.

      • Well modern LED flat screens, are just LCD flat screens using LED back lighting, instead of incandescent back lighting. The LCD is simply modulating the lighting .

        And my house has been all LED lighting for some years now.


        PS: I design LED lighting.

      • true LED (no LCD) screens are around the corner. BUT in order to be visible at all a screen MUST use energy to generate the photons. That is a point many people especially of the green persuasion, completely fail to understand. They confuse rising efficiency with ultimately almost no energy use at all. Manufactured items represent a certain mount of energy ‘locked in’ in terms of the processing needed to construct them in the first place, and a certain minimum amount of energy to perform their function. Even a flush toilet needs energy to pump the water to where it can deliver the flush.

        The blatantly naive attitude of greens towards their own carbon footprint would be amusing if they weren’t so dangerous. They think that by eating grains and riding bicycles and insulating their houses and using LED lighting they are drastically reducing their carbon footprint whilst completely ignoring the massive energy hungry infrastructure in which they live and without which they would die.

        Modern life is energy intensive, and whilst a limited number of people can live off grid, a large number cannot.

        I was cured of ‘back to naturism’ buy the first UK open air woodstock style festival held at the Isle of Wight,: we arrived and set up camp in the corner of an idyllic green field surrounded by a small wood. WE left a mud churned litter hell, with the wood replaced by excrement and toilet paper, and every last tree cut down to make firewood. 250,000 people eat a lot of food and leave a lot of waste ,and those few fields were not able to produce or process either.

        The people who arrived late and left early, who didn’t see this, became the hippies who now infest the Eco movements.

        We called them ‘weekend hippies’ – they never actually lived the dream. And discovered its real nightmare nature.

    • Yet the complete removal of CO2, a trace gas, from the Earth’s atmosphere would cause the Carbon cycle of life to cease and thus the end of all life as we know it.

    • Steven Mosher
      May 17, 2016 at 9:46 am

      Co2 is a trace gas.
      It can’t cause anything.
      Skeptics argument 101.

      Mosher for once please, show that you are not making things up as you go.
      Please show one single person, a skeptic. who says the above.
      Prove it please….must not be as hard as trying to prove your AGW unicorn……


      • There have been a couple who have made that claim. The rest of us usually shout them down.
        Mosh is once again being dishonest by trying to claim that this is a position that most if not all skeptics hold.
        But then again, Mosh being dishonest is the only intellectual weapon he has left.

      • I’m a skeptic — about everything — I’ll say it !

        EVERY claim by the climate change cult should be questioned.

        They have proven themselves to be dishonest and should not be trusted.

        Their false environmental “crises” have been ‘coming’ for over 50 years … and they must get lost on the way, because they never show up.

        CO2 is a trace gas that benefits green plants, and the humans and animals who eat those plants.

        I want a lot more CO2 in the air.

        We should all want much more CO2 in the air to accelerate green plant growth, as greenhouse owners have known for decades.

        There is no scientific proof CO2 caused any of the warming in the past 150 years, since there has never been a CO2 level – average temperature correlation in Earth’s 4.5 billion year history, except for a few decades between 1975 and 2005 … and that brief correlation does not prove anything.

        While the first 100 ppmv CO2 in the air may cause some warming, that doesn’t mean more CO2 ALWAYS causes more warming.

        The highly political IPCC group says CO2 itself does not cause much warming when increasing above current levels — most of the IPCC-claimed warming would be from a huge, unproven, positive feedback = pure nonsense.

        There is no evidence that CO2 is a climate controller in climate proxy studies, and some evidence that warming by natural causes leads to more CO2 in the air (outgassing from oceans).

        It is certainly possible that CO2 levels rising above 400 ppmv will cause some warming, but that warming is likely to be insignificant, and possibly too small to measure.

        Only leftists, or people with ulterior motives (I repeat myself), demonize CO2 — CO2 is beneficial airborne plant food.,

        Adding CO2 to the air was (inadvertently) the best thing humans have ever done to improve life on our planet.

        The goal now should be to add MORE CO2 to the air in a way that does not add real air pollution.

        Greening the Earth, from more CO2 in the air, will accelerate plant growth, which will reduce malnutrition and starvation that affects the poorest people on our planet — those are people “environmentalists” could not care less about … as they fly around the world on their private jets to attend climate conferences!

        The climate in 2016 is the best climate in at least 500 years — the cold – low CO2 centuries from 1300 to 1800 are history, and we should be happy about that.

        ENJOY THE GREAT CLIMATE — don’t listen to the leftist climate warnings!

        The Earth is greening.
        That’s good news.

        Nighttime low temperatures are not as cold as they used to be.
        That’s good news too.

        How can anyone who regularly goes outside, over several decades, think there is anything unusual, or va problem, with the current climate?

        And how can anyone continue listening to leftist climate catastrophe forecasts after 40 years of wrong predictions and false warnings — 50 years if you start counting with the false DDT “crisis”?

        (OT) Defining a leftist:
        The other day I was at home telling a ‘friend’, who was visiting, about a great deal I got on weed killer at Wal-Mart, and I mentioned the wife and I were surprised by how clean the store was, how well stocked it was, and how nice the employees were. I hadn’t been there in at least a year.

        The ‘friend” proceeded to give me a lecture about shopping at Wal-Mart — he would NEVER go there — and a few days later I got a letter in the mail from him, with some claims about Wal-Mart selling something that kills bees. I couldn’t figure it out. I filed it with the “GMO food crisis” information another ‘friend’ gave me.

        Leftists can never be happy unless they see a catastrophe coming, and are busy like rodents using that alleged catastrophe as a political tool to tell everyone else how to live.

        Leftists are very annoying.

        You say “Nice weather today!” to them, and you get a lecture on the coming climate change catastrophe … that never comes .

        PS: While Stephen Masher’s climate knowledge is roughly equivalent to a trained parrot, repeating the global warming party line his owner has taught him, Masher is good at stirring up skeptics, who know they should just ignore him, but can’t resist posting and kicking him one more time.

        Climate Change blog for non-scientists
        Free, No ads. No money for me.
        A public service.
        Leftists with high blood pressure should stay away

    • One constant with warmista trolls, they can’t tell the truth.
      There are a couple of skeptics who have made such claims.
      The vast majority never did, none of the scientists ever did.

      I would say that you are destroying your reputation, but you finished that task months ago.

    • CO2 is a poisonous gas.
      If allowed to continue to increase it will destroy the world.
      Alarmists argument 101.

      • ” CO2 is a poisonous gas.” Actually, it is at high enough concentrations, but then so is O2 at high enough concentrations, and just about eveything else.

    • Steven Mosher May 17, 2016 at 9:46 am

      Co2 is a trace gas.
      It can’t cause anything.
      Skeptics argument 101.

      Nah, Skeptics argument 101 is that Catastrophic CO2-Climate Change is Scientifically Falsified by its record of [100%] Prediction Failure.

      Meanwhile I know some higher up United States Forest Service CO2 Progressives who were surprised to find out from me that CO2 is the main nutrient involved in the growth of trees. How many other Progressives don’t know this?

    • CO2 is nowhere near as “trace” abundance, as is the Boron doping concentration in a P-type silicon layer in a CMOS structure. (might be 1 ppmm of B:Si)

      And you would be totally amazed at what such a “trace” amount does to that silicon.


  10. The only problem with using the UN’s “estimates” on population growth is that historically these estimates have always come in substantially higher than the actual population growth.

    The reason for this is simple, it’s the assumptions.
    1) They assume that any country with falling birth rate, that birth rate will stop falling when the rate reaches 2.0 live births per woman. (This has never happened, the rate has always kept falling, most countries that have stabilized their birth rates, have stabilized somewhere between 1.0 and 2.0)

    2) They assume that all countries with current birth rates at less than 2.0 will within the next decade have their rates return to 2.0. (That has never happened. To date, no country with a birth rate below 2.0 has returned to that level. Japan for one, has been below replacement level for almost 20 years now.)

    • Good points. I suspect we will never get to 10b… peaking in the 9s. When I die in 2048, I will start the decline in world population

      • you sound like some anti-typhoid mary!

        “Do you realise that somewhere in the world a woman is giving birth every 50 seconds! What do you think we should do about this? ”

        “I think we should find her and stop her!”

  11. None of the options are correct, the relation with population is coincidental. It could equally be aligned to motor vehiclea or the number of schools built, but these are not the reason either. It is far more complicated.

  12. I wouldn’t discount option 1 just out of hand. It’s not that far fetched that the earth is warming, humans prefer warming and CO2 follows temperature

  13. The possibility number 3 is very “scary” indeed.
    In the possibility of CO2 causing the population, where by default the CO2 concentration increment is solely natural and at some point it will decrease as fast as it increased, there is a question to be considered if a connection of causality exist in between.

    The question to be considered….will the population follow in the same rapid decline when the concentration start declining?
    It will be silly to ignore it or hand-waving at it simply because there is 97% consensus in AGW with no any bases at all in empirical measurements or evidence…..

    The empirical measurement and the evidence suggest that the way the anthropogenic emissions trend stands in accordance and relation to the concentration trend, that the population does not cause the ppm(s) of CO2 go up, because for these two trends to be the way as per the reality shown by the measurements and the actual data, the residence time of CO2 in atmosphere must be very short, much shorter than estimated or assumed, approximately smaller by a factor of 10, making the anthropogenic effect towards the CO2 concentration in atmosphere basically insignificant…….

    Contrary to o what some one like Mosher may say……..residence time of CO2 is much much important than ECS or TCS or whatever like that, in the assessment and understanding of climate and CO2 relation to it.


  14. In possible explanation #2: You missed obvious cause – human respiration. Humans, especially at the 7+ billion level, create a great deal of CO2 every. Probably more than our fuel combustion generates!


    • The CO2 that we resperate comes from the plants and animals that we eat. So that CO2 is taken directly from the air. It balances out.

  15. Well, I dunno. Two parameters that change smoothly, without any real ups and downs, will always by highly correlated if we use a third order polynomial. I bet could get a very nice correlation coefficient between CO2 and my personal weight gain across the same time interval, which probably makes me a plant.

  16. You have omitted the most likely option:

    5. Population growth and CO2 increase are both caused by some third factor (as yet unknown though several hypotheses jump to mind).

    I also think that you are much to cavalier in your dismissal of option 1. The geologic record shows periods of CO2 variance that cannot possibly have been caused by human population levels. If you extend your analysis further back in time,your fit will drop off sharply. Even an apparently high R-squared value means little when based on too few data points.

  17. Population growth is a quantity which can be reasonably well predicted for one or two decades into the future.

    Didn’t that ‘famous population expert’ Paul Ehrlich predict that the UK would cease to exist by the year 2000 because it would have consumed all its resources?

  18. Population growth doesn’t directly cause CO2 levels to increase.

    So why would you put both of them on a chart?

    Also, extending trend lines is nonsense.
    You should know better.

    Predicting the future is usually a waste of time.
    You should know better.

    If the point of your post was to “prove” humans are adding CO2 to the air, we already knew that.

    The important question is whether the added CO2 is good news or bad news.

    I submit there is no scientific evidence that adding CO2 to the air is bad news, and a lot of evidence that adding CO2 is good news.

    I believe adding CO2 to the air, and greening the Earth, was (inadvertently) the best thing humans have ever done to improve our planet.

    The next step is to clean up the dirtiest forms of combustion that add CO2 to the air — mainly in Asia now — but not to stop adding CO2 — greenhouse owners know a lot more CO2 will accelerate plant growth — and accelerating plant growth will help feed those who are malnourished or starving,

    So I guess you could say my “theory” is adding CO2 to the air accelerates green plant growth, which helps increase the food supply, which allows our planet to support more human life.

    Burning fossil fuels helps keep us alive.

    • Indeed, all that carbon in the ground (coal, oil, gas) was once in the air. We are just liberating it.

    • Well Richard, I’m happy to see that not everyone is taken in by the pretty pictures.

      You can make a scatter plot with any two sets of numbers, whether they are related or completely unrelated.

      Excel will do it for you.

      Some such plots are pretty; others are scruffy. That’s why they are called scatter plots.

      No matter how pretty they are, it doesn’t prove any causal relationship, or establish any expectancy for the consequences of extrapolation, outside those two sets of numbers.


  19. My take on this post is that there appears to be a strong correlation between population and CO2. So, if one assumes that the climate models are correct and CO2 = global warming, then it follows that climate control = population control.

  20. I suspect it is almost all because of Option 2. Every human has a carbon dioxide footprint. The more humans, the bigger the collective footprint.

    The other options are minor or non-existent.

    I also assume that footprints will decline due to efficiency over the next few decades and the UN will over-forecast population. This combination puts us at about 450ppm by 2050

    • Mary, you do realize don’t you that with your belief, you must also accept that the ENTIRE growth in atmospheric CO2 abundance must be due to humans.

      I don’t know of anyone who believes that humans alone are entirely responsible for all of the CO2 above 280 ppmm in the atmosphere.


      • George,
        You said, “I don’t know of anyone who believes that humans alone are entirely responsible for all of the CO2 above 280 ppmm in the atmosphere.”

        I guess you really don’t know me or Ferdinand. However, am I to understand that you believe that it is entirely a coincidence that the scatter plots that Graves and I produced show such a high correlation between the population and CO2, both of which are increasing?

    • Well actually for the ML data it was 315 ppm in 957/58, the year of the International Geophysical Year (IGY).


  21. The slight warming has been beneficial for both humans and plants, which is also good for humans.
    The rise in CO2, probably mostly caused by humans has been beneficial for plants, which is good for humans, who then produce further CO2.
    Uh-oh, I see a problem. Paradise on earth, Garden of Eden style. No need for God then. Can’t have that.

    • Any two variables in a rising trend will have good positive correlation.

      Any two in a declining trend too.

      The variables don’t have to be related in any way

  22. This graph is data forcing in it’s purest form… the data point MUST match a population in that layout.

  23. I compiled the following statistics via reliable sources, to wit:

    Increases in World Population & Atmospheric CO2 by Decade

    year — world popul. – % incr. — Dec CO2 ppm – % incr. — avg increase/year
    1940 – 2,300,000,000 est. ___ ____ 300 ppm est.
    1950 – 2,556,000,053 – 11.1% ____ 310 ppm – 3.3% —— 1.0 ppm/year
    1960 – 3,039,451,023 – 18.9% ____ 316 ppm – 1.9% —— 0.6 ppm/year
    1970 – 3,706,618,163 – 21.9% ____ 325 ppm – 2.8% —— 0.9 ppm/year
    1980 – 4,453,831,714 – 20.1% ____ 338 ppm – 4.0% —– 1.3 ppm/year
    1990 – 5,278,639,789 – 18.5% ____ 354 ppm – 4.7% —– 1.6 ppm/year
    2000 – 6,082,966,429 – 15.2% ____ 369 ppm – 4.2% —– 1.5 ppm/year
    2010 – 6,809,972,000 – 11.9% ____ 389 ppm – 5.4% —– 2.0 ppm/year
    2015 – 7,349,472,000 – 07.9% ____ 401 ppm – 3.1% —– 2.4 ppm/year

    Source CO2 ppm:

    Based on the above statistics, to wit:

    Fact #1 – In past 75 years – increases in world population per decade shows no correlation between increases in atmospheric CO2 ppm per decade.

    Fact #2 – Atmospheric CO2 has been steadily and consistently increasing at a rate of 1 to 2 ppm per year for the past 75 years, …… whereas human generated CO2 releases have been increasing exponentially every year for the past 75 years.

    Fact #3 – Global Average Ocean Surface Temperatures have been steadily and consistently increasing a few hundredths or tenths of a degree for the past 75 years, ……. whereas human created infrastructure, housing, vehicles, etc. (Heat Islands) and the quantity of fossil fuels being burned ……. have been increasing exponentially every year for the past 75 years.

    Conclusion: the gradual warming of the ocean waters during the past 75 years is the “driver” of the gradual increase in atmospheric CO2 ppm quantities.

    • You had me going there, for a moment — all that pseudo-logic and math.
      I added up all the numbers, and the total made no sense to me.

      While many people will think your comment is cool, calm, and logical,
      I DID NOT SEE the obvious conclusion:
      Life on Earth will end as we know it

      • If anything, we may be postponing the return of tne glaciers, which is due anytime soon. You want to see theend of life as we know it, just wait till then. Might be a few or tens of thousands of years, though, so don’t
        be impatient.

      • Richard Greene said:

        I added up all the numbers, and the total made no sense to me.

        Well now, Richard, at least you got that part right.

        There were no numbers in my above post that could have “made sense” iffen they were added up.

        Those numbers represent: Increases in World Population & Atmospheric CO2 by Decade

        By Decade, Richard, ….. by Decade.

      • Note to Sam Cogar:

        “I added up all the numbers, and the total made no sense to me.”

        That was a joke, Sam.
        My whole post was meant to be funny.

        I should have just commented that your post was excellent, because it was.
        However I was in a mood to not take any real climate science seriously, and tried to be Rodney Dangerfield in my comment.

        I am obviously not Rodney Dangerfield, although my wife often compares me to him:
        She always says: “You look just like Rodney Dangerfield.”

        I now realize attaching my humor post to your serious post was a mistake, like dog excrement on the heel of an expensive shoe, and if there was any way I could remove my prior post, I would do so … assuming you would be willing to pay me enough money.

        Oh, and keep up the good work.

  24. 1. Roger Graves says it

    is possible to make an accurate prediction of future CO2 levels using readily available information.

    The graph shown below plots CO2 levels as a function of world population,

    2. Assuming world poulation means ‘human population’ ~2 mil ys

    3. CO2 levels on this planet change ~4.3 bl ys

    4. Roger Graves does’nt mention ‘warming’

    5. watch Steve Mosher stick together

    CO2 levels; 2 mil human / 4.3 bl worlds; add some ‘warming’ -> here we go

  25. How came cancer into the world. Before Glyphosat urin Tests.

    And before EPA.

  26. It is quite surprizing and as well shocking, how the reports presents such a beautiful graphs — population versus CO2, when the data availability is unreliable and inaccurate?

    Dr. S. Jeevananda Reddy

    • cont— why I said that is, we have seen hundreds of papers saying CO2 is contributed by Agriculture, animals, etc, etc. are these bogus studies!!!

      Dr. S. Jeevananda Reddy

  27. Wouldn’t it be more informative and helpful to look at the actual CO2 levels above human cities using the new CO2 detection sensors on orbiting satellites? As I recall, from the early photos, the higher concentrations of CO2 had very little connection to human cities, except in northeast China. It appeared like there was a much closer connection between higher CO2 concentrations and effects of relatively warm summer temperatures, which caused decaying biomass on land and out-gassing in the relatively warm ocean water.

    Call me crazy, but I say we take a look…

      • This site shows maps of urban sprawl. I’m not claiming cars and electrical generation doesn’t cause some emission of CO2. I’m talking about how that CO2 stays or does not stay in the atmosphere. I’m talking about a picture from space about the actual CO2 concentrations. And, from my recollection of the early views, they don’t mesh with your urban sprawl maps.

      • To Mike Reno at 9:25
        High CO2 is created in urban sprawl. This is where energy is consumed. Your oco2 carbon map does not refute the fact that CO2 is created in urban sprawl, just as it is created everywhere else. Your map does not indicate where the CO2 is created. Then look at your map again, see how much difference there is between the low and high concentrations. You think this indicate where CO2 is produced? And why no update of this old map?

    • Mickey Reno sayeth:

      ……. to look at the actual CO2 levels above human cities using the new CO2 detection sensors on orbiting satellites?

      Mickey, there are no CO2 detection sensors on orbiting satellites. NONE, NADA, ZILCH, ZERO.

      The satellites you are referring to are affixed with IR sensors (infrared radiation) that can detect and measure the intensity of IR radiation that is being radiated from the earth’s surface/atmosphere toward outer space where said satellite is orbiting.

      The satellite can detect the IR radiation, ……. but the satellite can’t “see” what the source of that radiation is or was.

  28. Quoting the author of this post;

    “One advantage of a trend line is that we can then extend it to make predictions of what the future may hold,”

    Well…. the operative word in your sentence is of course “MAY HOLD”…

    Sure, it could all work out exactly as you predict, or it could all go in a totally different direction….

    Who thought the “Great Depression” could occur after a stock market crash…. Heck all the wise predictions of what MAY happen where quite sure that the “roaring twenties” would just keep on rolling…..

    And then there was that whole Dictator thing going on in the 1940’s…. Who knew that crazy people (Hitler was a documented Meth addict) could gain total control of the government of a previously civilized country (the Germans did contribute a great deal to chemistry, music (Wagner), and culture)…

    Extend your carefully crafted trend-lines at your own risk my good man, those of us that use curve fitting techniques to implement actual real world solutions to actual problems insist on some proof of causation before we wander off into the curve fitting weeds…

    I can fit third, fifth, seventh, ninth and other order polynomials to the supplied data and make any “future” prediction you desire. Heck I bet I can fit a polynomial to the data and predict everybody “MAY” be deceased in 23 years (or 27 years if I add just one more order to the “magic” polynomial).

    Be very careful with that “curve fitting” magic, it is very easy to convince yourself that you “know” the future……

    Cheers, KevinK.

    • Kevin,
      You said, “Sure, it could all work out exactly as you predict, or it could all go in a totally different direction….” Extrapolations are always at risk of being wrong I would say that as a rule of thumb, if one is using a polynomial fit to extrapolate, the risk is greater as the order is increased. On the other hand, fitting a linear trend to what is obviously a curvilinear relationship guarantees the extrapolation will be wrong. The question is, how wrong? Is it useful for what one is trying to do?

    • Kevin,
      You said, “Sure, it could all work out exactly as you predict, or it could all go in a totally different direction….”
      Extrapolations are always risky because of unpredictable changes in other influences. However, I would say that a general Rule of Thumb is that the higher the order of a polynomial fit, the greater the risk of being wrong. On the other hand, fitting a linear trend to what is obviously a curvilinear relationship is bound to give an incorrect extrapolation. The question is, how wrong? Is it good enough for government work?

  29. This issue was covered elsewhere a few years back, and I cant remember the exact place, but the key point is that there is an intermediate graph to be drawn, and that is per capita energy use versus population density. i.e hunter gatherers at uber low density use very little per capita energy – they eat and they wander.
    But the modern metrosexual Green living in an air-conditioned city has a carbon footprint that is far far higher due to use of fossil energy to grow his fertilised beansprouts, manufacture his eco bicycle, pump his uber regulated water and process all his shit….

    Joking apart, the point is that whilst nature at low energy input can manage to clean water, grow food and process manure, at high population density natural processes can no longer cope. European populations recovered extremely slowly after the Black Death over a period ofcenturies until (mainly agricultural initially) advances allowed a rapid population growth in the 18th 19th and 20th centuries. London became almost uninhabitable in the 19th century due to the massive volume of shit it produced, and required a massive sewerage project and steam pumps to solve it. Until the development of the steam railway the ability to actually transport food into the city was also limited. The US railroad is likewise associated with the development of high density cities.

    I am surprised the author here was not aware of this study. I seem to recall that per capita energy is correlated extremely closely with population density across the world as it is today, and of course a rising total world population must at least be absolutely correlated with average population density in a finite sized planet…

    I have a personal opinion, unsupported by data, that the modern western city is in fact a massive energy sink, that produces nothing of any value at all, all the manufacturing having gone to china, and in fact if e.g. London were wiped out in a nuclear blast, the rest of Britain would benefit enormously. And to plagiarise the great Billy Connolly , it wouldn’t look substantially different afterwards anyway.

  30. Every breath we humans take increases the CO2 in that lung full from 400ppm to 40,000ppm. It’s patently obvious why there is correlation between population growth an CO2.

  31. Advances in civilization, technology, medicine and standard-of-living in general all add to total CO2 production, but also reduce death rates for children, injured and sick, therefore increasing population.
    Perhaps a global average SoL (Standard-of-Living) factor should be applied to the population numbers?

  32. Option 5: There are other influences on the levels of both population and carbon dioxide left out by this perspective that would be obvious if plotting population v CO2 for the last million years. But I agree that short-term we expect both pop and CO2 to rise. Temp and sea level less so.

  33. Let me get this straight; the time period, 2006 to 2015, is really short for a statistical analysis. Anthropic CO2 is less than 5% of the total CO2 increase, so, unless all other CO2 increase is abnormally held constant, how are we even able to even see the anthropic CO2 fraction? How is this a valid analysis? I vote for option 1. You could just as easily plot CO2 vs. GDP per person or the price of tea in china. Correlation does not imply cause and effect. Everyone drinks water and everyone dies, but drinking water does not cause death.

  34. There is a rough correlation between fossil fuel consumption and population growth, largely because human economic activity requires energy. Although the energy consumed per unit of GDP is either modest or declining within developed economies, it has accelerated in emerging economies in the Middle East and the Western Pacific (among others). I have the data to graph if anyone is interested.

  35. I’ve got a horrible doubt about this analysis. if taken literally it would seem to imply that if the population stopped growing then so would the CO2 ppm. That seems a very unlikely outcome. The reason this analysis is flawed is that it is plotting tw trends that are strongly corrleated to other trends (per capita GDP for instance) which are far more important.

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