I gave my talk on SE for the Planet again this afternoon, to the local audience. We recorded it, and will get the whole thing up on the web soon.

I mentioned during the talk that the global greenhouse emissions growth curve and the world population growth curve are almost identical, and speculated that this means effectively that emissions per capita has not changed over the last century or so. After the talk, Jonathan pointed out to me that it means no such thing. While globally the average emissions per capita might have remained roughly constant, the averages probably hide several very different trends. For example, in the industrialized world, emissions per capita appears to have grown dramatically, while population growth has slowed. In contrast, in the undeveloped world the opposite has happened: huge population growth, with very little emissions growth. When you average both trends you get an apparent static per capita emissions rate.

Anyway, this observation prompted me to go back and look at the data. I’d originally found this graph, which appears to show the growth curves are almost identical:

Greenhouse gas emissions versus population growth

Greenhouse gas emissions versus population growth

The problem is, I didn’t check the credibility of the source. The graph comes from the site World Climate Report, which turns out to be a denialist site, full of all sorts of misinformation. In this case, they appear to have cooked the graph (note the low resolution and wide aspect ratio) to make the curves look like they fit much better than they really do. To demonstrate this, I reconstructed them myself.

I got amazingly detailed population data by year from digital survivors. They’ve done a wonderful job of collating data from many different sources, although their averaging technique does lead to the occasional anomaly (e.g. in 1950, there’s a change in availability of source datasets, and it shows up as a tiny glitch on my graph). I got the CO2 emissions data from the US government’s Carbon Dioxide Information Analysis Center (CDIAC).

Here’s the graph from 1850 to 2006 (click it for a higher resolution version):

Notice that emissions grew much more sharply than population from 1950 onwards, with the only exceptions being during the economic recessions of the early 1980’s, early 1990’s, and around 2000. Since 2000, emissions have been growing at more than double the population growth rate. So, I think that effectively explodes the myth that population growth alone explains emissions growth. It also demonstrates the importance of checking your sources before quoting them…


  1. Glad you checked this — they not only distorted the chart’s ratio, they seem to have either conservative CO2 numbers or exaggerated population numbers, as the curves in their graph cross several times.

    A graph using the same data as yours, but showing the ratio of CO2 per capita, would help tell the story of industrialization.

    It was a great talk; thanks for giving it!

  2. Is it possible to run an analysis of variance on the data? Rather than eyeballing it, I mean.

    Sorry to miss your talk!

    [sure, but I think it would only be worthwhile if we had a specific research question / hypothesis we were exploring – Steve]

  3. It is pretty obvious that the majority of the proportionality and correlation is from population growth, yes affluence brings toys and large animal heards to eat that will increase their share, and growth in 3rd world nations brings deforestation. Primary driver to all of this is too many folks, and not enough biological growth from living material that eats CO2/

  4. Pingback: Getting population dynamics into the models | Serendipity

  5. I fully believe in human-caused global warming. Anyone who doesn’t is an idiot.

    That said, I have created charts going back 12000 years using data from the Vostok cores as well as modern weather data comparing that to population and the charts bear an uncanny resemblance to each other.

    The world population has grown about 100% in the last 50 years. It should be obvious that a 22% atmospheric increase in our main gas by-product that every human produces virtually non-stop is the fault of people.

  6. Hi,

    Can I use the World Population vs. Global CO2 emissions 1850-2006 figure in an e-learning material?


  7. “For example, in the industrialized world, emissions per capita appears to have grown dramatically, while population growth has slowed” – in which countries have the emissions per capita grown dramatically since 2000? Would that be countries like China? Korea or Japan?

    How are emissions per capita measured? Do they factor in the declining capacity of the planet to absorb the C02 and the subsequent feedback loop that emerges?

    The countries with rapid population growth and huge populations have smaller emissions per capita simply because they have no choice – hence, most population growth in developed nations is driven by people seeking better population to resource ratios or fleeing conflict (usually resulting from overpopulation pressures). It’s a complex subject worthy of considerable discussion because population growth in this day and age is about government policy (which by and large keeps people ignorant rather than empowering them to make decisions on family size and giving them the means) rather than being incidental.

    I suppose at the end of the day, we should also be looking at the looming correction and asking ourselves, how can we soften the blow. Ensuring all people at child bearing age or coming into it have access to free family planning and education (particularly on environmental limits and the role that population plays) would be where I’d suggest we focus our efforts 🙂

  8. Your population curve is low by a billion people.

  9. @d.stangl: no it isn’t. Look carefully at the dates on the x axis. The rise to over 7 billion happened in the last decade, after this chart stops.

  10. SME: You are grasping at straws. Go ahead and plot 7.5 billion people at 2017. The curves are still amazingly parallel. You can not separate world consumption and population growth. World consumption provides the capital for populations to expand.

  11. It would be good to see deforestation plotted on here too.

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