The demographic fantasies of the IPCC

Climate change is now unequivocally an emergency according to the latest report from the IPCC. Our only hope lies in extremely rapid abandonment of fossil fuels and reversal of forest loss. But these lifeline scenarios also assume birth rates plummet in high-fertility regions. Jane O’Sullivan offers a reality check.

By Jane O’Sullivan

The Intergovernmental Panel on Climate Change (IPCC) recently released the first part of its Sixth Assessment Report (AR6-WG1). United Nations Secretary General António Guterres called it a “code red for humanity.” Climate change has already degraded many of our planetary support systems and the urgency of decarbonising human activities is beyond dispute. All of the IPCC’s scenarios see global temperature rise exceeding 1.5oC by 2040. If heating continues, planetary systems will cross “tipping points” which might escalate the heating uncontrollably: “hell on earth” according to an Oxford climatologist.

But hope is proffered that, if we halve emissions by 2030 and decarbonise completely by 2050, then global heating could be halted and eventually reversed. The report explores five scenarios, with our ray of hope dependent on the two with the lowest emissions.

The modelling for these scenarios uses the “shared socioeconomic pathways” (SSPs) that were developed in 2013 for use in AR5. The scenarios allow climate modellers to incorporate a wide range of socioeconomic variables in a consistent and relatively transparent way. But they have the problem of bundling different components, such as low global cooperation and high population growth, so that the effects of these factors can’t be explored individually.

In AR6, our lifeline scenarios are SSP1-1.9 and SSP1-2.6. These are both built on the SSP1 settings, and both reduce emissions rapidly, one achieving a radiative forcing of 1.9 W m–2 in the year 2100, and the other 2.6. These forcings correspond to roughly 1.5oC and 2oC global heating, respectively (Figure 1).

Figure 1. Projected global heating under the five scenarios featured in the AR6-WG1 report. Shaded areas show the spread of uncertainty for SSP1-2.6 (blue) and SSP3-7.0 (pink).

The problem is, SSP1 assumes a pathway for global population that is very far from the one we’re on. Achieving something approximating it is conceivable, but it would require strong and explicit efforts to get birth rates down rapidly in all high-fertility countries. According to most projections, virtually all the population growth this century will be accounted for in Africa (elsewhere, modest growth in some countries will be off-set by modest shrinkage in others). SSP1 anticipates Africa would fall below two children per woman around 2042, and end the century averaging 1.3 children per woman (Figure 2). Such rapid fertility decrease is highly unlikely with current levels of inattention to the issue. Can we expect diverse and dispute-ridden Africa to emulate South Korea’s rapid demographic transition, when that country had a single, stable government, a high-profile national family planning program and a secular, culturally homogeneous population?

Most unrealistically, SSP1 assumes that this rapid transformation has been happening for a decade already, positing a fertility rate of 3.2 for Africa in 2020, where the latest data put it at 4.3 (and that might be optimistic, given that the impacts of the pandemic on family planning access and child marriage are yet to be measured).

Figure 2. Africa’s (a) total fertility rate (average number of births per woman) and (b) total population, under projections from the UN (World Population Prospects 2019) and the SSP1, SSP2 and SSP3 scenarios. (SSP5 is similar to SSP1, and SSP4 is similar to SSP2).

Even the “middle of the road” SSP2 scenario anticipates much lower population growth than does the United Nations. For Africa, SSP2 is similar to the UN’s low projection, which the UN considers unrealistic. (It is merely illustrative of the impact of having half-a-child fewer births per woman than the medium projection in all countries). Only SSP3 lies within the UN’s range of probable population outcomes. Climate modellers have found it impossible to contain global heating to less than 2oC using SSP3. This is at least partly due to the expanded agricultural area needed to feed more people.

So, the IPCC report’s most hopeful global scenarios assume rapid fertility decreases in Africa and other high-fertility regions that are not happening and that would take much greater efforts to achieve. But the IPCC’s climate change commentary contains nothing at all to encourage greater investment and attention to extending family planning in under-served regions. It contains nothing to inform people in developed countries that having fewer children is a powerful way to reduce future emissions. We are left to assume, as the SSP scenarios do, that improvements in development and education, by themselves, will drive the rapid birth reductions needed.

That is a serious mistake. Where birth rates have fallen rapidly, they were invariably due to family planning efforts. While improved education and incomes can help reduce fertility, such improvements are rarely possible to sustain while population growth remains high. By allowing infrastructure and services to get ahead of the growing needs of the people, lower birth rates enable poverty reduction and better access to education more strongly than the reverse.

Let’s not exaggerate the implications. Changes to birth rates take time to affect the number of people present in a big way. Between now and 2050, when decarbonisation needs to happen, the contribution of any feasibly lower population pathway would be relatively small, perhaps 10%. (The ship has already sailed on earlier estimates that put it at 16%.) But the importance of population cumulates over time. The ability of nations to feed themselves, preserve their remaining biodiversity and live sustainably after 2050 will depend crucially on overall human numbers, the fewer the better. What we do about population in this decade might make the difference between having 12 billion or 7 billion people to sustain in 2100.

More immediately, their rate of population growth will have a very large impact on whether poor countries will have the resources to achieve “clean development”, to invest in education and to reverse deforestation. It not only affects how many people are exposed to climate disasters, but how well equipped they will be to cope with them. For them, population growth itself is a greater threat to the sufficiency of infrastructure and government stability, and a far greater threat to food, water and energy security, than is climate change.

The SSPs are right to link population outcomes with economic development, but assume causation in the wrong direction. They consequently neglect the important initiatives needed to reduce birth rates fast enough. This can be done with voluntary measures that empower women and families to achieve their goals, but it will not be done by pretending population growth is going to fix itself. If people’s future security depends on most of them choosing small families, they have a right to be told this. UN charters assert that people have a right to choose their family size freely and responsibly, but they can’t choose responsibly if the consequences of population growth are hidden from them, or are actively denied.

Nigeria’s former President Olusegun Obasanjo loses sleep over how to keep Nigerians fed and “how to keep the keg of gunpowder of the large army of unemployed youth from exploding.” But many current leaders dream on that youthful, growing populations are a boon. The IPCC is not providing the wake-up call they need.

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38 thoughts on “The demographic fantasies of the IPCC

  1. At some time in the future the resources necessary to maintain civilization will no longer be available to humanity– all resources necessary to maintain our civilization are finite and limited. No action taken by humanity can convert those finite and limited resources into infinite resources such that our civilization can continue forever into the future. The collapse of civilization due to the lack of resources is coming much more quickly than 99.9% of humanity believes. In plain and simple terms humanity will revert to the Stone Age in the very near future. Read the book “Blip” written by Chris Clugston and read the comments of Jared Diamonnd, Professor at UCLA, Pulitzer prize-winning and expert on the collapse of civilizations. Upon returning to the Stone Age the human population will fall to less than 125 million. There are two, and only two, ways humanity will reach that number– the stupidity or the intelligence of humanity. Almost everyone on the face of the earth wants to choose the path of stupidity.

    1. Most or many will at least agree that there are way too many humans currently [7.5 billion]; but beyond this simple “sustainability” observation, is there any country trying to establish a sustainable population?

      I agree with James Lovelock and Paul Erhlich who said sustainable is ~ 2 billion, but how this could be done they did not say. The human race is probably not evolved sufficiently to mange this problem or govern itself to this extent.

      1. Please get up to date on Human overpopulation numbers, NOT 7.5Billion, now 7.9Billion.

  2. We have always know that fossil fuels are finite and our use of them will come to an end. Our industrial society/civilization has always been a temporary blip in human history. And it is now coming to an end

    1. I can live with ‘our industrial society’ but certainly not ‘civilisation’. We ‘humans’ are NOT civilised.

  3. quote from lorribre: “Upon returning to the Stone Age the human population will fall to less than 125 million.” That is the BEST case scenario. More likely is that humanity will go EXTINCT!!!

    1. If we (Humans) return to the ‘stone age’, Ireland could be a great place to live, loads os stones here.

  4. Thank you, Jane (and OTP) for an excellent article. I entirely agree that the answer to population growth is family planning. Studies have been done comparing girls’ education to FP provision and it’s the contraceptive supplies and services that do it, although formal education at secondary level is a contributing factor. Not many girls in poor countries achieve that, and it’s a very expensive and indirect way of trying to enable choice about having a baby. It also assumes that poor women without education can’t understand the issues. That’s patronising, and wrong.

    Just a couple of comments here:

    1) I don’t think women and men living with poverty will reduce their births because they know about world population. It will be about their own numbers: how many children in the family (and how to feed them all) and the size of the community relative to land, work, housing and other resources. As well as the suffering and deaths involved in too many closely spaced pregnancies, including an epidemic of dangerous abortions which is occurring in almost all countries which lack good family planning services.

    2) Could we all agree to stop using the “half a child” phrase? I think it dehumanises the people and choices involved. It’s less snappy, but I suggest “half the women having one less child”.

    As a practical way forward, we should campaign for the climate change mitigation funds to include support for family planning. This would really make a difference. There is a quiet hope that we might achieve this with the UK contribution, and it could be raised with other donor governments including of course the US. I also suggest some moves at the UN, especially the General Assembly, that would bypass the obstruction encountered in the increasingly frustrating special conferences on this issue.

    Barbara Rogers
    Author of “Children by Choice?” on Amazon Kindle

    1. It’d be interesting to figure out how much the possibility of migration offers an incentive to have more children. Some parents might realise they can’t afford more children or that their area is overpopulated, by the possibility of one child migrating and sending money home is an incentive to have more. I’ve read interviews to that effect.

      1. If they are of a ‘pro-natalist’ mentality, they will do that, have more children than their local circumstances can sustain. I live in Ireland, we have always done that, ‘the Irish’, had much more children than our island could sustain knowing that there was a big World out there for our excess human population numbers. We are now in 2021, an island of 7 million yet we claim a diaspora of around 60 Million. This is like China, with a current population of 1.4 billion claiming a diaspora of 11 billion, or worse, China and India combined, current population 2.8 billion, claiming a diaspora of 22 billion. Do the math.

      2. That’s one of the biggest problems with this issue, and the idea of reducing birth rates (which I agree with) in countries where they are already low: if you don’t also reduce immigration, it’s useless and actually breeds resentment (“we’re getting outnumbered”, “we can’t afford children but these people who are poorer can”, etc).

        Italy did the same as Ireland, by the way; it seems that only a few societies didn’t, and got outnumbered and swept aside by others.

        Even looking at Afghanistan now, there’s a huge dilemma there, since obviously one of the problems is the conflict and much foreign meddling, and yet, given its geography, arid climate and high birth rate, Afghanistan has been overpopulated for a long time, and that’s one of the reasons it keeps producing refugees. Syria is the same, plus continuous water problems – no water, no food.

        So what do you do, where there’s a serious conflict, and yet also an obvious overpopulation problem that isn’t the fault of the countries that people want to seek refuge into, and that actually feeds into the conflict (youth bulge, poverty, unemployments…)?

  5. It’d be interesting to figure out how much the possibility of migration offers an incentive to have more children. Some parents might realise they can’t afford more children or that their area is overpopulated, by the possibility of one child migrating and sending money home is an incentive to have more. I’ve read interviews to that effect.

    1. This is an important issue that is largely unexplored by demographers, as near as I have been able to determine. What is clear is that many families in Central America currently plan much of their economic lives around getting themselves or their children into the United States: saving money for the trip and to pay smugglers at the border, etc. It seems common sense that such thinking is also playing a role in people’s reproductive decisions–but again, there appears to be little effort by researchers to look at this systematically.

      Lack of opportunities or worries about the future would likely lead Central Americans to have fewer children, as would a concern for the common good for their home countries. But a desire to get one or two children across the border up North might incentivize having more children instead. At a minimum, thinking in terms of making a better future elsewhere seems likely to undermine personal or political efforts to make a better life at home.

  6. Family planning will not reduce the human population fast enough to prevent the collapse of civilization, the deaths of billions and the extinction of humanity. No one in favor of family planning has produced an estimate of the human population for the next 150 years, in 10 year intervals such that the estimates can be compared to the actual figures. No one in favor family planning has written a detailed paper showing, with at least 80% certainty, that the human population will be reduced to whatever level is necessary to prevent the collapse of civilization. Until someone produces such a paper family planning is a bad joke on humanity.

    1. It’s not a bad joke. It would be absurd to present family planning as the perfect solution, because it does not work fast enough, as you say. Family planning is not sufficient. Nevertheless, it is necessary.
      It produces long-term results. This means that, if we are able to survive for a century and limit as much as possible environmental damages, then ecosystems can recover thanks to a reduced population, climate can stabilize and biodiversity can flourish again. The children of our children could live in a stable world with a reasonable number of people (something between 2 and 5 billion) and enjoy both: wilderness and technolgical advances. Conversely, if we don’t reduce population, we do not have any hope of saving civilization and preserving nature, not even in the long term, not even for our grandchildren. Whatever we do, if we want to survive, family planning must be part of the strategy.

      Thank you Jane for your great article!

  7. I agree with Lucia. Even if you think it’s remotely possible to reduce the numbers of humans on the planet (unless you are planning mass extermination), I think you would agree that family planning is a necessary part of that, and it can’t possibly happen without people having good choices about how many children to have.
    In the wealthier countries we have transitioned from rapid population growth to more or less stable numbers, with much less suffering and premature deaths along the way, and this has been done with safe and effective family planning.
    The next step is to combat the idea, often seen in the media, that any small reduction in our numbers (following the post-war “baby boom”) is some kind of disaster. I have complained successfully to the BBC news people about their rather hysterical coverage of “falling numbers” in the UK and Europe, and they have accepted the point that this is a critical contribution to combatting climate change and environmental destruction..

    1. I agree with Lucia and Barbara! None of us can predict the distant future. What seems clear from the recent past is that societies can choose smaller families and end or greatly reduce their population growth. We should continue to advocate for that, in our own societies and encouraging it in others.

      It is critical, in the developed world, to combat the “falling numbers” hysteria. Aging societies with smaller populations are a good development, and we need to make that case.

      1. We also need, however, to convince people that they cannot retire as early as they do now. In Italy, if you take the average life expectancy, people work overall less than half the time they are alive. That puts a huge burden on everyone else. Early, well-paid retirement is seen as an inalienable right. You see many pensioners over here enjoying a lavish lifestyle and brag about how fun their life is now that they don’t have to work, while their children struggle to raise children of their own or to pay a mortgage.

  8. When I read the words “Family Planning” I want to vomit on the page. Someone comes to you and asks you to help plan his family and you respond “great”. Then the person states he and his wife want to plan for eight children. Do you respond “great” or do you respond “your an idiot “. ? Humanity must have “birth control” and if we refuse to use the proper words we do not deserve to survive. It is that simple!

    1. lorribre, please don’t vomit! Family planning is the best available term to cover contraception and pregnancy terminations (abortion). By definition it is about limiting the number and spacing of pregnancies. If someone wants more babies then that would come under the heading of IVF or fertility treatment.
      If your man wants more children, it is very likely the woman involved wants fewer. Which is why it is so important to provide information and support for women to enable them to decide.

  9. A short response to Professor Cafaro: Every major problem humanity faces today, without a single exception, will not be solved or even ameliorated unless the number of people on the planet is reduced and/or the per capita usage of resources/materials is reduced. In fact, unless the human population is substantially reduced together with a substantial reduction in the per capita usage of resources/materials human civilization will collapse in less than 500 years. And Family Planning will not achieve the necessary reduction in the human population in time to prevent the collapse of civilization and the extinction of the human species. Advocating small families together with Family Planning will fail. I challenge everyone on the planet to write a paper showing that three or more major problems faced by humanity today will be solved or even ameliorated without a reduction in population. And remember the UN is predicting that the population will grow by about 3 billion, reaching 10.9 billion in the year 2100. Also consider that is absolutely certain that the per capita usage of resources between now and the year 2100 will increase due to the demands of the billions living in the underdeveloped and undeveloped nations of the world.

  10. A very thoughtful perspective, Jane, thank you.

    What has the IPCC said in response to you pointing out their glaring omission in logic and data analysis?

    Indeed it would be helpful for the rest of us if we knew who are these well-intentioned IPCC specialists are — which specific team was responsible for the SSG calculations in the AR6-WG1?

    ( One might also legitimately ask, Was this SSG calculating team composed solely of scientists . . . or also sprinkled with ethicists, moral philosophers, and front-line philanthropists? )

    From the data you’ve presented, their conclusions contain unacceptable logical fallacies. Yet would they agree with your view?
    My guess is not: it’s hard to imagine them saying, “OMG!!! Sorry, we totally goofed. Jane’s alerted us to a HUGE oversight. Our bad, let’s fix it.”

    I’m not saying that either your or their perspective is the better, more accurate, or more valuable. It’s just that the forum the Overpopulation Project can afford or has imagined (a well-intentioned critique from one side of a multi-sided issue) is inadequate to the task.

    At the least, you and Phil Cafaro should get these well-meaning SSG-calculators equally involved in this discussion. Either in print or on the tv show. Or both.

    In contrast, preaching to the choir only goes so far. . . . about as far as the choir.

    Again, thank you for pointing out the deficits as you see them. Let’s keep the ball in play — it’s their turn to volley!

  11. Family Planning ( which I call voluntary population control) will not reduce population fast enough to prevent the collapse of civilization, the deaths of billions and even the extinction of the human species. To the best of my knowledge, no one has written a paper showing that family planning will reduce the population fast enough to prevent the collapse of civilization. I challenge anyone reading this document to send me such a paper. My email address is To the best of my knowledge no one on the face of the earth has determined the chance that family planning will fail.. Anyone taking the position that family planning has a zero chance of failure is an —-. To gamble the extinction of humanity on family planning without attempting to determine the chance that it will fail is —-. To the best of my knowledge, no one in favor family planning has set forth the following numbers in 10 year intervals for the next 100 years– the population, TFR, and the per capita usage of resources. For example, in the year 2050 population will be X, the TFR will be Y and the per capita usage of resources will be 200% of what it was in the year 2020. Those numbers are absolutely essential so that predictions of those in favor of family planning can be compared to the actual numbers at 10 year intervals. If the actual numbers are substantially in excess of the predictions, humanity will be forced to immediately impose coercive population on all of humanity to prevent the collapse of civilization and the extinction of our species. I have written a number of papers that show, in my opinion, that Family planning has zero chance of preventing collapse of civilization and the only way to save civilization and prevent the extinction of humanity is to immediately impose coercive population control on a worldwide basis. If you desire a copy of the papers I have written please contact me at the email address given above

    1. Thank you, Jane, for your integrity and passion to face the truth of human overpopulation and the utter collapse and even total extinction of our species in the near future. This scenario and the numbers you request are contained in my 2018 publication of the free e-book, “Stress R Us”, available at and other sites on the net, as well as a print on demand PB at Amazon Books. Briefly put, all of the animal crowding researches done over the past century culminate in the same extinction event. For the movie fans, watch “The Children of Men” (Clive Owen, Juliette Moore, Michael Caine, etc.), or read the 1992 novel by P. D. James. By a curve fitting estimate of the human population curve compared to that published by Calhoun in the publication of “Symposium of Man and His Place”, we may see total extinction between 2,100 and no later than 2,300, if exhaustion of natural resources or climate disaster doesn’t take us out first. I am a retired physician and have been watching the exploding incidence/prevalence of human disease due to what I call “population density stress” and wrote the 623page book summarizing my lifetime observations.

      My question to any prospective parent today is this: do you really want to bring another of of the 206,000 innocent lives into this dying planet only to watch him/her suffer and die from population density stress and hate you for your selfishness? Mother Nature always knows best and She is very clearly attempting to rid Herself of us through exploding disease and Her own long evolved population regulation mechanisms of the collapse of healthy parenting and the neurochemical mechanism of the stress hormone “cortisol” and “CRH” turning off the reproductive hypothalamic hormone GNRH. I saw an article yesterday decrying the loss of fertility in 1 out of 4 female physicians (and all performance athletes), the collapse of male sperm production is well known, and the IVF docs are getting rich. What more evidence do we need? Mother Nature has made a terrible mistake and She is busily trying to clean-up Her mess. Thank you for all your efforts, but Mother Nature is already taking care of the problem, and only the exploding Healthcare Industry is allowing us to avoid the reality of Her efforts to clean house, Her house.

      1. Jane, you asked about the population reduction possible with family planning. Voluntary one-child families, when driven by the honest Apocalyptic future facing any potential new innocent thoughtlessly brought into this world, could reduce our worldwide populations to a barely sustainable 1950 level of 2.5B by 2,100, although many think this is still far too large a number to save the planet and humanity. Sadly, only an involuntary die-off from our myriad and rapidly increasing “diseases of civilization” caused by a collapse of our unsustainably expensive healthcare “industry” is a certainty. 725,000 here and 600,000 in Brazil, but we haven’t even begun to see what’s coming as we hack our way into the remaining isolated viral disease refuges, which the experts out in NM tell us house another 600,000 viruses capable of infecting humans! Stress R Us

  12. Jane, please stop referring to ‘human civilisation’ as that ‘human civilisation’. Our species are anything but ‘civilised’, otherwise we wouldn’t be in the mess that we are in.

    “The Ecological Crisis in short is the Population Crisis. Cut the Population by 90% and they aren’t enough people left to do a great deal of damage”. Mihael Gorbachev.

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