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Eight things we learned from the pope's climate change encyclical

Posted on 18 June 2015 by Guest Author

Pope Francis has released an unprecedented encyclical on climate change and the environment. The 180-page document calls on rich nations to pay their “grave social debt” to poorer countries and lambasts the UN climate talks for a lack of progress. Here are eight things we learned:

1) He thinks we should phase out coal

While renewable power from wind and solar gets up to speed as a solution to our energy needs, it’s worth considering gas over coal, he said:

We know that technology based on the use of highly polluting fossil fuels – especially coal, but also oil and, to a lesser degree, gas – needs to be progressively replaced without delay. Until greater progress is made in developing widely accessible sources of renewable energy, it is legitimate to choose the lesser of two evils or to find short-term solutions.

He says more than 20 years of summits have produced “regrettably few” advances on efforts to cut carbon emissions and rein in global warming. The encyclical says:

It is remarkable how weak international political responses have been. The failure of global summits on the environment make it plain that our politics are subject to technology and finance. There are too many special interests, and economic interests easily end up trumping the common good and manipulating information so that their own plans will not be affected.

3) He doesn’t like carbon trading

In this passage he seems to be referring to the only current global carbon trading scheme, the CDM:

The strategy of buying and selling “carbon credits” can lead to a new form of speculation which would not help reduce the emission of polluting gases worldwide. This system seems to provide a quick and easy solution under the guise of a certain commitment to the environment, but in no way does it allow for the radical change which present circumstances require. Rather, it may simply become a ploy which permits maintaining the excessive consumption of some countries and sectors.

4) But he does like community energy

From Francis’s point of view, small and local is beautiful:

In some places, cooperatives are being developed to exploit renewable sources of energy which ensure local self-sufficiency and even the sale of surplus energy. This simple example shows that, while the existing world order proves powerless to assume its responsibilities, local individuals and groups can make a real difference.

5) He is neither pro nor anti genetically modified food

It is difficult to make a general judgement about genetic modification (GM) ... The risks involved are not always due to the techniques used, but rather to their improper or excessive application ... This is a complex environmental issue

6) He thinks consumption is a bigger problem than population

Perhaps unsurprisingly given the church’s stance on birth control, and in common with many environmentalists, he thinks consumption rather than overpopulation is the bigger environmental problem:

To blame population growth instead of extreme and selective consumerism on the part of some, is one way of refusing to face the issues.

Click here to read the rest

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Comments 51 to 83 out of 83:

  1. Wol @45:

    "If the planet is facing a future catastrophe on the climate change issue, surely reducing our numbers is the very first thing to address, even before carbon reduction?"

    In order to address AGW we need to scale back CO2 emissions by about 50% by 2050, and to effectively 0% of current emissions by 2100 at a minimum.  I have to wonder how it is you intend to address even the first target by "reducing our numbers"?

    Even if we have a mandatory and enforced replacement rate only birth rate (ie, 1 child per person, or 2 children per couple), the global population would still increase in the short term due to increasing life expectancy.  To actually reduce populations we would need a global, mandatorally enforced below replacement birth rate.  To achieve that, in turn, we would need totalitarian control of the world's population.

    To see what is involved, consider China's "one child policy" which was introduced in 1978, ie, has been in effect for 37 years.  It has been effective in reducing the fertility rate which has dropped from 6.16 children per woman in the 1965 to 1.66 children per woman as of 2012.  The later is 17% below the replacement rate, yet China's population continues to grow at 0.5% a year as of 2012 (down from a peak at 2.8% per year in 1971.  Granted that the fertility rate is above the theoretical fertility rate of a one child policy (ie, 1 child per woman), but after 37 years China's policy still entails a growing population when on the same time scale we need to reduce emissions by 50% (at least).

    In short, the only way population control can be an effective policy to reduce emissions on the time scale required to tackle global warming is by deliberate reduction of life expectancy.  Unless we deliberately use the grim reaper as an agency of government, perhaps by introducing Logan's law, population is essentially an uncontrollable part of the equation for climate change policy.

    I assume that is not what you are suggesting.

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  2. Population growth is a major factor that increases global warming, and I don't think anyone disputes this. It's interesting to review what has caused this population growth. The almost exponential rates of population growth in recent centuries were partly caused by improving incomes and health standards allowing most offspring to survive.

    However the increase in wealth and health standards ultimately also slowed population growth in the western world, as people realised they didn't need such large families to secure future generations. This is the well known demographic transition.

    Therefore the most fundamental answer to reducing population growth is to improve living standards, and this means reducing inequality, both within countries and between countries. Reducing inequality is an economic, social, and political question.

    Of course contraception is a major factor, but wont be fully adopted unless people are secure that they have rising living standards, and can securely have smaller families, backed up with good healthcare.

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  3. It would be nice if Ryland could cease not only in misrepresenting me, but also in misrepresenting the Catholic Church in this debate.  The Catholic Church is not opposed to birth control per se, but only to the use of contraception and abortions for birth control.  That leaves some form of natural familly planning, most notably the Billings method for birth control (along with the elimination of pregnacy outside marriage by complete abstinence, of course).  Further, as the Catholic Church is unequivocally opposed to marital rape, it follows that they do leave woman in controll of their own fertility, if restricting the means they can use to controll that fertility.  Based on Catholic teaching, no man can force a woman to become pregnant against her will, nor any woman force a man to impregnate her against his will.

    I think there are many things wrong with Catholic teaching on fertility and sex, but characterizing the Catholic position as preventing woman from controlling their own fertility is simply an emotive strawman.  

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  4. nigelj @52, had the West's affluence (and hence per capita energy use) grown at historical levels while its population remained at preindustrial levels we would be nowhere near as close to dangerous thresholds of global warming as we now are, and would have far longer to convert to renewable energy.  However, likewise, if the West's population had grown as it did but its per affluence remained static we would also be no where near dangerous thresholds of global warming.  Indeed, per capita GDP of the US grew between 1960 and 2013 by 30% more than North American population grew from 1850 to 2012.  That is, per capita GDP growth over the last fifty odd years has exceeded population growth over the last 160 odd years.  Given that, there is no doubt as to which is the greater contribution to the problem.

    More importantly, population levels are inflexible and difficult to alter in the short term (see my post @51) and the necessary policies to significantly reduce populations on a centenial scale would be politically very hard to impliment.  Policies to restrict affluence could be implemented far quicker, although they would face similar political resistance.  If one or the other must give, however, the fact is we could viably reduce affluence without significantly effecting well being on a time scale of decades, something we could not do with population.

    More responsive than either, and facing far less political opposition, is reduction in Carbon intensity, ie, the total emissions per unit GDP.  In fact, carbon intensity in the US had been decreasing naturally with almost no policy help in the decades following the 1970s, and can be brought down to zero at need in a matter of decades with an economic cost approximately equal to or less than the economic growth rate.  That is, it can be realistically done without a decline of either affluence or population.  As the least cost, most rapidly implimentable, and politically least intractable solution, surely it must be our first option.

    That is particularly the case given that global population is likely to peak under 10 billion around 2075 with almost no policy intervention, and then decline slightly in any event (a pattern it would be very difficult to alter with our available policy implements over this century in any event). 

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  5. Tom Curtis you accuse me of misrepresenting you.  This is what you wrote at 35

    I also do not believe in using another persons agreement on one topic as a means to leverage their agreement on a different topic and think it is fairly much an open and shut case that unrestrained affluence has a more harmfull impact on the global ecosystem than third world population growth; and that therefore if we must make a choice between the two, restraint of the affluence is a more sensible strategy to preserve that ecosystem than preventing the third world playing catch up on population growth at the same time as they are playing catch up in affluence.

    This comment was in reply to my comment on contraception and women hving control of thei own fertility.  As I am accused of misrepresenting you will you explain exactly what you mean by the comment I have emphasised?  

    You may be sicvk of being misrepresented but equally I am sick of your evasion of the point I am making which is your comment is putting restraining affluence ahead of the right of women to control their own fertility.  In your many words on this you have not directly addressed this point. 

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  6. ryland @55, in my comment @53 I was not referring to any particular case of misrepresentation, but your general tendency to do so as already commented on by PhilippeChantreau:

    "Ryland, re-read Tom Curtis' post. What he says is quite clear and does not seem to correspond to what you object; your post seems to consist mostly on grasping at specific words in his, and ascribing to them a meaning that their original context does not support."

    However, as you bring it up, you clearly misrepresent my position in your post @55 when you say my comment " putting restraining affluence ahead of the right of women to control their own fertility".  

    Not having a particular policy to restrain population growth is not equivalent to having a policy of not permitting women to have the right to control their own fertility.  Indeed, the Chinese "one child policy" represents a greater control on the fertility of woman than anything proposed by the Catholic Church.  The forced abortions implimented as part of that policy are, to my mind, morally equivalent to rape, and the absolute abnegation of giving women control over their own fertility.  In the case of China, giving woman control over their own fertility would almost certainly increase the fertility rate, and consequently population growth.

    Not only is giving women control over their own fertility not the same as restraining population growth (and having the potential to increase population growth in particular contexts); but people can be in favour of giving women controll over their own fertility for no other reason than to give women control over their own fertility.  Indeed, that is my own position.  I want women to have control over their own fertility whether it is likely to lead to increased fertility (as in China) or decreased fertility (likely in India) or have no effect at all.  I want it because their not being in controll of their own fertility is a moral wrong.  It treats woman as objects to satisfy male wants rather than as ends in themselves.

    Your unjustified equation of my position on population with a quite distinct and morally offensive position is deeply offensive to me.  It is also a very clear misrepresentation that permeates your argument.

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  7. Tom Curtis @ 54. I have to agree with you on all that. Reducing population growth is a difficult task, and I have also read that on current policies and trends its likely to peak at 10 million around 2070, then stabilise. The figure I saw was 9.2 million. As you say its about affluence and carbon reductions and the costs of the transition are not as huge as some people claim

    However there are many reasons to reduce inequality,  and one of the side effects is it should lead to lower population growth as well.

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  8. ryland @58, I had already repeatedly addressed the issues.  What I did @56 and also @53 was address the misrepresentation.

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    Moderator Response:

    [JH] Your discourse with Ryland has run its course because he is now engaging in excessive repeitition which is prohibited by the SkS Comments Policy

  9. Tom Curtis,

    No matter how clear one's views may be in one's own mind, the language one uses to express those views is laden with ambiguity.  Especially in such a complex and historically rich subject as morality and ethics.  It's not anybody's fault.  That's how natural language breaks.  Patience furthers.

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  10. As this site is about evidence, and given the comments about overpopulation, I believe that it is entirely on topic to ask these questions, especially as the evidence I have asked for regarding carrying capacity has remained unanswered. Without evidence, it is a myth, or at least a fiction, that the planet is not already overpopulated, and that adding even more people will not increase the rate of extinction of other species and exacerbate all the other problems created by sheer human numbers.

    1. At what level of total impact/total consumption/total production of waste (pick the metric) is our current population sustainable?  Please quantify.

    2. What will be the impact on that total if we add another 3 billion people to the human population?

    3. What is the evidence that Herman Daly's projection of about 2 billion people being approximately the sustainable population level is incorrect?

    4. What is the evidence that our agricultural practices, fossil-fuel dependent or not, are sustainable (see my reference earlier to Peter Salonius and "The Ten Thousand Year Misunderstanding)?

    5. There is a focus amongst some on the habits of the highest consumers (and I don't disagree that it is an enormous problem), but what is the mechanism whereby we can reduce their consumption, and what impact will that have on the sustainable human population level?  Please quantify.

    If I forget humility for some reason and start to believe that humans are somehow special, unique, and moral, I go back to Lovelock's comment to the effect that humans are no more qualified to be stewards of the planet than goats are to be gardeners, and Eliot's comment that most of the evil in this world is done by people with good intentions.

    Herman Daly

    Peter Salonius

    Recent commentary on Daly

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    Moderator Response:

    [JH] Please note that no one is obligated to answer the questions that you have posed. 

  11. @34.  You make all sorts of comments about animals, and infer all sorts of things, but have not provided the evidence.  For example, the language of prairie dogs has been described as perhaps one of the most complex non-human languages observed, describing predators in detail in a single "chirp," dolphins have a complex language, chimpanzees have made tools and use them, animals demonstrate reasoning and compassion, and so on. In an opinion developed from purely personal observation, humans are not the unique and chosen species that we often try to make ourselves out to be. If we define morality or reasoning or ethics in terms of what humans do, then we have a nice bit of circular reasoning to say that we are the only moral or ethical species.

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  12. SkepticalinCanada,

    Humans, like all other species of life on this amazing plant, are comprised of sub-species. Identifying the sub-species of concern, not humanity generically, is what needs to be done.

    So here is my summary based on:

    • my MBA education (that helped make me aware of the motivations of many people in business and the potentially unacceptable power of marketing)
    • my Engineering education (That help me arrive at acceptable conclusions without the need for absolute certainty)
    • my Professionalism as an Engineer in Canada (The obligation to ensure I protect people and the environment from desired pursuits of profit)
    • and my many decades of observing what is going on and attempting to come up with the best explanation for all of the observations.

    The group of to be concerned about is the sub-species of humans who focus on maximizing the personal benefit that they can obtain, those who are not interested in the development of a lasting better future for all life on this amazing planet if such pursuit would potentially reduce the amount of personal benefit they can get.

    • Within that sub-species, is a sub-group of greater concern, those who deny or dismiss any developed understanding of the unacceptability of what they prefer to try to get away with.
    • Within that sub-group, the real trouble-makers are the ones who actually better understand what is going on but deliberately try to discredit any developing understanding that is contrary to 'their interests'. They abuse their power and wealth to delay the broader understanding in humanity of the unacceptability of what they try to get away with.

    That last group clearly is the root cause of the problem. That is the group that needs to be be blocked from any success, preferably by them just changing their minds. With that group gone the larger group of deniers will fade away. And with that group faded the free-market competition has a better chance of developing decent results because unacceptable pursuers of profit and pleasure would not be in the game with their competitive advantage over the ones who care more about their impacts on other life.

    The ones among the trouble-maker core who are unwilling to change their minds are just like any other criminals and should be dealt with in the same manner, except that the wealthier ones in that group should be treated more harshly because they have less excuse to 'not know better'.

    So a key part of the solution to the known problem would be an International Criminal Court and Investigation/Prosecution Team that looks for evidence of people who know better or should know better yet deliberately try to mislead others so they can personally obtain more benefit from an activity that is understood to be unacceptable (even understood by them to be unacceptable).

    Another part of the solution is ensuring that everyone understands that the profitability or popularity of an activity is not to be considered when deciding what activities are acceptable.

    As for references, there are many books written by many people about the challenge of creating lasting Civil Society with an Economy that can actually grow in perpetuity because it could last in perpetuity and only gets improved by newly developed ways of living that could also be enjoyed by all and last in perpetuity.

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  13. In case you are not aware, today is World Refugee Day and its theme echoes what is contained in the Pope's encyclical.

    Excerpted from a CNN article about this day:

    In a statement, Guterres* warned that "a spreading global violence has come to threaten the very foundations of our international system" and urged the world not to turn its back on those who most need its help.

    "More people fled last year than at any other time in our records. Around the world, almost 60 million have been displaced by conflict and persecution. Nearly 20 million of them are refugees, and more than half are children," he said.

    Their numbers are growing every day, on every continent, he said. And they rely on the world for their survival.

    "They will remember what we do," he said. "Yet, even as this tragedy unfolds, some of the countries most able to help are shutting their gates to people seeking asylum. Borders are closing, pushbacks are increasing, and hostility is rising. Avenues for legitimate escape are fading away."

    At the same time, he said, humanitarian organizations like the UNHCR run on shoestring budgets, unable to meet the spiraling needs of such massive numbers of people.In a statement, Guterres warned that "a spreading global violence has come to threaten the very foundations of our international system" and urged the world not to turn its back on those who most need its help.

    "More people fled last year than at any other time in our records. Around the world, almost 60 million have been displaced by conflict and persecution. Nearly 20 million of them are refugees, and more than half are children," he said.

    Their numbers are growing every day, on every continent, he said. And they rely on the world for their survival.

    "They will remember what we do," he said. "Yet, even as this tragedy unfolds, some of the countries most able to help are shutting their gates to people seeking asylum. Borders are closing, pushbacks are increasing, and hostility is rising. Avenues for legitimate escape are fading away."

    At the same time, he said, humanitarian organizations like the UNHCR run on shoestring budgets, unable to meet the spiraling needs of such massive numbers of people.

    *U.N. High Commissioner for Refugees Antonio Guterres.

    U.N. World Refugee Day: Richer nations urged to shoulder burden by Laura Smith-Spark, CNN, June 20, 2015

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  14. @62  I prefer to look to the experts in the field of the human impact on the planet.  To this point, I have provided references to the works of Daly, links which lead eventually to Cornell University ecologists, the work of soil scientists (more than one), and others.  It seems that all I get are responses reminiscent of the responses from deniers of human-caused global warming.  So, I'll leave this thought, and I realize that it wanders into an area that is really not the topic of this website, but it is related to the objectives:  is it a myth that human overpopulation is contributing to global warming, and that we cannot hope to live sustainably on this planet - in terms of energy and resource use; and in terms of emissions, the waste we produce, and our impact on the climate and the planet in general - unless we reduce human numbers. Is overpopulation denial hindering our progress toward solving our problems?

    Does anyone care to add that to the list of climate myths, even in modified form?

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  15. Skeptical in Canada,

    The questions you ask do not have answers that are a consensus of scientists.  You are asking questions where the answers depend on personal choices.  For example, it may be possible to support 15 billion people on Earth if 90% of other species are wiped out.  I might choose that because I value humans most (that is not my choice).  OPOF may not think that is a good choice and to preserve more species (s)he chooses a lower number of humans.  These are not scientific choices but personal, moral choices.  Science cannot determine which is a better choice.

    The impact of a given number of humans depends on many factors.  If everyone used as much carbon as current Americans, the total that could survive would be much less than if everyone used as much carbon as the Tuvalu islanders.  How will we all live?  Ca nenough renewable energy be made to supply the other needs of billions?  Your citations, while interesting, are not scientific consensus.  Others have different conclusions.

    Overpopulation is a big problem.  As Tom pointed out above, it is difficult to make the math work without a lot of starvation.  Can you suggest a solution that is more moral than China's one child policy and forced abortion?  I doubt the world would agree to that.  While I care a lot about overpopulation, it is difficult to see a good solution everyone would implement.  

    AGW has a scientific consensus about the problem and what needs to be done to work toward a solution.  Attaching another big, intractable problem does not seem to me to be a good way to resolve AGW.  Overpopulation needs to be dealt with separately.  SkS works on the problem of AGW.  

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  16. Can I suggest a solution?  More informed people that I already have, per the links I have provided. I hope that people actually read them, and even further, think about them. Unlike you, I do not assume that there is no significant consensus is about overpopulation among the experts on the impact of humans on this planet, but I do not have the experience or the means to do such an analysis. And assuming that the problem is intractable...doesn't that just fit another of the denialist responses?

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  17. skepticalincanada @66.

    Your accusations of denial cannot be merited as the discussion you seek is more one of philosophy than one of science. Indeed, your attempts to discuss here 'sustainable population' is not really in tune with what SkS is about which is specifically "The goal of Skeptical Science is to explain what peer reviewed science has to say about global warming."
    I would also say that your 'links' @60 do not at all adequately prepare the ground for a general discussion of 'sustainable population'. (And I wonder if perhaps the Daly link you should have used is not Daly at all but GC Daily et al (1994) ). The links you provide are certainly entirely inadequate to lay the basis for discussion of the specifically-cllimatological implications of global population size.
    Do bear in mind that many would see such a discussion here as a distraction, deflecting attention away from the urgency of addressing/discussing AGW and onto a plethora of other urgencies, major and minor. It is a whole different ball game you attempt to kick off here.

    The questions you pose @60 are mainly not trivial at an academic level. They are not trivial even at a logical level. For the sake of illustration, consider the following.

    It is of course true in a simplisitic sense that were global population smaller, then the stress inflicted by humanity on its ecosystem would be smaller. It is also true that the present use of many global resources by humanity greatly exceed the natural re-supply of those resources.
    Yet a more thorough consideration shows this sustainable population question is in itself a pretty intractable one.
    The world food supply impacts very greatly on our ecosystem. Historically food supply was the big limiting factor on all humanity. The future suggests human population will reach a peak level but will that level inflict unacceptable damage to our ecosystem? Will there be enough food to go round? And if these were intractable problems, what do we do about it?
    Even consideration of mineral resources is not easy. Simplistically, digging a bucketful of iron ore from the ground is unsustainable on today's earth as the processes that layed down that iron ore no longer occur. A more sensible approach perhaps would be to estimate how long before such resources would run dry given present-day usage. The results from this are usually quite scary but, as with this graph based on 1992 data, prove to be not entirely sensible. The same difficulties are encountered with the concept of 'peak' resource.
    The resources we actually use depends not just on population but also technology and lifestyle. Daily et al's calculation of 2 billion being sustainable depends solely on assumptions of global sustainable energy production (6TW) and an accceptable average per capita energy use (3kW). The latter is less than a third of North American per capita usage (and that's ignoring the imported goods) and is taken from Holdren (1991) who projects a reduction of economic energy intensity 2000-2050 to achieve a 3kWpc usage in North America. I think this example well demonstrates the speculative nature of such sustainability assessment which is quite apparent as soon as you scratch the surface of this subject.

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  18. So, what does the peer reviewed science say about the contribution of human population level to global warming? 

    So far at this website, I have very clearly stated where I do not have answers and have pointed to a few places where I believe the answers are starting to take shape.  I have requested evidence to support the repetitive and vague handwaving responses that are typical of overpopulation deniers. I have seen evidence of the same arrogant anthropocentricism that is clearly evident among AGW deniers.  I have been met with "there's no consensus about overpopulation" but no numbers or studies of the peer-reviewed science from the experts on our impact on the planet.  I'm guessing (!) that the amount of money behind the "there is no overpopulation" campaign (official or unoffial) far exceeds the funding of the AGW denialist organizations (and I expect you know to whom I refer) with very little funding for actual research.

    In short, all along I have been saying that we don't know, but there is evidence that it is imperative that we do know.  Otherwise, it's entirely possible that "what peer reviewed science has to say about global warming" is missing a crucial element. The very fact that the Pope brought up this issue in the encyclical indicates that there is a significant level of discourse that might at some point be addressed from a scientific perspective. Is all the work we are doing to combat the most urgent threat - AGW - pointless if sheer human numbers mean that we have an unsustainable presence on this one planet that we have forever, or at least until the planet is gone?

    In any case, it's abundantly clear that I am wasting my time here trying to bring this issue to the level of meaningful discussion.  This is my last comment at this website, and I will not be returning.  Moderator, feel free to delete my account.

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    Moderator Response:

    [JH] Sory, but you do not get to define what constitutes a "meaningful discussion" on this website.

  19. Discussions over will humanity breed itself out of existence are akin to discussions in earlier years of how many angels can dance on the head of a pin.  No one relly knows with certainty.  What is certain however if there were to be a reduction in population that would be beneficial to the terrestrial ecosystem  Of course so would a reduction in materialism. It is fascinating reading opinions here which are from humans who are alive and who enjoy access to the internet.  By definition the latter suggests all posters have a relatively affluent and enviable lifestyle.  How many posters here drive cars, have fridges,  air conditoners, take plane trips are not starving, have access to clean water and efficient  health services and state pensions?  I suspect pretty much everyone including of course myself.  So are we going to get rid of our cars and fridges and air conditioning and our stop taking our plane trips?  Others consider overpopulation is the major problem 

    In the Factoids and Facts on World population ( it is stated:

    What do you think is the main factor(s) that contribute to overpopulation?

    and answered:

    Anything that gets in the way of a woman's ability to control her own reproduction. This would include: patriarchal traditions, lack of contraceptive choices, lack of education, child or forced marriages, banned or unsafe abortions, disenfranchisement, misinformation about birth control, doctor's ill-informed or prejudiced attitude, and use of a less effective method of birth control, such as the pill, condoms, or withdrawal - the three most common methods in the U.S.  Some commenters here have said they approve of abortion.  Personally I don't but accept it is a valid option for any woman but as they say prevention is better than cure.  This is not a view shared by all.

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    Moderator Response:

    [PS] "will humanity breed itself out of existence" sounds like strawman rhetoric. As far as I can see no commentator has proposed such a thing nor am I aware of any scientific arguments in support of such a notion.

  20. @51

    but after 37 years China's policy still entails a growing population when on the same time scale we need to reduce emissions by 50% (at least).

    Why, exactly, do we need to reduce emissions by 50% (at least) circa 2050?

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  21. Lots of valid points and valid concerns here. Eventually, it will be inevitable that a range of living standards be defined that will be sustainable at the scale of the total world population, or to have airtight barriers between the affluent places and the rest. Right now the flow of reugees show an almost osmotic kind of pressure drawing in the poor where the rich are, it is quite interesting. Screams about one world government will ensue no matter how much our thinking has evolved by the time we get there.

    I do agree with some here that overpopulation is likely one of the most important problems faced by our species. We are even less well equipped to tackle this problem than AGW. It is also a much more difficult problem to treat scientifically. It may be where our psyche and emotional make up lacks the most far behind the reality of our situation.

    As for reproductive decision making being the single most important factor on population increase, it is true, but only because we have immunizations and antibiotics. The main reason why the human population has increased so much in the past century is because humans don't die at anywhere near the rate they used to. The chief cause of death for people, at any time in our short history, always was infection. Not so long ago, in the Western World, the rule was that people had 7 to 12 children, of which 4 or 5 reached reproductive age, and perhaps 2 or 3 achieved some reproductive success. Almost everybody else died of some sort of infection. 

    The population is not increasing because women don't have enough of a say in their reproductive role but because virtually everyone reaches reproductive age. Women had even less of a say in the past when the population was not increasing at the rate we have seen lately. I am not proposing anything here, just stating a fact. 

    Heart disease and cancer were once luxuries affecting only those who had managed to escape infections for long enough to develop them. Now we throw enormous resources in prolonging the life of people terminally ill with chronic cardiovascular or pulmonary diseases, keeping them alive for weeks in the ICU just so that the families can wrap their minds around the inevitability of the end. One of these ICU stays cost enough money to feed an entire village for year in Africa. Food that's only for thought on our end...

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  22. bozza @70, in a nutshell, to a significant risk of dangerous climate change, we need to avoid warming greater than 2 C relative to preindustrial temperatures.  As seen in the figure below, that means we need an emissions pathway approximating to the RCP 2.5 scenario, as shown in the left hand panel:

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  23. The discussion about population distracts the focus of action away from rapidly curtailing the burning of fossil fuels. Curtailing the benefiting from burning fossil fuels (not reducing) clearly needs to be achieved. And that means dramatic rapid reduction of benefiting from the burning by the most fortunate (the biggest trouble-makers have the most capacity to reduce their impacts), with the most fortunate also helping the less fortunate develop to better ways of living with the least possible amount of burning along the way (and the most fortuate not expecting top personally benefit from those actions).

    So, the curtailing of the burning of fossil fuels is what is required regardless of any action to limit the total population.

    Ryland @2 claimed “It is an undeniable fact that humans all over the world want the best life possible and cheap, reliable energy is an essential element in attaining this.” I am proof that that can actually be denied. As I posted, the humans who focus on getting more of anything cheaper are a sub-set of the human population. Ryland may have been projecting a personal preference onto all others, sort of like the way that deniers who try to use twists and tricks to create claims that may be believed by some people think that that is what everyone else does. And it is done to try to diovert attention from the required rapid reduction of benefit that already fortunate humans get from burning fossil fuels. The most fortunate humans should be required to behave better.

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  24. Returning to the population discussion, MA Rodger conveniently links to a paper by Daily, Erhlich and Erhlich (1994).  They write:

    "A scheme that might possibly avoid such a collapse was proposed by John Holdren of the Energy and Resources Group at the University of California, Berkeley. The Holdren scenario (Holdren, 1991) postulates expansion of the human population to only 10 billion and a reduction of average per-capita energy use by people in industrialized nations from 7.5 to to 3 kilowatts (kW), while increasing that of the developing nations from 1 to 3 kW. The scenario would require, among other things, that citizens of the United States" cut their average use of energy from almost 12 kW to 3 kW. That reduction could be achieved with energy efficient technologies now in hand and with an improvement (by most people's standards) in the standard of living.

    While convergence on an average per-capita consumption of 3 kW of energy by 10 billion people would close the rich-poor gap, it would still result in a total energy consumption of 30 TW, more than twice that of today. Whether the human enterprise can be sustained even temporarily on such a scale without devastating ecological consequences is unclear, as Holdren recognizes. This will depend critically on the technologies involved in the future as reserves of fossil fuels, especially petroleum, are depleted. Perhaps through funkier development and widespread application of more benign technologies (such as various forms of solar power and biomass-derived energy), environmental deterioration at the peak of human activities could be held to that of today."

    They go on to suggest that more than 9 TW global energy consumption is incompatible with sustainable development, requiring not only an equalization of resource consumption at lower than western levels of affluence, but actual population reductions to achieve a sustainable target - but transparently (and as they state) the appropriate target depends "...critically on the technologies involved in the future...".

    Consider the situation in which all energy is supplied by renewable energy sources.  Even limiting ourselves to just 0.5% of total available renewable energy (excluding tidal energy) allows 600 TW of global energy consumption.  That is, if we successfully convert to renewable energy consumption, and limit human population to 10 billion or less (ie, less than current projected peak population), we can successfully provide around 5 times the current per capita energy needs of a US citizen to all citizens of the world.  Supply of energy by nuclear technologies (fission or fusion) is less efficient because waste heat becomes a relevant climate forcing at that level of production, limiting the sustainable energy supply for a 10 billion population to below current US per capita consumption levels, but at levels consistent with global affluence at US levels given current trends in energy intensity.  The upshot is, on current technological development pathways, energy ceases to be an environmental constraint on human population within this century, provided we seriously tackle global warming and given the reasonable accuracy of current population projections.  In short, Daily, Erhlich and Erhlich have been rendered obsolete by new technological developments.

    Energy use is not the only limit on population growth and affluence.  SkepticalinCanada has earlier linked to Daly and Townsend (1993) who argue for limits on growth based on the fact that humans already appropriate 40% of Net Primary Production (NPP) and that it is impossible that they should appropriate more than 100%, and inconsistent with healthy ecosystems to appropriate even that 40%.  Again this analysis is obsolete.  Using a more justifiable definition of Human Appropriation of Net Primary Production, it is seen that only 23.8% of NPP is appropriated (Haberl et al, 2007, Erb et al, 2009).  Further, NPP can be expanded (by irrigation schemes, for instance) so that it is not strictly true that we cannot go beyond 100% of currrent NPP.  HANPP can be increased without reducing NPP available to natural ecosystems.  In addition, as Haberl et al show, some of the NPP "appropriated" by humans is returned to local ecosystems in the form of animal waste, and "waste" plant matter.

    To maintain a healthy global ecosystem we certainly should not significantly reduce the absolute NPP currently available to natural ecosystems.  Fortunately human food consumption does not increase with affluence at anything like the rate of human energy consumption (differing by only a factor of 2.4 between the lowest and highest national averages).  More importantly, there is evidence that we may be able to increase NPP for human consumption without any reduction of NPP for ecosystems, either by more intensive farming of current low value agricultural land, or changes in pastoral practises.

    Terrestial Net Primary Production is only part of the human food chain, and there are genuine risks that we are over fishing the ocean.  We certainly overfishing particular fisheries.  Given that, however, assessments of the risks of global overfishing from as little as two years ago have been rendered obsolete by the discovery that there are 10 times more fish in the ocean than previously estimated.

    There are also genuine risks about loss of access to fresh water, but again new technologies have the potential to make this a risk of the past.

    The upshot of all this is not that there are no ecological risks.  Rather it is that there are good reasons to think that those risks can be addressed with currently available, or likely near future technologies along with some changes in behaviour, management and governance.  Good reasons are not guarantees.  You can have good reasons to choose a particular strategy, and have that strategy still fail.  But that is no reason to not try those strategies, and certainly no reason to adopt alternative strategies (massive GDP reduction and population decreases on scales only achievable by totalitarian persecution) that appear to aim at failure of the human project.

    Finally, consider this graph of the global ecological footprint from the WWF:


    (Full report, methodology)

    In principle, if we had an ecological footprint of one or less we could support the global population without species losses, or other degradations of the environment.  In practise that is not quite true, but an ecological footprint of one or less would certainly allow us to come close to that ideal, and meet it with appropriate management practises and (in some instances) changes of behaviour.

    Currently the global ecological footprint is approximately 1.5, but 53% of that footprint comes from carbon emissions.  Put another way, if we could solve the problem of global warming, the global ecological footprint would be approximately 0.75 giving us leeway to live in an ecologically sustainable way in principle, and with suitable conservation laws (including protection of fisheries), in practise as well.

    SkepticalinCanada in his parting shot trotted out that old staple of deniers, the conspiracy theory.  In this case, however, he requires that the conspiracy include the WWF.  Perhaps he needs to consider why he is basing his theories and policies on obsolete minority views among scientists. 

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  25. Tom Curtis #50, I'm glad to hear that you did not intend to equate life with DNA. This was the passage that mislead me as to your position on the subject (@#19):

    "In terms of genetic diversity, 26% of human genes can be found in yeast. 92% can be found in mice, and 98% in chimpanzees. Humans are by no means unique in the degree to genetic similarity to other species. Consequently the loss of any given species is likely to result in the loss of very few, and in some cases no, genes from the total global genetic diversity."

    If people are constantly mis-interpretting your position, is it possible that some of the blame at least some of the time is with your presentations of your positions? Or is it always someone else's fault, in your mind?

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  26. wili @76, here is the quoted section in context:

    "Again, the loss of any species is a loss to us all; but it is not necessarilly a significant loss. In terms of genetic diversity, 26% of human genes can be found in yeast. 92% can be found in mice, and 98% in chimpanzees. Humans are by no means unique in the degree to genetic similarity to other species. Consequently the loss of any given species is likely to result in the loss of very few, and in some cases no, genes from the total global genetic diversity.

    In terms of ecology, many species occupy niches occupied ..."

    (Emphasis added)

    The bolded words clearly mark out that my discussion considered two distinct aspects of the loss related to species loss.  Further they clearly mark out the discussion immediately following each bolded phrase as being relative to those terms, ie, genetic diversity and ecology respectively.  Ergo they made no claim to reduce the value of life to just one of those terms as you claimed I was doing.  So in this particular case, the misunderstanding clearly is an example of your ignoring the clear import of my words.  In effect you treated my post @19 of consisting of just one paragraph, ignoring the rest of the content in order to accuse me of genetic reductionism.

    Trying to avoid responsibility for your misinterpretation by suggesting that I always blame others for any misinterpretation rather than accept responsibility when it is due is rather contemptible.

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  27. Tom@74

    Supply of energy by nuclear technologies (fission or fusion) is less efficient because waste heat becomes a relevant climate forcing at that level of production, limiting the sustainable energy supply for a 10 billion population...

    How much "relevant" climate forcing is nuke waste heat? Can you be more specific and tell us the actual numbers backed by relevant references? I think fusion WH would be somewhat different (much smaller) than fission WH because background radiation be smaller.

    We know that FF waste heat (defined as all energy from FF burning converted to equivalent heat) is 100 times less that the anthropo change in greenhouse effect and still 10 times less than e.g. solar variations, so indeed irrelevant.

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  28. chriskoz @77, the "fossil fuel waste heat" you cite includes all non-renewable resources including nuclear power.

    To a close approximation the waste heat from nuclear industries cannot be less than the waste heat from total power consumption.  Thus, if human energy consumption rises to 600 TW, waste heat will generate a forcing of at least 1.176 W/m^2 averaged over the Earth's surface.  That low value assumes 100% efficiency in energy generation, with the only waste heat being the unavoidable waste heat from end use.  Because this is a forcing on top of any excess CO2 retained in the atmosphere, over the next several thousand years it would lift global surface temperature very close to the 2 C target even if we ceased all emissions now.  On the other hand, if return emissions to preindustrial levels that would represent about half of the current anthropogenic forcing.

    With respect to the difference between fusion and fission waste heat, fission waste heat is partially compensated for by the reduction in geothermal heat by removal of radioactive ores from the natural ore bodies.  That, however, is compensated by the generation of short lived radioisotopes that mean the waste heat of the waste is greater than that of the original ore body.  Whether this balances I do not know, but the balance is likely to be small relative to the additional waste heat from inefficiencies in energy generation.  Because current fusion designs require a large energy usage to maintain the reaction, fusion reactors would likely be less energy efficient but some of the waste heat from energy used maintaining the reaction may be usable to generate power.  Consequently, if anything I would suspect fusion reactors would generate more waste heat for a given power output, but that is by no means certain.

    Finally, I made a mistake in my energy calculations above (for which I apologize).  Specifically, I described 600 TW as sufficient for 10 billion at 5 times current US per capita energy usage when it is actually 20 times.  I translated that mistake through to my estimate of nuclear waste heat.  Correcting for that, nuclear waste heat for total energy generation for 10 billion people at current US per capita levels would be about that of the current forcing of CFC11 (0.06 W/m^2).  Consequently it would not be a problem for nuclear power supply at that level, but waste heat is a limiting factor on sustainable nuclear power supply unlike the case with traditional renewable energies (solar, wind, wave etc).

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  29. Tom@78,

    Thanks for your explanation which makes perfect qualitative sense to me.

    Your numbers do not make good sense though (careful back-envelope arithmetics may not be one your strongest skill) because you seem to sway with your energy numbers and are not sure which numbers are correct.

    I checked your numbers from last paragraph, based on the energy consumption data from wikipedia (Table of Regional energy use kWh/capita - column Year 2008, which is fine for our estimates here):

    Given 8760 hours/year:

    Per capita:

    USA - 87,216kWh, or 87,216/8760 = almost 10kW

    World - 21,283kWh or 21,283/8760 = 2.43kW

    So, current world per capita power is ~1/5 of US power


    USA - 10kW * 300mln = 3TW

    World - 2.43kW * 7bilion = 17TW

    If you want to give world per capita power the same as US you get:

    17TW * 5 = 85TW

    Then if you want to increase population from 7 to 10bln you get:

    85TW*10/7 = 120TW

    which is exactly 1/5 of your number 600TW

    So, your original estimate "600 TW as sufficient for 10 billion at 5 times current US per capita energy usage" was spot on and you made a mistake by "correcting" it.

    Now, for the radiative forcing of those numbers, if current world total energy of 17TW yields 0.028 W/m2 (from Flanner (2009) I quoted above), then, your number of 10bln of 5 times US affluence 600TW yields 0.028*600/17 = 1W/m2 which is close to your original number (your "corrected" number 0.06 W/m^2 is way too low).

    I agree that such scenario (although unrealistic) results in signifficant forcing. The more realistic (frankly quite likely if we do not stop FF burning) scenario - 10bln reaching current US affluence would be 0.2W/m2 which is within the range of solar variations.

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  30. chriskoz @79, thankyou for correcting my corrections.  Unfortunately I do have a history of messing up the arithmetic, especially on my insomnia specials (ie, posts made when I try to make productive use of my insomnia such as the one above).

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  31. Fascinating! I came here to read comments about the Pope's Encyclical on AGW/CC and instead found a dicsussion absolutely dominated by a focus on what Pope Francis did not address - overpopulation.  Of course, it is indeed a valid subject about a crucial factor that is frequently ignored, and one that I see as the elephant in the room. 

    It is likely that a complex mixture of issues will lead to the demise of modern civilization. Many civilizations have perished in the past, and some were grand and high tech for their day.  I believe that the analysis and models in Joseph Tainter's 1988 book, "The Collapse of Complex Societies," have merit.  It seems logical that a complex combination of factors will lead to the collapse of our modern civilization.  This will likely triggered by an increase in the severity and length of drought, floods, as well as and unrelenting sea level rise at ever increasing rates. There will also be ever more costly severe weather events and food production impacts that will impact societies and their economies. 

    If I have my numbers correct 500 million people live on river deltas including 250 million on the Pearl River Delta in China, will have to migrate and relocate.  All of the worlds seaports and naval stations will have to be moved - repeatedly.  This will break the world's economy if it survives that long.  Sea level rise may be a serious long-term problem, even if the world follows the Pope's advice and takes action to mitigate AGW/CC. 

    Humans - overall as a species - just cannot seem to recognize and acknowledge future problems, much less effectively deal with them.  Andvested interests like the FF incustries, feed that weakness.  Like other animals, we often only react to serious danger if it is iminent - and obvious. Look at the number of people - even in the U.S. - who are killed in floods.  This occurs mostly with people in their cars trying to drive on flooded streets and roads.  If they cannot see such  obvious dangers, how do we expect them to see the much less apparent dangers of AGW/CC, and support mitigation measures that will inconvenience them? 

    I applaud the Pope's efforts, even though he does not address the over-population issue, and hope that it will help tilt the balance in the direction of at least recognizing the seriousness of AGW/CC.  Even though I amnow a retired U.S. expat living in a small tourist and farming town in the mountains of Western Panama, I am watching the ridiculously long American election campaign with great interest. 

    Will the younger generation step up and vote?  Or will they allow the older genertions - who have failed them so miserably in the past - determe their future.  

    Will the Pope's Encyclical, and the possible El Niño-related severe weather and weather pattern changes have an effect?  Or will most people yawn and go back to their old patterns and ignore the problems that civilization faces? 

    Only time will tell.

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  32. Of course, population needs to be curbed and the Pope's willful blindness to the issue makes huge amounts of trouble across the globe.  But if, as seems likely, 20% of world population are presently consuming 80% of the resources and most likely causing the warming--not to mention past pollution that is still up there--, they are the ones that are truley over-populated. Resource control (which is the opposite of consumerism)--not exactly population control is the main need. The disconnect between the labor of production--the sweat if you will--and consumption by the planet's priviledged is what needs to end quickly. 

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  33. Xulonn@81,

    number of people - even in the U.S. - who are killed in floods [These are] people in their cars trying to drive on flooded streets and roads [...] If they cannot see such obvious dangers, how do we expect them to see the much less apparent dangers of AGW/CC

    That's a very good observation. Concerning AGW/CC, it applies to politicians who usually look no further than next election cycle, whereas AGW mitigation they need to legislate requires much longer inter-generational timescale. Humans in general are incredibly short-sighted, even blatantly silly when not vividely threatened but rather inconvenienced by invisible threat. Like real boiling frogs. But that anecdote is not true. Hopefully, it also turns out not true for boiling humans and something like this encyclical or next more dire warnings prompt them to jump out while they can.

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