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I think it is unhelpful to look at something like population in isolation from other deeply related issues, such as affluence, pollution per affluence, technolo

by shoo 11y ago

I think it is unhelpful to look at something like population in isolation from other deeply related issues, such as affluence, pollution per affluence, technology, unsustainable consumption of resources / production of pollution, changes in efficiency. For example, one simple way of modelling things is the `I=PAT` equation (see also the critique under "Reception") [0]. I'll quote from VHEMT [1]: > For example, in terms of energy consumption, > when a North American couple stops at two it’s > about the same as an average East Indian couple > stopping at 30, or a Bangaledesh couple stopping > at 97. Maybe energy consumption is a bit abstract - it is not immediately obvious what, if anything, is wrong with that. Instead we could consider per-capita CO2 pollution, taking the 2005 statistics from Wikipedia [2]: United States: 19.3 tonnes CO2 / (person year) Bangladesh: 0.3 tonnes CO2 / (person year) From these numbers, a 1 additional US person has the same immediate short-term impact in terms of CO2 pollution as about 64 additional Bangladeshi people [2]. CO2 pollution produced by humans is primarily the cause of recent global warming. If the current trend in greenhouse gas pollution continues to track the high end of (conservative) IPCC baseline models [3] then it will not be surprising if we end up with a world that is +3.5C -- +4C -- or more higher than baseline, by the year 2100 (from memory, we're already at about +0.6C this year). It really doesn't look like we will limit the temperate increase to the "agreed 'safe'" +2C in the real world, outside of modelling scenarios[4]. It doesn't appear that the world has experienced a temperature of +4C for quite a long time (either hundreds of thousands or millions of years, depending on which graphs you look at)[5][6]. The last time it was that warm certainly pre-dates human agriculture (~12000 years ago) [7], and perhaps the human species (100s of thousands of years ago)[8]. I.e., we are rapidly pushing the climate toward a state where humans and human civilisation have never previously existed. The result will likely be unpleasant, in the sense that many people will suffer and die, due to heat stress, natural disasters, reduced crop yields, disease, and conflict caused by displaced people / resource shortages [9][10]. I have focused here on climate change in isolation, but that is just the first hurdle. Other serious concerns are human impacts upon biodiversity and the nitrogen cycle - and those are just the impacts that we're able to measure [11]. There's reasonable evidence that the world is currently experiencing a period of mass extinction [12]. So -- bringing it back to population. From the perspective of everyone else alive right now, assuming they are well informed and rational, should they think it is a good idea for me to have a child, particularly if I live in an affluent, polluting society[13]? I doubt it very much. Of course, it isn't all grim. There is still time for us all to get better at being altruistic, thinking clearly, predicting the future, cooperating, changing our minds about what might be important, and modifying our environment (for better or worse). But, at best, it is obviously a race between positive and negative trends. There is not much time left. But, from historical evidence, so far the metrics of biodiversity and CO2 pollution are very much going in an undesirable direction, with no sign yet of change. edit: I'll finish by quoting David MacKay out of context. He is talking about the UK's sustainable energy debate [14]: > We need to choose a plan that adds up. It is possible > to make a plan that adds up, but it’s not going to be > easy. > > We need to stop saying no and start saying yes. We need > to stop the Punch and Judy show and get building. I pretty much agree with this sentiment in the realm of sustainable energy, and I'd also agree with the sentiment if it were extended much more broadly, beyond MacKay's intended context, to questions of population, affluence, equality, poverty, intergenerational fairness, and how economies should be run. [0] https://en.wikipedia.org/wiki/I_%3D_PAT#Reception https://en.wikipedia.org/wiki/I_%3D_PAT#Reception [1] http://www.vhemt.org/demography.htm http://www.vhemt.org/demography.htm [2] we're glossing over the fact that some of these additional people might choose to have children, or that annual per-capita CO2 pollution could change. [3] For 2014 data, see figure 3 (a) of https://www.lakeheadu.ca/sites/default/files/uploads/53/outlines/2014-15/GEOG4411/Friedlingstein%20et%20al.pdf https://www.lakeheadu.ca/sites/default/files/uploads/53/outl... [4] http://www.rtcc.org/2015/06/19/is-avoiding-2c-of-global-warming-possible/ http://www.rtcc.org/2015/06/19/is-avoiding-2c-of-global-warm... [5] http://earthobservatory.nasa.gov/Features/GlobalWarming/page3.php http://earthobservatory.nasa.gov/Features/GlobalWarming/page... [6] https://upload.wikimedia.org/wikipedia/commons/5/5f/All_palaeotemps.svg https://upload.wikimedia.org/wikipedia/commons/5/5f/All_pala... [7] https://en.wikipedia.org/wiki/History_of_agriculture https://en.wikipedia.org/wiki/History_of_agriculture [8] https://en.wikipedia.org/?title=Human https://en.wikipedia.org/?title=Human [9] http://www.worldbank.org/en/news/feature/2012/11/18/Climate-change-report-warns-dramatically-warmer-world-this-century http://www.worldbank.org/en/news/feature/2012/11/18/Climate-... [10] http://www.eci.ox.ac.uk/4degrees/ http://www.eci.ox.ac.uk/4degrees/ [11] See figure 6 of: http://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1063&context=iss_pub&sei-redir=1&referer=http%3A%2F%2Fscholar.google.com.au%2Fscholar%3Fq%3Decosystem%2Bsafe%2Bboundaries%26btnG%3D%26hl%3Den%26as_sdt%3D0%252C5#search=%22ecosystem%20safe%20boundaries%22 http://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?articl... [12] http://www.researchgate.net/profile/Jenny_Mcguire/publication/50267709_Has_the_Earth%27s_sixth_mass_extinction_already_arrived/links/00b7d5183edf5b6c76000000.pdf http://www.researchgate.net/profile/Jenny_Mcguire/publicatio... [13] assuming they don't have some kind of interest in driving down the cost of labour in the short term, to reduce the labour cost of producing this season's model of useless widget. [14] http://www.withouthotair.com/c32/page_250.shtml http://www.withouthotair.com/c32/page_250.shtml

im3w1l 11y ago
> For example, in terms of energy consumption, > when a North American couple stops at two it’s > about the same as an average East Indian couple > stopping at 30, or a Bangaledesh couple stopping > at 97. The Americans in this example behave like O(1) and the Bangladeshi as O(48.5^n). No matter the constants the Bangladeshis' resource consumption will eventually outstrip the Americans'.
- shoo 11y ago
  I can see what you are saying, but I think we can both agree that the literal interpretation of families with 97 children isn't particularly realistic. A similar objection goes for asymptotic time horizons: we don't have infinite time to work with, this is reality, we have a handful of critical decades. Climate models are typically run to year 2100, where of course the world hasn't ended, but it's probably a +3.5C ... +4C ... scenario, so options are dramatically restricted, and continuing to diminish, for the surviving people. Another way to think about the population would be to simply consider how we might expect the US and Bangladesh populations to change over a reasonable time horizon, to figure out how many person-years of consumption (and pollution) we get for each individual and half of their descendants. Here are some parameters and assumptions for a rather simple model: Parameters: Bangladesh United States ---------------------------------------------------------------- Fertility rate, births per woman 2.2 (y2013) 1.9 (y2013) life expectancy at birth, female 71 (y2013) 81 (y2013) life expectancy at birth, male 70 (y2013) 77 (y2013) life expectancy mf geom average 70.5 79 average age of first child birth 18 (y2011) 25.4 (y2010) This data in itself is pretty interesting! The fertility rate for both countries is similar (although on different sides of the 2.0 fence), but the "average age of first child birth" is very different! Simplifying assumptions: assume everyone in each country behaves the same: everyone lives until their birth life expectancy everyone has same number of kids uniform life expectancy divide birth rate by 0.5, everyone gives birth everyone has children at the same age all these parameters are stationary wrt time These are pretty severe assumptions, obviously, but let's see where they take us. Using these parameters, over a time horizon of 100 years, starting with a 0-year old US person, and a 0-year old Bangladeshi person, we obtain [0]: Bangladesh: 343.8 person-years of consumption United States: 214.7 person-years of consumption If we multiply this by the country specific per-capita per-year rates of CO2 pollution, we get Bangladesh: 343.8 * 0.3 = 103.14 tons of CO2 pollution United States: 214.7 * 19.3 = 4143.7 tons of CO2 pollution The US person (and their descendants), have contributed ~40x the CO2 pollution as the Bangladeshi person (and their descendants) over this time horizon! We can compare this to a US person who has no children over the same time horizon: United States, no children: 79 * 19.3 = 1524 tons of CO2 pollution If we extend the time horizon to look at a ridiculous 900 year period, then we get the following: Bangladesh: 71650.5 * 0.3 = 21495.2 tons of CO2 pollution United States: 1308.8 * 19.3 = 25259.84 tons of CO2 pollution The single United States person (and their finite number of descendants) have still produced more CO2 pollution than the single Bangladeshi person (and their large and growing number of descendants)! ### What, if anything, can we conclude? Over a time horizon of 100 years, a cartoon typical US person (and their descendants) will be responsible for about 40x the CO2 emissions as a cartoon typical Bangladeshi person (and their descendants). A cartoon typical US person can reduce the CO2 emissions they are responsible for by around 60% if they make a decision to have no children, over a 100 years time horizon. Over a 900 year time horizon, ridiculously assuming parameters to not vary over time, a cartoon typical US person will still be responsible for more CO2 emissions than a cartoon typical Bangladeshi person. [0] via a hastily written python script: https://gist.github.com/fcostin/2225b2a51ad8859b5d1b https://gist.github.com/fcostin/2225b2a51ad8859b5d1b

by shoo 11y ago

im3w1l 11y ago

> For example, in terms of energy consumption, > when a North American couple stops at two it’s > about the same as an average East Indian couple > stopping at 30, or a Bangaledesh couple stopping > at 97. The Americans in this example behave like O(1) and the Bangladeshi as O(48.5^n). No matter the constants the Bangladeshis' resource consumption will eventually outstrip the Americans'.

shoo 11y ago
I can see what you are saying, but I think we can both agree that the literal interpretation of families with 97 children isn't particularly realistic. A similar objection goes for asymptotic time horizons: we don't have infinite time to work with, this is reality, we have a handful of critical decades. Climate models are typically run to year 2100, where of course the world hasn't ended, but it's probably a +3.5C ... +4C ... scenario, so options are dramatically restricted, and continuing to diminish, for the surviving people. Another way to think about the population would be to simply consider how we might expect the US and Bangladesh populations to change over a reasonable time horizon, to figure out how many person-years of consumption (and pollution) we get for each individual and half of their descendants. Here are some parameters and assumptions for a rather simple model: Parameters: Bangladesh United States ---------------------------------------------------------------- Fertility rate, births per woman 2.2 (y2013) 1.9 (y2013) life expectancy at birth, female 71 (y2013) 81 (y2013) life expectancy at birth, male 70 (y2013) 77 (y2013) life expectancy mf geom average 70.5 79 average age of first child birth 18 (y2011) 25.4 (y2010) This data in itself is pretty interesting! The fertility rate for both countries is similar (although on different sides of the 2.0 fence), but the "average age of first child birth" is very different! Simplifying assumptions: assume everyone in each country behaves the same: everyone lives until their birth life expectancy everyone has same number of kids uniform life expectancy divide birth rate by 0.5, everyone gives birth everyone has children at the same age all these parameters are stationary wrt time These are pretty severe assumptions, obviously, but let's see where they take us. Using these parameters, over a time horizon of 100 years, starting with a 0-year old US person, and a 0-year old Bangladeshi person, we obtain [0]: Bangladesh: 343.8 person-years of consumption United States: 214.7 person-years of consumption If we multiply this by the country specific per-capita per-year rates of CO2 pollution, we get Bangladesh: 343.8 * 0.3 = 103.14 tons of CO2 pollution United States: 214.7 * 19.3 = 4143.7 tons of CO2 pollution The US person (and their descendants), have contributed ~40x the CO2 pollution as the Bangladeshi person (and their descendants) over this time horizon! We can compare this to a US person who has no children over the same time horizon: United States, no children: 79 * 19.3 = 1524 tons of CO2 pollution If we extend the time horizon to look at a ridiculous 900 year period, then we get the following: Bangladesh: 71650.5 * 0.3 = 21495.2 tons of CO2 pollution United States: 1308.8 * 19.3 = 25259.84 tons of CO2 pollution The single United States person (and their finite number of descendants) have still produced more CO2 pollution than the single Bangladeshi person (and their large and growing number of descendants)! ### What, if anything, can we conclude? Over a time horizon of 100 years, a cartoon typical US person (and their descendants) will be responsible for about 40x the CO2 emissions as a cartoon typical Bangladeshi person (and their descendants). A cartoon typical US person can reduce the CO2 emissions they are responsible for by around 60% if they make a decision to have no children, over a 100 years time horizon. Over a 900 year time horizon, ridiculously assuming parameters to not vary over time, a cartoon typical US person will still be responsible for more CO2 emissions than a cartoon typical Bangladeshi person. [0] via a hastily written python script: https://gist.github.com/fcostin/2225b2a51ad8859b5d1b https://gist.github.com/fcostin/2225b2a51ad8859b5d1b