Our lifestyle choices determine our individual carbon footprints, including the decision whether or not to have children. In these posts, Philippe van Basshuysen and Eric Brandstedt debate whether parents should be held responsible for the emissions of future generations.
Let me say this right away: as long as we live in a society that critically relies on fossil fuels, population increase will lead to higher carbon emissions and it follows that we can reduce the expected carbon levels in the atmosphere by bringing fewer children into the world.
In a widely discussed study, Seth Wynes and Kimberly Nicholas (2017) quantify the expected emissions that are caused by different lifestyle choices of persons in developed countries. They show that, under current conditions, if a person decides to have one less child her emissions amount to almost 60 tons less CO2e1 annually. Which makes it by far the most effective lifestyle choice with regards to anthropogenic climate change, assuming per capita emissions will not rapidly decrease and approach zero (more on this below). Compare it to the second most effective choice, namely to live car-free, which saves little more than 2 tons CO2e.
Now, a different question is what normative recommendations to draw from these findings. The question I shall concentrate on here is who bears responsibility for the emissions of future people. Scientists and philosophers are debating this question heatedly (see Basshuysen & Brandstedt (2018) and Wynes & Nicholas (2018)), and it has figured prominently in the media. Let me sketch the problem, my solution to it, and what lessons I believe should be drawn from this.
The problem of quantifying responsibilities for future emissions
When considering the emission consequences of the choice to have a child, responsibility and causal contribution seem to fall apart. Unlike for example the choice to drive a car, having children does not directly release carbon dioxide. But children grow up and, just like you and me, emit through their consumption behaviour – their mobility, housing, eating habits and so on. Their parents causally contributed to those emissions by creating the persons who produce them. Who is responsible for those emissions? The children, their parents, both?
All three options seem problematic. If parents were alone responsible for their children’s emissions then we wouldn’t treat children as persons who are responsible for their own emissions, which would be wrong. On the other hand, suppose the direct polluter is alone responsible, that is, parents are not responsible for their children’s emissions. Then it would follow that having children would play no role in the calculation of individual emissions. Which would again be wrong: some of us will be among the first generation to testify, around 2100, the largest human population that the earth will ever see (see Figure 1). Even if per capita emissions will decrease substantially until then, the number of humans could outweigh those reductions, and I am not optimistic about the prospects of proceeding to a zero-carbon society soon.2 If you causally contribute to more emitting people then, arguably, you carry some responsibility for those emissions.
A third method – the one that Wynes and Nicholas apply, following Murtaugh & Schlax (2009) – is to distribute a person’s responsibility for a descendant’s emissions proportional to the genetic relatedness to her. In practice, this means that a mother (and likewise, a father) is responsible for her own emissions, half of her children’s emissions, a quarter of her grandchildren’s emissions and so on. The problem with this method is that, if it is to be equally applied to children, it follows that they are responsible for their emissions even though their parents are also responsible for their emissions. In statistics, this is called double-counting, which may lead to corruption of results. To avoid double-counting was also identified as a goal in the Paris agreement from 2015.
A solution: parents are responsible for children’s emissions up to their legal age
My proposal, which avoids double-counting, is to count parents fully responsible for their children’s emissions until they reach legal age. As soon as a person has the right to vote and is of criminal responsibility, she is also fully responsible for her own emissions. (Whether this should be 18 years or younger is up to debate. I presume that the effect would be better if we apply a younger age in order to make young people aware of their responsibility early on.)
This also means that the emissions of the first 18 years of every life are the parents’ responsibility. Thus, a couple with two children would be responsible for the same number of years as if you hold them responsible for all and only their direct emissions. But the effect makes sense: more children mean responsibility for more emissions. This could give people who are concerned about their emissions incentives to reflect on their intentions to have children, or, if they decide to have children, to educate those to live a low-emission lifestyle.
The proposal, I believe, also makes it a less abstract endeavour to deliberate the choice to have children with regards to its carbon consequences than is the case with the proposal of genetic relatedness. A person would not be responsible for her grandchildren’s, or further descendants’ emissions, unless they were born when her child was still underage.
It remains to quantify the emission savings of the decision to have one less child under this proposal, to which I shall turn now.
Can we reduce our carbon footprint by having fewer children?
Suppose you are considering whether to have an (additional) child and are concerned about what this would mean for your carbon footprint. For a very rough calculation, assume that average per capita emissions per year are 5 tons CO2. Per capita emissions of infants may be lower than the average, but 5 tons is a conservative assumption, as emissions in developed countries like the UK are considerably higher. Together with your partner, you would thus share responsibility for 5 additional tons times 18 years, equalling 90 extra tons of CO2. So each parent can be attributed 45 extra tons. This is substantially higher than the lifecycle emissions of a passenger car.3
I am aware that comparing children to cars is provocative. It is meant to show that the emissions of having a child can be meaningfully quantified, just as for many other decisions that individuals make. I acknowledge that there are other reasons for and against a decision to have a child, and its carbon consequences will for many people not be the decisive one. But it remains true that you can substantially reduce your emissions by having fewer children, and this should be commonly known.
In anticipation of possible counterarguments, let me just mention three things. First, my proposal is not meant to, and does by no means imply, that there are trade-offs between the decision to have a child and other lifestyle choices (“since I decided to live childless, my holidays in Australia are consistent with my low-emission lifestyle”). Second, emission trajectories should be included in analyses of future generations’ emissions, which I have neglected here. Let me only repeat that I interpret research on future trajectories as by no means suggesting that we will reach a zero-emission society soon. Third and finally, if everyone were an environmentalist who would refuse to reproduce because of the emission consequences then humanity would go extinct. But not everyone is. There is nothing perplexing about the decision not to reproduce for environmental reasons. The reason for anthropogenic climate change is our lifestyle combined with the fact that we are too many not too few.
Part 2 →
Philippe van Basshuysen is a PhD candidate in the Department of Philosophy, Logic and Scientific Method at LSE. He works on the question of how institutions such as markets should be designed in order to achieve fair and efficient results. The areas of application include topical issues such as the distribution of refugees, climate and population ethics.
- Basshuysen, Philippe van and Eric Brandstedt, 2018. “Comment on ‘The climate mitigation gap: education and government recommendations miss the most effective individual actions'”. Environmental Research Letters 13, 048001.
- Murtaugh, Paul A. and Michael G. Schlax, 2009. Reproduction and the Carbon Legacies of Individuals. Global Environmental Change 19, 14-20.
- Pretis, Felix and Max Roser, 2017. Carbon dioxide emission-intensity in climate projections: Comparing the observational record to socio-economic scenarios. Energy 135, 718-725.
- Wynes, Seth and Kimberly A. Nicholas, 2017. “The climate mitigation gap: education and government recommendations miss the most effective individual actions”. Environmental Research Letters 12, 074024.
- Wynes, Seth and Kimberly A. Nicholas, 2018. “Reply to Comment on ‘The climate mitigation gap: education and government recommendations miss the most effective individual actions'”. Environmental Research Letters 13, 048002.
 CO2e stands for carbon dioxide equivalent, which includes greenhouse gases such as carbon dioxide (CO2), methane (CH4), or nitrous oxide (N2O).
 See the IPCC reports for different global socio-economic scenarios and their associated projected emissions. Pretis & Roser (2017) show that there is substantial uncertainty about the scenarios and that they typically underestimated the global emission intensity in the past.
 Here is a rough set of assumptions: the EU target for the fleet average to be achieved by all new cars by 2021 is 95 grams CO2/km. Suppose the average distance driven per year is 14,000 km, and that a car is used on average for 11 years. The total CO2 emissions of the use phase of such a car would then equal 14.63 tons. A very rough rule of thumb is that between a third and the full use phase emissions should be added to account for production and disposal phases. Thus, the cradle-to-grave emissions under these assumptions amount to between 20 and 30 tons CO2.”
Given there is as yet no EMPIRICAL evidence that any degree of any global warming is anthropogenic, what evidence of, and what anthropogenic degree of any global warming would be required to make this question sensible, rather than a purely academic pseudo-scientific problem ?
There is plenty of empirical evidence for anthropogenic climate change, e.g. check out the IPCC reports, or in fact work done by members of this department. Higher concentrations of carbon dioxide (and other greenhouse gases such as methane) in the atmosphere strengthen the greenhouse effect, which warms the earth’s surface. Human activities, especially burning of fossil fuels, have increased greenhouse gases in the atmosphere. For example, the concentration of atmospheric CO2 has risen from between 200 and 300 parts per million, where it was for half a million years before the industrial revolution, to over 400 ppm since then.
This is all empirically well established, and a short inference to the fact that there is anthropogenic climate change. Uncertainty only arises when it comes to quantitative predictions of climate sensitivity, future emission trajectories, and the consequences of a given increase in temperature. But these questions are quite remote from my blog post, which is about quantifying individual emissions (of course, the more harm will be done by anthropogenic climate change the more important it is to reduce individual emissions).
Thanks! But would you please kindly provide the specific references to the empirical evidence for some anthropogenic degree of global warming you allege is cited in IPCC reports (e.g. page numbers) and also that in the alleged work done by LSE philosophy department members on identifying/producing any such evidence (e.g. in published or even unpublished papers).
Please note it is important to distinguish EMPIRICAL evidence from ‘scientists’ ‘ purely speculative beliefs about anthropogenic warming such as reported in IPCC reports.
Contrary to your claim that “these questions of whether any degree of global warming is anthropogenic are quite remote to my blog post”, surely the question of whether there is any evidence of such is absolutely fundamental to the post’s basic presupposition that children contribute to global warming ? For if there is no evidence that humanity significantly does so, then surely nor is there that children do.
Check out the literature on attribution. These are two useful sources:
IPCC: e.g. here: http://www.ipcc.ch/report/ar5/wg1/, chapter 10 “Detection and Attribution of Climate Change: from Global to Regional”, especially §10.2 and p. 894 f. for an explanation of fingerprinting.
Departmental: Frigg, Roman, Erica Thompson, and Charlotte Werndl, 2015b, “Philosophy of Climate Science Part I: Observing Climate Change”, Philosophy Compass, 10(12): 953–964. doi:10.1111/phc3.12294
Dear mr Bellamy
Forgive me for judging you so swiftly, but to me it seems that you do not think there is empirical evidence for anything whatsoever. But If you are interested in a summary of evidence you can check this out:
Dear Mr Karlman
Your hasty presumption is quite mistaken. I believe there has been empirical evidence for many scientific theories as useful instruments for the growth of knowledge, namely in the form of their successful predictions of novel facts. But I know of none such for the theory that at least some or even substantial degree of global warming is anthropogenic.
I would therefore be grateful if you could direct me specifically to any empirical evidence that any global warming is anthropogenic. A brief glance at your nasa link did not immediately show any such, but rather only evidence of global warming, But this is not the disputed issue here. So I fear your kind assistance may be logically irrelevant.
However, I note I do owe Philippe a reply to his post of 15 May on why it is unclear why the IPCC Report links he kindly cites provide any evidence of specifically anthropogenic global warming. I hope to do so soon.
Do you know of any philosophical discussion of suicide (admittedly, quite a drastic “lifestyle adjustment” as they put it) as a mean to reduce carbon emission?
It is quite a controversial topic that you have here. I would say you are right, yes, you can reduce emissions by having fewer children. But then, similarly to that you can say you can reduce emissions by ending our own existence, and that would be true also. In reference to your point on having fewer children to reduce emissions I would argue: protecting the environment off course is important, but there are so many other things we can do before we give up something that matters so much for some people. I would never consider having fewer children as no 1 action to reduce emissions.