Why having fewer children won’t save the earth

A study that claims having one fewer child will reduce your carbon footprint by 58 metric tons a year is getting attention.  Especially from progressives who already tend to look down on big families.

But Lyman Stone shows that the study is fake science based on ludicrously fake mathematics.

From Lyman Stone,  Why The Latest Study Saying ‘End Kids To Save Earth’ Is Junk Science, The Federalist:

It’s in vogue for people on the Left to look down on big families as not just socially gauche, but actually morally troubling: as if rearing up the next generation were some ethically suspect endeavor. Last week gave another instance of that trend, with an article in The Guardian discussing an academic paper which claimed having one fewer child could reduce one’s carbon footprint by 58 metric tons per year.

It’s easy to see the politically motivated reasoning in why the piece went viral: reading between the lines, it argued that the way to be a truly environmentally conscious person is to be a childless vegan working a professional job in a dense urban area. Quelle surprise.

But for someone like me who works on demographic and economic issues all the time, it was particularly frustrating because the basic mathematical logic of the article makes no sense. When you strip apart the bad reasoning that informs the more-kids-more-emissions story, it becomes clear that in the vast majority of cases, how many kids you have just won’t affect any environmental outcomes. . . .

That paper, however, didn’t count the carbon footprint of, say, a child, or how adding a child to a household changes that household’s carbon footprint. Rather, they calculated the “carbon legacy” of a person. They calculated this “carbon legacy” by assessing the plausible per-person carbon emissions of future generations, then assigning a share of each of a person’s descendants’ emissions to the original parent.

So, for example, if I have three children, I would be assigned half of each child’s lifetime carbon emissions, and my wife would be assigned the other half. Then if each of those three people have three kids, I would be assigned a quarter of each of my nine grandchildren’s emissions. Then if we multiply by three again, I am assigned an eighth of my 27 great-grandchildren’s emissions, and so on.

The result is that, in the United States, having one child adds 470 life-years of carbon emissions to a person’s carbon footprint. The authors of the most recent study take those emissions, divide by lifespans in developed countries, and voila, you get about 58 tons of emissions per parent per year per child. . . .

First, the authors of the underlying “carbon legacy” study do not do any “carbon discounting.” That is, they treat one metric ton of carbon emitted 100 years from now by my grandchildren as equivalent to one metric ton emitted today by me. No respectable climate scientist would ever endorse this view: delaying emissions by a century would be unambiguously good for the climate if you believe any of the major climate models! Emissions now are of far greater concern than emissions in 100 years! Without discounting, we understate the importance of carbon emissions today, and overstate the importance of carbon emissions further down the road.

It’s worth noting here that one of three things will be true in 100 years. Either the climate will be about what it is now because the climate models were wrong and thus we don’t need to worry about emissions 100 years from now, or humans will have found a way to effectively manage emissions and thus we don’t need to worry about emissions 100 years from now, or the dire forecasts of climate models will come true and we will all be drowned and dead and thus we don’t need to worry about emissions 100 years from now.

Under any scenario, the common thread is that we don’t need to worry about emissions 100 years from now. We’ve got enough to worry about for today. To compare the generationally distant emissions of my grandchildren buying diapers for their kids to emissions from me joyriding out to Italy for a tomato-sampling tour is utterly preposterous.

Illustration by bykst,  “Crowd, Women, one child,” from Pixabay, CC0, Public Domain

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