The methodology here is kinda bs IMO.

They're adding up the emissions of the descendants and dividing that by a parents life expectancy.

However, if a society achieves net 0, then surely the emissions of every person there in are 0, so it's disingenuous to count them at today's rates.

Its an attempt to illustrate the environmental cost of over-population, but it needs to be considered within the context of that methodology.

Live Carfree (from petrol) - 2.4
Petrol to hybrid - 0.52
Electric Car to Carfree - 1.15

Seems they left out a pretty large item in "switch from petrol to electric - 1.25"

capitalism hates this one weird trick

Not for the carbon reduction, but for the reduced ~~slave labor~~ work force

So I just have to upgrade my lightbulbs 8 time and I'm effectively vegan!

The big assumption is that the child you have will likely consume carbon-emitting goods and services at the same rate as whatever average they're assuming.

Breaking down by country shows that people's emissions vary widely by year and by country:

https://ourworldindata.org/grapher/co-emissions-per-capita

So if the UK spent most of the 20th century, and into the beginning of this century, emitting about 10 tonnes per person per year. Now it's down to less than 5. Since your linked article was written in 2017 to the latest stats for 2023, the UK has dropped per capita emissions from 5.8 to 4.4, nearly a 25% reduction.

During that same 125 years, the US skyrocketed from about 7 tonnes to above 20, then back down to 14.

The European Union peaked in around 2001 at 10, and have since come down to 5.6.

Meanwhile, China's population has peaked but their CO2 emissions show no signs of slowing down: https://ourworldindata.org/co2-emissions-metrics

So it takes quite a few leaps and assumptions to say that your own children will statically consume the global or national average at the moment of their birth. And another set of assumptions that a shrinking population will actually reduce consumption (I personally don't buy it, I think that childless people in the West tend to consume more with their increased disposable income). And a shrinking population might end up emitting more per capita with some sources of fixed emissions amounts and a smaller population to spread that around for.

If the US and Canada dropped their emissions to EU levels we'd basically be on target for major reductions in global emissions. If we can cap China's and India's future emissions to current EU per capita levels that would go a long way towards averting future disaster, too.

It can be done, and it is being done, despite everything around us, and population size/growth is not directly relevant to the much more important issue of reducing overall emissions.

So I wanted to have 9 kids but ended up finishing out at 3. So technically a savings of 6 kids! I'm helping the environment!

Being pedantic a nebulous "having one fewer kid" means nothing unless there's a benchmark. I think they mean "having one fewer kid as a country average" so if the average Canadian has 1.26 children per women we want to see it .26 per women.

On an individual level I can't unalive a child.