It is a lot more complicated than that. However, Goodchild also puts population decline with declining fossil fuels.
As a population scientist since 1967, I say that it is both coincidental and triggering in action. I saw it then.
With the latest data, it looks far more grim. The 2050 crash of yore would be far too late to save the entire biosphere.
The only real hope of lowering emissions enough in time to prevent the tundra methane self release, to oceanic self release, to deep heat in rock deposits to release them, then everything gives up its sequestered CO2, too,
is to have the human population go down 95% within 8 years.Let us hope for a bunch of huge disasters that are due to happen, very soon.