The industrial revolution, especially since the start of modern science, let's say around 1920 was more like an addict on a constant high. Everything seemed possible, and you still think it does, don't you?
It should be fairly fast, once enough of those tipping points coincident, and they will take others with them. Create new ones, 'unforeseen' as the saying goes.
Maybe 2040 is too optimistic, but it's a minimum. 16 years away.
Migrations, over fishing, habitat exploits, ocean temperatures, dead zones, industrial farming, The Haber Bosch process running on fossil energy, artificial fertilizers, topsoil depletion's, clean water, urbanization's, wars. And then the time scale for them which are ours, outrunning natures timescales.
This one is interesting, from a lot of perspectives, one is Saudi Arabia and those Gulf states economical situation, able to afford those imports, basing it on fossil exploit revenues. Without those there would be a water and food shortage. Another is the link between that and wars. You will see a lot more of those as global warming, topsoil, groundwater and water shortages accelerates. There are other aspect too, but those two are quite sufficient. Although they create a third loss.