M1Astray posted... TLDR: the AMOC is one of the planets main temperature regulating systems and if it shuts down it will affect the entire planets weather.
Put very simply it will create a world where there is vastly less ability to run agriculture and thus dramatically reduce the planets ability to feed humans (and animals of course.)
Ever seen people meme about the Water Wars? This is one of those systems that causes those wars. Lots of places on land will dry out due to the new weather systems (and a bunch of other areas will get so many extreme wet events that they lose the ability to be stable agriculture land).
There's a lot of other possible side-effects though. Certain parts of the worlds oceans will end up far hotter than they are now, that will lead to algal bloom outbreaks that essentially sterilize those parts of the ocean (there's an ongoing situation where I live right now about this, but there's still the possibility it might dissipate in 18 months. Yay!)
But for humanity the big reason to have trouble sleeping at night over this news is the effect on agriculture. If people cannot grow enough food to eat you will see hundreds of millions on the move, you will see nuclear powers attacking other nuclear powers for access to their dwindling AG sector (and also to try and stop the wave of mass migration as well), and in general you're going to see death on a scale nobody here can actually conceive of, where the surviving nations survive because they make the Nazis look like friendly teddybears.
This is a major Collapse vector and yet another warning sign we have five to ten years to get our collective shit in order or say goodbye to the species in the next 50-60 years.
Yeah but if they make it so that food cant grow naturally, they can do it in labs and sell it! Destroy everything and profit from it!