I got a science degree in the late 90’s. Back then my eco profs talked about a lot of worst case scenarios that might occur in 2050’s and beyond. Things like the break down of the mid-atlantic conveyor current, the collapse of the antarctic ice shelf, weakening of the air currents that feed the amazon with sand from the Sahara, and sudden drops of sea life populations (like crabs). Things that are all actively in progress now - 50 years ahead of those “worst case scenarios” of the 90s. Oops was a while back.