As the other commenter said, Global Warming fell out of favor because it underlines only one part of the full problem. The weather in most places is getting warmer, but other things are also happening connected to it: extreme events are becoming more and more common, such as drought, flooding and forest fires, that might not seem included in the wording global warming but is clearly described by climate change.

The science is still very unclear, both from a modeling perspective (what are the pieces of the puzzle and how to connect them), a simplified perspective (what pieces are most important) and a theoretical perspective (what typical behavior should we detect close to the collapse).

Unfortunately, the latter one’s answer seems to be that close to bifurcations in statistical differential equations the variance of a system increases. Decrypting the math: close to a sudden change, we should experience a wider variety of events that usual, in particular more extreme events. This seems to be happening to the AMOC, but support for the claim is still weak and unclear (because the modeling is unclear, so we don’t know what pieces should be included in the problem).