> If the author means literally everyone dead, planet gone, then obviously it won't be "apocalyptic", but the science is suggesting it's likely to be really bad.

No, the science doesn't imply that climate change is going to mean literally everyone dead, only a massive cost to maintain things as they are today. Contrawise, Alexandria Ocasio-Cortez said "the world will end" by 2030 if we don't stop climate change. (Source: https://thinkprogress.org/we-dont-have-12-years-to-save-the-...)

So, yes there are people being absolutely, ridiculously, unscientifically hysterical about the effects of climate change. Unscientific alarmism is just as harmful toward efforts to properly manage the global ecology as the unscientific denial of changes.

I'm not sure what the scientific definition of "apocalyptic" is, but in my mind the biggest aspect of climate change people seem to overlook in assessing the potential fallout is mass displacement of people.

We've already witnessed extreme political radicalisation within Western countries as a result of displacement of people from Syria: numbers in the order of a few million. It seems likely that displacement from climate change would be a significant percentage of world population (8+ billion soon). The reaction to that will be apocalyptic.

I often wonder if we would be better off framing it in terms of the financial costs. How much is it going to cost to build a wall around New York, evacuate low lying areas in Florida, move agricultural production around the world, accept millions of climate refugees.

For example, you could have read the article.

It tries to counter claims of "4 billion casualties".

What does "really bad" mean? How is the current situation "this dire"?

This kind of statements is exactly what this article is about.

No, that is not what the article is about. One of the researchers he interviewed asked the Guardian to correct its quotation but stood by his prediction of four billion deaths caused by climate change. The article in no way denies that the situation is bad or dire.