> if you sell a doomsday scenario and nothing happens, people will start to dismiss your claims

You are massively missing the point: what is happening in Australia the past few weeks / months, the 4-50°C temperature, the gigantic fires, ... Are not warning signs or a possible doomsday scenario people are trying to sell.

It is the doomsday scenario actually happening in its early phase. It's too late to avoid it, it's happening, now the best we can do is slow it down and try to reverse course.

> I recall 20 years ago seeing articles claiming that "Snow will be a thing of the past" or "Arctic to be ice-free by 2020". Nothing happened.

Of course, if by nothing happened you mean it is actually happening faster than even predicted and the ice coverage is thinning so fast you can see it on year-on-year comparisons.