Arrhenius predicted that global warming would have positive humanitarian impacts, for reasons that are retrospectively wrong, and instead global warming appears to have negative humanitarian impacts.
This seems like an oversimplification. It would seem more accurate that Arrhenius thought on balance it would have a net positive humanitarian impact and current consensus is that it is net negative.
One must be very careful here: Arrhenius is almost certainly using a different utility function for 'positive' than current consensus uses today. As I understand it, fewer people die yearly of heat than freezing and warming opens more land than it closes off, but in today's environment more concern is given to things like "OMG GLOBAL WARMING" than actual data.
[edit]I was not referring to temperature or the temperature calculation model. I was referring to the net positive or negative effect on society. Sorry for the confusion.[/edit]
In Intelligence Explosion analysis draft: introduction, Luke Muehlhauser and Anna Salamon wrote
As a part of the project "Can we know what to do about AI?", I've summarized my initial impressions of Arrhenius's predictions and the impact that they might have had. The object level material is all draw from Wikipedia, and I have not vetted it.
Taking this all together, based on my surface impressions, I think that this case study gives evidence against attempting to predict the far future being useful: