Comment by krick

I don't really want to participate in developing this silly argument, but people making such comments should always consider the possibility that there is a reason for somebody to say things the way they do, and that your "simplification" in fact loses the point of what author is trying to say.

So let me translate for you.

He doesn't "consider it reasonable to believe that collapse is unlikely to happen by 2030", in fact he believes that given the importance of the matter, he is better to assume the scenario, in which his project will turn out to be life-saving. But if it doesn't seem likely to you, that collapse will happen before 2030, and you don't believe the evidence supporting that claim, he wouldn't call you silly (unreasonable) for that, so we (he and you) can work on the project together even if our forecasts are different, don't worry about that too much.