Since history is like weather and climate (accurate short time predictions are nigh-impossible, accurate long term predictions are possible), he's banking on lo

Since history is like weather and climate (accurate short time predictions are nigh-impossible, accurate long term predictions are possible), he's banking on long-term predictions. But just like with the climate, the exact trajectory by which the system arrives at a changed climate is unpredictable. With climate and weather, the mechanisms are well understood, with human history, the mechanisms are subject to change and are changing all the time. (Edit: So as far as mechanisms are cited, e.g. Neon for lasers, I personally don't give much credence to it, the more specific the mechanism is)