The author writes about his personal extensive efforts, and that of his friends, extending over many years to warn about the future destabilization of the biosphere followed by the likely extinction of humans and other "higher" life forms.
I personally, in a number of public meetings, was called a “kook catastrophist,” a “Neo-Malthusian,” an “apolitical tree hugger,” and many other negative epithets – I haven’t heard any of that in-your-face name calling in the last six or seven years.
So what has changed? Reality. If you have been paying attention and are not mired in rigid ideology, then continued denial is no longer an option.