Some decades ago, we were warned that global warming was happening and that we should initiate measures to slow it down. At some point, we were warned that we must initiate measures to slow it down within the next few years. More recently, we were warned that we must initiate measures to slow it down now. I haven’t heard anyone say that “now” has passed, but my impression is that we’ve gone from “must act soon” to “should have acted earlier.” Whenever most people think that there’s no hope — that conditions will get worse no matter what we do — there will be even less impetus to slow global warming. The extinction of the human species will be hastened.