Clearly, the earth without humankind's technological civilization has had truly monumental climate gyrations. Alternate scenario: aliens ("us") came along and intelligently bio-engineering tinkered with the biosphere/climatological machinery. Possibly those gyrations were even beyond modern technology's control, although I want to be alien-ly optomistic.

Well, in an emergency situation, in a martial law premises-allowing scenario, you use "proximate cause" processes of decision. Executions on the spot? So, ?too conveniently the primitively found easily visible "patsy" scapegoat would seem to be the ?unstoppable surge of fossil fuels users.