Not all life is connected to earths atmosphere. That that doomsday weapon is missing caves which contain multicellular life across geologic timescales. The ecosystems dependent on chemical synthesis at deep ocean vents would similarly be unaffected.
You might kill off plants though frozen seeds are viable for an extended period, but the incoming ice age is going to preserve aglee until atmospheric CO2 returns to normal even if we’re talking millions of years.
You might kill off plants though frozen seeds are viable for an extended period, but the incoming ice age is going to preserve aglee until atmospheric CO2 returns to normal even if we’re talking millions of years.