The global disaster in that movie was a plausible plot concept. Humanity is already talking about geo-engineering concepts based on aerosols to reflect sunlight

The global disaster in that movie was a plausible plot concept. Humanity is already talking about geo-engineering concepts based on aerosols to reflect sunlight. The Snowpiercer universe just kinda took the 'Ice 9' from Vonnegut's "Cat's Cradle" book and used it for geo-engineering. If we had that kind of technology, we would probably consider it with similar disasterous results. Technology that impacts the entire planet, wielded by a desperate species, can have disasterous consequences if things go wrong. Lucky for us, a form of ice that is stable and has a higher melting point isn't a thing in our world... Us genetically engineering hardy organisms to terraform our way out of the climate crisis is the more plausible 'oops' scenario. All it takes is one project underestimating the results of their work for things to go wildly wrong.