Yes CO2 is the existential threat. Even in socialist countries CO2 is produced.
Economic systems and forms of production do not make energy sources clean. Socialist and capitalist countries both ought to and must fight against CO2 production.
Socialist countries? Of course definitions vary, so which ones are you referring to?
Also neo-libs don't want any state interference on business, unless it involves bailing them out with tones of money. So which capitalist country will do otherwise with so much lobbying going on?