Honestly? A major breakthrough in fusion, or to a lesser extent, any other clean energy. We’ve decarbonised a decent chunk of the world’s energy profile, but there’s a strong financial incentive that politicians are vulnerable to protecting oil and gas, slowing down further decarbonisation. Batteries and supercapacitors also could do the trick.
Wow, a calamity of epic proportions, who could’ve predicted it? /s
But for real, plastic manufacturers have a lot to answer for.