Maybe it would be simpler at an international level rather than for individual companies? E.g. based on last year's co2 vs rolling 5 years average, calculated

Maybe it would be simpler at an international level rather than for individual companies? E.g. based on last year's co2 vs rolling 5 years average, calculated by weather satellites rather than self-reported. I've got no idea how gdp would be taken into account though. Enclaves and disputed borders are also less clear.