FWIW I think the counterfactual is not asking what the impact is if Australia stopped emitting greenhouse gases directly, but what the impact would be if it sto

FWIW I think the counterfactual is not asking what the impact is if Australia stopped emitting greenhouse gases directly, but what the impact would be if it stopped producing coal (for both domestic use and export). Given Australia is a substantial producer and exporter of coal (responsible for around 7% of global production [1]), and that coal (+ natgas + oil) power generation are responsible for around 30% of global greenhouse gas production [2], and assuming that coal is responsible for between half and all of GHG emissions from power plants [3], you could ballpark that Australian-produced coal is responsible for an incremental 1-2% or so of global greehouse gas emissions (0.3 * 0.07 * [0.5~1]). [1]: https://en.wikipedia.org/wiki/Coal_in_Australia https://en.wikipedia.org/wiki/Coal_in_Australia [2]: https://www.c2es.org/content/international-emissions/ https://www.c2es.org/content/international-emissions/ [3]: https://www.worldcoal.org/coal/uses-coal/coal-electricity https://www.worldcoal.org/coal/uses-coal/coal-electricity