Zero. Australia's position on coal is absurdly outdated, but even a complete cessation of greenhouse emissions by Australia would've only been a drop in the global bucket at about 1%. They'd still be having these fires even if the entire country ran on unicorn farts since the 1800s.
Australia's emissions are smaller, however they enable much larger emissions elsewhere. Without that coal, India and China would be accelerating their transition to renewables.
Which is still not the same thing as 7% of global greenhouse emissions. Plenty of non-fossil fuel sources for emissions, like burning trees, cows making methane, etc.
Even if Australia were responsible for 7% of global greenhouse emissions, ceasing wouldn't be enough.
Meanwhile, if you want to convince other countries to reduce their emissions, it's much easier when you're part of the solution.
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 [2]: https://www.c2es.org/content/international-emissions/ [3]: https://www.worldcoal.org/coal/uses-coal/coal-electricity