Australia exports more like 7% of total fossil fuels by CO2, according to this: https://www.abc.net.au/news/science/2019-08-19/australia-co2...
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.