For the fifth election in a row, Australia is facing a campaign in which the Coalition is demanding the ALP come clean about the cost of its policies to fight climate change. Yet it is the Coalition which should be under pressure to explain why, after six years in government, it has no plan at all.

The esoteric debate over the minutiae of macroeconomic modelling of climate policy has resurfaced this week after a former executive director of the Australian Bureau of Resources and Agricultural Economics, Brian Fisher, now a consultant, published a 23-page document comparing the economic impacts of the ALP's target of cutting emissions to 45 per cent below 2005 levels by 2030 and the Coalition's plan to only cut by 26 per cent.

Climate change protesters outside Scott Morrison's office. Credit:John Veage

The rather unsurprising conclusion was that the ALP's more ambitious target will probably cost more.

Economic modelling has a place but it can be confusing. While the estimate of the cumulative cost over 11 years of a particular climate change policy may sound like a very big number, often it turns out to be more like a rounding error compared to Australia's $1.9 trillion annual economic output.