Australian exporters face growing scrutiny and financial costs under a potential US border adjustment scheme that Joe Biden has threatened to put at the centre of his fight against climate change.

At last week’s 40-country climate summit hosted by Mr Biden, which heralded Washington’s emphatic return to global carbon policymaking with a bold pledge to cut greenhouse gas emissions by 50 per cent to 52 per cent by 2030, the administration also quietly sharpened its warning to laggards: failure to curb emissions means America will tax your exports.