National pledges to cut carbon emissions fall well short of what's needed to avoid dangerous climate change, with Australia likely to miss its 2030 commitment by a wide margin, a United Nations body said.

The UN Environment Program's Emissions Gap 2017 report found pledges to cut pollution made at the Paris climate summit two years ago are only about one-third of what's needed to be on a "least-cost pathway" to stopping the worst effects of climate change.

The target is to stop global average temperatures from rising 2 degrees or more above pre-industrial levels. Change on that scale is expected to cause major droughts, food shortages and damaging sea level rise.

The emissions gap to keep with a 1.5-degree goal is 16-19 gigatonnes of carbon-dioxide equivalent, while the 2-degree target would need an extra 11.13.5 gigatonnes of CO₂-e of cuts by 2030 to be attained, the report said.