The commission, established by Labor to spruik the case for tackling dangerous climate change, is also calling for a fresh approach to reducing carbon emissions.
It suggests that rather than focusing on interim targets based on percentage cuts, governments should commit to emitting no more than an agreed carbon dioxide "budget" by 2050. This so-called budget approach would allow greater flexibility and encourage investment in the most-effective technologies rather than quick-fix solutions.
The commission is releasing its first major report, The Critical Decade, on Monday.
"A plausible estimate of the amount of sea-level rise by 2100 compared to 2000 is 0.5 to one metre," it says.
That's higher than the Intergovernmental Panel on Climate Change's top range of 0.18m to 0.76m.
Commissioner Will Steffen, a Canberra-based climate scientist, made the assessment after surveying the existing literature and speaking to experts.
"Some people may take issue with that - but that's my judgment," Professor Steffen told AAP ahead of the report's release at Parliament House.
The report states that even a rise of 0.5m could lead to an increase in extreme flooding events for coastal areas of Sydney and Melbourne "by factors of 1000 or 10,000 for some locations". More >>>
Location: Cayman Islands