Bernie Fraser, the former head of the Reserve Bank and Climate Change Authority, says it is "nonsense" and "obscene" for the Federal Government to argue there is a "moral case" to open new coal mines.

Mr Fraser has joined 60 other public figures in signing an open letter which calls for a global moratorium on new coal mines to be negotiated at the United Nations climate talks in Paris at the end of next month.

Mr Fraser conceded the idea, put forward by Kiribati president Anote Tong, may be too late to make it onto the official agenda.

"These kinds of conferences don't like surprises, particularly at late stages but it's a timely occasion to be discussing the idea even if it transpires that it's only around the fringes of the formal meeting," Mr Fraser said.

Federal Resources Minister Josh Frydenberg recently told Insiders there is a "moral case" for Australia to export coal, to help provide electricity to millions of impoverished people in countries like India.

But Mr Fraser said in his personal view that was "nonsense".

"It's the vulnerable people around the world that are going to suffer the most, and have the greatest difficulty adjusting to global warming, even to a two-degree (Celsius) global warming, and a lot of those people are in developing countries, including countries like India," he said.

"It's a nonsense argument really and to sort of put a moral label to it is quite obscene really."

Mr Fraser quit as the founding chairman of the Climate Change Authority in September, after criticising the post 2020 targets the Government will take to the Paris talks.

He said that there is not a case for shifting to cleaner coal production, instead of a total moratorium on new coal mines.

"The reality is that even with those targets for post-2020 emissions reductions the world is headed for, not two degrees, but for at least a three-degree increase in temperatures, and that has some pretty worrying and harmful consequences," he said.

"None of these changes, these types of policies, are without cost but the costs of not doing these kinds of things and having to contend with a three-degree increase in global warming, or even something bigger than that, those costs are even greater.

Prime Minister Malcolm Turnbull has indicated he will personally represent Australia at the climate talks in Paris, which begin on November 30.

Mr Fraser said that was encouraging, but he was still waiting for Mr Turnbull to announce changes in policy.

"He better understands and is more favourably disposed to the need for all countries, including Australia to be doing more down the track so I'm pleased he's going and I'm hopeful that something more ambitious on Australia's part might emerge," he said.

The Federal Opposition is signalling it wants to ramp up the political debate over climate change.

Opposition Leader Bill Shorten is taking a team of frontbenchers to the Pacific on Sunday for a four day visit to discuss the challenges faced by tiny Pacific nations like Kiribati.