Yvo de Boer, the UN climate chief during the 2009 Copenhagen climate change talks, said his conversations with scientists working on the next report of the Intergovernmental Panel on Climate Change suggested the findings would be shocking. 

"That report is going to scare the wits out of everyone,'' Mr de Boer said in the only scheduled interview of his visit to Australia. "I'm confident those scientific findings will create new political momentum.''

The IPCC's fifth assessment report is due to be published in late 2013 and early 2014.

Before then is the next end-of-year UN climate meeting in Doha, Qatar. Delegates will discuss a second commitment period for the Kyoto Protocol, the only legally binding accord to cut greenhouse gas emissions.

Last December nations agreed in South Africa to work on a binding agreement that would cover all countries. That work is expected to continue until 2015.

Mr de Boer, who is now special global advisor on climate change for KPMG, said the best prospect may be for nations to settle on targets that they write into their national laws, rather than a binding international deal.