AS THE world's elite global warming experts begin poring over the drafts of the latest Intergovernmental Panel on Climate Change report this week, one leading scientist doesn't believe the process should be happening at all.

''I think it will be less successful than the last assessment, and I think it will be blander - I'm disappointed in what I've seen so far,'' said Kevin Trenberth, the head of the climate analysis section at the US National Centre for Atmospheric Research.

Climate expert Kevin Trenberth is frustrated that bureaucracy is hindering the UN body's efforts. Credit:Sahlan Hayes

Professor Trenberth's misgivings are not based on doubts about the strength of the science underpinning human-induced climate change, but on frustration with the bureaucratic nature of the IPCC.

Dozens of Australian scientists are among hundreds of international experts who started reviewing the IPCC's fifth summary report this week, with the final version to be published next September. The previous report, released in 2007, declared global warming ''unequivocal'' and said it was ''very likely'' to be being driven by human emissions of greenhouse gases.