"Many key climate indicators are already moving beyond the patterns of natural variability within which contemporary society and economy have developed and thrived," the report states.

"These indicators include global mean surface temperature, sea-level rise, global ocean temperature, Arctic sea ice extent, ocean acidification, and extreme climatic events.

"With unabated emissions, many trends in climate will likely accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts."

A tone of frustration, reflecting the slow progress made at Copenhagen, is evident throughout the report, compiled by an international team including several Australians.

"Past societies have reacted when they understood that their own activities were causing deleterious environmental change by controlling or modifying the offending activities," the report's Executive Summary states.

"If humanity is to learn from history and to limit these threats, the time has come for stronger control of the human activities that are changing the fundamental conditions for life on Earth."

The report concludes that the danger of "catastrophic outcomes" are high, and that action on greenhouse gas reduction is urgent.

"… in 2009 society cannot precisely determine the 'right' or the 'best' pathway all the way to 2050 and beyond.

"There will be technological, societal and value changes in the future that will cause the trajectory to change.

"There should be no penalty for not getting it absolutely right the first time.

"The most important task is to start the journey now."