The key United Nations report used as the basis for climate change policies in many countries, including Australia, seriously underestimated the dangers of global warming, one of its leading compilers has warned.
Professor Chris Field, of Stanford University in California, was a co-ordinating lead author of the Fourth Assessment Report (AR4) published in December 2007 by the Intergovernmental Panel on Climate Change (IPCC).
The report was prepared for more than five years by hundreds of scientists from numerous countries. The AR4 aimed to set out what science could dependably say about global warming and its outcomes.
At the time, the AR4 was attacked by climate change sceptics as "alarmist" and as overstating the perils. But addressing a US science conference in Chicago on February 15, Field argued that the reverse was true.
The report, he stated, was "very conservative". The scientists who prepared it did not have access to data that have since revealed a dramatic speed-up of greenhouse emissions in the new century.
According to the US National Oceanographic and Atmospheric Administration, atmospheric carbon dioxide increased by 2.2 parts per million (ppm) in 2007, compared with an average of 2ppm in the years from 2000 through 2006, and 1.5ppm in the 1990s.
These figures track above even the worst-case possibilities considered in the AR4.
"Fossil emissions have proceeded much more rapidly than anticipated in any of the scenarios that were considered in detail", Field explained.
"The consequence of that is that we are basically entering a domain of climate change that has not been explored by the models.
"We're on a different trajectory of emissions and therefore an unknown trajectory of warming."
Likely effects of this upward spiral of emissions and heat, he observed, included vast releases of greenhouse gases from the warming of the Siberian tundra; the drying and burning of forests, with further big releases; and the decreased ability of a warmer and windier Southern Ocean to absorb carbon dioxide.
"We don't want to cross a critical threshold where this massive release of carbon starts to run on autopilot", he told his audience.
A long and detailed work, the AR4 assembled a huge amount of valid and useful information. At one point, it did the struggle to halt climate change a vital service by concluding flatly that global warming was "unequivocal".
Unfortunately, the AR4 also had the character of a "snapshot" — freezing the picture that science had of climate change at a particular, arbitrarily selected instant.
In this case, the instant was the editorial deadline in 2005 after which authors were no longer permitted to cite new evidence.
This was in a period when knowledge of climate change was advancing rapidly. Even before the AR4 was officially released, it was out of date in key respects.
Many of the new findings that appeared in 2006 and 2007 pointed to threats from climate change considerably more dire than had earlier been recognised.
It is also fair to say that the lead authors of the AR4, trained as scientists to be cautious in their judgments, showed a bias against taking positions that would have been viewed as controversial. In part, this may have reflected a desire to produce a report so powerfully buttressed in its arguments that global warming deniers would have no comeback against it.
The AR4 has since acquired a life of its own, distinct from the bubbling pot of investigation and argument that is climate-change science proper. In Australia, it is still the IPCC's outdated modelling, not the disturbing real-world data published since, that Rudd government staffers are said to refer to reverently as "the science".
It was the AR4 that in 2008 provided the basis for Ross Garnaut's report on climate change; for the Australian government's Green Paper; and in December, for Rudd's White Paper with its derisory target for emissions reduction of 5% by 2020.
Contributors to the AR4 are now reportedly working with the Danish government to prepare an updated version for the Copenhagen climate conference late this year. Work has already begun on the Fifth Assessment Report, to be presented in 2014.
According to the redOrbit site, Field is to help lead the group that will assess the impact of climate change on natural, economic and social systems.
One thing is certain: nothing the IPCC publishes in future will enjoy the same authority and influence as the AR4.
The genie is well clear of the bottle; the climate change movement now contains a growing cadre of activists, many with scientific backgrounds, who go straight to the best new research to inform their public campaigning.
Neither UN officials nor thought police from government ministries will have the same impact on the climate debates of the future.