The work of the United Nations’ Intergovernmental Panel on Climate Change, a team effort by several thousand scientists that yields cautiously worded assessments, attracts repeated criticism from sceptics. Inevitably, there is much that is uncertain, even unknowable, about the complexities of the planet's climate system: thresholds exist, unexpected feedbacks will occur, and, anyway, we cannot foretell how future societies will behave. Such uncertainty is grist to the critics' mill.

You don't need much knowledge of climate science to belittle the IPCC's estimated range of 1.8 to 4.0 degrees increase in global average temperature by 2100. Today, though, a different concern is emerging over IPCC assessments.

Already some key aspects of its Fourth Assessment Report (2007) look conservative against new evidence that climate change is proceeding unexpectedly fast. This presents a dilemma for society: thorough and laborious scientific assessments, wrestling with inherently uncertain and complex issues, may lag behind the realities of rapid change.

There will be discussion of the latest evidence on climate change at a conference imagining the Real: Life on a Greenhouse Earth at the Australian National University tomorrow and on Thursday at Manning Clark House, in honour of Barry Jones. The sessions will explore recent evidence of top-of-range increases in temperature and of accelerations in polar-ice melting, the emission and atmospheric accumulation of carbon dioxide, sea- level rise, and ocean acidification. Meanwhile, the likely consequences for Australia include southward migration of climate zones, changes in rainfall and drought patterns, and storm and flood intensification.

A small but growing number of high-profile international scientists argue that humankind is at increasing risk of failing to avert a ''greenhouse world'' that would differ radically from the world we know. Will life be possible on such a greenhouse Earth? Today's familiar Earth is the one which, via biological evolution, shaped all forms of extant life. Those species are finely attuned to current planetary conditions. That includes us, Homo sapiens. (We may be more adaptable than other species, but the things we depend on are not.) In 1987, eminent American oceanographer Wally Broecker wrote, ''The inhabitants of Earth are quietly conducting a gigantic experiment. So vast and sweeping will be the consequences that, were it brought before any reasonable council for approval, it would be firmly rejected. We play Russian roulette with climate, hoping that the future will hold no unpleasant surprises. No one knows what lies in the active chamber of the gun.'' Today that concern looks more urgent, as extraordinary global temperature rises of five or more degrees over the next several centuries now loom as plausible, if not yet probable.

The second day of the conference will focus on impacts, risks and policy responses. It will explore the consequences for life and civilisation of the severe greenhouse conditions that could emerge. Meanwhile, how best can government, society and researchers cope with climate change? There is a growing realisation that climate change poses a fundamental threat to life processes.

This realisation is overdue. We have been preoccupied with threats to the economy, jobs, physical infrastructure, tourism and iconic species. Meanwhile, climate change is already affecting diverse species and ecosystems marine life, the breeding and feeding rhythms of birds, bugs and bears, growth and flowering of vegetation, agricultural yields, and some infections in livestock. For humans the health risks include thermal stress, the consequences of weather disasters,  effects on food yields and nutrition, altered infectious disease patterns, mental-health impacts (for example, in rural Australian communities as drying trends emerge), and heightened conflicts over dwindling natural resources.

These health risks also underscore the great moral challenge posed by the geographic, socio-economic and inter-generational disparities in climate-related exposures and anticipated adverse health impacts.

The timeliness of the conference is underscored by today's emerging climatic trends.

Oil prices are rising, as energy producers and consumers sense that the ''peak oil'' moment may have arrived. This, in turn, is exacerbating widespread shortages and rising costs of basic foods. Australian government policy responses to these great challenges have been to date, slow and limited. Viewed within short time horizons, fossil fuels seem indispensable (electorally, if not economically), and hence incentives for developing renewable energy, sustainable transport and more efficient energy use remain seriously inadequate. By grappling with global climate change we will understand better the fundamental rationale for seeking ''sustainability'', and the need for a cultural transformation that ensures ''bio-sensitive'' ways of living.

Dr Tony McMichael is National Health and Medical Research Council Australia Fellow at the Australian National University. He will speak at imagining the real Life on a Greenhouse Earth, a conference organised by Manning Clark House in honour of Dr Barry Jones, at Manning Clark Lecture Theatre No3, Union Square, ANU, and tomorrow and on Thursday. More information: www.manningclark.org.au

Source: Global News Wire