In a series of four United Nations reports this year, the Intergovernmental Panel on Climate Change (IPCC) will spell out the huge impact of global warming, humankind's responsibility for it and what measures can be taken to prevent and reverse its effects.
In particular, the IPCC's fourth report, due in September, will synopsise the other three and wrap up a remarkably detailed and convincing case for urgent action.
The IPCC's second report, published last week, dealt with the impact of global warming on areas as diverse as water availability, sea levels, species survival, agriculture, ocean acidification, coral reefs, storms and hurricanes and the impact on vulnerable low-lying areas and river deltas. One of its principal conclusions is that these changes will predominantly affect poorer people all round the world who in fact have least responsibility for the carbon emissions which cause them. Political lobbying in Brussels to amend the published report concentrated on modifying its sharper findings on this score, including reference to the billions of poorer people directly involved. Russia, China and Saudi Arabia are interesting new players in this political game.
The report draws on a formidable range of scientific studies which have increased greatly in volume and quality over the last 10 years. Work on it began five years ago and involved contributions from more than 1,500 scientists. As a result, its findings are based on a remarkable level of confidence in spelling out and predicting the impact of climate change. According to Martin Parry, one of the drafting panel's co-chairmen, "we are no longer arm-waving with models. This is empirical information on the ground". The overwhelming scientific consensus is that this phase of global warming - which is bringing Earth by 2050 to its warmest period in 100,000 years - is anthropogenic or man-made.
Human action can also reverse this climate change with environmental knowledge and political will. Last week's report identifies measures capable of reducing carbon emissions, mitigating their effects and making the transition to a sustainable economy which will not undermine the welfare of future generations. The panel's third report will spell these out in more detail next month.
Crucially, the IPCC warns there is only a decade or two left to make the radical changes necessary. It will be a far more expensive exercise if left later than that. Indeed many of these scientists believe we are perilously near to tipping points in which change becomes "non-linear", leading to irreversible transformation of the environment. We ignore these findings and warnings at our peril.