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Thursday, 18 November, 1999, 16:36 GMT
Climate change warning
By Environment Correspondent Alex Kirby A draft report on the probable impacts of climate change, written by the world's leading climate scientists, carries a stark warning - that the world may be in for some nasty shocks. BBC News Online has seen a summary of the report, which was prepared by the members of Working Group Two of the Intergovernmental Panel on Climate Change (IPCC), the authoritative group containing many of the world's most respected climatologists. The report, entitled "Climate change: Impacts, adaptation and vulnerability", is undergoing expert review and is unlikely to be published for some months. Pulling the trigger In its most disturbing section, it deals with the subject of thresholds. These are levels of environmental disruption or pollution below which no observable effect occurs. However, exceeding the threshold can trigger major climatic changes in short periods of time.
Examples that have been given include the instability of the thermohaline circulation that drives warmer water to the North Atlantic and the collapse of the west Antarctic ice sheet. If the warm waters of the Gulf Stream ceased to flow, the British Isles would be plunged into severe winters. The authors say other surprises could include the release of methane - a potent greenhouse gas - from frozen gas hydrates trapped in permafrost. Best-laid plans They go out of their way to warn that unpredictable impacts of climate change could have unforeseeable consequences. "Surprises can make even the most careful calculation of impacts way off the mark." And they say the speed at which the climate heats up is crucial. "Non-linear systems, when rapidly forced, are particularly subject to unexpected behaviour. A fast rate of change is likely to generate more 'surprises' which inhibit the effective adaptation of both natural and managed systems." The report includes a number of more detailed impact assessments for particular sectors:
The report also says that the composition of the world's forests is likely to change because some tree species will not be able to move northwards (or to higher altitudes) to escape the encroaching warmth.
Nor will humans escape unscathed. The report says land lost to rising sea levels is likely to affect about 70 million Chinese and the same number of Bangladeshis. The IPCC still faces criticism from those who do not accept that climate change is inevitable, or that it matters, or that it is caused to some degree by human activity. But this sober and detailed report - even while it remains in draft form - will command wide respect as an all too credible warning of what possibly awaits the world.
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