| Fish stocks could plummet further
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
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.
| It is thought 70 million Bangladeshis will suffer from
sea level rise
Acknowledging the incorporation of such thresholds in some
climate models, the authors write: "In climate change, thresholds have been proposed
which are much more worrying than this. Below the threshold there may be some impacts, but
they will be smoothly varying with the change in the climate. Above the threshold
something really nasty may happen.
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
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.
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:
- A probable decrease of crop yields in the tropics and sub-tropics "raising enormous
problems because of the serious potential for exacerbated deprivation".
- Drought and floods "are projected to become a larger problem in many temperate and
- Soil degradation could be worsened by increased erosion caused by higher rainfall, while
elsewhere more land could become desert.
- Existing stresses on fish stocks could be worsened as water temperature, salinity and
entire ecosystems change.
- Insect species may expand their ranges towards the poles, increasing the risk of crop
loss and, in Africa, there could be significant changes in tsetse fly distribution.
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.
| Forests types could vanish
"Entire forests types may disappear" and there is
likely to be "a net decrease in global biodiversity."
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.