A tendency to highlight worst-case scenarios undermined parts of the last assessment by the Intergovernmental Panel on Climate Change, according to a (PBL).
The inquiry was ordered by embarrassed Dutch ministers after it emerged that a mistake in originated with its own scientists. The report stated that 55 per cent of the Netherlands is below sea level, when in fact the true figure is half that.
Overall, the Dutch investigators said, the IPCC report鈥檚 conclusions were 鈥渨ell-founded鈥�. But it found several judgements that were 鈥渕isleading鈥� and appeared to have no firm research basis.
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For instance, the IPCC concluded that by 2050, 鈥渇reshwater availability in central, south, east and south-east Asia, particularly in large river basins, is projected to decrease鈥�. This matters because some 3 billion people live in this part of the world and most rely on river flows to irrigate their crops.
Confusion over data
However, the Dutch investigators found confusion over data. Some studies cited measured absolute river flows, while others assessed per-capita flows. This made it 鈥渉ard to establish the line of reasoning鈥� and meant the conclusion could not be relied on, they said.
In another case, the IPCC stated that 鈥渙n balance health risks are very likely to increase鈥� as a result of climate change. The PBL researchers said the report lacked a 鈥渜uantitative underpinning for the statement鈥�.
The PBL report also investigated an IPCC claim that yields from rain-fed agriculture in some African countries could be reduced by up to 50 per cent by 2050, a claim repeated in speeches by IPCC director Rajendra Pachauri. The potentially misleading claim was first highlighted by New Scientist earlier this year.
鈥淢inor errors鈥�
The PBL found that 鈥渢his statement is not directly a statement of climate change, but of climate variability: in individual years, drought can cause up to 50 per cent yield reductions鈥�. This already happens in some years, the Dutch researchers said, regardless of future climate change. Thus 鈥渢he statement could easily mislead readers.鈥�
The source of the claim was a paper by a Moroccan academic that referred to other studies the PBL researchers said they 鈥渨ere unable to trace鈥�, concluding: 鈥淎s it stands, the statement cannot be traced back to any original scientific research.鈥�
The chairman of the IPCC report, of the Centre for Environmental Policy, Imperial College London, said minor errors had been found and . 鈥淲e welcome the conclusion of this report, which is essentially that our conclusions are safe, sound and reliable.鈥�
