From Martin Parry, Imperial College London, and nine others
On behalf of the authors of those parts of the IPCC report on the impacts of climate change that were criticised by Fred Pearce (27 February, p 8) may I reply to his points?
He describes our interpretation of Nigel Arnell’s work on the impact of drought in Africa as “questionable”, implying that we ignored findings that in some regions climate change will reduce water stress. We specifically sought Arnell’s advice on this. He believes it is appropriate to use only the number of people exposed to increased water stress as the headline impact indicator. In fact, your story misrepresents Arnell’s original paper, which did not give “equal prominence” to increased impact and reduced impact.
Nothing in your report undermines the IPCC’s headline message that “agricultural production… in many African countries… is projected to be severely compromised by climate variability and change… In some countries, yields from rain-fed agriculture could be reduced by up to 50 per cent by 2020”.
We did not conclude there was a simple link between worsening natural disasters and climate change. The graph to which your story refers is not in the published chapter but appears in the supporting material.
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Our biodiversity risk calculation was based on 19 studies, two of a global scope, and had no single study as a “key source”. It took into account the relevant critical literature while balancing possible over- and underestimation.
We have always tried to be clear about uncertainties in our current knowledge and welcome questions about findings in the report, which is why we were happy to provide Pearce with many pages of explanation of our workings. But none of Pearce’s findings undermine the conclusions of the assessment.
London, UK
