Klimaatwetenschapper Martin Parry wil helderheid scheppen rond IPCC-rel

De toonaangevende Britse wetenschapper professor Martin Parry van het Grantham Instituut en Centrum voor Milieubeleid aan het Imperial College te London wil de onduidelijkheid rond het IPCC-rapport uit de wereld helpen. Hij heeft daarom in een brief de hete hangijzers op een rijtje gezet en van commentaar voorzien.

I am writing to give you a summary of what I believe has been greatly exaggerated press reporting about so-called 'errors' in the IPCC WG2 report.
 
In summary,  I think there was a single important error (on Himalayan glaciers).  The other so-called 'errors' have been fabricated by press hype; and some press reporting has certainly been driven by political, not scientific, objectives.  You only need read the blogs of so-called 'sceptics' to detect the origins of these stories.
 
I am clear that the IPCC WG2 report is a robust and cautious assessment of our current knowledge, the result of careful and professional analysis by its authors.
 

Here are the facts behind the stories:

1. The statement about the likely disappearance of Himalayan glaciers by 2035 was clearly incorrect.  This was in the chapter on Asia but was not in either the Policymakers or Technical Summary of the Assessment.  The authors considered the source (the Chair of the Himalayan Sub-group of the World Glacier Commission) to be reliable, but a proper check would have revealed that his report was later revised.  The IPCC has  corrected this error, and has issued a notice that its procedures to check sources were not properly followed in this instance: read more here.
2. Chapter 1 authors did not conclude (as some press reports had it) that there was a link between increasing economic losses and climate-related disasters. They noted (correctly) that one study found an increasing trend in such losses, while other studies did not.
3. Chapter 1 authors did not use ice-climbing records as evidence of possible changes in snow and ice cover.  They did, quite properly, use them as evidence of the effects of altered snow and ice cover on ice climbing as a recreational activity. This is a typical example of either sloppy or mischievous reporting by some press.
4. The chapter on Latin America correctly reported the current evidence regarding how Amazonian forests could respond to reductions in precipitation.  Incidentally, the source, the WWF Global Review of Forest Fires (which included the evidence in Nature, as well as much more), was extensively reviewed prior to publication.
5. Authors of the chapter on Europe quoted 55 percent of the Netherlands being below sea-level, but this is actually the area at risk of flooding. These data were supplied by the Dutch national environment agency, which has acknowledged its error.  The numbers did not affect any conclusions in the Assessment.
6. Authors of the chapter on agriculture correctly reported the evidence that 'in some countries, yields from rain-fed agriculture could be reduced by up to 50 percent by 2020 '.  This relates to the possible increase in frequency or intensity of drought periods, which can have effects of such magnitude.
7. It is reasonable to use increases in water stress as a headline impact indicator, as was done by the authors of the African chapter. This mode of reporting is widely adopted in the reviewed journal literature.  Those incoming to the stress category are the most at risk and represent the main adaptation challenge.  The number incoming cannot be 'traded-off' against the number outgoing because the trends are occurring in different places.

Professor Martin Parry is werkzaam aan het Grantham Institute and Centre for Environmental Policy, Imperial College London, London SW7 2AZ.