The BBC's Executive Complaint Unit has now upheld my complaint about the above report, which presented computer models as factual.
Here is their formal response to me:
Thank you for contacting the Executive Complaints Unit and asking it to consider your concerns about the above article on the BBC News website. I know you are familiar with the BBC's complaints process and so I hope I can offer a swift response, particularly in light of the time which has elapsed since you first raised your concerns.
The original headline of the article stated there was a link between climate change and the heatwaves in America and Mexico and presented this as a matter of fact rather than indicating it was the finding of an attribution study conducted by a group of climate scientists. The headline therefore failed to meet the requirements for due accuracy which are set out in the BBC's Editorial Guidelines. The subsequent edit to the headline and the addition of a note explaining the change were, however, sufficient for this Unit to consider the matter to have been appropriately resolved.
I note you have asked for "a formal correction be listed on your complaints site" and so I hope you'll be reassured to know the Executive Complaints Unit publishes the outcome of its investigations every fortnight and a summary of our finding in this case will be published in the complaints section of the BBC website, bbc.co.uk, later today. This ensures the error you identified will be corrected as a matter of public record, over and above the correction now at the foot of the article itself.
In response to the second point you raised in your correspondence to this Unit, I can also assure you our finding has been discussed with relevant managers and editors in BBC News. This has included the way in which the findings of attribution studies are reported to try to ensure members of the audience are not misled in the future.
The edit to the headline, made after my initial complaint, consisted of putting quotation marks around "35 times more likely", which was hardly a correction!
But my main reason for taking this up to the ECU was that "corrections" made months after publication will be seen by nobody.
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They have now confirmed that their next fortnightly complaint report will include this finding:
Climate change made US and Mexico heatwave 35 times more likely, bbc.co.uk.
Complaint
A reader complained the above headline was published without qualification, suggesting it was an undisputed fact that Climate Change had made heatwaves in US and Mexico 35 times more likely. The ECU considered the complaint against the standards for accuracy set out in the BBC Editorial Guidelines.
Outcome
The ECU considered the evidence, which came from climate scientists, was put into proper context in the body of the article, with readers informed about its nature and the uncertainty which accompanies the use of computer modelling in this area - but the original headline presented the precise link between climate change and the heatwaves in America and Mexico as a matter of fact, and failed to meet the requirements for due accuracy in that respect. However, the subsequent edit, with the addition of quotation marks round "35 times more likely" and a note explaining the change, were sufficient for the Unit to consider the matter to have been appropriately resolved.
Resolved
My second reason for involving the ECU was to get them to lay down future guidelines for using attribution models, which they have now published here.
It probably will not make much difference to the Justin Rowlatts of the BBC, but at least we now have a precedent laid down if further complaints are made in future. The ECU have made it clear that computer models cannot be treated as factual.