A cautionary tale about experts
We decided early not to follow every twist and turn of this story and, as it turned out, it went full circle - a massive balloon, now deflated. But it nevertheless contains an interesting message. A retired German doctor, a pneumologist, published private research showing that the nitrogen dioxide emissions that have triggered the diesel bans were not damaging to the human lung after all. As a lung doctor, he would know.
So he enlisted over 100 co-conspirators and got himself on to the talk-show circuit. It was the news people wanted to hear: the diesel ban was a conspiracy by the Green Party and the World Health Organisation, who want nothing more than to destroy the German car industry. Once the doctor's finding hit the news, the German transport minister ordered a review of the targets. But, as it turned out, the doctor got his numbers wrong by a factor of 100. Worse still, the methodology is also wrong. He is a doctor, not an epidemiologist. If you want to know how toxins spread from a source to a target, you should pick the latter kind of expertise and not the former.
Die Tageszeitung has a very detailed take on this that goes deep into the scientific aspects, going well beyond our scope here. The bottom line is that even if you take his dubious methodology at face value, TAZ noted the author committed a rookie multiplication error when he calculated a number of 1m as opposed to 10,000.
The more substantive criticism is methodological. The emissions targets are not discretionary political numbers, but based on scientific research that was translated into an official recommendation by the WHO.
This story tells the real problem with expert opinion as it interacts with the media. Not every expert is the right expert. And experts, too, have political agendas. Their findings are not always based on knowledge but are often politically motivated. The diesel bans are a big story in Germany. Many people, possibly including the doctor himself, are affected. If someone who poses as an expert comes along and tells you that this is just a hoax, you listen up. You want it to be true.
As this story has run its course, the facts on the ground have not changed. But the story had a useful effect beyond its function as a cautionary tale: Germans know a lot more about emissions now than they did before. And they know, or at least suspect, that the targets are not accidental.