I experienced that trial first-hand - as one of two scientific expert witnesses that were invited to testify. In this capacity, I answered questions for over an hour on the IPCC special report on global warming of 1.5°C, on which I had been a lead author2. I noted that the single judge paid close attention to my testimony, and, in pronouncing his verdict, mentioned that this testimony and the evidence from the IPCC report had convinced the court ("ont emporté la conviction du tribunal").
The prosecutor for the canton of Vaud, who didn't attend the first trial, however, was not convinced. In his view, no such state of necessity could be invoked in this case. So he appealed. Interestingly, he based his appeal on one of my statements, namely that I wasn't saying that nothing is happening at all, as there are also some positive developments. This was of course very selective, because elsewhere I made it very clear that too little progress has been made since the Paris Agreement was adopted, and that the progress mentioned was by no means in line with what had been agreed.
Broader scope of the process
The case was heard this week in second instance at the Vaud Cantonal Court, and the verdict announced yesterday: the climate activists were sentenced to fines, partially on probation. The verdict may well be reviewed at the Federal Supreme Court in a few months. In the view of the defence lawyers, scientific evidence was crucial to this appeal process. However, no scientific witness was allowed. The lawyers therefore addressed a series of questions to me and other scientists, asking us to answer them in writing so that they could be shared in court.
As a team of eight scientists, we wrote a statement3 summarising once again the state of climate science and the urgency of responding to climate change. The further authors included Thomas Stocker, professor at the University of Bern and former co-chair of the IPCC Working Group 1. A number of Swiss and international climate experts co-signed the statement, including several of my colleagues at ETH Zurich (David Bresch, Andreas Fischlin, Nicolas Gruber, Reto Knutti, Christoph Schär and Heini Wernli). In all, the document was co-signed by 21 climate researchers.