Here’s a fascinating paper that changed my mind about the IPCC. Contrary to what many denialists claim, the IPCC is not overly “alarmist”. If anything, the reverse is true. We can now establish this, by comparing the earliest IPCC predictions from the 1990 report (about ice sheets, CO2 levels, droughts, etc.) to current observations. It turns out that IPCC consistently undershoots its targets. The authors give sensible explanations for this directional bias. In general, scientists are a conservative bunch. The ethos of science dictates that extraordinary claims demand extraordinary evidence. Dramatic predictions about catastrophic events are met with a hefty dose of scepticism. Besides, climatologists are under enormous pressure from fossil fuel companies and other political interest groups. They know that these people will try to discredit them if they make a dramatic predictions that then turns out to be false, even just once. As a consequence, the IPCC tends to “err on the side of least drama”, as the authors put it. There are sure alarmists and doomsday prophets out there, but generally speaking, those people are environmental activists and journalists, not the actual climatologists. One reason why I had the wrong impression about the IPCC was that the most notorious spokesman in Belgium, climatologist Jean-Pascal Van Ypersele, former vice-chair of IPCC, is generally quite alarmist in the media, emphasizing the worst case scenarios and going beyond the evidence to scare people into action. But I think Van Ypersele is not representative for the IPCC as a whole.