"There are many types of conceivable extreme, such as for different regional entities or time periods as well as different weather parameters (some 27 indices for extremes have been proposed). To pick the type of extreme post hoc — for example, to study Pakistan rainfall extremes after a record-breaking event there — risks selection bias, that is, bias by selecting just the kind of time series that shows recent extremes. Proper statistical analysis of changes in the observed number of extremes thus requires: (1) a single, comparable type of extreme; (2) selection of time series by a priori objective criteria; and (3) sufficiently long-running high-quality data."This is important, and, I suspect, where many AGW believers like Bill McIbben start to go wrong.
Tuesday, March 27, 2012
Selection Bias on Extreme Events
I meant to write more about extreme events but I haven't yet figured out exactly how to say what I want to say, so in the meantime here is an crucial paragraph from the recent Coumou and Rahmstorf paper (emphasis mine):
Posted by David Appell at 3/27/2012 11:18:00 AM