By Michael Mann
8 December 2014
(Huffington Post) – Just a couple months ago, I critiqued a pair of studies that disputed any linkage between human-caused climate change and the exceptional 2014 California drought. Now comes yet another study ("Causes and Predictability of the 2011-14 California Drought") with the imprimatur of the National Oceanic and Atmospheric Administration (NOAA), announced with great fanfare (a NOAA press conference), drawing yet again the same conclusion. My criticisms of the latest study are yet again basically the same, but for reasons I explain below, that conclusion is even more implausible now than it was just two months ago.
Let me start by noting that this latest report (unless I've missed something?) doesn't appear to be an actual peer-reviewed scientific article, but rather, an internal NOAA report. That causes me some concern, as the claims have not yet been submitted to the independent scrutiny of the larger scientific community in the manner it would have if it were published in a peer-reviewed scientific journal.
That having been said, my main concerns are far more fundamental. The methodology used in the current article, in my view, is deeply flawed because it doesn't properly account for a number of potentially important factors behind the record California drought. […]
Most inexplicable of all, though, is the fact that the authors pay only the slightest lip service to the role of surface temperature in drought, focusing almost entirely on precipitation alone. That neglects the fact that California experienced record heat over the past year, and this anomalous heat certainly contributed to the unprecedented nature of the current drought. Another article published just a week ago in one of the premier peer-reviewed journals in the field, Geophysical Research Letters (GRL), preemptively critiqued the present study, by stressing the importance of looking at the role of extremely high surface temperatures as well as precipitation in assessing the factors behind, e.g., the 2014 California drought:
And most ironic of all, just days ago, another article in GRL concluded that the record heat played a role in making the current California drought the worst such drought in at least 1200 years! (see also this discussion by Peter Gleick). [more]