THE EXTRAORDINARY CALIFORNIA DROUGHT OF 2013/2014: CHARACTER, CONTEXT, AND THE ROLE OF CLIMATE CHANGE

[...]neither our probability quantification nor our compositing methodology quantifies the amplitude of extreme ridging events. Because we do not explicitly consider geopotential heights outside the North Pacific, it is likely that our inclusion of all years that exceed the 99th percentile P.L GPH leads to inclusion of some events that have lower amplitude than that associated with either the 99th percentile P.I. GPH or the 2013 event. [...]our present methodology cannot reject the possibil- ity that the frequency of occurrence of years with anomalous GPH gradients-and the risk of extreme drought associated with a perturbed North Pacific storm track-has not changed between the prein- dustrial period and the present.