 Werndl (2016) provides a critical, philosophical examination of several definitions of climate and proposes a novel, model-immanent definition on which a climate is a distribution of values of climate variables over a suitably-long but finite time period, under a regime of external conditions and starting from a particular initial state. Roughly speaking, a regime is a pattern of variation in external conditions that has an approximately constant mean value over different sub-periods of a chosen time period. This definition is model-immanent because it refers to the distribution of conditions that would obtain (i.e., the conditions that a perfect model of the climate system would indicate) if the climate system were subjected to a regime for a suitably-long time period; this distribution defines the climate of periods in which that regime actually obtains, even if those periods are relatively short. Werndl’s definition avoids many of the problems that she finds with other definitions, but still some questions remain, including how to employ the regime concept when external conditions are changing rapidly.