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Biosphere Atmosphere Change Index
Abstract:
Daily rainfall extremes and annual totals have increased in large parts of the global land area over the last decades.
These observations are consistent with theoretical considerations of a warming climate. However, until recently these global
tendencies have not been shown to consistently affect land regions with limited moisture availability. A recent study, published
by Donat et al. (2016), now identified rapid increases in globally aggregated dry region daily extreme rainfall and annual
rainfall totals. Here, we reassess the respective analysis and find that a) statistical artifacts introduced by the choice of the
reference period prior to data standardization lead to an overestimation of the reported trends by up to 40%, and also that b)
the definition of ‘dry regions of the globe’ affect the reported globally aggregated trends in extreme rainfall. Using the same
observational dataset, but accounting for the statistical artifacts and using alternative, well-established dryness definitions, we
find no significant increases in heavy precipitation in the world’s dry regions. Adequate data pre-processing approaches and
accounting for uncertainties regarding the definition of dryness are crucial to the quantification of spatially aggregated trends
in the world’s dry regions. In view of the high relevance of the question to many potentially affected stakeholders, we call
for a cautionary consideration of specific data processing methods, including issues related to the definition of dry areas, to
guarantee robustness of communicated climate change relevant findings.
