Editing IPCC:AR6/SROCC/Chapter-2 (section)

==== 2.2.1.2 Rainfall and Snowfall ====

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Past precipitation changes are less well quantified than temperature changes and are often more heterogeneous, even within mountain regions (Hartmann and Andresky, 2013 <sup>[[#fn:r32|32]]</sup> ). Regional patterns are characterised by decadal variability (Mankin and Diffenbaugh, 2015 <sup>[[#fn:r33|33]]</sup> ) and influenced by shifts in large-scale atmospheric circulation (e.g., in Alaska; Winski et al., 2017 <sup>[[#fn:r34|34]]</sup> ). While mountain regions do not exhibit clear direction of trends in annual precipitation over the past decades ( ''medium confidence'' that there is no trend), snowfall has decreased, at least in part due to higher temperatures, especially at lower elevation (Table SM2.4, ''high confidence'' ).

Future projections of annual precipitation indicate increases of the order of 5 to 20% over the 21st century in many mountain regions, including the Hindu Kush and Himalaya, East Asia, eastern Africa, the European Alps and the Carpathian region, and decreases in the Mediterranean and the Southern Andes ( ''medium confidence,'' Table SM2.5). Changes in the frequency and intensity of extreme precipitation events vary according to season and region. For example, across the Himalayan-Tibetan Plateau mountains, the frequency and intensity of extreme rainfall events are projected to increase throughout the 21st century, particularly during the summer monsoon (Panday et al., 2015 <sup>[[#fn:r35|35]]</sup> ; Sanjay et al., 2017 <sup>[[#fn:r36|36]]</sup> ). This suggests a transition toward more episodic and intense monsoonal precipitation, especially in the easternmost part of the Himalayan chain (Palazzi et al., 2013). Increases in winter precipitation extremes are projected in the European Alps (Rajczak and Schär, 2017 <sup>[[#fn:r38|38]]</sup> ). At lower elevation, near term (2031 – 2050) and end of century (2081 – 2100) projections of snowfall all indicate a decrease, for all greenhouse gas emission scenarios ( ''very high confidence'' ). At higher elevation, where temperature increase is insufficient to affect rain/snow partitioning, total winter precipitation increases can lead to increased snowfall (e.g., Kapnick and Delworth, 2013; O’Gorman, 2014) ( ''medium confidence'' ).

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