Mechanisms and reliability of future projected changes in daily precipitation

Abstract

We isolate the contribution of warming, other large-scale changes and soil moisture decline and feedbacks in driving future projected changes in daily precipitation across Europe. Our confidence in each of these mechanisms differs, so this analysis then allows us to determine an overall confidence (or reliability) in the projected changes. In winter, increases in extreme precipitation over Europe as a whole are judged to be reliable, dominated by increased atmospheric moisture with warming. At scales less than about 2,000 km changing circulation patterns could enhance or offset this increase. Additionally, over the Scandinavian mountains warming-induced circulation changes do offset the effect of increased moisture and the overall change is unreliable. In summer, increases in extreme precipitation over northern Scandinavia and decreases over the Mediterranean are reliable in the absence of considerable circulation change. Over central Europe, an increase in the proportion of summer rainfall falling as extreme events is reliable. © 2009 Crown Copyright.