The Collaborative International Dictionary of English v.0.48:
Sober \So"ber\, v. t. [imp. & p. p. Sobered; p. pr. & vb. n. Sobering.] To make sober. [1913 Webster] There shallow draughts intoxicate the brain, And drinking largely sobers us again. --Pope. [1913 Webster]WordNet (r) 3.0 (2006):
sobering adj 1: tending to make sober or more serious; "the news had a sobering effect"