Source : Webster's Revised Unabridged Dictionary (1913)

Sober \So"ber\, v. t. [imp. & p. p. {Sobered}; p. pr. & vb. n.
   {Sobering}.]
   To make sober.

         There shallow draughts intoxicate the brain, And
         drinking largely sobers us again.        --Pope.

Source : WordNet®

sobering
     adj : tending to make sober or more serious; "the news had a
           sobering effect"