For smooth linear group schemes over \bbZ we give a cohomological
interpretation of the local Tamagawa measures as cohomological periods. This is
in the spirit of the Tamagawa measures for motives defined by Bloch and Kato.
We show that in the case of tori the cohomological and the motivic Tamagawa
measures coincide, which reproves the Bloch-Kato conjecture for motives
associated to tori.Comment: 20 pages, reference adde
