  The continuous spectrum to the spectral side of the Arthur-Selberg trace
formula is described in terms of intertwining operators, whose normalising
factors involve quotients of $L$-functions. In this paper, we derive two
expressions in the case of SL(2) over a number field in terms of the
Riemann-Weil explicit formula: as a sum over zeroes of the associated
$L$-functions, and as a sum of adelic distributions on Weil groups. As an
application, we obtain an expression for a lower bound for the sums over zeroes
with respect to the truncation parameter for Eisenstein series.
