  We present the first calculation of the possible (local) cosmic string
contribution to the cosmic microwave background polarization spectra from
simulations of a string network (rather than a stochastic collection of
unconnected string segments). We use field theory simulations of the Abelian
Higgs model to represent local U(1) strings, including their radiative decay
and microphysics. Relative to previous estimates, our calculations show a shift
in power to larger angular scales, making the chance of a future cosmic string
detection from the B-mode polarization slightly greater. We explore a future
ground-based polarization detector, taking the CLOVER project as our example.
In the null hypothesis (that cosmic strings make a zero contribution) we find
that CLOVER should limit the string tension \mu to G\mu<0.12e-6 (where G is the
gravitational constant), above which it is likely that a detection would be
possible.
