  Most of the baryons in the low-redshift universe reside in a warm/hot
component which is difficult to detect with standard absorption/emission line
techniques. We propose to use quasar refractive scintillation as an useful,
complementary probe of such ionized, intergalactic gas. In particular, an
application to the case of the intracluster medium is presented. We show that
clusters located at z approx 0.02 should produce a source rms intensity
fluctuation at 50-100 GHz of several tens of percent and on time scales ranging
from days to months, depending on the projected location of the source on the
foreground cluster. However, in order to produce such a signal, the source
needs to be very compact. This effect, if observed, can be used as an
independent test of the baryonic mass fraction in clusters.
