  We explore several strategies of eliminating (or nulling) the small-scale
information in weak lensing convergence power spectrum measurements in order to
protect against undesirable effects, for example the effects of baryonic
cooling and pressure forces on the distribution of large-scale structures. We
selectively throw out the small-scale information in the convergence power
spectrum that is most sensitive to the unwanted bias, while trying to retain
most of the sensitivity to cosmological parameters. The strategies are
effective in the difficult but realistic situations when we are able to guess
the form of the contaminating effect only approximately. However, we also find
that the simplest scheme of simply not using information from the largest
multipoles works about as well as the proposed techniques in most, although not
all, realistic cases. We advocate further exploration of nulling techniques and
believe that they will find important applications in the weak lensing data
mining.
