Analysis of the Hanle effect in solar molecular lines allows us to obtain empirical information on unresolved, tangled magnetic fields at subresolution scales in the (granular) upflowing regions of the `quiet' solar photosphere. Here we show observations of scattering polarization in selected C_2 lines at increasingly closer distances to the solar limb, pointing out that the ratio of polarization amplitudes between suitably chosen line pairs varies in a systematic way. We interpret this variation in terms of a microturbulent magnetic field of the order of a few gauss whose strength decreases with height in the solar atmosphere.