  We present observations of methanol lines in a sample of Class 0 low mass
protostars. Using a 1-D radiative transfer model, we derive the abundances in
the envelopes. In two sources of the sample, the observations can only be
reproduced by the model if the methanol abundance is enhanced by about two
order of magnitude in the inner hot region of the envelope. Two other sources
show similar jumps, although at a lower confidence level. The observations for
the other three sources are well reproduced with a constant abundance, but the
presence of a jump cannot be ruled out. The observed methanol abundances in the
warm gas around low mass protostars are orders of magnitude higher than gas
phase chemistry models predict. Hence, in agreement with other evidences, this
suggest that the high methanol abundance reflects recent evaporation of ices
due to the heating by the newly formed star. The observed abundance ratios of
CH3 OH, H2 CO, and CO are in good agreement with grain surface chemistry
models. However, the absolute abundances are more difficult to reproduce and
may point towards the presence of multiple ice components in these regions.
