  Charged-particle production was studied in proton-proton collisions collected
at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36
TeV in the pseudorapidity range |$\eta$| < 1.4. In the central region (|$\eta$|
< 0.5), at 0.9 TeV, we measure charged-particle pseudorapidity density
dNch/deta = 3.02 $\pm$ 0.01 (stat.) $^{+0.08}_{-0.05}$ (syst.) for inelastic
interactions, and dNch/deta = 3.58 $\pm$ 0.01 (stat.) $^{+0.12}_{-0.12}$
(syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dNch/deta
= 3.77 $\pm$ 0.01 (stat.) $^{+0.25}_{-0.12}$ (syst.) for inelastic, and
dNch/deta = 4.43 $\pm$ 0.01 (stat.) $^{+0.17}_{-0.12}$ (syst.) for
non-single-diffractive collisions. The relative increase in charged-particle
multiplicity from the lower to higher energy is 24.7% $\pm$ 0.5% (stat.)
$^{+5.7}_{-2.8}$% (syst.) for inelastic and 23.7% $\pm$ 0.5% (stat.)
$^{+4.6}_{-1.1}$% (syst.) for non-single-diffractive interactions. This
increase is consistent with that reported by the CMS collaboration for
non-single-diffractive events and larger than that found by a number of
commonly used models. The multiplicity distribution was measured in different
pseudorapidity intervals and studied in terms of KNO variables at both
energies. The results are compared to proton-antiproton data and to model
predictions.
