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In the present-day atmosphere, sulfuric acid is the most important vapour for aerosol particle formation and initial growth. However, the growth rates of nanoparticles (< 10 nm) from sulfuric acid vapour remain poorly measured. Therefore, the effect of stabilizing bases, the contribution of ions and the impact of attractive forces on molecular collisions are under debate. Here we present precise growth-rate measurements of uncharged sulfuric acid particles in the size range 1.8-10 nm, performed under atmospheric conditions in the CERN CLOUD chamber. Our results show that the evaporation of sulfuric acid particles above 2 nm is indeed negligible and growth proceeds kinetically even at low ammonia concentrations. The experimental growth rates exceed the geometric hard-sphere kinetic limit for condensation of sulfuric acid, and reveal an enhancement resulting from dipole-induced dipole interactions between the vapour molecules and particles. We are able to disentangle the effect of charge-dipole interactions and van-der-Waals forces and observe a steep increase of particle growth rates with decreasing size. Including the experimental results in a global model, we find the enhanced growth rate of sulfuric acid particles increases predicted particle number concentrations in the upper free troposphere by more than 50 %. [ABSTRACT FROM AUTHOR]