New particle formation (aerosol nucleation) happens frequently in the troposphere. It has large impact on the aerosol lifecycle and can substantially change the number concentrations of cloud condensation nuclei (CCN) and ice-nucleating particles. Consequently, it may change cloud properties and the associated precipitation processes. Here we use a global atmospheric model to investigate the impact of various new particle formation mechanisms on warm and cold cloud processes and the anthropogenic aerosol forcing estimate. The model we use is the atmospheric component of the Energy Exascale Earth System Model (E3SM), with a revised Modal Aerosol Module that has a nucleation mode to better represent the evolution of newly formed particles. Results show that both the boundary layer nucleation and free-troposphere binary nucleation have a large impact on the CCN number concentration and liquid cloud formation. In addition, the free-troposphere binary nucleation greatly changes the number concentration of small aerosol particles (Dp<50nm), which promote the homogeneous ice nucleation in cirrus clouds. We find the two nucleation mechanisms have very different impacts on the estimated anthropogenic aerosol effect, even with opposite signs in some regions. This suggests that it’s important to improve/constrain the representation of aerosol nucleation and its interaction with cloud processes in global aerosol-climate models.