We investigate the production of aerosols induced by the propagation of TW-class laser filaments through the real atmosphere. We demonstrate that filaments generate new, stable, particles in ambient air, in conditions typical of the lower troposphere. We examine the dependence of this effect on atmospheric parameters and characterize the chemical species produced, identifying several chemical pathways leading to particle formation. By investigating this phenomenon in a cloud simulation chamber, we show that filaments can assist not only the growth of existing particles, but also the direct gas-to-particle conversion. We check that the laser-generated aerosols are potentially capable to serve as cloud condensation nuclei. Furthermore, we prove that filaments can modify the optical properties of cirrus clouds, by increasing the density of pre-existing ice crystals. These remarkable findings suggest new all-optical methods for cloud seeding and climate engineering, provided that the laser effect is extended to a macroscopic volume. We demonstrate that increasing the laser power is an effective strategy to approach this issue.